Enhanced Mechanical and Anti-Wear Properties of Magnesium by Alloying and Subsequent Extrusion–Aging Treatment

In this work, the microstructure, mechanical, and anti-wear properties of the alloyed-extruded-aged Mg-8.3Gd-4.5Y-1.4Zn-0.3Zr (wt%) alloys were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), nanoindentation, and wear tests. Results showed that the alloying—extrusion processing induced a significant grain refinement of magnesium resulting in the formation of bulk Mg24(GdYZn)5 at the grain boundaries. The grain size decreased from 116 μm in pure magnesium to 17 μm in alloyed-extruded magnesium, while the grain refinement, solid solution and second phase strengthening led to a hardness enhancement from 0.67 GPa in pure magnesium to 1.64 GPa in alloyed-extruded magnesium. Aging treatment further drove the structural homogenization of the alloyed-extruded magnesium resulting in an enhanced hardness of 1.83 GPa. During the sliding wear tests, a large-area plastic deformation layer formed on the wear track surface of pure magnesium, leading to an unstable friction coefficient and a high wear rate of 2.64 × 10−3 mm3·N−1·m−1. The alloying—extrusion—aging treatments effectively inhibited the formation of the plastic deformation layer. The wear rate of the alloyed-extruded material decreased to 1.60 × 10−3 mm3·N−1·m−1. In contrast, the alloyed-extruded-aged material showed a lower wear rate of 1.16 × 10−3 mm3·N−1·m−1. The wear failure mechanisms of all fabricated materials were further discussed according to the characterization results.