Integration of Experimentation and Modeling in Heterogeneous Microstructures by Precision Nanocrystallization

Heterogeneous microstructures offer a complementary approach to balance strength and ductility. In their various forms, regions of nanoscale grains provide strengthening to regions of coarser grains in which dislocation mediated plasticity is maintained. These interfaces result in hetero-deformation induced (HDI) hardening, which causes a back stress in the coarse-grained regions and forward stress in the nanoscale regions. These unique microstructures require multi-scale modeling to fully capture the interactions, and they are often challenging to control experimentally. We have developed methods to precisely induce local deformation hardening in materials, such that modeling can be accurately validated. Characterizing the behavior and interaction of grain boundaries and dislocations is vital to predict mechanical properties and performance of the selected material. Many historical and novel material behavior modeling techniques validate the application of some algorithm or implemented codes against physical experiments, but uncertainty in predicting material behavior increases if the modeling technique does not well capture many features of mechanical performance that may arise from complex microstructures. Integrated Computational Materials Engineering (ICME) is a physics-based modeling paradigm to characterize a material’s properties to predict its performance for some boundary conditions which may vary drastically with time. At the electronic and atomistic length scales, ICME relies on Density Functional Theory (DFT) to characterize the quantum mechanics interactions between electrons and Modified Embedded Atom Method (MEAM) interatomic potentials to characterize how a unit cell of material interacts with its neighbors given so much strain. The change in microstructure can then be examined by Dislocation Dynamics (DD), which relies on the formulated MEAM potential and dislocation velocity quantified at the lower length scales. Again, the ability of DD to characterize interactions between dislocations and grain boundaries is only as good as the techniques at the lower length scales. DD simulations and later Finite Element Analysis (FEA), is also only as confident as the data is for the MEAM potentials and dislocation velocity. These multiscale factors in the development of a computational framework and the real-world performance of heterogeneous microstructures created through precision nanocrystallization will be discussed.