Microstructure and mechanical properties of bioinspired laminated CoCrFeNiMn high entropy alloy matrix composites reinforced with graphene

Abstract

Due to the hierarchical structure and associated multi-scale toughening mechanisms of biological materials such as shells in nature, they often have unique properties that differ from the synthetic materials. Inspired by the ultra-tough nacre structure, the laminated CoCrFeNiMn high entropy alloy (HEA) and the laminated graphene nanoplatelets (GNPs) reinforced CoCrFeNiMn HEA matrix composites were fabricated by flake powder metallurgy and vacuum hot-pressure sintering (VHPS) to create a "brick-mortar" structure of nacre based on HEAs. Tensile and compression tests were used to test the mechanical properties, the results showed that the laminated HEA and composites yielded tensile strengths of 673.49 MPa and 826.39 MPa while maintaining good elongation of 21.22% and 16.31% respectively, whose compressive strengths achieved 2177.47 MPa and 2530.13 MPa at 50% elongation. The laminate structure leads to crack deflection and microstructure has numerous dislocations and twins, which further increase strength with good plasticity, leading to excellent strength-plasticity synergy. The strengthening and toughening mechanisms are discussed based on the fracture morphology and microstructure of the SEM and TEM images. Bioinspired laminated HEA have been an innovative direction in recent years. This study provides a relatively simple method for the development of HEAs in combination with nacreous lamellar structure.