Effect of T6 heat treatment on the microstructure and wear performance of a hypereutectic Al-28Si-4Cu-3Mg alloy

The effect of T6 heat treatment on the microstructure, hardness, and dry sliding wear behaviour of a hypereutectic Al-28Si-4Cu-3Mg alloy was investigated. The alloy was solution-treated at 525°C for 1 h, water-quenched, and artificially aged at 210°C for 2, 4, and 6 h. Optical microscopy and SEM/EDS revealed progressive spheroidization of eutectic Si, partial dissolution of Cu-rich phases, and precipitation of θ-Al₂Cu and β-Mg₂Si. The combined area fraction of θ-Al₂Cu, β-Mg₂Si, and S-AlMgSi increased from 22.0% in the as-cast alloy to 48.2% after 4 h of aging, while eutectic Si decreased from 12.0% to 9.2%. Hardness increased from 120 HV to 155 HV after 4 h of aging and then decreased to 145 HV after 6 h. Dry sliding tests at loads of 10–50 N and sliding speeds of 0.5–1.5 m/s showed that the 4 h aged alloy exhibited the lowest wear rate and coefficient of friction. Its mild-wear region covered 68% of the mapped domain, compared with 53% for the as-cast alloy. These results confirm that T6 treatment enhances wear resistance in hypereutectic Al–Si-Cu-Mg alloys by strengthening the microstructure–hardness–tribology relationship, supporting their use in high-load applications.