Microstructure and wear behavior of friction stir processed cast hypereutectic aluminum silicon

Hypereutectic as-cast Al-18Si-Cu-Ni alloy was subjected to friction stir processing (FSP). The resultant effect of FSP on the alloy was evaluated by microstructure analysis and wear tests (dry sliding). A significant microstructural modification and enhancement in wear behavior of Al-18Si-Cu-Ni alloy was recorded after friction stir processing. Wear resistance improvement was related to considerable modification in size, morphology and distribution of silicon particles, and hardness improvement. It was found that lower tool rotation speed was more effective to refine silicon particles and in turn increase wear resistance. Minimum Si particle mean area of about 47.8 µm2, and wear rate of 0.0155 mg/m was achieved.