The Microstructure, Microhardness, and Density Investigation of T6 Heat Treated Al-5Cu Composites Reinforced with Alumina

Aluminium-copper (Al-Cu) metal matrix composites combine the best qualities of copper and aluminium, providing exceptional electrical and thermal conductivity, high strength and a lightweight design. These composites have attracted significant interest for use in advanced manufacturing, electronics, the automotive industry and the aerospace sector. In this work, powder metallurgy was used to fabricate and analyze Al-5Cu composites reinforced with aluminum oxide (Al2O3). High-purity Al and Cu powders were mixed with different ratios of Al2O3 (1%, 3%, and 5% by weight) to examine their effects on microstructure, microhardness, and density of Al-Cu composite. The T6 process, which includes solution treatment and artificial aging, was used to heat treat the powder blends following cold pressing. The results showed that density increased along with the Al2O3 content, reaching a peak of 3%. Vickers microhardness tests showed a significant improvement, with the 5% Al2O3 composite having the highest microhardness (64 HV0.1). Microstructural analysis confirmed a uniform distribution of Al2O3, even though etching made it difficult for optical microscopy to clearly show grain boundaries. The Al2O3 particles mechanistically increased microhardness by preventing dislocation movement and encouraging grain refinement, despite the difficulty of making accurate measurements of grain size. The composites displayed a consistent microstructure with no observable phase segregation, and the mechanical improvements were in line with predictions made by the rule of mixtures and particle reinforcement theories. It was concluded that Al2O3 addition successfully increases the microhardness and microstructural stability of Al-5Cu composites.