Symposium Organizers
Erica Lilleodden GKSS Forschungszentrum
Paul Besser Advanced Micro Devices, Inc.
Lyle Levine National Institute of Standards and Technology
Alan Needleman Brown University
EE1: Size Effects in the Deformation of Nanocrystalline Materials
Session Chairs
Erica Lilleodden
Dierk Raabe
Monday PM, November 27, 2006
Back Bay B (Sheraton)
9:30 AM - EE1.1
Grain Size Controlled Deformation Process in Nanocrystalline Nickel.
Scott Mao 1 , Steven (Zhiwei) Shan 1 , Jörg Wiezorek 2 , James Knapp 3 , David Follstaedt 3 , Eric Stach 4
1 Mechanical Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 Materials Science and Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 3 Physical, Chemical and Nano Sciences Center, Sandia National Laboratories, Albuquerque, New Mexico, United States, 4 School of Materials Engineering, Purdue University, West Lafayette, Indiana, United States
Show Abstract9:45 AM - EE1.2
Fatigue Behavior of High Purity Ultra Fine Grain Copper.
Kai Zhang 1 , Anthony Escuadro 1 , Julia Weertman 1
1 , Northwestern University, Evanston, Illinois, United States
Show Abstract10:00 AM - **EE1.3
From micro-to Macro Plasticity.
Helena Van Swygenhoven 1 , Stefan Brandstetter 1 , Steven Van Petegem 1 , Peter Derlet 1
1 ASQ/NUM - Materials Science & Simulation, Paul Scherrer Institute, PSI-Villigen Switzerland
Show Abstract10:30 AM - EE1.4
What is behind the Inverse Hall-Petch Behavior in Nanocrystalline Materials?
Christopher Carlton 1 , Paulo Ferreira 1
1 Materials Science and Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractAn inverse Hall-Petch effect has been observed for nanocrystalline materials by a large number of researchers. This effect implies that nanocrystalline materials get softer as grain size is reduced below a critical value. Postulated explanations for this behavior include a dislocation mechanism or grain boundary sliding. In this paper, we report an explanation for the inverse Hall-Petch effect based on the statistical absorption of dislocations by grain boundaries, showing that the yield strength is dependent on strain rate and temperature, and that deviates from the Hall-Petch relationship at a critical grain size.
10:45 AM - EE1.5
Atomistic Simulations of Grain Size Dependent Deformation Behavior of Nanocrystalline Al and Cu at Continuum Timescales.
Vikas Tomar 1
1 Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN, Indiana, United States
Show AbstractA majority of computational mechanical analyses of nanocrystalline materials have been carried out using classical molecular dynamics (MD). Except in a very limited number of cases, such as experimental verification of the MD results of Yamakov et al.1 on deformation twinning in nanocrystalline Al by Liao et al.2, results of MD simulations have not been directly verified using experiments. The primary reason for this discrepancy has been the limitations on timescale (of the order of nanoseconds) of MD simulations. Due to the fundamental reason that the MD simulations must resolve atomic level vibrations, they cannot be carried out at the timescale of the order of microseconds. Solutions to this problem are methods that allow the use of larger time-steps in MD simulations with simultaneous resolution of atomic level vibrations, such as MD time-acceleration methods, see Voter et al.3, and hybrid-Monte Carlo (HMC) method (cf. e.g. Mehlig et al.4). In this investigation, a modified HMC method is used to analyze time-dependent mechanical deformation of nanocrystalline Cu and Al at experimentally realistic loading rates (~104 s-1). The framework of analyses is based on the work of Tomar and Zhou5. Well established EAM potentials for Cu and Al are used during simulations. The essential idea of the HMC algorithm, see Mehlig et al.4, is to construct a global-update Monte Carlo (MC) algorithm by introducing momenta conjugate to the system coordinate variables and performing a MD integration of the associated Hamiltonian equations of motion for accelerated global MC sampling. The HMC algorithm is modified to simulate non-equilibrium atomistic deformation with alternating steps of stretching using non-equilibrium MD and equilibration steps using MC. The analyses primarily focus on comparison of defect formation and its effect on strength of the nanocrystalline samples as a function of average grain size and at a range of strain rates during HMC analyses at macroscopic loading rates (104 s-1) with that during MD analyses at very high loading rates (~108 s-1) characteristic of MD. It is found that defect formation as a function of grain size and its effect on the overall strength in the nanocrystalline materials is indeed strongly dependent upon the imposed loading rates. Interaction and relaxation of defects as a function of time is different at macroscopic timescale (HMC) from that at nanoscopic time scale (MD). Qualitative experimental observations, however, are in close agreement with the results of both HMC and MD simulations. :References:: 1 V. Yamakov, D. Wolf, S. R. Phillpot, and H. Gleiter, Acta Materialia 50, 5005 (2002):: 2 X. Z. Liao, F. Zhou, E. J. Lavernia, D. W. He, and Y. T. Zhua, Appl. Phys. Lett. 83, 5062 (2003)::3 A. F. Voter, F. Montalenti, and T. C. Germann, Annu. Rev. Mater. Res. 32, 321 (2002)::4 B. Mehlig, D. W. Heerman, and B. M. Forrest, Phys. Rev. B 45, 680 (1992)::5 V. Tomar and M. Zhou, Phys Rev B 73, 174116 (1 (2006).
11:30 AM - EE1.6
Role of Grain Boundaries and Crystal Anisotropy on Grain Size Effects in Polycrystals.
Amit Ghosh 1
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show Abstract11:45 AM - EE1.7
Grain Growth During Compression Testing of Nanocrystalline fcc Metals.
Kai Zhang 2 , A. Escuadro 2 , Julia Weertman 2 , Stefan Brandstetter 1 , Steven Van Petegem 1 , Helena Van Swygenhoven 1
2 , Northwestern University, Evanston/Chicago, Illinois, United States, 1 ASQ/NUM - Materials Science & Simulation, Paul Scherrer Institute, PSI-Villigen Switzerland
Show Abstract12:00 PM - EE1.8
Microstructural Evolution in Nanoscale Alloys Under Plastic Deformation.
Samson Odunuga 1 , Pavel Krasnochtchekov 1 , Pascal Bellon 1 , Robert Averback 1
1 Materials Science and Engineering, University of Illinois Urbana Champaign, Urbana, Illinois, United States
Show Abstract12:15 PM - EE1.9
Atomistic Investigation of Grain Boundary Sliding, Migration, and Dislocation Emission under Multi-Axial Stress States.
Derek Warner 1 , Jean-Francois Molinari 1 , William Curtin 2
1 Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Engineering, Brown University, Providence, Rhode Island, United States
Show AbstractWhen the dimensions of metallic materials are decreased to a few micrometers or even less, changes from traditionally observed mechanical behavior become evident. The changes can often be attributed to an increased surface to volume ratio and/or a microstructure with nanometer sized grains. The small grain size limits the role of traditional intragranular deformation mechanisms such as dislocation multiplication and tangling. Consequently, a majority of the plastic deformation is thought to be accommodated by grain boundary based deformation mechanisms such as grain boundary sliding, migration, and dislocation emission. In order to better understand these deformation mechanisms, an increasing number of researchers have performed atomistic simulations investigating the mechanical behavior of grain boundaries within bicrystals. However, the application of these finding to coarser scale models such as discrete dislocation dynamics or finite element methods requires knowledge of how these mechanisms react to complex stress states. Our work seeks to explore this issue through individual studies of the three grain boundary deformation mechanisms. First, the influence of normal stress on grain boundary sliding of a Σ27(552) Cu boundary is investigated. This study emphasizes the complex nature of high energy grain boundaries, as multiple behaviors are observed for different regimes of normal loading. By conducting calculations at both 300 and 0K, the atomistic mechanisms associated with each regime are identified. Second, the effect of a multi-axial stress state on nucleation of the leading partial dislocation from a Σ9(221) Cu boundary reveals that this process does not resemble a simple criteria involving the critical resolved shear stress; but rather, it is a highly asymmetric function of the local stress state. Finally, the stress activated migration of a Σ11(113) Cu grain boundary was found to exhibit the least multi-axial dependence of the three grain boundary mechanisms investigated in this work. Examination of the atomic movements associated with the initial stages of this process give insight into this behavior. In all, this talk aims to encourage the use of more realistic, multi-axial, criteria for modeling grain boundary deformation mechanisms.
12:30 PM - EE1.10
Grain Boundary Sliding Under Pressure.
Eduardo Bringa 1 , Alfredo Caro 1 , Ricardo Lebensohn 2
1 , Lawrence Livermore National Laboratory, Livermore, California, United States, 2 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract12:45 PM - EE1.11
Grain Boundary Motion Coupled to Shear: A Novel DeformationMechanism of Nanostructured Materials.
Vladimir Ivanov 1 , John Cahn 2 , Yuri Mishin 1
1 Department of Physics and Astronomy, George Mason University, Fairfax, Virginia, United States, 2 Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show AbstractEE2: Size Effects in Bulk Materials
Session Chairs
Lyle Levine
Alan Needleman
Monday PM, November 27, 2006
Back Bay B (Sheraton)
2:30 PM - **EE2.1
Correlating Dislocation Behavior With Macroscopic Mechanical Properties.
Bryan Miller 1 , Khalid Hattar 1 , Dong Su 1 , Jamey Fenske 1 , Ian Robertson 1
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractWe remain challenged by our inability to adequately predict the mechanical response of a material as the composition and microstructure are altered and the material is exposed to different loading histories. As an example consider our lack of understanding of the deformation mechanisms that occur in ultra-fine and nano grained pure metals, how the dominant processes change as the grain size decreases and how these processes, in conjunction with the microstructure, result in the characteristic stress-strain behavior in which the work hardening and tensile strain is limited. The problem is two-fold; we do not fully understand the complex deformation processes, the interrelations between them, and how they are linked to microstructure and microchemistry, and how to incorporate the dominant processes into predictive models. In this talk, we will emphasize how grain boundaries respond to the applied and local stresses to generate in some cases perfect and partial dislocations as well as twins from the same grain boundary; the effectiveness of annealing and deformation twins as sources of and barriers to further deformation; and how these processes are impacted by both grain size and composition. A strategy for incorporating the dominant processes into a model, and its success at predicting response, will be presented.
3:00 PM - EE2.2
Microstructural Modeling of Grain Subdivision and Large Strain Inhomogeneous Deformation Modes in F.C.C. Crystalline Materials.
Omid Rezvanian 1 , Mohammed Zikry 1
1 Mechanical and Awrospace Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show Abstract3:15 PM - EE2.3
The Effect of Twins and Dislocations on X-ray Diffraction Peaks.
Stefan Brandstetter 1 , Peter Derlet 1 , Steven Van Petegem 1 , Helena Van Swygenhoven 1
1 ASQ/NUM - Materials Science & Simulation, Paul Scherrer Institute, PSI-Villigen Switzerland
Show Abstract3:30 PM - EE2: Bulk
BREAK
4:30 PM - EE2.4
Equilibrium And Dynamic Properties Of Dislocation Dipoles.
Patrick Veyssiere 1
1 LEM, CNRS-ONERA, Chatillon France
Show AbstractThe constraint of plastic deformation in channels between fatigue walls involves deformation mechanisms where, relative to unconstrained situations, the role of screw dislocations is enhanced while that of edge segments is substantially lessened. Interactions between dislocations are essentially dipolar in nature. The present contribution addesses properties of dislocation dipoles in isotropic and anisotropic cubic systems in the case of dissociated and undissociated dislocations.In the isotropic approximation, the habit plane of dipoles at equilibrium lies at 90° to the slip plane up to a critical character whose exact nature depends only on the Poisson coefficient but which can be as large as 40°. In anisotropic fcc crystals, the habit plane of screw dipoles at equilibrium is hardly at 90° to the slip plane. In Al, Si, Ni and Cu for instance this angle amounts to approximately 85°, 77°, 65° and 59°, respectively. In the edge orientation, the equilibirum angle deviates by less than 5° from the 45° isotropic.The passing stress is the highest for screw dipoles and not the lowest in the edge orientation but for some dislocation character whose value again depends on the Poisson coefficient. The orientation dependence of the passing stress is hardly influenced by anisotropy. The passing stress is perceivably affected by dislocation dissociation for dipoles heights of the order of and smaller than the equilibrium dissociation distance of a stress-free isolated dislocation. Below that height, 2D dislocation dynamics simulations demonstrate a complex passing mechanism where two partial partners successively interact with those of the other dislocation, including cases of partial decorrelation and production of extended stacking faults. Some consequences of these properties in situations of constrained deformation are discussed.
