Effect of Different Mg₂Si Concentrations on the Wear Properties and Microstructure of Mg₂Si/Al–5 wt.% Cu Composites

In this paper, x wt.% Mg₂Si/Al–5 wt.% Cu (x = 5, 10, 15, 20, and 25) composites were prepared by an in situ process. The effect of phase content of Mg₂Si on their microstructures and performances was investigated; the dry sliding wear behavior under room temperature was examined. The results show that with the increase in Mg₂Si (Mg and Si) concentration, the microstructure of the Al–Mg₂Si composite changes significantly. The eutectic microstructure changes from lamellar labyrinth to long rod, along with the long-range order Al₂Cu phase to island and plate-like morphology, and the primary Mg₂Si phase becomes more compact. The hardness increases from 117 HV to 163 HV. The friction coefficient, wear rate, wear width, and wear depth decrease from 0.368 ± 0.048, 2.7 × 10⁻⁵ mm³/m, 1.93 mm, and 133.3 μm to 0.315 ± 0.016, 1 × 10⁻⁵ mm³/m, 0.94 mm, and 70.2 μm, respectively. The tested composites worn surfaces exhibit adhesion, peeling, microcutting wear, abrasive, and oxidation.