Shock-induced amorphization in medium entropy alloy CoCrNi

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.

Automated summary

Molecular dynamics simulations were used to study shock-induced amorphization in the CoCrNi medium entropy alloy. It was found that a critical velocity exists above which amorphization occurs, and as shock velocity increases, the deformation mechanism transitions from slip and twinning to solid-state amorphization. Under ultra-high shock velocities, extensive amorphization occurs, eliminating anisotropy in spall strength. Comparatively, lattice distortion in the MEA causes more amorphization and lower spall strength due to preferential void nucleation and growth in the amorphous regions.