4:45 PM - **EE2.5
A Discrete Dislocation Study of Size Dependence: From Single Crystals to Polycrystals.
Ranjeet Kumar 2 1 , Lucia Nicola 3 5 , Vikram Deshpande 4 , Alan Needleman 5 , Erik Van der Giessen 1
2 , Netherlands Institute for Metals Research, Delft Netherlands, 1 Applied Physics, University of Groningen, Groningen Netherlands, 3 3ME, Delft University of Technology, Delft Netherlands, 5 Division of Engineering, Brown University, Providence, Rhode Island, United States, 4 Department of Engineering, Cambridge University, Cambridge United Kingdom
Show Abstract5:15 PM - EE2.6
Hierarchical Multiscale Characterization of Compressed Copper Single Crystals.
K. Magid 1 , J. Morris 1 , J. Florando 2 , D. Lassila 2 , M. LeBlanc 2 , N. Tamura 3 , A. Minor 4
1 Materials Science & Engineering, University of California, Berkeley, Berkeley, California, United States, 2 Engineering Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States, 3 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 4 National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractA top-down multiscale characterization technique is being developed to characterize dislocation processes and further the understanding of plastic deformation across the entire range of length-scales at high levels of detail. Bulk single crystals compressed with a unique six-degree of freedom test are mapped with speckle strain gaging and x-ray microdiffraction. These techniques map the inherent inhomogeneity of the plastic deformation and provide the locations of interest for sample extractions for study with high-resolution TEM. The copper samples primarily analyzed to date were compressed in a unique six-degree of freedom compression test with a single-slip orientation by maximizing the Schmid factor on one slip system; however, in all but one case, multiple slip systems were activated. The patterns of strain emerged as two orthogonal slip systems, oriented at 45 degrees to the compression axis. The x-ray microdiffraction maps the heterogeneity to the micron scale, showing planar bands of high dislocation density separated by relatively dislocation-free regions. The regions with the highest dislocation density appear between the most severely deformed areas of the crystal, where a strain gradient appears. Based on the microdiffraction maps, locations for the extraction of samples for TEM are being chosen for the complete analysis of active slip systems in each of the observed regions of the sample.
5:30 PM - EE2.7
X-ray Microbeam Measurements of Elastic Strains Within Individual Dislocation Cells in Deformed Copper.
Lyle Levine 1 , Bennett Larson 2 , Wenge Yang 2 , Michael Kassner 3 , Jonathan Tischler 2 , Michael Delos-Reyes 3
1 , NIST, Gaithersburg, Maryland, United States, 2 , ORNL, Oak Ridge, Tennessee, United States, 3 , USC, Los Angeles, California, United States
Show Abstract5:45 PM - EE2.8
Multiscale Dislocation Arrangements from Neutron and X-ray Microbeam Diffraction.
Rozaliya Barabash 1 2 , Y. Sun 3 , H. Choo 3 , P. Liaw 3 , Y. Lu 3 , D. Brown 4 , G. Ice 1
1 Materials Science and Technology Div., Oak Ridge National Laboratory, Oak Ridge TN, Tennessee, United States, 2 Center for Materials Processing, University of Tennessee, Knoxville, Tennessee, United States, 3 Materials Science and Engineering Department, University of Tennessee, Knoxville, Tennessee, United States, 4 Materials Science and Technology Div., Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractEE3: Poster Session: Size Effects in Deformation I
Session Chairs
Tuesday AM, November 28, 2006
Exhibition Hall D (Hynes)
9:00 PM - EE3.1
Simulation Study of Size Effects on Elastic Coefficients in Nanometer Sized Tungsten Layers.
Pascale Villain 1 , Pierre Beauchamp 1 , Frederic Badawi 1
1 Laboratory of Physical Metallurgy, University of Poitiers, Futuroscope Chasseneuil France
Show Abstract9:00 PM - EE3.10
Nanomechanics and Structure Formation of Thin Polypropylene Films.
Mechthild Döring 1 , Christian Dietz 1 , Sabine Scherdel 1 , Robert Magerle 1 , Nicolaus Rehse 1
1 Chemische Physik, TU Chemnitz, Chemnitz Germany
Show Abstract9:00 PM - EE3.11
Out-of-Plane Stresses Arising From Grain Interactions in Thin Films With Mixed Texture—Experiments and Analysis.
Aaron Vodnick 1 , David Nowak 1 , Stephane Labat 2 , Olivier Thomas 2 , Shefford Baker 1
1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 TECSEN, Universite Paul Cezanne, Marseille France
Show AbstractThin films with mixed texture components are known to exhibit large stress inhomogeneities. X-ray diffraction using variations of the “sin2ψ” technique provide common and straightforward methods for determination of the average stresses within each component. However, these methods often rely on the assumption of a zero out-of-plane stress. Recently, finite element modeling and complex x-ray microdiffraction techniques have shown that triaxial stress states are more likely. Here, a new sin2ψ technique has been developed to quantify the thermomechanical behavior of passivated thin copper films while accounting for out-of-plane stresses. It is shown that analysis methods which neglect the presence of a triaxial stress state can lead to a gross misunderstanding of thin film mechanical behavior.
9:00 PM - EE3.12
Out-of-Plane Stresses Arising From Grain Interactions in Thin Films With Mixed Texture—Finite Element Simulations.
Stephane Labat 2 , Aaron Vodnick 1 , Shefford Baker 1 , Olivier Thomas 2
2 TECSEN, Universite Paul Cezanne, Marseille France, 1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Show AbstractThe thermoelastic behavior of thin films having mixed texture is investigated with Finite Element Modeling (FEM). The films contain two different texture components with (111) and (100) oriented grains. Thin copper films on silicon substrates are modeled using an axisymmetric geometry and anisotropic elastic constants. Strain is applied to the film by differential thermal expansion between the Si substrate and the Cu film. The average strain and stress tensors in the two constituents are calculated for a large range of the grain aspect ratio, and volume fraction of (111) and (100) texture components. In addition the effect of different substrate constraints and the presents of a passivation layer are considered. The effect of these parameters on the stress in the out-of-plane direction in the two texture components, and the effect of the stress state on common sin2ψ analyses will be discussed.
9:00 PM - EE3.13
Size Effects in Nanoindentation Creep of Plasma-enhanced Chemical Vapor Deposited Silicon Oxide Films.
Zhiqiang Cao 1 , Xin Zhang 1
1 Manufacturing Engineering, Boston University, Brookline, Massachusetts, United States
Show Abstract9:00 PM - EE3.14
Heteroepitaxial Integration of Metallic Nanowires: Transition from Coherent to Defective Interfaces via Molecular Dynamics.
Arvind Arumbakkam 1 , Eric Davidson 1 , Alejandro Strachan 1
1 School of Materials Engineering, Purdue University, West Lafayette, Indiana, United States
Show Abstract9:00 PM - EE3.15
Unusual Mechanical Properties of Nanocrystalline Tantalum Processed by High Pressure Torsion.
Qiuming Wei 1 2 , Gang Li 1 , Zhigang Xu 4 , Sergey Yarmolenko 4 , Brian Schuster 3 2 , Laszlo Kecskes 3 , Kaliat Ramesh 2 , Ruslan Valiev 5
1 Mechanical Engineering, University of North Carolina at Charlotte, Charlotte, North Carolina, United States, 2 CAMCS, The Johns Hopkins University, Baltimore, Maryland, United States, 4 , NC A&T SU, Greensboro, North Carolina, United States, 3 , US ARL, Aberdeen Proving Ground, Maryland, United States, 5 , Ufa State Aviation Tech Univ, Ufa Russian Federation
Show Abstract9:00 PM - EE3.16
Size Effects During Twin-related Deformation in Copper.
Zhiwei Shan 1 3 , Lei Lu 2 , Andrew Minor 1 , Eric Stach 4 , Scott Mao 3
1 , Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Mechanical Engineering, , Uniervisty of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2 , Institute of Metal Research, Shenyang China, 4 , Purdue University, West Lafayette, Indiana, United States
Show Abstract9:00 PM - EE3.17
Nano-mechanical Characterization of Ultra-Thin Films.
Norm Gitis 1 , Michael Vinogradov 1 , Ilja Hermann 1
1 , CETR, Campbell, California, United States
Show Abstract9:00 PM - EE3.18
Study of the Effects of Si Addition on the Properties of Hard Nanocomposite Thin Films.
Jose Endrino 2 , Sergio Palacin 1 , Alejandro Gutierrez 1
2 , Instituto de Ciencia de Materiales de Madrid, Madrid, Madrid, Spain, 1 Dep. Fisica Aplicada, Universidad Autónoma de Madrid, Madrid, Madrid, Spain
Show Abstract9:00 PM - EE3.20
Statistics of 3D Dislocation Systems.
Jie Deng 1 , Anter El-Azab 1 2 , Meijie Tang 3
1 Mechanical Engineering Department, Florida State University, Tallahassee, Florida, United States, 2 School of Computational Science, Florida State University, Tallahassee, Florida, United States, 3 Physics and Advanced Technology Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show Abstract9:00 PM - EE3.21
Formation Mechanism and Evolution of Stress-induced Surface Damage in Al Thin Films.
Soo-Jung Hwang 1 , Kwang-Ho Jang 1 , Young-Bae Park 2 , William D. Nix 3 , Young-Chang Joo 1 3
1 Department of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Department of Advanced Materials, Andong National University, Andong Korea (the Republic of), 3 Department of Materials Science and Engineering, Stanford University, Palo Alto, California, United States
Show Abstract9:00 PM - EE3.22
The Atomistic Modelling of Dislocation Interactions with Interfaces.
Christian Brandl 1 , Peter Derlet 1 , Helena Van Swygenhoven 1
1 ASQ/NUM - Materials Science & Simulation, Paul Scherrer Institute, PSI-Villigen Switzerland
Show AbstractLarge-scale molecular dynamics of fcc metalic interface-dominated structures reveals a plasticity dominated by slip in which dislocations nucleate at interface regions and subsequently strongly interact with nearby interfaces as they propagate. In particular, in nanocrystalline Al, the leading and trailing partial dislocation are nucleated at different regions in a grain boundary or even different grain boundaries, and propagate via a thermally activated pinning–depinning mechanism influenced by the relative orientation between the Burgers vector and the ledge geometry of the grain boundary and mechanical (Acta Materialia 54 (2006) 1975). In the present work the details on the nucleation mechanism are addressed: i(1) the role played by a material’s general stacking fault curve calculated using both empirical and ab-initio methods, (2) the role of the atomistic-scale interface structure on dislocation transmission via finite temperature molecular dynamics, and (3) the detailed kinetics of nucleation and propagation using the nudged elastic band method.We request this abstract be considered for the joint session with FF
9:00 PM - EE3.3
Substrate Size Effects on Growth Mode of Heteroepitaxial Pt on Au(111).
Anant Mathur 1 , Jonah Erlebacher 1
1 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Show Abstract9:00 PM - EE3.4
Effects of Length Scale on Fracture Behavior in an Fe-3%Si Alloy Single Crystals.
