Physio-mechanical and tribological characterisation of sintered aluminium 7068 modified with NiTiFeAlCu high-entropy-alloy for engineering applications

Abstract

ABSTRACT Metal particles are gaining attention as reinforcement in metal matrix composites owing to their ductility as compared with ceramic particles, which are inherently brittle. High-entropy-alloy (HEA) particles belong to this category based on their high strength, ductility, and thermal stability. Aluminium-7068 is a new aerospace alloy in the 7000 series that possesses higher strength than aluminium-7075, yet very few studies have considered reinforcement with high-entropy alloy particles. For strength improvement, NiTiFeAlCu (HEA) powder was introduced into the aluminium-7068 matrix at 0, 4, 8, and 12 wt. % at 500 °C via vacuum sintering. The microstructure depicted dispersed particles in the matrix with a linear reduction in porosity as the HEA dosage increased. Consequently, there was a linear increase in density and relative density. 4–12 wt.% HEA engendered linear improvements in yield and ultimate tensile strength, elastic modulus, and hardness; meanwhile, elongation was a progressive decline. The outcome of this study shows that HEA particles in AA-7068 resulted in an improvement of the tensile and hardness properties. The particle addition was observed to reduce the composite’s friction coefficient and wear rate. This report revealed that the performance of AA-7068 can be improved up to 12 wt. % NiTiFeAlCu HEA addition.