Effect of Microstructural Evolution and Hardening in Subsurface on Wear Behavior of Mg-3Al-1Zn Alloy

Dry sliding tests were performed on as-cast AZ31 alloy using a pin-on-disc configuration. Coefficient of friction and wear rate were measured within a load range of 5-360 N at a sliding velocity of 0.785 m/s. Worn surface morphologies were examined using scanning electron microscopy. Five wear mechanisms, namely abrasion, oxidation, delamination, thermal softening, and melting, have been observed. Surface hardness, subsurface plastic strain, worn surface temperature, and cross-sectional optical microscopy were used to characterize hardness change, plastic deformation, and the microstructure evolution in subsurface. The results illustrate the correlation between the wear behavior and evolution of microstructure and hardness in subsurface, and reveal that in the load range of 5-120 N, surface oxidation and hardening originating from large plastic deformation play an important role in maintaining the mild wear, and softening originating from dynamic recrystallization in subsurface and surface melting are responsible for the severe wear in the load range of 120-360 N.