Kazuki Takashima 1 , Eiji Taki 1 , Yuji Kawakami 2 , Masaaki Otsu 1
1 Materials Science & Engineering, Kumamoto University, Kumamoto Japan, 2 Materials & Environment, Industrial Technology Center of Saga, Saga Japan
Show AbstractIn order to design reliable MEMS devices, it is required to know the mechanical properties of micro-sized elements used in the devices. In particular, fracture properties of micro-sized elements are important, because even a nano-sized flaw may provide stress concentration site leading to crack initiation. When considering the fracture properties of micro-sized elements, we have to note the scale length effects on the fracture properties. In this investigation, fracture tests have been performed for both macro- and micro-sized specimens prepared from an Fe-3%Si alloy single crystal, and the effects of length scale on fracture behavior have been considered. Micro-sized cantilever beam specimens with dimensions of 10 x 10 x 50 μm3 were prepared by focused ion beam machining. Notches with a depth of 5 μm were introduced into the micro-sized specimens and fatigue pre-crack was also introduced ahead of the notch. Macro-sized three-point bending specimens with dimensions of 2 x 2 x 10 mm3 were also cut from the same Fe-3%Si alloy single crystal. Notches with a depth of 1mm were introduced into the macro-sized specimens, and fatigue pre-crack was also introduced. Notch plane was set to be (100), which is a cleavage plane of this material, and notch direction was set to be [010] for both type of specimens. For macro-sized specimens, cleavage fracture occurred during introducing fatigue pre-crack. In contrast, the micro-sized specimens were fractured by ductile manner. A plastic zone was clearly observed on the specimen surface near the crack tip and dimples were found on the fracture surface. The plastic zone size of this material is calculated to be 90 μm. This size is small enough to satisfy small scale yielding for macro-sized specimens, although this size corresponds to large scale yielding in micro-sized specimens. This may cause the size effect on the fracture behavior of this material. The results obtained in this investigation provide important information for designing actual MEMS devices.
9:00 PM - EE3.5
Processing and Mechanical Properties of Nanostructured Yttria-Zirconia Ceramics.
Jianyi Cui 1 , Jackie Ying 3 2
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 , Institute of Bioengineering and Nanotechnology, The Nanos Singapore
Show Abstract9:00 PM - EE3.6
Work Hardening in Pure Copper with Nanoscale Twins.
Lei Lu 1 , Xianhua Chen 1
1 Shenyang national laboratory for materials science, Institute of Metal Research, CAS, Shenyang China
Show AbstractWork hardening, relevant to the processing and use of materials, is one of the most important factors to evaluate the plastic deformation. It is a challenge to find out an optimum microstructure that can impart high strength, without at the expense of adequate work hardening ability, even at high stress/stain stages. Nanocrystalline metallic materials generally exhibit substantially high strength, but very limited ductility and diminishing work hardening ability, as compared to their conventional coarse-grained counterparts. In this work, the influence of TBs on the work hardening behavior will be systematically investigated in Cu samples. A series of ultrafine-grained pure Cu specimens with different densities of growth nano-scale twins were synthesized by means of pulsed electrodeposition technique. Systematical uniaxial continuous tensile, loading-unloading tensile tests as well as cold rolling tests were employed to evaluate the work hardening in the Cu specimens. Significant work hardening is observed in the Cu specimens with twins and the work hardening rate in Cu specimens increases evidently with increasing the twin density. The work hardening rate for the Cu with a twin lamellar spacing of 20 nm is about 1187 MPa, which is close to its ultimate tensile strength and more than twice of that for the UFG Cu without essential twins. The significant work hardening behavior of the nano-twin Cu are rationalized through the mechanism based on the numerous nanoscale twin lamellar structure which provides an effective barrier for the motion of dislocations while preserving a comparable capacity for efficient dislocation storage, as normally impossible in the coarse-grained and ultrafine grained, even in the nanocrystalline materials.
9:00 PM - EE3.7
Atomistic Simulations of Dislocation-Grain Boundary Interactions in Tungsten.
Matous Mrovec 2 1 , Yuanfeng Cheng 2 , Christian Elsaesser 2 1 , Peter Gumbsch 2 1
2 IZBS, University of Karlsruhe, Karlsruhe Germany, 1 , Fraunhofer IWM, Freiburg Germany
Show AbstractMechanical properties of polycrystalline materials are greatly influenced by the motion of dislocations and their interaction with grain boundaries (GBs). However, details of the atomic-scale mechanisms, which determine whether and why the dislocations are transmitted, absorbed, or impeded by the GBs, are difficult to discern by experimental observations and are therefore largely unknown. In this study we investigate several model cases of interactions between dislocations and GBs in the body-centered cubic (bcc) transition metal tungsten by computer simulations. In order to verify the theoretical predictions two models for the description of interatomic interactions with a different level of sophistication have been employed — the empirical Finnis-Sinclair potential which is a central-force scheme, and a bond-order potential. The bond order potential is based on tight-binding theory and is therefore able to describe correctly directional covalent bonds that are crucial for the cohesion and structure of bcc transition metals. We compare results of the simulations for the interaction between both edge and screw dislocations and a variety of symmetric tilt grain boundaries. Interesting observations are that dislocations which would be perfectly aligned to pass the boundary did not do so even under large applied stresses, while others managed to pass the boundary. We discuss these results with respect to the importance of the model describing the interatomic forces as well as the relation between atomic-level phenomena and macroscopic crystal plasticity.
9:00 PM - EE3.8
Size Effects in the Deformation Behavior of Nanocrystalline Nanowires.
Joshua Monk 1 , Diana Farkas 1
1 Materials Science, Virginia Tech, Blacksburg, Virginia, United States
Show AbstractVirtual tensile tests of nanocrystalline nickel wires of initial 5 to 10 nm grain size were simulated at 300K, reaching deformation levels up to 36%. The virtual tensile tests allowed the study of the strain rate sensitivity of these nanowires, yielding an activation volume of ~2 b3, where b is the Burger’s vector, consistent with grain boundary mechanisms of plasticity. Most importantly, after 3% deformation the grain size increased significantly during the deformation, with larger grains growing at the expense of the smaller ones as the deformation levels increase. The effects of the wire diameter on the deformation response were also studied.
9:00 PM - EE3.9
Thickness and Temperature Dependence of Stress Relaxation in Thin Metal Films in the Micro to Nano Thickness Regime.
Seungmin Hyun 1 2 , Walter Brown 2 , Richard Vinci 2
1 Nano-Mechanical Systems Research Center, Korea Institute of Machinery &Materials, Deajeon Korea (the Republic of), 2 Materials Science and Engineering, Lehigh Univ., Bethlehem, Pennsylvania, United States
Show Abstract
Symposium Organizers
Erica Lilleodden GKSS Forschungszentrum
Paul Besser Advanced Micro Devices, Inc.
Lyle Levine National Institute of Standards and Technology
Alan Needleman Brown University
EE4: Geometric Size Effects I: Wires, Pores and Particles
Session Chairs
Erica Lilleodden
Cynthia Volkert
Tuesday AM, November 28, 2006
Back Bay B (Sheraton)
9:30 AM - **EE4.1
Stress and Interface Energy Driven Morphology Changes in Metal Micro- and Nano-Wires.
Richard Vinci 1 , Jason Perkins 1 , Jeffrey Biser 1 , Hongwei Li 1 , Helen Chan 1
1 Materials Sci & Engr, Lehigh University, Bethlehem, Pennsylvania, United States
Show AbstractStress development and stress-related effects in metal “wires” attached to silicon substrates have been the subject of considerable study. These wires are typically of micrometer and sub-micrometer thickness and width. In these structures, phenomena such as plasticity and hillock development are both driven by thermal stresses that arise from substrate constraints. Freestanding metal wires with nanometer dimensions are now receiving substantial attention. In these systems, surface energy drives many of the morphological changes that have been observed. One extreme example is breakdown of the wires at elevated temperatures caused by Rayleigh instabilities. This presentation will bridge the gap between the micrometer and nanometer length scales, exploring size effects associated with the morphological changes induced in metal wires adhered to a substrate. The critical dimensions of these wires are in the range of 50 nm – 200 nm. Particular attention will be paid to the effects of mechanical constraints, and to the transition from surface energy driven phenomena to stress driven phenomena.
10:00 AM - EE4.2
Yield Behavior of Metallic Nanopillars.
Karl Sieradzki 1 , Antonio Rinaldi 1 , Cody Friesen 1 , Pedro Peralta 1
1 , Arizona State University, Tempe, Arizona, United States
Show AbstractSignificant effects of sample dimension on the yield strength of metallic crystals have been known for more than 50 years when researchers identified this phenomenon in metallic whiskers. These sample-size effects are once again attracting great interest with the discovery of the indentation size effect and the enhanced yield strength found for sub-micron diameter focused ion beam machined (FIB’d) metallic pillars. Here we discuss these issues and suggest mechanisms that may be responsible for the observed behaviors. In the case of the FIB’d pillars we draw an analogy between the yield strength of these structures and the fracture strength of glass rods and suggest that the experimentally observed power-law behavior of the yield stress versus pillar diameter is consistent with that expected from extreme value statistics. The appropriateness of extreme value statistics to yield behavior can in principle be tested in the case of FIB’d pillars by examining the nature of the strength fluctuations at fixed pillar diameter. We will present new experimental results for the yield strength of FIB’d metallic pillars aimed at exploring these issues.
10:15 AM - EE4.3
From Nanoscale Au Columns to Nanoporous Au: Simulation and Experiment.
Juergen Biener 1 , Andrea Hodge 1 , Luis Zepeda-Ruiz 1 , Jaime Marian 1 , Cynthia Volkert 2 , Alex Hamza 1 , Mark Duchaineau 1 , Farid Abraham 1
1 Nanoscale Synthesis and Characterization Laboratory, Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Institute for Materials Research, Forschungszentrum Karlsruhe, Karlsruhe Germany
Show Abstract10:30 AM - EE4.4
First Principles Calculation of the Young's Modulus of Silicon <001> Nanowires.
Byeongchan Lee 1 , Robert Rudd 1
1 , Lawrence Livermore National Laboratory, Livermore, California, United States
Show Abstract11:15 AM - **EE4.5
Dislocation-Escape Related Size Effects in Geometrically Confined Systems with Free Surfaces.
Horacio Espinosa 1 , Huang Tang 1 , Klaus Schwarz 2
1 Mechanical Engineering, Northwestern University, Evanston, Illinois, United States, 2 , IBM, New York, New York, United States
Show Abstract11:45 AM - EE4.6
Size Effects in Elastic and Plastic Deformation of Nanoparticles.
Yoshiaki Kogure 1 , Masao Doyama 1
1 Environmental Science, Teikyo University of Science and Technology, Uenohara, Yamanashi, Japan
Show AbstractA molecular dynamics simulation on elastic and plastic deformation in copper nanoparticles with various diameters has been performed. Each particle consists of 1000 - 100000 atoms. The embedded atom method potential functions developed by the present authors are adopted in the simulation. The copper nanoparticles of crystalline state have been produced by slowly cooling (0.005 K/step) the molten state (1800 K) in a computer, where one step of the molecular dynamics correspond to the time interval 10^(-15) sec. The particles of amorphous state are produced by rapidly quenching (10 K/step) the molten state and by some relaxation. The particles are deformed by applying shear and tetragonal stresses, and the displacement and the changes of the potential energy of individual atoms are recorded. The elastic and the plastic component of the deformations can be separated by releasing the applied stresses and by comparing the position of each atom with the original atomic configuration. The potential energy .vs. strain relation for crystal and amorphous state is compared, The increase of the potential energy in amorphous state is always smaller than crystalline state. These results are examined on the basis of effective elastic constants. The temperature effects on the plastic deformation are also important. Deformation at elevated temperatures, 400 K, 600 K and 800 K, is simulated, and the trajectory of atoms under the constant temperature .is monitored to investigate the fundamental nature of thermal relaxation. The thermal motion of surface atom may be strongly influential on the size effects in the plastic deformation of nanoparticles.
12:00 PM - EE4.7
Large Scale Indentation of Single Au Asperity: A Molecular Dynamics Study.
