Effect of solution time on microstructure and properties of AlFeNiCoCr high entropy alloy particle reinforced 7075 aluminum matrix composites

AlFeNiCoCr high entropy alloy powders were prepared by the atomization method, and the AlFeNiCoCr high entropy alloy particle reinforced 7075 aluminum matrix composites ((AlFeNiCoCr)_p/7075Al) were prepared by cold isostatic pressing combined with equal-channel angular pressing. The (AlFeNiCoCr)_p/7075Al composites were subjected to solution treatment at 490 ℃ for different times. The influence of solution time on the microstructure and mechanical properties of the (AlFeNiCoCr)_p/7075Al composites was investigated. The results show that the solution treatment intensifies the movement of atoms. A transition layer with high strength interface bonding is formed between the high-entropy alloy reinforcement particles and the Al matrix by element infiltration. A good bonding interface can effectively transfer loads, thereby significantly improving the comprehensive performance of the composites. When the solution treatment lasts for 1.5 h, the mechanical properties of the composites are the best. The tensile strength, elongation, and hardness are 507.14 MPa, 11.43%, and HV 158.27, respectively; compared with the 7075Al alloy matrix, the tensile strength and hardness are improved significantly. When the solution treatment lasts for 3.0 h, due to the long duration of the solution treatment, the low-melting-point Al and Ni elements are separated from the transition layer. The proportion of the solute elements in the original transition layer becomes unbalanced. The Cr element combines with Al and Mg in the matrix to form the Al₁₈Mg₃Cr₂ phase. After the solution treatment for 3.0 h, the holes appear in the composites, the 7075Al alloy particles became coarse, the transition layers start to disappear, the interface bonding between the reinforcement and the matrix deteriorates, and the composite performance seriously declines.