Reinforcement and substrate interaction in laser surface forming of AlCoCrCuFeNi particle reinforced AZ91D matrix composites

AlCoCrCuFeNi high-entropy alloy (HEA) particles were laser melt injected on AZ91D substrates using a one-step blown powder method to investigate the interaction between the reinforcement and the substrate in laser surface forming of AlCoCrCuFeNi HEA particle reinforced AZ91D metal matrix composites (MMCs). The results show that some Cu was rejected into the substrate melt during the processing. The Cu content in the melt has a great impact on the microstructure evolution of the formed MMC. When the Cu concentration reached a level of about 30 at.%, the CuMg₂ phase was formed instead of the predicted λ₁ phase. As the Cu content decreases, the λ₁ phase as well as different Mg + CuMg₂, Mg + λ₁ and Mg + Q eutectics will be formed depending on the Cu concentration in the remaining melt. Moreover, decreasing the Cu content in the AlCoCrCuFeNi HEA particles can also affect the wear properties of the formed MMC because it could result in a plastic deformation to the brittle-like transition of the reinforcement.