Effects of grain size on the wear of recycled AZ91 Mg

Magnesium alloy AZ91 chips have been recycled using mechanical milling to yield samples with fine grain sizes. Together with cast samples of the same alloy, the wear behavior of these materials was studied through pin-on-disc sliding, with speeds varying from 1 to 10ms-1, under a normal load of 10 N. Despite the differences in grain size (0.6–28.9μm) and mechanical properties, the various specimens did not differ significantly in their wear performance. Scanning electron microscopy observed abrasive wear to be dominant under low-speed sliding, and a transition to the formation of a protective mechanically mixed layer (MML) as sliding speed increased.