Dynamic polymorphization of the impact-resistant fcc high-entropy alloy

CrCoNi-based high-entropy alloys have demonstrated exceptional impact resistance which stems from their diverse energy dissipation pathways. However, the underlying mechanisms are not yet fully understood. Here we present a rich paradigm of the polymorphization in the CrMnFeCoNi high-entropy alloy subjected to dynamic shear experiments, including the formation of a hexagonal close-packed phase, nano-sized 9R phase, and, more extremely, amorphization. Molecular dynamics simulations corroborate the experimental results and illustrate that the generation and gliding of partial dislocations play a central role in the phase transformations. These progressive phase transformations not only enhance the alloy’s strength but also preserve plasticity through the slip of partial dislocations. The high density of dislocations provides the necessary energy for phase nucleation, leading to high absorbed strain energy and a substantial failure strain. The synergy of these coordinated plastic deformation mechanisms renders these high-entropy alloys highly promising for impact-resistant applications.