Improving wear performance of dual-scale Al-Sn alloys by adding nano-Si@Sn: Effects of Sn nanophase lubrication and nano-Si polishing

In this work, an attempt was made to further promote the wear and friction behavior of dual-scale structured Al-12 wt% Sn bearing alloys by coupling with a nano-Si@Sn composite. A so-called tri-modal Al-Sn-Si (denoted as CG-30 Si-containing alloy), which exhibited increased bulk hardness and improved distribution and refinement of the Sn phase, was produced by combining mechanical alloying and conventional powder sintering. The wear performance of the Si-containing and Si-free alloys was differentiated by performing both block-on-ring and ball-on-disk testing. Moreover, the addition of nano-Si@Sn composites to the dual-scale Al-Sn matrix resulted in significant reductions of the friction coefficient and wear volume. These improvements in wear behavior stemmed from the polishing effect of fine Si particles on the counterface, and Sn-rich clusters that acted as lubricants on the worn surface; together, the polishing effect and lubrication led to the formation of a smooth tribolayer, and hence, a decrease in the tendency for abrasive wear. Abrasive wear was also reduced by an increase in the alloy hardness with the addition of Si. As such, Sn-phase modification via Si addition constitutes a promising method for preparing self-lubricating Al-based alloys.