Strengthening effect of high-entropy alloys endowed by monolayer graphene

Abstract

The graphene (Gr) can effectively confine the dislocation propagation, allowing for the pronounced strengthening effect. However, due to the technical limitations of atomic resolution, an in-depth understanding regarding the potential strengthening mechanisms at atomic level is still insufficiently comprehended. In this paper, molecular dynamics (MD) simulations were performed to investigate dislocation-Gr interactions and strengthening mechanisms in FeNiCrCoCu high-entropy alloy (HEA)/Gr nanopillars. The hindrance of Gr sheet to mobile dislocations was demonstrated to promote the onset of massive immobile dislocations, especially the Stair-rod dislocation which gave rise to the remarkable strengthening effect. The immobile Hirth, 1/3<110> and 1/6<301> dislocations exerted the subsidiary effect on strengthening the composite pillars. Meanwhile, the diminished dislocation length induced by dislocation reactions and the absorption effect to mobile dislocations was verified to endow a more appreciable dislocation starvation for composite pillars which was conducive to forming more Stair-rod dislocations. In addition, the results also confirmed that the reduction in Gr diameters would directly weaken the pillars attributing to the fact that the Gr edges acted as a dislocation source. These findings may contribute to the design of HEA/Gr composites toward better mechanical properties.