Donald Ward 1 , William Curtin 1 , Diana Farkas 2
1 , Brown University, Providence, Rhode Island, United States, 2 , Virginia Tech, Blacksburg, Virginia, United States
Show AbstractLarge scale Molecular Dynamics and FEM simulations of the deformation of a single Au asperity under compression from a rigid platen are undertaken to examine size scaling of contact deformation. Asperity structure, initial contact area, and temperature are examined to determine their effects on the force and pressure versus compression depth. The asperities are Au pyramids with (114) and (118) facets, a flattened top of sizes of ~2.21 nm^2 and heights from ~17 nm to ~42 nm, containing between ~2-16 million atoms, respectively. The material is modeled by EAM potentials, and the MD is performed using the LAMMPS code at temperatures of 1K and 300K and at a compression displacement rate of 0.01 nm/ps. Early stages of deformation are elastic with the peak pressures at a compression of ~0.4 nm at which point the first plane of atoms at the top of the pyramid are forced into the underlying atomic layers. The deformation is accommodated by the emission of dislocations from the surfaces steps of the pyramid, forming junctions and stacking fault tetrahedral. The applied pressure decreases upon further compression, accompanied by the emission of dislocations from the prior stacking fault tetrahedra. The pressure approaches a constant flow value as dislocations continue to be emitted from the surface steps. Comparisons are made with experiments on similar structures while Finite Element simulations supplement the analysis by determining the over all elastic response of the structures for varying contact areas. Examining different sizes and initial contact areas reveals a decrease in stiffness and a lower flow stress with an increase in pyramid size while forces increase and become more linear with greater initial contact areas.
12:15 PM - EE4.8
The Effect of Size and Shape on Yield Nucleation in Gold Nanopillars.
Eugen Rabkin 1 , Ho-Seok Nam 2 , David Srolovitz 3
1 Department of Materials Engineering, Technion, Haifa Israel, 2 Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States, 3 Yeshiva College, Yeshiva University, New York, New York, United States
Show AbstractWe report on a series of molecular dynamics simulations of the uniaxial compression of gold nanopillars. Simulations were performed for different nanopillars crystallographic orientations, nanopillar cross-sections and over a range of temperatures using several different interatomic potentials. For some nanopillar orientations, the initially perfect samples exhibit buckling or shear instabilities that can be interpreted in terms of the fcc-hcp phase transition at high pressure and the stress dependence of the shear modulus. For the others, the yield stress was observed to be either a linear or parabolic function of temperature, depending on the choice of interatomic potential, nanopillar cross-section and/or nanopillar size. For example, the temperature dependence of the yield stress of the <111> oriented nanopillars was linear for those with hexagonal and square cross-sections, but parabolic for those with circular cross-sections. We suggest a simple yield nucleation criterion in which the nucleation of the first Shockley partial at the surface of a nanopillar occurs at a critical strain at the surface, which includes contributions from thermal vibration, elastic loading and thermal expansion. We demonstrate that the yield condition correctly describes the temperature dependence of the yield stress observed in the full set of computer simulations.
12:30 PM - EE4.9
Effects of Microstructure on the Mechanical Response of Nanoporous Gold Thin Films.
Ye Sun 1 , John Balk 1
1 Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky, United States
Show AbstractNanoporous gold (NPG) thin films, which exhibit an interconnected, porous structure with ligament widths on the order of 10 nm, offer an opportunity to investigate the effects of nanoscale geometric confinement on the mechanical properties of metals. In the present study, NPG films supported by substrates were fabricated by dealloying Au-Ag films on Kapton and silicon. The microstructural evolution of NPG at various stages of dealloying was observed and analyzed by scanning electron microscopy and transmission electron microscopy. Cracking occurred at grain boundaries during dealloying and is believed to result from pre-existing tensile stress in the film. Stress evolution of NPG films on silicon substrates during dealloying was measured with the wafer curvature technique and revealed an overall shift toward compressive stress. This will be discussed in light of surface stress and the high amount of surface area inherent to the nanoporous structure. Additionally, the thermomechanical behavior of NPG films, as a function of ligament/pore size that is adjusted via annealing, will be presented.
12:45 PM - EE4.10
Role of Surface Stress in the Deformation of Nanoporous Gold.
D. Crowson 1 , Diana Farkas 1 , S. Corcoran 1
1 MSE, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States
Show AbstractAtomistic simulations were used to probe the effects of varying surface stress on the stability of nanoporous gold formed by dealloying. Dealloying is an electrochemical process in which one component of a binary alloy is selectively removed. This process results in the formation of a "sponge-like" bicontinuous metal void structure. A phase-field model was used to generate model bicontinuous porous structures which have the same morphology as nanoporous metals formed by dealloying.A series of Embedded Atom Method potentials with increasing values of the predicted surface stress was used to mimic the electrocapillary effect. A mechanical instability of the structure was found to be dependent upon the size scale of the structure and the applied surface stress. At very large values of the applied surface stress the instability manifests itself in a complete collapse of the nanoporous structure.
EE5: Geometric Size Effects II: Pillars and Micro-samples
Session Chairs
Tuesday PM, November 28, 2006
Back Bay B (Sheraton)
2:30 PM - **EE5.1
Nucleation, Percolation and Size-Scaling in Microcrystal Plasticity.
Dennis Dimiduk 1 , Chris Woodward 1 , Michael Uchic 1 , Satish Rao 2 , Triplicane Parthasarathy 2 , Edward Nadgorny 3
1 AFRL/MLLM Bldg 655, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 2 , UES, Inc., Dayton, Ohio, United States, 3 , Anteon Corporation, Dayton, Ohio, United States
Show Abstract3:00 PM - EE5.2
Large-scale 3-dimensional Dislocation Simulations of the Deformation Behavior of Micron Sized FCC Single Crystals.
Satish Rao 1 , Triplicane Parthasarathy 1 , Meijie Tang 3 , Dennis Dimiduk 2 , Michael Uchic 2 , Christopher Woodward 4
1 , UES Inc., Dayton, Ohio, United States, 3 , Lawrence Livermore National Laboratory, Livermore, California, United States, 2 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio, United States, 4 Materials Science and Engineering, NorthWestern University, Evanston, Illinois, United States
Show Abstract3:15 PM - EE5.3
Modeling Size Effects in Sub-Micron Scale Samples.
Peter Anderson 1 , Lin Li 1 , William Nix 2
1 MSE, Ohio State University, Columbus, Ohio, United States, 2 MSE, Stanford University, Stanford, California, United States
Show Abstract3:30 PM - EE5.4
Strain Rate, Temperature and Size Dependence of Surface Dislocation Nucleation in Nanopillars.
Ting Zhu 1 , Ju Li 2 , Amit Samanta 2 , Austin Leach 3 , Ken Gall 3 1
1 Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Department of Materials Science and Engineering, Ohio State University, Columbus, Ohio, United States, 3 School of Material Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show Abstract3:45 PM - EE5.5
In-situ X-ray Micro-diffraction of Micro-pillars.
Robert Maass 1 , Daniel Grolimund 1 , Markus Williman 1 , Steven Van Petegem 1 , Helena Van Swygenhoven 1
1 , Paul Scherrer Institute, PSI-Villigen Switzerland
Show Abstract4:30 PM - **EE5.6
The Search for Evidence of Strain Gradient Hardening in Au Submicron Pillars under Uniaxial Compression Using Synchrotron X-Ray Microdiffraction.
Arief Budiman 1 , Julia Greer 2 , Nobumichi Tamura 3 , Jamshed Patel 1 3 , William Nix 1
1 Materials Science & Engineering, Stanford University, Stanford, California, United States, 2 , Palo Alto Research Center (PARC), Palo Alto, California, United States, 3 Advanced Light Source (ALS), Ernest Orlando Lawrence Berkeley National Laboratory (LBNL), Berkeley, California, United States
Show Abstract5:00 PM - EE5.7
Examining Small-scale Plasticity and Source-limited Deformation Through in situ TEM Nanoindentation and Compression Tests.
Andrew Minor 1 , Z. Shan 1 , R. Mishra 2 , E. Stach 3 , O. Warren 4 , S.A. Syed Asif 4
1 NCEM, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 , General Motors Research and Development Center, Warren, Michigan, United States, 3 School of Materials Engineering, Purdue University, West Lafayette, Indiana, United States, 4 , Hysitron Incorporated, Minneapolis, Minnesota, United States
Show Abstract5:15 PM - EE5.8
Size Effects in the Deformation Behavior of Micro-meter Sized Pillars: A Three Dimensional Discrete Dislocation Dynamics Study.
Daniel Weygand 1 , Magali Poignant 1 , Jochen Senger 1 , Peter Gumbsch 1 3 , Oliver Kraft 1 2
1 IZBS, University of Karlsruhe, Karlsruhe Germany, 3 IWM, Fraunhofer Institut für Werkstoffmechanik, Freiburg Germany, 2 IMF II, Forschungszentrum Karlsruhe, Karlsruhe Germany
Show Abstract5:30 PM - EE5.9
In-situ Micro-compression Tests: Observing the Deformation Behavior of Micron Sized Columns in the SEM.
Benedikt Moser 1 , Ruth Schwaiger 2 , Kilian Wasmer 1 , Fredrik Oestlund 1 , Johann Michler 1
1 Materials Technology, EMPA, Thun Switzerland, 2 Institute for Materials Research II, Forschungszentrum Karlsruhe, Karlsruhe Germany
Show Abstract5:45 PM - EE5.10
Characterizing the Effective Modulus of Freestanding Nanostructures.
William Mook 1 , Julia Nowak 1 , C. Carter 1 , William Gerberich 1
1 Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractEE6: Poster Session: Size Effects in Deformation II
Session Chairs
Paul Besser
Erica Lilleodden
Wednesday AM, November 29, 2006
Exhibition Hall D (Hynes)
9:00 PM - EE6.1
Calculating the Elastic Modulus from Instrumented Nanoindentation and Microindentation Reload Curves.
David Shuman 2 , Margareth Andrade 2 , Andre Costa 3
2 Metallurgical Technology Division, CETEC, Belo Horizonte, MG, Brazil, 3 Department of Materials Engineering, Universidade Federal do Pará, Marabá, PA, Brazil
Show AbstractThe small sample elastic modulus was measured using the instrumented indentation reloading curve which showed better results than the traditional unloading curve method. The reload indentation elastic modulus for fused silica and several metals were equivalent to the tensile test values given in reference literature. This method was applied to load-unload-reload-unload, multistep, and cycle indentation testing procedures at various hold times and force rates. Both nanoindentation and microindentation testing instruments were used over a broad range of forces. The fused silica, a monolithic amorphous material, was indifferent to either unload or reload elastic modulus calculation. In the case of the metals, on unloading the reverse plasticity dislocation pile-up added to the elastic recovery which increased the apparent elastic modulus. The reload method had pure elastic deformation making it more reliable to calculate the elastic modulus. It was also found that the metals started yielding between 70-100% of the reload curve.
9:00 PM - EE6.10
On the Characterization of Thin Film-only Mechanical Property Based on the Indentation Image Analysis.
Yun-Hee Lee 1 , Yong-Il Kim 1 , Seung-Hoon Nahm 1 , Hoon-Sik Jang 1 , Ju-Young Kim 2 , Dongil Kwon 2 , Jae-il Jang 3
1 Division of Metrology for Quality Life, Korea Research Institute of Standards and Science, Daejeon Korea (the Republic of), 2 School of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 3 Department of Materials Science and Engineering, Hanyang University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - EE6.11
Grain Size Strengthening Effect vs. Indentation Size Effect in Advanced High Cr Heat-Resistant Steel.
Jae-il Jang 1 , Sanghoon Shim 2 3 , Shin-ichi Komazaki 4 , Tetsuya Honda 4
1 Division of Materials Science and Engineering, Hanyang University, Seoul Korea (the Republic of), 2 Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee, United States, 4 Department of Materials Science and Engineering, Muroran Institute of Technology, Muroran Japan
Show Abstract9:00 PM - EE6.12
Size Effect in the Initiation of Plasticity for a Semiconductor in Nanoscale Contact Loading.
