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The influence of protruding silicon particle shape on the friction performance of Al–Si alloy

The surface of Al–Si alloy samples was produced by chemical etching and laser finishing. After both chemical etching and laser finishing, the silicon particles could be exposed on the surface, resulting in improving the friction performance of Al–Si alloy. The edge shapes of the protruding silicon particles were different in the two surface treatments. Besides, the edges of protruding silicon particles were sharp after chemical etching. As a result, the edges were damaged in friction, and even some of silicon particle could shed. Then, it was easy for the abrasive wear to occur on the surface. There were obvious vortices on both sides of protruding silicon particle with sharp edge in the fluid region, resulting in a comparatively weak lubrication. In contrast, the edges of protruding silicon particles were round after laser finishing. Moreover, silicon particles could be closely combined with aluminum matrix due to the rapid cooling after being heated by laser, meanwhile, it was difficult for them to be separated from the matrix during friction. There were no vortices occurring on both sides of protruding silicon particle with round edge in fluid region, presenting excellent lubrication. Besides, the samples by laser finishing owned a low friction coefficient. Thus, the Al–Si alloy samples by laser finishing, with round edges of silicon particle, exhibiting a better friction performance. Consequently, the micro-mechanisms of friction performance associated with the edge shape of protruding silicon particle such as better lubrication and uniform stress distribution of rounded edge were determined.