Interactions of Multiple Phase Transformations and Dislocations: Modeling and Simulation from Atomistic to Microscale

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This award supports fundamental research to provide knowledge toward understanding phase transformations, plasticity, and their interactions. The research under this award will focus on phase transformation and plasticity in silicon and germanium. Predicting the deformation response in these materials is important for semiconductor engineering. This research will lead to a multifaceted computational tool for quantitative predictions of properties of these materials. The computer simulations enabled by the computational tool would reveal the main mechanisms during the interaction between phase transformation and plasticity from the atomic to the macroscopic level. As an extension, the computational tool can also find applications to other material processes and technologies, including the thermomechanical treatment of steel, the behavior of shape memory alloys, and the synthesis of superhard ceramics. The software developed under this award will be shared with the research community on the team's webpages and high performance computing clusters. The research team will also participate the Freshman Honor Program that connects undergraduates with research activities at Iowa State University. Two new graduate courses on phase transformations and plasticity, and atomistic-continuum modeling will be developed. This research will also promote active participation from under-represented groups through the Program for Women and Science in Engineering in the College of Engineering at Iowa State University. The objective of this research is to establish a predictive multiscale modeling framework by linking a reactive concurrent atomistic-continuum method and a continuum phase field approach. The reactive concurrent atomistic-continuum method will be based on a finite element implementation of an atomistic field formalism. Simultaneous phase transformations and dislocation-mediated plasticity as a consequence of chemical bond breaking and reforming, changes of the crystal structures and slip will be simulated for micron-sized domains of silicon and germanium. The phase field approach will be based on a new multiphase thermodynamic potential for large strains and will enable large-scale simulations of coupled phase transformation and plasticity in materials. Formations of multiple phases and evolutions of dislocation microstructures in silicon and germanium will be simulated at the macroscale. The research team will validate the predictive capability of the multiscale computational tool through fully atomistic simulations and also experimental measurements. Lastly, the team will apply the multiscale simulation tools to find methods for promoting or suppressing dislocation activities and phase transformations through tailoring the microstructures of materials and controlling applied loading conditions.