Significantly improving strength and plasticity of Al-based composites by in-situ formed AlCoCrFeNi core-shell structure

Abstract The mechanical properties of Al matrix composites reinforced by AlCoCrFeNi high entropy alloy particles were greatly enhanced after spark plasma sintering at 600 °C accompanied with the formation of reinforcement core-shell structure. The dependence of mechanical properties and fracture behavior of the composites on the reinforcement core-shell structure was investigated and discussed based on the modified Ramakrishnan model and finite element simulation. The FCC equiaxed grains (Shell-1) and BCC columnar grains (Shell-2) were found in the shell. Thus, three kinds of interfaces were generated in the composite, where there is a coherent relationship between Shell-1 and Al matrix. The shell with appropriate plasticity can restrain cracks propagation and is considered as one part of matrix during analyzing cracks nucleation and propagation. However, the core-shell structure segments the Al matrix and the shell is regarded as one of reinforcement during inspecting the yield strength. Thus, as compared with the composite without core-shell structure, at 5 vol.%, 10 vol.%, and 15 vol.% plasticity of composites with core-shell structure is respectively improved by 42.7%, 6.6%, and 3.2%. Meanwhile, the yield strength is increased about 1.9 times higher of the composites with HEA volume fraction at 15%.