Surface alloying of an Mg alloy subjected to surface mechanical attrition treatment

A 100 ∼ 200 μm thick Al-enriched surface alloyed layer was formed on an AZ91D Mg alloy subjected to surface mechanical attrition treatment and diffusion coating at temperature as low as 400 °C. Transmission electron microscopy observations indicated the formation of a large volume fraction of pearlite-like lamellar microstructure within the surface alloyed layer, which was identified to be Mg17Al12 precipitates (γ phase) in Mg solid solution matrix. The Al-enriched alloyed layer enhanced the wear resistance of the alloy in comparison with the un-treated AZ91D Mg alloy substrate under the same dry sliding wear condition. Examination of the worn surface indicated that the enhanced wear resistance of the alloyed layer was mainly attributed to the strengthening effect of γ phase.