An Investigation on Subsurface Microstructural Evolution and Mild to Severe Wear Transition in AZ51 Magnesium Alloy

The wear behavior of as-cast AZ51 alloy was investigated using a pin-on-disc configuration within a load range of 20–380 N and a sliding speed range of 0.1–4.0 m/s under dry sliding conditions. The coefficient of friction and wear rate were measured as a function of applied load at various sliding speeds. Morphologies and chemical compositions of worn surfaces were analyzed for determination of wear mechanisms using scanning electron microscope (SEM) and energy-dispersive X-ray spectrometry (EDS). Microstructural evolution, plastic deformation, and hardness of the subsurfaces as well as worn surface hardness were characterized by confocal scanning laser microscopy and hardness testing for the establishment of a corresponding relationship between microstructural evolution and mild to severe wear transition in AZ51 alloy. The results show that there exists a strong relationship between wear behavior and subsurface microstructural evolution; that is, surface oxidation and strain hardening originating from pl...