Sliding Wear Map for AZ31 Magnesium Alloy

Abstract

Dry sliding wear tests were performed on AZ31 magnesium alloy using a pin-on-disc configuration. Wear rates were measured within an applied load range of 5–360 N and a sliding range of 0.1–4.0 ms−1. The morphologies and compositions of worn surfaces, microstructures, plastic strain, and hardness of subsurfaces were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), optical microscopy, and hardness testing. The results reveal that the sliding wear behavior of AZ31 alloy can be classified into two wear regimes, namely, mild wear and severe wear. Before the transition from mild to severe wear, substantial strain hardening that originates from large plastic deformation in the subsurface plays an important role in maintaining the wear rate regions with low slopes in delamination in the mild wear regime under sliding speeds of 0.1, 0.5, 0.785, and 1.5 ms−1, whereas after the mild to severe wear transition, realization of dynamic recrystallization in the subsurface is the main factor in thermal softening. Wear rate and wear transition maps were drawn, and they consist of a mild wear regime and a severe wear regime. In the mild wear regime, three different wear mechanisms operated—that is, oxidation, abrasion, and delamination—whereas in the severe wear regime, two wear mechanisms were responsible for extensive surface damage, namely, thermal softening and surface melting.