Dislocation Emission from Grain Boundaries in High-Entropy Alloys: Influence of Atomic Composition at Grain Boundaries

High-entropy alloys (HEAs) are solid solutions with five or more elements in near equiatomic fractions and exhibit excellent mechanical properties. However, the mechanism has not been fully understood yet. Because general grain boundaries (GBs) contain various sizes of atomic free volumes, a deviation of atomic composition at GBs may appear in HEAs by replacing atoms with ones having different atomic sizes to reduce atomic free volumes at GBs. Various equiatomic HEAs with five elements are modeled by a modified Morse (two-body interatomic) potential. Thermal equilibrium GBs at finite temperatures are obtained by hybrid Monte Carlo-molecular dynamics simulations. As results, GBs in HEAs mainly consist of two elements with the minimum and maximum atomic size and the critical stress to emit dislocations from the GBs increases as the deviation of atomic composition becomes large.