Abstract
In this study, surfacing-welding magnesium alloys with different compositions were prepared by changing the Al content in the Mg-Al-Zn alloy welding wire. Also, the effects of the Al content on the dry sliding tribological performance and wear mechanism at room temperature were investigated. The results revealed that the macro-hardness of the surfacing-welding Mg-Al-Zn alloy gradually increases. Also, the coefficient of friction and wear rate gradually decreases with the increase in the Al content from 3 to 9 % within the parameter range. Among these alloys, the surfacing-welding alloy containing 9 % Al exhibited the best wear resistance. The mechanism revealed that with the increase in the Al content, the grain size and amount of the β-Mg17Al12 phase in the alloy gradually increased, and the phase evolved into a reticular shape from the originally dispersed particles. During the wear process, the reticular phase can resist the plowing action caused by microscopic hard protrusions on the grinding disc and the wear debris, protect the α-Mg matrix, decrease the amount of fine granular debris generated by the abrasive wear mechanism, and enhance the wear resistance of the surfacing-welding alloy. Four wear mechanisms were observed during the friction and wear process of the surfacing-welding Mg-Al-Zn alloy, among which the abrasive wear and plastic-extrusion of the surface metal were the principal wear mechanisms, while the oxidative wear and delamination wear were the secondary wear mechanisms.

Key words
surfacing welding, Mg-Al-Zn, magnesium alloy, friction and wear, wear resistance

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