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

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%.