Effect of crystallographic orientations on shock-induced plasticity for CoCrFeMnNi high-entropy alloy

• Shock-induced plasticity depends on crystallographic orientations of CoCrFeMnNi HEA . • Preferred orientation exists for structural transition during plasticity. • BCC and disordered structures provide nucleation sites for incipient plasticity. • A Mn-rich composition characteristic is confirmed in BCC and disordered structures. • Structural transition and chemical composition heterogeneity drive plasticity. Using nonequilibrium molecular dynamics simulations, we studied the crystallographic-orientation-dependence shock-induced plasticity for the face-centered cubic (FCC) equiatomic CoCrFeMnNi high-entropy alloy (HEA). The local FCC-BCC (body-centered cubic) structural transition was identified by shock loading in the [001] direction, which is attributed to the compression along the <001> direction of original body-centered tetragonal (BCT) structure, and then the BCC structures trend to activate the dislocation nucleation. Further, dislocations slip to produce HCP (hexagonal close-packed) structures in the FCC lattice. In contrast, for the shock loading along the [110] and [111] directions, numerous disordered structures were found due to the insufficient lattice displacement along the <112> direction on the {111} crystal plane of FCC structure and the nonsynergistic behavior of the deformation between the <001>, <110> and <111> directions of BCT structure. In particular, both BCC structures and disordered structures with the Mn-rich composition characteristics play a significant role to promote the development of localized plastic deformation, which is related to the stress concentration around Mn caused by the inherent local inhomogeneity in the CoCrFeMnNi HEA. Moreover, under shock loading, the high atomic fraction of the local BCC structures and disordered structures can further promote chemical composition heterogeneity in these structures. Our results provide some significant insights for understanding the shock-induced plasticity of the CoCrFeMnNi HEA.