Ting Zhu 1 , Ken P'ng 1 , Chris Walker 1 , Xiao Hou 1 , Andrew Bushby 1 , David Dunstan 1
1 Center for materials research, Queen Mary University of London, London United Kingdom
Show Abstract9:00 PM - EE6.13
Effect of the Spherical Indenter Tip Assumption on Nanoindentation.
Li Ma 2 1 , Lyle Levine 1
2 , Kent State University, Kent, Ohio, United States, 1 , National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show Abstract9:00 PM - EE6.16
Nanoindentation and ESBD Study of Nano-scale Property Variations in Al-Li-X Alloys.
Kathleen Tran 1 , John Wagner 2 , Marcia Domack 2 , Roy Crooks 3 , Abdelmageed Elmustafa 1
1 Mechanical Engineering, Old Dominion University, Norfolk, Virginia, United States, 2 , NASA Langley Research Center, Hampton, Virginia, United States, 3 , National Institute of Aerospace, Hampton, Virginia, United States
Show Abstract9:00 PM - EE6.17
A Combined Indentation and Microcompression Study of Nanoporous Ceramics.
Erica Lilleodden 1 , Ruth Schwaiger 1 , Michael Mertler 2
1 Institut für Materialforschung II, Forschungszentrum Karlsruhe, Karlsruhe, BW, Germany, 2 Institut für Technische Chemie, Forschungszentrum Karlsruhe, Karlsruhe, BW, Germany
Show Abstract9:00 PM - EE6.18
Swelling-induced Buckling in Nanopatterned Hydrogels.
Vijay Tirumala 1 , Christopher Stafford 1 , Leonidas Ocola 2 , Rui Huang 3
1 Polymers Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 2 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 3 Department of Aerospace Engineering and Engineering Mechanics, University of Texas, Austin, Texas, United States
Show Abstract9:00 PM - EE6.19
The Mechanical Properties of 3D Polymeric Microframes and Quasicrystals on the Submicron Length Scale.
Taeyi Choi 1 , Ji-Hyun Jang 1 , Ion Bita 1 , Edwin Thomas 1
1 Institute for Soldier Nanotechnologies, Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - EE6.21
Hardening in Face Centered Cubic Crystals Linked to the Bilinear Behavior in Indentation Experiments.
Abdelmageed Elmustafa 1 , Winston Soboyejo 2
1 Mechanical Engineering, Old Dominion University, Norfolk, Virginia, United States, 2 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States
Show AbstractThis paper presents dislocation mechanics-based arguments that explain the bi-linear nature of the indentation size effect in face centered cubic crystals (Au, Ag, Ni, Ir, and α-brass). A bilinear behavior is observed in the plots of hardness squared versus the inverse of indent size for indent sizes in the micro and nano regimes. Organized dislocation substructures tend to form in these regimes. The indent sizes corresponding to the onset of the transition from micro and deep nano indents to shallow nano indents represent deformation conditions that result in organized dislocation structures that are akin to those observed during strain hardening under tensile loading. In this paper, relationships between hardness and stacking fault energies are established such as in tensile deformation, for which correlations are well established between the stacking fault energies and hardening. The paper also examines the dependence of the transition points on stacking fault energy prior to exploring the effects of indent size and stacking fault energy on material pile-up. Finally, a strain energy – based model is used to explain the transition from discrete source – limited structures to organized low energy dislocation structures.
9:00 PM - EE6.23
Microsample Mechanical Testing of a Single Crystal Nickel Superalloy.
Paul Shade 1 , Michael Uchic 2 , Dennis Dimiduk 2 , Hamish Fraser 1
1 Materials Science and Engineering, The Ohio State University, Columbus, Ohio, United States, 2 , Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
Show Abstract9:00 PM - EE6.24
Size Effects in Microcrystals of LiF.
Edward Nadgorny 1 , Michael Uchic 2 , Dennis Dimiduk 2
1 Physics, Michigan Technological University, Houghton, Michigan, United States, 2 , AFRL/MLLM , Wright-Patterson AFB, Ohio, United States
Show Abstract9:00 PM - EE6.25
Towards a Multipurpose on-chip Nanomechanical Laboratory.
Thomas Pardoen 1 3 , Damien Fabregue 1 3 , Michaël Coulombier 1 3 , Nicolas Andre 2 3 , Jean-Pierre Raskin 2 3
1 Department of Materials Science and Processes, Université catholique de Louvain, Louvain-la-Neuve Belgium, 3 CeRMiN, Research Center in Micro and Nanoscopic Materials and Electronic Devices, Université catholique de Louvain, Louvain-la-Neuve Belgium, 2 Department of Electrical Engineering, Université catholique de Louvain, Louvain-la-Neuve Belgium
Show Abstract9:00 PM - EE6.4
Mechanical Properties of Nanoporous Gold Membranes.
Anant Mathur 1 , Jonah Erlebacher 1
1 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Show Abstract9:00 PM - EE6.5
Atomic Mechanisms of Plasticity in Twin-dominated Metal Nanopillars.
Konstantin Afanasyev 2 , Frederic Sansoz 1
2 Physics Department, The University of Vermont, Burlington, Vermont, United States, 1 School of Engineering, The University of Vermont, Burlington, Vermont, United States
Show Abstract9:00 PM - EE6.6
Sample Size Effect on Nanoindentation of Small Scale Structures.
Zhi-Hui Xu 1 , Xiaodong Li 1
1 Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show Abstract9:00 PM - EE6.7
True Elastic vs. Recovered Elastic Modulus Measured with Scanning Nanoindenter.
Aleksey Useinov 1
1 Scanning Probe Microscopy, Technological Institute for Superhard and Novel Carbon Materials, Troitsk, Moscow region, Russian Federation
Show Abstract9:00 PM - EE6.8
Atomic Events at the Onset of Plasticity in the Au(001) Surface.
Esther Carrasco 1 , Oscar Rodríguez de la Fuente 1 , Juan Rojo 1
1 Física de Materiales, Universidad Complutense, Madrid Spain
Show Abstract9:00 PM - EE6.9
Thermo-mechanical and Size-dependent Behavior of Freestanding Au-Ag and Nanoporous-Au Beams.
Erkin Seker 1 , Jianzhong Zhu 1 , Hilary Bart-Smith 2 , Matthew Begley 3 2 , Robert Kelly 3 , Michael Reed 1 , Giovanni Zangari 3
1 Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia, United States, 2 Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia, United States, 3 Materials Science and Engineering, University of Virginia, Charlottesville, Virginia, United States
Show Abstract
Symposium Organizers
Erica Lilleodden GKSS Forschungszentrum
Paul Besser Advanced Micro Devices, Inc.
Lyle Levine National Institute of Standards and Technology
Alan Needleman Brown University
EE7/FF7: Joint Session: Size Effects in Composites
Session Chairs
Neville Moody
Ruth Schwaiger
Wednesday AM, November 29, 2006
Back Bay C (Sheraton)
9:30 AM - EE7.1/FF7.1
Experimental Study of Size-effects on the Mechanical Elastic Properties of Nanometric W/Cu Multilayers.
Pascale Villain 1 , Baptiste Girault 1 , Pierre-Olivier Renault 1 , Eric Le Bourhis 1 , Philippe Goudeau 1 , Frederic Badawi 1
1 Laboratory of Physical Metallurgy, University of Poitiers, Futuroscope Chasseneuil France
Show Abstract9:45 AM - EE7.2/FF7.2
Tensile Behavior of Cu/Nb Nanoscale Multilayers.
Nathan Mara 1 , Yun-Che Wang 1 , Alla Sergueeva 2 , Richard Hoagland 1 , Amit Misra 1 , Amiya Mukherjee 2
1 Center for Integrated Nanotechnology, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Chemical Engineering and Materials Science, University of California, Davis, Davis, California, United States
Show AbstractMost earlier work on mechanical behavior of nanoscale multilayers has utilized room temperature nanoindentation, giving some valuable insight to the properties of these materials, but little direct experimental data pertaining to yield stress, ductility to failure, or fracture characteristics. In this work, the microstructure and tensile properties of free-standing textured, polycrystalline Cu-Nb nanolayered composites prepared by magnetron sputtering were evaluated. Samples of various layer thickness ranging from 75 to 5 nm were tested at temperatures varying from 20° to 700°C. At all temperatures tested, mechanical behavior is dominated by the large number of Cu-Nb interfaces in the composite. Maximum strength at room temperature is seen to be approximately 1.5 GPa, which far exceeds the strength dictated by rule-of-mixtures calculations. Effects of decreasing layer thickness on high temperature properties show a dependence of strength and ductility on layer thickness and test temperature. Increasing test temperatures results in greater ductility of up to 0.30 true strain at decreased flow stresses (~200 MPa for 60 nm layer thickness). Elevated temperature strain rate jump tests reveal strain rate sensitivities ranging from m= 0.35 to 0.8 over a range of strain rates, indicating that several mechanisms may be occurring during deformation. These dependencies are associated with microstructural changes observed during tensile testing. The role of elevated-temperature deformation mechanisms such as interlayer and grain boundary sliding, as well as interface-related strengthening at room temperature is discussed.
10:00 AM - **EE7.3/FF7.3
Fabrication and Mechanical Behavior of Nanocomposite Thin Films
Robert Cammarata 1 2
1 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Mechanical Engineering , Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractNanocomposites are multiphase materials where the characteristic microstructural length scale is of order 100 nm or less. Examples of such nanocomposites are multilayered materials where the characteristic length scale is the layer thickness, and nanoparticulate composites where the characteristic length scale is the particle diameter. Thin film deposition methods have proven to be particularly useful with regard to producing these types of nanostructured materials with very precise microstructural control. Nanocomposites have displayed novel and in many cases enhanced properties compared to bulk materials. This has often been shown to be the case for mechanical properties such as hardness, tensile strength, and fracture. Nanoprobe techniques such as nanoindentation have been shown to be extremely effective in the investigation of these properties of nanostructured thin films. In addition, there has been evidence that other properties such as damping capacity and fatigue can be significantly changed as the characteristic length scale is reduced below 100 nm.Examples of physical vapor deposition and electrochemical deposition methods used to produce nanocomposite materials will be discussed. This will be followed by the presentation of a selection of results from the study of mechanical behavior of nanoscale multiayered and nanocomposite thin films. A variety of mechanical properties will be discussed in both crystalline and amorphous systems. It is noted that the deposition of a completely amorphous multilayered thin film, for example, allows for the introduction of a microstructural length scale, the layer thickness in an otherwise amorphous material. The observed mechanical properties will then be considered in terms of micromechanisms used to model bulk materials in order to determine if such mechanisms are still valid when the microstructural length scale approaches nanoscale dimensions.
10:30 AM - EE7.4/FF7.4
Strength of Coherently Strained Nanolayers Under High Temperature Nanoindentation.
Ken P'ng 1 , A. Bushby 1 , D. Dunstan 1
1 Centre of Materials Research, Queen Mary, University of London, London United Kingdom
Show AbstractSemiconductor strained layer superlattices are an ideal model material to study the effects of coherency strain in plasticity, due to the fine control of nanolayer thickness and internal strain afforded by MBE deposition. Previously, nanoindentation of bulk InGaAs at 300K gave a yield pressure of 6GPa (Jayawera et al Proc. Roy Soc, A459, 2049, 2003) while bending at 500°C gave a yield value of 30MPa (P’ng et al Phil. Mag. 85, 4429, 2005). In contrast, coherently strained InGaAs superlattices gave nanoindentation values of 3GPa at room temperature and bending at 500°C gave a yield value also around 3GPa. It appears that the coherency strain can impart an athermal strengthening to the superlattice. It is clearly necessary to do mechanical testing over the range 300-800K that will be able to link the room temperature nanoindentation with the results from the high temperature bending experiment and to determine the relationship between strength, coherency strain and temperature. Preliminary experiments on these samples at elevated temperatures using a hot stage and the UMIS nanoindentation system is difficult but feasible with the help of AFM to verify the contact area. Consideration is given to the uncertainty in measurement due to thermal instability in the system and suitable reference materials for calibration in high temperature nanoindentation.
