Effect of microstructure on mechanical properties of FeCoNiCrAl high entropy alloys particle reinforced Cu matrix surface composite prepared by FSP

In this paper, FeCoNiCrAl high-entropy alloy particles were used as reinforcement to fabricate Cu matrix surface composites by friction stirring processing. The x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDS), and electron backscattered diffraction (EBSD) were used to characterize the microstructure and phase composition of the composites. The microhardness tester and universal testing machine were also used to investigate the mechanical properties of the composites. The results demonstrated that the FSP and the adding of HEA particles greatly reduced the average grain size of the composites and increased the percentage of high-angle grain boundaries. A diffusion layer of AlCoCrFeNiCux solid solution with a single face-centered cubic structure was formed between the HEA particles and the Cu matrix. The thickness of the diffusion layer was about 0.9μm. The microhardness, tensile strength and elongation of the prepared composite increased by 54.86%, 17.17% and 8.4% respectively in comparison to the base Cu. The fracture morphology showed that most of the fracture locations occurred at the junction of diffusion layer and HEA particle, and a small number of fracture locations occurred at HEA particle, which ensured the joint enhancement of plasticity and strength of the composite. The fracture mode of Cu matrix in the composite was mainly ductile fracture. The fracture pattern at the HEA/Cu interface was mainly brittle fracture, accompanied by a small amount of ductile fracture.