Shock-induced amorphization in medium entropy alloy CoCrNi

WR Jian and ZC Xie and SZ Xu and XH Yao and IJ Beyerlein, SCRIPTA MATERIALIA, 209, 114379 (2022).

DOI: 10.1016/j.scriptamat.2021.114379

We perform molecular dynamics simulations to investigate shock-induced amorphization in CoCrNi, a medium entropy alloy (MEA) and its mean-field variant without lattice distortion. We show that a critical velocity exists above which amorphization occurs. At a low shock velocity of 800 m/s, dislocation slip and twins dominate and amorphization does not happen, but as the shock velocity increases, the deforma-tion mechanism transitions from slip and twinning to solid-state amorphization. Under ultra-high shock velocities, extensive amorphization occurs, following the precursor of shock wave, eliminating anisotropy in spall strength. Compared to the mean-field model, lattice distortion in the MEA causes substantially more amorphization, resulting in a lower spall strength, since voids nucleate and grow preferentially in the amorphous regions. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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