Sparse identification-assisted exploration of the atomic-scale deformation mechanism in multiphase CoCrFeNi high-entropy alloys

This study investigated the atomic-scale deformation mechanism of multiphase CoCrFeNi high-entropy alloys (HEAs) at liquid helium, liquid nitrogen, and room temperatures. A million-atom multiphase HEA was prepared using molecular dynamics simulation involving melt and quench processes. The HEA exhibited high-density dislocations and some twins, consistent with experimental observations. Quantitative analysis revealed an inconsistent evolution of the microstructure under tensile deformation. In particular, the elastic and initial plastic stages exhibited an increase in the disordered structure at the expense of the face-centered cubic and hexagonal close-packed structures, followed by a subsequent transformation involving multiple structural rearrangements. Furthermore, through sparse identification, a model depicting microstructural evolution during tension was extracted for the CoCrFeNi HEA at three typical temperatures and three tensile rates. The model highlighted the importance of the body-centered cubic structure in the evolutionary process.