10:45 AM - EE7.5/FF7.5
Internal and Effective Stress in Nanocrystalline Metals.
Steven Van Petegem 1 , Stefan Brandstetter 1 , Helena Van Swygenhoven 1
1 ASQ/NUM - Materials Science & Simulation, Paul Scherrer Institute, PSI-Villigen Switzerland
Show Abstract11:30 AM - **EE7.6/FF7.6
Microstructure and Mechanical Strength Evolution With Scale Refinement in Metallic Multilayers.
Marc Verdier 1 , Muriel Veron 1
1 , LTPCM-CNRS, St Martin d'Heres France
Show Abstract12:00 PM - EE7.7/FF7.7
Size Effect in the Plasticity of Multiscale Nanofilamentary Cu/Nb Composite Wires During in-situ Tensile Tests Under Neutron Beam.
Vanessa Vidal 1 2 , Ludovic Thilly 2 , Steven Van Petegem 3 , Uwe Stuhr 3 , Florence Lecouturier 1 , Pierre-Olivier Renault 2 , Helena Van Swygenhoven 3
1 , Laboratoire National des Champs Magnétiques Pulsés - CNRS, Toulouse France, 2 , Laboratoire de Métallurgie Physique - University of Poitiers, Poitiers France, 3 , Paul Scherrer Institute, Villigen Switzerland
Show AbstractCopper-based high strength nanofilamentary wires reinforced by bcc nanofilaments (niobium or tantalum) are prepared by severe plastic deformation (repeated hot-extrusion, cold-drawing and bundling steps) for the windings of high pulsed magnets. The fabrication process leads to a multi-scale Cu matrix containing up to N=85^4 (52.2 10^6) continuous parallel bcc filaments, ribbons or tubes with diameter down to few tens nm.The magnet application requires a complete characterization of the microstructure, the strength and their relationship for further optimization: after heavy strain, the multi-scale Cu matrix is nanostructured and the bcc reinforcing phase is strongly refined. The resulting macroscopic strength is in excess from rule of mixture predictions calculated from bulk coarse-grained counterparts: an Ultimate Tensile Strength up to 2 GPa is reached at 77K. Using TEM in-situ tensile tests, it was shown that the observed strengthening is related to dislocation starvation in the nanostructured phases (single dislocation regime) added to the barrier role of fcc/bcc interfaces.In-situ tensile tests under neutron beam were performed on Cu/Nb nanocomposite wires composed of Nb nanofilaments with a diameter of 267 nm and spacing of 45 nm. The evolution of elastic strains and peak profiles versus applied stress evidenced the co-deformation behavior with different elastic-plastic regimes: the Cu matrix exhibit size effect in the finest channels while the Nb nanowhiskers remain elastic up to the macroscopic failure, with a strong load transfer from the Cu matrix onto the Nb filaments. The measured yield stress in the finest Cu channels is in agreement with calculations based on a single dislocation regime.
12:15 PM - EE7.8/FF7.8
Effects of Interfacial Topography on Fracture at the Nanoscale
Neville Moody 1 , Marian Kennedy 2 , Alec Talin 1 , David Bahr 2 , E. David Reedy 3
1 , Sandia National Laboratories, Livermore, California, United States, 2 , Washington State University, Pullman, Washington, United States, 3 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractInterfaces play a critical role in determining thin film component performance and reliability. They are defined by composition, structure and the nature of bonding at the atomic scale, and by the variations in surface topology at larger scales. These variations are used to great advantage in improving reliability of thin film devices at the micron and sub-micron scales. However, limitations in test capabilities have prevented a direct measure of surface topology contributions to adhesion of thin films at the nanoscale. We have therefore begun a program integrating nanomechanics tests and finite element-based simulations to develop an understanding of how patterns of small-scale interfacial heterogeneities affect interfacial crack nucleation and crack propagation. For this work, tungsten films were deposited onto smooth silicon substrates for reference and onto nanopatterned silicon substrates to determine the effects of surface topography. The tests showed that adhesion increased significantly for films on the nanopatterned substrate. Detailed finite element analyses were conducted in parallel with these tests to define the effects of nanopatterned surfaces on fracture resistance. In this presentation, we will use the test results and finite element simulations to show how creation of an energy-absorbing crack trajectory at the nanoscale increases resistance to fracture while providing a means to tailor nanoscale film device performance and reliability. This work was supported by Sandia National Laboratories under USDOE grant DE-AC04-94AL85000. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04 94AL85000.
12:30 PM - EE7.9/FF7.9
Fracture in Thin Film Metal Sandwich Structures.
Audrey Chng 2 , William Curtin 1 , Michael O'day 3
2 , National University of Singapore, Singapore Singapore, 1 , Brown University, Providence, Rhode Island, United States, 3 , Intel Corporation, Chandler, Arizona, United States
Show Abstract12:45 PM - EE7.10/FF7.10
Repeated Stress Relaxation Experiments in Probing Mechanical Behavior of Nanostructured Materials.
Yinmin (Morris) Wang 1 , Alex Hamza 1
1 Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractEE8/GG12: Joint Session: Multiscale Approaches in Modeling Size Effects in Deformation
Session Chairs
William Curtin
Lyle Levine
Wednesday PM, November 29, 2006
Constitution B (Sheraton)
2:45 PM - EE8.2/GG12.2
Dislocation Density Based Modelling of Plastic Flow and Size-effects in Single Crystals.
Thomas Hochrainer 1 , Peter Gumbsch 1 2
1 Institut fuer Zuverlaessigkeit von Bauteilen und Systemen, izbs, Universitaet Karlsruhe (TH), Karlsruhe Germany, 2 , Fraunhofer Institut fuer Werkstoffmechanik, IWM, Freiburg Germany
Show AbstractWe recently proposed an advanced tensorial dislocation density measure which makes the distinction between geometrically necessary and statistically stored dislocations dispensable. Within this object all dislocations are in equal measure represented as line like objects which evolve accordingly. Based on this measure we show at simple example problems how line-tension effects, assumptions on Taylor hardening and predefined dislocation sources and sinks influence the onset of plastic flow as well as the hardening behaviour of single crystals in a single slip configuration solely from the physical properties and microstructural state of the crystal. Theresults are compared to experimental data found in the literature. We furthermore discuss the different size-effects which are inherent to or may meaningfully be included into the approach.
3:00 PM - **EE8.3/GG12.3
Three-dimensional Boundary Element- Dislocation Dynamics Modeling of Plastic Flow in Small Volumes.
Nasr Ghoniem 1 , Jaafar El-Awady 1
1 Mech & Aerospace, UCLA, Los Angeles, California, United States
Show Abstract3:30 PM - EE8.4/GG12.4
Discrete Dislocation Dynamics Simulation fo Plasticity in Small Systems Using ParaDiS.
Meijie Tang 1 , Guanshui Xu 2 , Gregg Hommes 1
1 , Lawrence Livermore National Lab. , Livermore , California, United States, 2 Mechanical Engineering, UC Riverside, Riverside, California, United States
Show Abstract4:15 PM - **EE8.5/GG12.5
PMFDM: A Tool for Modeling Size Effects and Dislocation Microstructure in Mesoscale Plasticity.
Amit Acharya 1 , Anish Roy 1 , Saurabh Puri 1 , Ankur Sepaha 1
1 , Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Show Abstract4:45 PM - EE8.6/GG12.6
Size Effects in the Creep of Ice Single Crystals in Torsion: Experiments and Modeling.
Vincent Taupin 1 , Satya Varadhan 2 , Juliette Chevy 3 , Claude Fressengeas 1 , Armand Beaudoin 2 , Paul Duval 3 , Maurine Montagnat 3
1 Laboratoire de Physique et Mecanique des Materiaux, Université Paul Verlaine - Metz / CNRS, Metz France, 2 Department of Mechanical and Industrial Engineering, University of Illinois at Urbana Champaign, Urbana, Illinois, United States, 3 Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS, Saint Martin d'Heres France
Show Abstract5:00 PM - EE8.7/GG12.7
Hierarchical Modeling of Failure Mechanisms and Grain-Boundary Effects in Nanocrystalline Aggregates
Jibin Shi 1 , Mohammed Zikry 1 , A. Rajendran 1 , Donald Brenner 2 , Tarek Hatem 1
1 Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Materials Science, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractNew computational methodologies have been developed to predict dominant material behavior and mechanisms at scales ranging from the nano to the macro. Physically based scaling relations have been developed to characterize mechanisms and grain-boundary effects. These scaling relations have been used to link molecular dynamic and microstructural modeling to delineate the interrelated effects of grain boundary orientation and structure, dislocation transmission, absorption, and blockage through GBs, such that dominant failure mechanisms can be accurately identified and predicted from initiation to unstable growth. Results are presented for a broad class of CSL and random boundaries, and the effects of these boundaries on crack propagation and void coalescence are investigated at the different physical scales.
5:15 PM - EE8.8/GG12.8
Dislocation Nucleation During Nanoindentation of Aluminum.
Richard Wagner 1 , Li Ma 2 , Francesca Tavazza 2 , Lyle Levine 2
1 Ceramics Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 2 Metallurgy Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show Abstract5:30 PM - EE8.9/GG12.9
Molecular Dynamics Simulations of Grain Boundary Sliding: The Effect of Stress and Boundary Mis-Orientation.
Yue Qi 1 , Paul Krajewski 1
1 Materials & Processes Lab, GM R&D Center, Warren, Michigan, United States
Show AbstractMolecular dynamics simulations were used to study the effect of applied force and grain-boundary misorientation on grain-boundary sliding in aluminum at 750K. Two grains were oriented with their <110> axes parallel to their boundary plane, and one grain was rotated around its <110> axis to various misorientation angles. For any given misorientation, increasing the applied force leads to three sliding behaviors: no sliding, constant velocity sliding and a parabolic sliding over time. The last behavior is associated with disordering of atoms along the grain boundary. For the second sliding behavior, the constant sliding velocity varied linearly with the applied stress. However, a linear fit of this relationship did not intersect the stress axis at the origin, implying that a threshold stress for sliding exists. This threshold stress was found to decrease with increasing grain boundary energy. Including the threshold stress in the continuum polycrystal plasticity model, improved the prediction of the stress-v-strain rate behavior comparing with the experimental measurements.
Symposium Organizers
Erica Lilleodden GKSS Forschungszentrum
Paul Besser Advanced Micro Devices, Inc.
Lyle Levine National Institute of Standards and Technology
Alan Needleman Brown University
EE9: Indentation Size Effects
Session Chairs
Richard Vinci
Joost Vlassak
Thursday AM, November 30, 2006
Back Bay B (Sheraton)
9:30 AM - **EE9.1
Adhesion and Friction of Well-Defined Rough and Patterned Surfaces.
Jacob Israelachvili 1 , Kenny Rosenberg 1 , Bruno Zappone 1
1 , University of California - Santa Barbara, Santa Barbara, California, United States
Show AbstractSurface Forces Apparatus measurements have been made of the adhesion force cycles (on loading and unloading) and friction forces of smooth and well-defined rough surfaces of RMS roughness varying from <1 nm (molecularly smooth) to >200 nm. Both randomly rough and patterned surfaces were used, and the adhesion cycles and friction processes involved both elastic, anelastic and plastic deformations. Qualitatively new features were found for the rough surfaces that do not arise with smooth surfaces, such as adhesion forces that depend on the "pre-loading" force, and different adhesion- and load-dependent contributions to friction. Some new scaling relations between these forces and surface texture have also been established.
10:00 AM - EE9.2
Surface Forces and Tip-surface Interaction on the Onset of Plasticity.
Asif Syed 1 , Oden Warren 1 , Zhiwei Shan 2 , Andrew Minor 2
1 , Hysitron, Incorporated, Minneapolis, Minnesota, United States, 2 National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract10:15 AM - EE9.3
Direct Measurement of Incipient Indentation Plasticity at the Atomic Scale.
