A novel eutectic high-entropy matrix composites were prepared by selective laser melting: Microstructure evolution, strengthening and fracture mechanism

In this study, WC particle with different contents (0 wt%, 5 wt%, 10 wt%) reinforced AlCoCrFeNi_2.1 eutectic high-entropy alloy (HEA) matrix composites (WC_x/HEA_1-x composites) prepared by selective laser melting (SLM), studyed the effect of WC addition on the microstructure and mechanical property of composites, and the strengthening and fracture mechanism of high-entropy matrix composites was revealed. The results show that enhanced phase WC is uniformly distributed in and forms metallurgical bond with the HEA matrix. The epitaxial acicular + equiaxial crystal structure and anisotropic texture were formed by adding WC into the HEA matrix. Compared with HEA matrix, average microhardness at the WC-HEA interface of WC_0.05/HEA_0.95 and WC_0.10/HEA_0.90 composites is increased by 21.99 % and 17.43 %; in addition compared to single HEA, the maximum value of UTS and EL of WC_x/HEA_1-x composites also reached 1269.84 MPa and 6.27 %, increasing respectively by 55.04 % and 67.65 %. The synergistic effect of interface strengthening, precipitation strengthening, solid solution strengthening and dispersion reinforcement contribute to the high strength and hardness of WC_x/HEA_1-x composites, but grain coarsening has weakened it to some extent. In addition, the crack of WC_x/HEA_1-x composites begins with microcracks caused by stress concentration and thermal expansion coefficient, and the crack tip expands in the HEA matrix in the way of intergranular fracture, which eventually leads to the failure of the component.