Effect of Ni content on the wear behavior of Al–Si–Cu–Mg–Ni/SiC particles composites

In recent years, the addition of Ni has been widely acknowledged to be capable of enhancing the mechanical properties of Al–Si alloys. However, the effect of Ni on the wear behaviors of Al–Si alloys and Al matrix composites, particularly at elevated temperatures, remains an understudied area. In this study, Al–Si–Cu–Mg–Ni/20wt% SiC particles (SiCp) composites with varying Ni contents were prepared by using a semisolid stir casting method. The effect of Ni content on the dry sliding wear behavior of the prepared composites was investigated through sliding tests at 25 and 350°C. Results indicated that the θ-Al₂Cu phase gradually diminished and eventually disappeared as the Ni content increased from 0wt% to 3wt%. This change was accompanied by the formation and increase in δ-Al₃CuNi and ε-Al₃Ni phases in microstructures. The hardness and ultimate tensile strength of the as-cast composites improved, and the wear rates of the composites decreased from 5.29 × 10⁻⁴ to 1.94 × 10⁻⁴ mm³/(N∙m) at 25°C and from 20.2 × 10⁻⁴ to 7 × 10⁻⁴ mm³/(N∙m) at 350°C with the increase in Ni content from 0wt% to 2wt%. The enhancement in performance was due to the presence of strengthening network structures and additional Ni-containing phases in the composites. However, the wear rate of the 3Ni composite was approximately two times higher than that of the 2Ni composite due to the fracture and debonding of the ε-Al₃Ni phase. Abrasive wear, delamination wear, and oxidation wear were the predominant wear mechanisms of the investigated composites at 25°C, whereas delamination wear and oxidation wear were dominant during sliding at 350°C.