Relationship of wear properties to basal-plane texture of worn surface of Mg alloys

The wear properties of pure-Mg, AZ31 extruded alloy, AZ91 cast alloy, and Mg90.5Cu3.25Y6.25 (at.%) cast alloy consisting of Mg and long-period-ordered (LPO) phases were investigated by pin-on-disk-type wear tests under dry sliding. The wear loss of the Mg90.5Cu3.25Y6.25 cast alloy at high-applied loads over 147 N was less than those of AZ Mg alloys, and about two-thirds of the AZ31 extruded alloy, which indicated that the Mg90.5Cu3.25Y6.25 cast alloy has superior wear-resistance. The basal planes (0 0 0 2) and (1 0 1¯ 1) were apparent in the X-ray diffraction patterns of worn surfaces of pure-Mg and Mg alloys. This XRD result indicated that basal planes in both the Mg and LPO phases were aligned to worn surfaces for the pure-Mg and Mg alloys, and this result was also supported by EBSD analysis. Because slip deformation tends to easily occur on the Mg basal plane at a low critical resolved shear stress (CRSS), formation of the basal-plane alignment on the wear surface negatively affects the wear-resistance properties. After the wear test of the Mg90.5Cu3.25Y6.25 cast alloy, a kink deformation in the LPO phase was frequently observed in the worn edge section. The kink deformation in the LPO phase contributes to improve wear-resistance properties by suppression of the basal-plane alignment.

Research highlights
► We have investigated wear properties of pure-Mg, AZ31 extruded alloy, AZ91 cast alloy, and Mg–Cu–Y cast alloy composed of Mg with a LPO phase by pin-on-disk-type wear tests under the dry sliding.
► Wear mechanism of the Mg alloy was crystallographically investigated by XRD and EBSD analyses.
► Suppressing the basal plane alignment that occurs during severe wear was effective for the wear resistance properties.