A comparative study on tribological and mechanical behavior of as-cast and aged Mg-6Gd-2Ag-0.6Zr alloy at elevated temperatures

The effects of aging treatment on the mechanical and tribological behavior of Mg-6Gd-2Ag-0.6Zr alloy were investigated. Shear punch testing and hot hardness measurements were conducted to evaluate the mechanical properties of the alloys at various temperatures of 25–350 °C. The aging treatment enhanced the mechanical behavior of the alloy, resulting in increases in hardness and ultimate shear strength by about 53–64% and 11–22%, respectively, at various temperatures. Dry sliding wear tests were carried out under the normal loads of 5, 20, 40, and 60 N within a temperature range of 25–325 °C using a Pin-on-disk tribometer against AISI52100 steel disks. Despite the improvements in mechanical properties, the aging treatment reduced wear resistance by about 45% under a normal load of 5 N at various wear temperatures. However, as the normal load was increased to 60 N the aged alloy showed about 11–23% lower wear rate at various temperatures. The characterization of the wear surfaces also showed that the oxidation wear became more dominant as the normal load and the wear temperature increased. Under higher normal loads of 40 and 60 N, a 54–88% greater transfer of magnesium oxides was observed on the steel disk, which reduced the contact between the steel disk and the magnesium alloy pin.