Abstract:The aim of the present study was to investigate the influence of Mg addition and T6 heat treatment on microstructure, mechanical and tribological properties of the Al-Si-Cu-Mg alloys. In this context, a series of Al-12Si-3Cu-(0.5-2.5)Mg (wt.%) alloys were produced by permanent mould casting, and then subjected to T6 treatment. Their microstructure and mechanical properties were investigated using OM, XRD, SEM, EDS along with hardness, tension, compression and Charpy impact tests. Dry sliding friction and wear properties of the alloys were studied using a ball-on-disk type tester. It was observed that the microstructure of as-cast Al-12Si-3Cu-Mg alloys consisted of α(Al), Si, θ-CuAl₂, β-Mg₂Si, Q-Al₅Mg₈Cu₂Si₆ and π-Al₈Mg₃FeSi₆ phases. T6 heat treatment gave rise to nearly spherodization of eutectic Si particles, formation of finer θ-CuAl₂ and β-Mg₂Si precipitates and elimination of Chinese script morphology of β-Mg₂Si phase. The addition of Mg up to 2.5 wt.% decreased the hardness, tensile and compressive strengths, tensile elongation and impact toughness of the as-cast and T6-treated alloys and increased their friction coefficient and volume loss. T6 treatment, on the other hand, led to a significant increase in mechanical properties and wear resistance of as-cast alloys.

Key words: Al-Si-Cu alloys; Mg content; T6 treatment; microstructure; mechanical properties; wear properties; fracture surface