Microstructural evolution during high temperature sliding wear of Mg-3% Al-1% Zn (AZ31) alloy

Deformation microstructures generated during the high temperature sliding of a wrought Mg-3% Al-1% Zn alloy (AZ31) were investigated to delineate the micromechanisms of wear and material transfer to a tool steel counterface. Dry pin-on-disc type tests were conducted at 673 K. Optical profilometry and analytical microscopy revealed that material transferred to the counterface was heavily deformed and partially recrystallized. The subsurface grains beneath the contact surface were subjected to large plastic strains, and experienced dynamic recrystallization and growth as a result. Grain growth occurred in the subsurface zone beneath the recrystallized zone and followed a parabolic kinetic law with an activation energy of 35 kJ/mol. Surface damage and material transfer events proceeded in a cyclical manner, bringing the sliding process to a dynamic equilibrium, and leading to a constant wear rate.