Abstract:
Microstructural evolution of die-cast and homogenized AZ91 Mg-alloys was investigated during dry sliding wear condition. Tribological tests
were performed using a pin-on-disc (EN8 steel) configuration with a normal load of 50 N at a constant sliding speed of 2.5 ms−1 under ambient
environment. Delamination was recognized as a predominant wear mechanism in both of these materials. The die-cast AZ91 Mg-alloy exhibits
lower coefficient of friction and higher wear rate. This can be ascribed to increase in the intensity of load bearing capacity of hard β-Mg17Al12 phase,
and crack formation/de-cohesion at the interface between primary α-Mg and discontinuous β-Mg17Al12 phases. On the contrary, the homogenized
AZ91 Mg-alloy experiences higher coefficient of friction and lower wear rate. The friction-induced microstructural evolution (supersaturated α-Mg
to eutectic (α+β-Mg17Al12)) tending to minimize the wear rate by providing barrier to material removal in the near surface region of homogenized
AZ91 Mg-alloy. Therefore, experimental observation revealed that an inverse relationship exists between wear rate and coefficient of friction for
the investigated materials. The analysis of worn surfaces and subsurfaces by electron microscopy provided evidence to delamination wear and
microstructural evolution
