Mesoscale Modeling of Shock Waves and Intermetallic Reactions in Ni/Al Multilayer Thin Films with Explicit Non-Ideal Interfaces

Solid heterogeneous materials exhibit a broad range of microstructural geometries when viewed at the meso(grain) scale. It is broadly recognized that these heterogeneous features play a role in the initiation and propagation of self-sustaining chemical reactions; however, layered reactive materials with a columnar grain structure have received less attention than for example granular/crystalline particle packs, porous materials with voids, and explicit particle size distributions, to name a few. In this talk, we will investigate shock induced reactions and phase change in Ni/Al reactive multilayers obtained from physical vapor deposition. These investigations are made via continuum-level simulations of thermal and mass transport, with explicit non-ideal interfaces.<br/><br/>While some shock-induced reactions have been simulated at the mesoscale for physical mixtures of nickel and aluminum powders (e.g., Austin and co-workers [1,2] and Xiong <i>et al</i>. [3]), the current talk will focus on advancements in three areas. (1) A new workflow is presented that is based on the Fast Fourier Transform, leading to an autocorrelation function which can mathematically generate multilayer geometries with non-ideal interfaces and columnar grain structures. This workflow is extended with machine learning; specifically, using style mapping and super resolution to combine features from the artificially generated layers and actual scanning electron microscope images. (2) Reaction is forced to begin at the Ni and Al interfaces by altering the thermal heat capacity of a small diffusion barrier that is present at the start of the simulations. Such diffusion barriers are observed in real reactive multilayers as a premix layer, following the physical vapor deposition process. (3) Arrhenius kinetics are used to propagate a reaction front following the arrival of a nonlinear shock wave. These (1)-(3) numerical methods are implemented and explored using Sandia National Laboratories’ Eulerian hydrocode, CTH, and the results will be discussed and compared to the previous approaches.<br/><br/>Other topics covered may include homogenized models for shocks, as well as comparisons of the mesoscale results to experimental data obtained from gas gun impacts and laser-driver flyer impacts, which have been conducted at Sandia National Laboratories and the Advanced Photon Source at Argonne National Laboratory.<br/><br/><i>Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.</i><br/> <br/>[1] R. A. Austin, D. L. McDowell, and D. J. Benson, “Mesoscale simulation of shock wave propagation in discrete Ni/Al powder mixtures,” <i>J. Appl. Phys</i>., <b>111</b>(12):123511, 2012.<br/>[2] I. Lomov, E. B. Herbold, and R. A. Austin, “Mesoscale studies of mixing in reactive materials during shock loading,” in <i>AIP Conf. Proc</i>., <b>1426</b>(1):733-736, 2012.<br/>[3] W. Xiong, X. Zhang, H. Chen, M. Tan, and C. Liu, “Multiscale modeling of the shock-induced chemical reaction in Al/Ni composites,” <i>J. Mater. Sci</i>., <b>57</b>:20224-41, 2022.