Role of lattice distortion on spallation of CoCrCuFeNi high-entropy alloy

High-entropy alloys (HEAs), known for their high strength and enhanced ductility, have promising applications across various fields. Lattice distortion is a key factor in their strengthening, yet its role in dynamic fracture strength or spall strength remains unclear. This study employs large-scale nonequilibrium molecular dynamics simulations to investigate the dynamic responses of equiatomic CoCrCuFeNi HEA under shock velocities ranging from 0.6 to 1.45 km/s. By comparing the systems described using an average-atom interatomic potential, we uncover the role of lattice distortion. Our results reveal that spall strength exhibits complex behavior depending on the HEA's shock response. As shock velocity increases, the deformation mechanism transitions from elastic to dislocation and stacking fault (SF) dominated, eventually leading to a face-centered cubic to body-centered cubic phase transition. Lattice distortion significantly alters the active slip planes of dislocations and SFs, resulting in more SF intersections, while its effect on compression-induced phase transition is minor. During shock-induced spallation, residual defects after decompression significantly affect spall strength. Lattice distortion introduces additional stress and strain concentration sites, facilitating void formation and reducing spall strength. The temperature at the spall region is identified as a major factor governing spall strength variation under different shock velocities. Although lattice distortion can mitigate the softening effect of elevated temperature, it ultimately reduces spall strength, challenging the traditional views on its strengthening role. Moreover, the effects of lattice distortions on spall strength are quantified in terms of lattice misfit under varying loading strain rates and initial temperatures.