Graham Cross 1 , Andre Schirmeisen 3 , Urs Duerig 2 , Peter Gruetter 4
1 Physics, Trinity College, Dublin Ireland, 3 Physikalisches Institut, Westfalische Wilhelms Universitat Muenster, Muenster Germany, 2 , IBM Research GmbH, Zurich Switzerland, 4 Physics, McGill University, Montreal, Quebec, Canada
Show Abstract10:30 AM - EE9.4
Experimental Studies on the Role of Yield Stress and Work Hardening Exponent on Plastic Strain Distribution Underneath the Vickers Indenter.
Upadrasta Ramamurty 1 , Gollapudi Srikant 1 , Nuwong Chollacoop 2
1 Metallurgy, Indian Institute of Science, Bangalore, KA, India, 2 , National Metals and Materials Technology Center (MTEC), 12120,, Pathumthani Thailand
Show Abstract10:45 AM - EE9.5
Size Effects on Yield Instabilities and Strain Rate Sensitivity in Nickel.
Megan Cordill 1 , Neville Moody 2 , William Gerberich 1
1 Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 2 , Sandia National Laboratory, Livermore, California, United States
Show AbstractDislocation events are seen as excursions, or pop-in events, in the load-displacement trace of nanoindentation experiments. When indenting single crystal metals these events occur frequently during quasi-static and dynamic loading. A single crystal of Ni (110) and a nickel thin film (30 nm) have been indented quasi-statically using three different loading rates (10, 100, and 1000 uN/s) as well as with three diamond indenter tips (1000 nm cone, 300 nm Berkovich, and 50 nm cube corner) to examine the occurrences of excursions. As expected, increased loads produce excursions at higher loads with larger displacements, and that the loading is strictly Hertzian up to the point of yield. Also, as the tip size in reduced the excursion loads are reduced. It will be shown that the loading rate has an effect on the excursion load and displacement, increasing the average time for an excursion to initiate with decreased loading rates. The excursion events depend mostly on the statistical distribution of surface sources and substructure dislocation arrangements. Activation volumes required for the onset of plasticity are determined using the excursion load and displacement at a constant loading rate. For verification strain-rate jump tests are also used for determining activation volumes.
11:30 AM - EE9.6
Subsurface Residual Stress in Single Crystals under Contact Loading: a Discrete Dislocation Plasticity Study.
Lucia Nicola 1 2 , Alan Needleman 2 , Allan Bower 2 , Kyung-Suk Kim 2 , Erik Van der Giessen 3
1 Materials Science and Engineering, Delft University of Technology, Delft Netherlands, 2 Engineering, Brown University, Providence, Rhode Island, United States, 3 Applied Physics, University of Groningen, Groningen Netherlands
Show AbstractRough surfaces pressed into contact are typically characterized by localized plastic deformation. Experimental observations have shown that often, after removal of contact loading, a state of tensile stress can be found close to therough surface. Such stress can be sufficiently high to promote crack nucleation, especially under cyclic loading conditions. The aim of this study is a prediction of local stress distribution, during and after contact loading, in single crystals that deform plastically by dislocation glide. The loading is imposed by indenting a two-dimensional large crystal having a sinusoidal profile with a rigid half plane. The limiting cases of sticking and frictionless contacts will be analysed and compared. In these discrete dislocation simulations the solution for the state of stress and deformation in the crystal is computed at every time increment as the superposition of two contributions: the known, analytical solution for individual dislocations in infinite space and a non-singular linear elastic, finite element solution that enforces the boundary conditions. The sum of these fields incorporates the long-range interactions.A set of constitutive rules is supplied for the glide of dislocations as well as their generation, annihilation and pinning at point obstacles.
11:45 AM - EE9.7
Indentation Size Effect in Binary Solid Solutions.
Karsten Durst 1 , Oliver Franke 1 , Björn Backes 1 , Mathias Göken 1
1 Materials Science, University Erlangen-Nürnberg, Erlangen Germany
Show Abstract12:15 PM - EE9.9
3D Study on Texture and Size Effects Below Nanoindents in Cu Single Crystals Using 3D FIB-EBSD and Crystal Plasticity Finite Element Simulations.
Dierk Raabe 1 , Nader Zaafarani 1 , Franz Roters 1
1 , Max-Planck-Institut, Duesseldorf Germany
Show AbstractThe microstructure and texture changes underneath a conical nanoindent in Cu (111) single crystals are investigated. The theoretical investigation is carried out by introducing the problem in a 3D crystal plasticity based finite element simulation where two different constitutive material models are used. The theoretical findings are compared with experimental observations revealed form a 3D experiment which uses sets of subsequent (112) planes conducted in serial sectioning by a focused ion beam (FIB) system in the form of a cross-beam 3D crystal orientation microscope (3D EBSD). The used elastic-viscoplastic crystal plasticity model predicts a pronounced deformation-induced 3D patterning of the lattice rotations below the indent. This is characterized by an outer tangent zone with large absolute values of the rotations and an inner zone closer to the indenter axis with small rotations. Yet it fails to predict the fine details of the rotation patterning with the frequent changes in sign observed in the experiment and over-emphasizes the magnitude of the rotation field compared with the experiments. These differences between simulation and experiment encouraged the implementation of a physically-based crystal plasticity model for FCC materials into the crystal plasticity FEM. The model adopts the evolution of the dislocation density as a source of material hardening. In addition to the statistically stored dislocations, the geometrically stored dislocation density is introduced in order to consider the strain gradients, which are of great importance due to the geometry of the loading.
12:30 PM - EE9.10
The Indentation Size Effect Compared with the Tensile Hall-Petch Behaviour on the Same Copper Samples.
Xiaodong Hou 1 2 , Andy Bushby 1 , Nigel Jennett 2
1 Centre for Materials Research, Queen Mary, University of London, London United Kingdom, 2 Materials Centre, National Physical Laboratory, Teddington United Kingdom
Show AbstractMethods to obtain tensile stress-strain properties of materials from a practically non-destructive indentation test are of great industrial interest. However, to do this successfully, indentation size effects must be accounted for. Many indentation size effects, such as strain gradient plasticity and micro-pillar experiments (Volkert and Lilleodden, Phil Mag 2006), show a size dependence proportional to the inverse square root of a length scale, in common with Hall-Petch behavior. Recently, however, the indentation size effect from small radius spherical indenters has been shown, for a range of fcc metals, not to follow a Hall-Petch-like relationship but to be proportional to the inverse cube root of indenter radius (Spary et al, Phil. Mag. 2006). Here, we investigate this difference further and present results for the indentation size effect with spherical indenters on Cu samples that have been engineered to have different grain sizes. Indentation results are compared to macroscopic tensile tests on the same samples. The important experimental control parameter of the relative size of the indentation compared to the grain size is also explored since the cross over from grains significantly smaller than the contact radius to grains significantly larger than the contact radius occurs at different length scales in each sample. A thorough understanding of the various length-scale effects in the different test methods (e.g. the Hall-Petch effect in tensile testing and the indentation size effect in indentation), is essential if a relationship, robust enough for industrial application, is to be defined to obtain tensile properties from an essentially non-destructive indentation test.
12:45 PM - EE9.11
An Atomistic Model of Grain Coarsening During Nanocrystalline Metal Indentation.
Frederic Sansoz 1 , Virginie Dupont 1
1 School of Engineering, The University of Vermont, Burlington, Vermont, United States
Show AbstractEE10: Size Effects in Thin Films and Fatigue
Session Chairs
Thursday PM, November 30, 2006
Back Bay B (Sheraton)
2:30 PM - **EE10.1
Size Effects in the Deformation of Materials: Experiments and Modeling.
Joost Vlassak 1
1 DEAS, Harvard University, Cambridge, Massachusetts, United States
Show Abstract3:00 PM - EE10.2
Strain Gradient Plasticity and the Hall-Petch Effect in Thin Nickel Foils.
Christopher Walker 1 , Ting Zhu 1 , XiaoDong Hou 1 , Ken P'ng 1 , Andrew Bushby 1 , David Dunstan 1
1 Centre for Materials Research, Queen Mary, University of London, London United Kingdom
Show Abstract3:15 PM - EE10.3
Effects of Local Microstructure on Evolution of Thermal Strains in a Polycrystalline Al-on-Si Thin Film.
G. Cargill 1 , L. Moyer 1
1 Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania, United States
Show AbstractIn-situ x-ray microbeam diffraction measurements of thermal strain evolution, on a grain-by-grain basis, in a polycrystalline Al-on-Si film have been analyzed in terms of effects of grain size, grain orientation, and orientations of adjacent grains. Experimental correlations have been compared with those expected from simple models based on Hall-Petch behavior, Coble creep, and Nabarro-Herring creep. Local strains deviate significantly from average strains. No single mechanism or grain-scale microstructural characteristic completely explains the observed behavior. The experimental data suggest weak correlations among the single-grain microstructural characteristics, and between these characteristics and rates of strain relaxation.
3:30 PM - EE10.4
Ductility of Thin Metal Films on Polymer Substrates Modulated by Interfacial Adhesion.
Teng Li 1 2 , Zhigang Suo 1
1 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Department of Mechanical Engineering, University of Maryland, College Park, Maryland, United States
Show AbstractThin metal films, deposited on polymer substrates, are used in flexible macroelectronic devices as electrodes and interconnects. When a laminate of a thin metal film on a tough polymer substrate is stretched, the metal film may rupture at strains ranging from a few percent to a few tens of percent. This variation in the ductility of the metal film is modulated by the adhesion of the metal/polymer interface. To study this modulation, here we use the finite element method to simulate the co-evolution of two processes: debonding along the interface and necking in the metal film. We model the interface as an array of nonlinear springs, and the metal and the polymer as elastic-plastic solids. The simulation shows that necking of the film is accommodated mainly by interfacial sliding, rather than interfacial opening. Depending on the resistance of the interface to sliding, the metal film can exhibit three types of tensile behavior: the film slides and ruptures at a small strain by forming a single neck, the film slides and deforms to a large strain by forming multiple necks, and the film deforms uniformly to a very large strain without sliding and necking. Our results shed light on improving the ductility of thin metal films on polymer substrates.
4:15 PM - **EE10.5
Microplastic Ratcheting and Fatigue Reliability of Metallic MEMS.
Brad Boyce 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show Abstract Through an application-driven study of the cyclic reliability of metallic MEMS, we can uncover size-dependent microstructural phenomena that govern behavior. In an electrical contact switch application, the MEMS component serves to provide the elastic restoring force necessary to operate the switch. In spite of low applied stresses that are less than half of the material’s 0.2% offset yield strength, the device suffers an immediate cycle-dependent degradation in performance. In this case, microplastic ratcheting causes the cyclic accumulation of strain, i.e. cyclic creep. Unlike conventional ratcheting behavior, microplastic ratcheting occurs well below the material’s nominal yield strength. Materials with a low elastic limit, such as electrodeposited alloys with no prior cold work, are particularly susceptible to this phenomenon. We will show examples of this behavior in both MEMS and conventional materials used in spring applications. The microplastic ratcheting mechanism is thought to be related directly to local microstructural inelasticity. Polycrystal plasticity modeling has been used to confirm the microstructural origins of this plastic accumulation mechanism, and provides insight into the length scales that govern this behavior. Besides this fatigue-driven evolution in device performance associated with microplastic ratcheting, another concern for device reliability is the high cycle fatigue life. In these and many metallic alloys, high cycle fatigue life is dominated by crack initiation. We compare the high-cycle fatigue life and crack initiation mechanism in three Ni-based MEMS alloys: fine grained Ni, ultra-fine grained NiMn, and nanocrystalline NiFe. In these alloys the microstructural length scale appears to play a critical role in governing crack initiation. Most importantly, in the nanocrystalline alloy, fatigue crack initiation appears to be dramatically suppressed leading to anomalously long fatigue lives. This effect appears to require stable grain boundaries of sufficiently close spacing to mitigate the necessary length scales for crack initiation. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.
