Understanding and Characterization of the Dynamic Deformation Behavior of Multiphase Metallic Microstructures using Virtual Diffraction

Multiphase metallic microstructures of immiscible FCC-BCC systems synthesized using advanced manufacturing techniques provide the ability to create complex microstructures that can render a distribution of interfaces and metastable phases. The response of metastable phases under applied strains is likely to be an interplay between the deformation behavior through nucleation and evolution of dislocations, twins, and the phase transformation to the equilibrium phase. Understanding the factors that govern the plasticity mechanisms and the stability of the non-equilibrium phases is essential to unravel the complexity of the deformation response of metallic microstructures with a distribution of metastable phases. Recent efforts to characterize these new materials have employed the use of in-situ x-ray diffraction (XRD), where the microstructure can be analyzed through peak split, shift, and broadening behavior, as well as new peak formation. However, the understanding of the role of interfaces and metastability of the phases on the deformation mechanisms is still unclear. This study uses molecular dynamics (MD) simulations to understand the mechanisms of plastic deformation in multiphase Cu-Fe and Cu-Mo microstructures with a distribution of Cu clusters in a BCC matrix of Fe or Mo and a distribution of Fe or Mo clusters in an FCC matrix of Cu at high strain rates and under shock loading conditions. The MD simulations investigate the deformation behavior of these materials with a distribution of cluster/matrix interfaces in the stable FCC/BCC or the metastable FCC/FCC and BCC/BCC structures. In addition, virtual x-ray diffraction simulations are carried out to correlate the density of defects or fraction of phases to the broadening, splitting, or appearance of peaks in a diffraction pattern. This talk will present our approach to fingerprint the contributions from the various deformation modes, including twinning, dislocations, and phase transformation to the diffraction pattern. This study is supported by the Department of Energy, National Nuclear Security Administration under Award No. DE-NA0003857.