Effect of Alloying Elements on the Dry Sliding Wear Characteristics of Gravity-Cast Mg-Sn Based Alloys

Abstract

The effect of solo and combined addition of Al (3wt. %) and Zn (1wt. %) into gravity-cast Mg-10 wt. % Sn binary alloy on the dry sliding wear test has been investigated using pin-on-disk configuration with varying rotational speed (100 and 200 rpm) under a range of test loads (10, 20, 30, and 40 N). Microstructural characterization and phase analysis of the as-cast Mg-Sn alloys using scanning electron microscope and x-ray diffraction, respectively, have revealed the refinement of the binary alloy microstructure in terms of smaller dendritic arm spacing, uniform and discrete distribution of eutectic phase mixture at the interdendritic locations owing to the alloying additions. Moreover, a significant improvement in microhardness is achieved with increase in amount (wt.%) of alloying elements, depicting the highest hardness in the Mg-10Sn-3Al-1Zn (wt.%) alloy. Simultaneously, the alloying addition even in micro-concentration has been found to reduce the specific wear rate than that of the binary alloy over the entire loading range. The post-wear topographical surface features and chemical analysis using scanning electron microscope and energy-dispersive x-ray spectroscopy of the investigated alloys have suggested the oxidation and abrasion as dominant wear mechanisms. The reduced wear rates in the Al containing alloys are ascribed to the protective and continuous mechanically mixed oxide scale formation during test, which acts as a lubricating layer between the pin and the rotating disk. The discrete oxide island formation at the Zn-lean regions of Zn containing alloys is responsible for their accelerated wear rates.