4:45 PM - EE10.6
Grain Size Effects on Contact Fatigue of Electrodeposited Ni.
Joerg Knyrim 1 , Ruth Schwaiger 1
1 Institute for Materials Research II, Forschungszentrum Karlsruhe GmbH, Eggenstein-Leopoldshafen Germany
Show AbstractNanocrystalline metals with grain sizes of typically < 100 nm have been intensively studied in recent years in order to understand how the properties of these materials could be related to the microstructural features. To date, however, the characteristics of cyclic contact have not yet been elucidated. Such information is vital for assessing the viability in structural materials in structural applications, where contact loading invariably occurs.Cyclic contact deformation of nanocrystalline Ni was studied by repeatedly sliding a spherical tip over the surface as well as by repeatedly indenting the surface. A systematic series of experiments were performed on Ni having different grain sizes. We observed prominent changes of the grain structure during these experiments. This microstructural instability is most apparent in materials with a very fine initial grain size. Furthermore, the contact fatigue resistance appears to be significantly improved for smaller grain sizes. In this presentation, the mechanical response as well as the corresponding changes in the microstructure for different initial grain sizes will be described.
5:00 PM - EE10.7
Degradation of Power Loaded SAW Cu Damascene Structures.
Daniel Reitz 1 , Hagen Schmidt 1 , Siegfried Menzel 1 , Thomas Gemming 1 , Klaus Wetzig 1
1 , IFW Dresden, Dresden Germany
Show Abstract5:15 PM - EE10.8
Length-scale Effects on Fatigue of Thin Cu Films.
Dong Wang 1 , Cynthia Volkert 1 , Patric Gruber 2 , Oliver Kraft 1 3
1 Insitut für Materialforschung-II, Forschungszentrum Karlsruhe, Karlsruhe Germany, 2 Institut für Metallkunde, Universität Stuttgart, Stuttgart Germany, 3 Institut für Zuverlässigkeit von Bauteilen und Systemen, Universität Karlsruhe, Karlsruhe Germany
Show Abstract5:30 PM - EE10.9
Mechanical Behavior of Nanocrystalline Cu Alloy Thin Film on Elastomer Substrates Under Constant Uniaxial Tensile Strain.
Junya Inoue 1 , Yosuke Fujii 1 , Toshihiko Koseki 1
1 Materials Engineering, The University of Tokyo, Tokyo Japan
Show Abstract5:45 PM - EE10.10
Plane-strain Bulge Test for Nanocrystalline Copper Nanoscale Films.
Xiaoding Wei 1 , Dongyun Lee 1 , Xi Chen 2 , Jeffrey Kysar 1
1 Department of Mechanical Engineering, Columbia University, New York, New York, United States, 2 Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, New York, United States
Show Abstract
Symposium Organizers
Erica Lilleodden GKSS Forschungszentrum
Paul Besser Advanced Micro Devices, Inc.
Lyle Levine National Institute of Standards and Technology
Alan Needleman Brown University
EE11: Size Effects in Amorphous Deformation and Phase Transformations
Session Chairs
Friday AM, December 01, 2006
Back Bay B (Sheraton)
9:30 AM - **EE11.1
Size Effects in the Deformation of Amorphous PdSi, Crystalline Cu, and PdSi/Cu Multilayers.
Cynthia Volkert 1 , N. Cordero 1 , E. Lilleodden 1 , A. Donohue 2 , F. Spaepen 2
1 , Forschungszentrum Karlsruhe, Karlsruhe Germany, 2 , Harvard University, Cambridge, Massachusetts, United States
Show Abstract10:00 AM - EE11.2
A Comparison of the Bulk and Microscale Mechanical Properties of a Pd-based Bulk Metallic Glass.
Brian Schuster 1 2 , Shailendra Joshi 2 , Stephan Hruszkewycz 3 , Qiuming Wei 6 2 , Haitao Zhang 7 2 , Matthew Ervin 4 , Michael Miller 5 , Todd Hufnagel 3 , Kaliat Ramesh 2
1 Weapons and Materials Research Directorate, US Army Research Laboratory, Aberdeen Proving Ground, Maryland, United States, 2 Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 3 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 6 Mechanical Enginering, Sincrotrone Trieste, Charlotte, North Carolina, United States, 7 Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, Austin, Texas, United States, 4 Secondary Electron Devices Directorate, US Army Research Laboratory, Adelphi, Maryland, United States, 5 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show Abstract10:15 AM - EE11.3
Size Effects in Metallic Glass.
Ju Li 1 , Futoshi Shimizu 1 2 , Shigenobu Ogata 1 3
1 Materials Science and Engineering, Ohio State University, Columbus, Ohio, United States, 2 , Japan Atomic Energy Agency, Tokyo Japan, 3 , Osaka University, Osaka Japan
Show AbstractShear bands form in most bulk metallic glasses (BMGs) within a narrow range of uniaxial strain ~ 2%. We propose this critical condition corresponds to embryonic shear band (ESB) propagation, not its nucleation. To propagate an embryonic shear band, the far-field shear stress must exceed the quasi steady-state glue traction of shear-alienated glass until the glass-transition temperature is approached due to frictional heating, at which point ESB matures as a runaway shear crack. The incubation lengthscale necessary for this maturation is predicted to be ~ 10^2 nm for Zr-based BMGs, below which sample-scale shear localization does not happen (Acta Mat., in print). Molecular dynamics simulations with up to 20-million atoms have directly verified the aged-rejuvenation-glue-liquid (ARGL) shear band structural model and "march-to-melting" instability, which occurs with a characteristic incubation timescale of ~ 10^2 ps and lengthscale of ~ 10^2 nm.
10:30 AM - EE11.4
Small Scale Plastic Flow in Silica Glasses: Can We Model Densification?
Antoine Perriot 1 , Etienne Barthel 1 , Damien Vandembroucq 1 , Bernard Champagnon 2 , Guillaume Kermouche 3 , Philippe Dubujet 3 , Erica Lilleoden 4
1 SVI, CNRS/Saint-Gobain, Aubervilliers France, 2 LPCML, CNRS/Université Claude Bernard, Lyon France, 3 LTDS, CNRS/ECL/ENISE, Saint-Etienne France, 4 , IM II, Karlsruhe Germany
Show AbstractIt has long been known that amorphous silica exhibits anomalous plastic flow at small length scales, resulting in densification. Despite the significance of this phenomenon for both the fundamental understanding of silica (and silica glasses) mechanical behavior and for the technological knowledge of silica contact mechanics (for instance in chemo-mechanical planarization), no in-depth studies have been conducted so far to model this anomalous plastic response at the continuum mechanics level and propose a suitable constitutive equation. One of the major reasons was the absence of adequate investigation tools for mechanical response at the local scale.For silica, the requirements are all the more stringent as the (isotropic) densification flow is coupled to the shear stress. Thus schemes must be developped to apply complex loadings and measure the response at the micrometer lengthscale.We report results obtained with an innovative experimental set-up (A. Perriot et al., J. Am. Ceram. Soc. 89 (2006) 596): microindentation experiments were performed on silica to provide a local complex loading resulting in sizeable plastic deformation with limited crack generation. Post-indentation Raman microspectroscopy scans on plane views and cuts provided maps of the indentation induced densification. Finite element (FE) simulations were performed with specific constitutive laws (inverse Drücker-Prager and Cam-clay) to couple shear and densification through isotropic flow.Comparison of the observed density maps and FE results for a variety of parameters suggest that these models cannot reproduce the data as such and show that strain hardening must be included to account for the measured density distributions. This considerably increases the number of parameters for the constitutive equation. Therefore additional independent experiments must be carried out to provide guidelines. This is why diamond anvil cell experiments at gradually increasing maximum pressure have been performed to provide a quantitative description of strain hardening on the isotropic loading axis.We believe that the present set of experimental data provides the basis for the best constitutive equation available to date to describe the plastic deformation of silica at small lengthscales. As a final test of the predictive power of the present model, we now consider carrying out uniaxial compression tests on micrometer sized pillars.
11:15 AM - EE11.5
Deformation Behavior of Ultralow-density Nanoporous Dielectrics.
S. Kucheyev 1 , P. Bythrow 1 , T. Baumann 1 , C. Cox 1 , Y. Wang 1 , A. Hamza 1 , J. Bradby 2
1 , Lawrence Livermore National Laboratory, Livermore, California, United States, 2 , Australian National University, Canberra, Australian Capital Territory, Australia
Show Abstract11:30 AM - EE11.6
Fracture of Constrained Nanoporous Polymers.
Andrew Kearney 1 , Heitor Chang 1 , Reinhold Dauskardt 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States
Show Abstract11:45 AM - EE11.7
Are Polymers Stiffer at the Surface? Mapping Nanoscale Confinement Effects in Amorphous Polymer Films.
Catherine Tweedie 1 , Georgios Constantinides 1 , Gregory Blackman 2 , Krystyn Van Vliet 1
1 Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 , DuPont Central Research and Development, Wilmington, Delaware, United States
Show Abstract12:00 PM - EE11.8
Study of the Kinetics of Phase Transformations on Unloading During Nanoindentation of Silicon.
Simon Ruffell 1 , Jodie Bradby 1 , Jim Williams 1
1 Research School of Physical Sciences and Engineering, Australian National University, Canberra, Australian Capital Territory, Australia
Show Abstract12:15 PM - EE11.9
Size Effects of the Martensitic Transformation in NiTi Thin Films.
Xi Wang 1 , Joost Vlassak 1
1 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show Abstract12:30 PM - EE11.10
Martensitic Phase Transformation and Plasticity of Shape Memory Alloy Sub-Micron Compression Pillars.
Carl Frick 1 , Steffen Orso 1 , Eduard Arzt 1
1 , Max Planck Institute for Metals Research, Stuttgart Germany
Show AbstractNickel-titanium (NiTi), is capable of undergoing relatively large amounts of inelastic deformation and subsequently recovering that deformation upon load removal (pseudoelasticity) or upon the application of heat (shape memory behavior). The displacement recovery is due to a stress-induced martensitic transformation where the atomic lattice experiences a “shear-like” distortion, allowing for a relative shape change that is entirely reversible. NiTi phase transformation behavior has already been utilized at small scales as a powerful actuator in various MEMS devices, and has the unique possibility to be used as a mechanical device at the nanoscale. Although the macroscopic behavior of NiTi has been extensively studied, a fundamental understanding of the nucleation and propagation of the martensitic phase transformation at small scales is lacking. This study investigates stress-induced martensitic transformation as well as plastic deformation in NiTi sub-micron diameter focused ion beam (FIB) prepared compression pillars. Specifically, aged [111] single crystal Ti-50.9 at% Ni is examined, and compared directly to bulk <111> textured polycrystalline behavior. Results clearly demonstrate pseudoelastic and shape memory effect in the sub-micron pillars, as well as permanent displacement at stresses well below bulk yielding values. Upon further displacement of the column, large plasticity bursts inhibit phase transformation recovery, and occur at stresses specific to the pillar microstructure. Slip bands ejected on the surface of the pillars demonstrate a distinct curvature rather then conventional due to the unique martensitic structure. It is expected that this study will shed new light on the mechanisms of the martensitic phase transformation and plasticity in NiTi.
12:45 PM - EE11.11
Evidence of Stress-induced Tetragonal-to-monoclinic Phase Transformation During Sputter Deposition of yttria-stabilized Zirconia.
Jeffrey Piascik 1 2 , Jeffrey Thompson 3 , Christopher Bower 1 , Brian Stoner 1 2
1 Center for Materials and Electronic Technologies, RTI International, Research Triangle Park, North Carolina, United States, 2 Curriculum of Applied and Material Science, University of North Carolina at Chapel Hill, Chapel Hill , North Carolina, United States, 3 Department of Biomedical Engineering, University of Texas at San Antonio, San Antonio, Texas, United States
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