Effect of Ni content on wear behavior of Al-Si-Cu-Mg-Ni/SiCp composites

In recent years, it has become widely acknowledged that the addition of nickel (Ni) can enhance the mechanical properties of Al-Si alloys. However, the impact of Ni on the wear behavior 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% SiCp composites with varying Ni contents were prepared by a semi-solid stir casting method. The effect of Ni content on the dry sliding wear behavior of the prepared composites was investigated by sliding tests at 25℃ and 350℃. The results indicated that the θ-Al₂Cu phase gradually diminished and eventually disappeared as the Ni content increases from 0 to 3wt%, accompanied by the formation and increase of the δ-Al₃CuNi phase and ε-Al3Ni phase in the microstructure. The hardness and ultimate tensile strength of the as-cast composites are both improved, and the wear rates of the composites are decreased from 5.29 to 1.94 at 25℃ and 20.2 to 7 mm³/(N∙m) at 350℃ with a rise in Ni content from 0 to 2wt%. The enhanced performance is due to the strengthening network structures and the presence of more Ni-containing phases in the composites. However, the wear rate of the 3Ni composite is approximately 2 times higher than that of the 2Ni composite due to the fracture and debonding of the ε-Al₃Ni phase. The predominant wear mechanisms of the investigated composites are abrasive wear, delamination wear, and oxidation wear at 25℃, while delamination wear and oxidation wear are dominant during sliding at 350℃.