Enhancement mechanism of fracture-resistance of CrMnFeCoNi high-entropy alloys: A molecular dynamics study

Abstract

It has been found that amorphization in high-entropy alloys (HEAs) can happen under the condition of severe plastic deformation. Therefore, understanding the interaction of amorphization with other kinds of deformations has become an important issue for the design of the mechanical properties of HEAs. However, the underlying mechanism of such interaction in HEAs remains unclear. Here we found in our molecular dynamics simulations that the synergistic effects of amorphization and dislocations could significantly improve the fracture-resistance of CrMnFeCoNi HEAs. It shows that amorphous structures and dislocations appeared simultaneously in HEAs, where the amorphous structures are confined by the surrounding dislocations. Once a crack propagates, some dislocation zones would become amorphous, and the local stress concentration could be relaxed during such kind of transformation instead of crack propagation, resulting in the improvement of the fracture-resistance of CrMnFeCoNi HEAs. In contrast, in nickel single crystals, only dislocations appear and fracture is more likely to occur when dislocations are emitted. It was also found that the length of cracks could affect the evolution of the microstructures in the HEAs. These findings provide new insights into the synergistic effects of the interaction between amorphization and dislocations on the enhancement of the fracture-resistance of the HEAs, which may help to improve the mechanical properties of high-performance HEAs.