Microstructure and dislocation density of AlCoCrFeNiSix high entropy alloy coatings by laser cladding

AlCoCrFeNiSix high-entropy alloy coatings were synthesized by laser cladding. The effect of Si element on the phase constitution, microstructure, and microhardness of the coating was investigated. The results show that the main phase in the coatings are disordered solid solution with a body-center cubic (BCC) structure. A small quantity of nano-sized precipitates of ordered BCC AlNi phase are distributed in the grain. The dislocation density and the microhardness increase linearly with the increase of the Si content. The improvement of the microhardness is due to the solid-solution strengthening, precipitation strengthening, and dislocation strengthening, and the quantitative analysis reveals that dislocation strengthening plays a dominant role.