Effect of implantation dose on surface gradient structure and properties of magnesium alloy AZ31

With an aim to address the issue of poor corrosion resistance in magnesium alloys, we implemented ultrasonic rolling pretreatment on magnesium alloy AZ31, followed subsequently by N-ion implantation treatment. The influences of various implantation doses on the surface structure and friction-corrosion performance of the magnesium alloy were examined. The outcomes disclosed that after N-ion implantation, a new phase Mg3N2 emerged, and the diffraction peak intensity increased as the implantation dose rose. The microhardness of the modified surface layer rose significantly with higher implantation doses due to the formation of nitrides and solid solution strengthening caused by N implantation. The results of the friction wear test showed that the average friction coefficient of the magnesium alloy samples decreased from 0.33 to 0.28 after ion implantation treatment. Notably, the samples with an implantation dose of 5 × 1016 ions/cm2 had the minimum mass loss during wear and demonstrated superior wear resistance, which was in line with the reduced friction coefficients. Electrochemical analysis indicated that increasing the implantation dose enhanced the self-corrosion potential of magnesium alloy samples from −1.39 (for the untreated sample) to −1.19 and significantly decreased the self-corrosion current density due to the diffusion protection provided by Mg3N2 formed on the surface along with the supersaturated nitrogen diffusion effect. These discoveries demonstrate that combining the ion implantation process following ultrasonic rolling pretreatment can further enhance the tribocorrosion resistance of magnesium alloys and serve as a valuable reference for improving the surface properties of these alloys through composite processes.