Strengthening mechanism and low-temperature hardening behavior of high-entropy alloy/graphene composite

Abstract

• The yield strength and elastic modulus of HEA/Gr composite material increased by 57.5 % and 19 %. • The graphene interface fosters immobile dislocation formation and blocks shear band propagation. • The aggregation of BCC atoms induced by FCC-BCC phase transition contributes to dislocation nucleation. • The consistency of FCC and BCC lattice structures is beneficial for dislocation slip. High-entropy alloy/graphene composites (HEA/Gr) have shown significant potential in various applications due to their exceptional mechanical properties, particularly their high strength. However, a comprehensive understanding of their strengthening mechanisms is still lacking, which hinders the design of their structures and optimization of their performance. This study systematically investigates the tensile behavior of the equiatomic CoCrFeMnNi HEA and HEA/Gr composite using molecular dynamics simulations, focusing on the microscopic strengthening mechanisms of the reinforcing phase and the low-temperature hardening behavior of the HEA/Gr composite. The results show that the yield strength and elastic modulus of the composite increased by 57.5 % and 19 %, respectively, compared to the HEA. The graphene interface effectively hinders dislocation propagation and enhances dislocation interactions, playing a crucial role in stress transfer and resulting in distinct stress and strain distributions within the matrix. Moreover, the low-temperature hardening mechanisms of the composite were explored. The study reveals that local BCC atomic clusters formed by FCC-BCC phase transition accelerate dislocation nucleation. The compatibility between the FCC and BCC lattice structures facilitates dislocation slip and promotes the interaction of intrinsic stacking faults (ISFs), leading to local stress concentration and increased dislocation entanglement.

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