Abstract : To enhance the frictional wear performance of AZ31B magnesium alloy, a nanocrystalline layer was prepared by ultrasonic impact (UI) treatment on magnesium alloy samples, and the effects of different ultrasonic impact times (5 min, 10 min, and 15 min) on the organization and wear resistance of the composite coating were studied. The findings revealed that the maximum thickness of the composite coating was about 50 μm after 10 min of impact time, which was approximately 15 μm higher than that of the MAO coating. The elemental composition of the composite coating was mainly Mg, O, and Si elements, and the phase structure of the coating, mainly MgO and Mg 2SiO 4, was the same before and after UI. The microhardness value gradually decreased in a gradient with the increasing distance from the sample surface. The coating had a lower average coefficient of friction (0.18) and lower wear loss (1.56 mg) for the 15 min impact time. Moreover, a small amount of abrasive and adhesive wear served as the primary modes of wear. Keywords: AZ31B magnesium alloy; ultrasonic impact; micro-arc oxidation; composite coating; friction wear performance Abstract : To enhance the frictional wear performance of AZ31B magnesium alloy, a nanocrystalline layer was prepared by ultrasonic impact (UI) treatment on magnesium alloy samples, and the effects of different ultrasonic impact times (5 min, 10 min, and 15 min) on the organization and wear resistance of the composite coating were studied. The findings revealed that the maximum thickness of the composite coating was about 50 μm after 10 min of impact time, which was approximately 15 μm higher than that of the MAO coating. The elemental composition of the composite coating was mainly Mg, O, and Si elements, and the phase structure of the coating, mainly MgO and Mg 2SiO 4, was the same before and after UI. The microhardness value gradually decreased in a gradient with the increasing distance from the sample surface. The coating had a lower average coefficient of friction (0.18) and lower wear loss (1.56 mg) for the 15 min impact time. Moreover, a small amount of abrasive and adhesive wear served as the primary modes of wear. Keywords: AZ31B magnesium alloy; ultrasonic impact; micro-arc oxidation; composite coating; friction wear performance Abstract : To enhance the frictional wear performance of AZ31B magnesium alloy, a nanocrystalline layer was prepared by ultrasonic impact (UI) treatment on magnesium alloy samples, and the effects of different ultrasonic impact times (5 min, 10 min, and 15 min) on the organization and wear resistance of the composite coating were studied. The findings revealed that the maximum thickness of the composite coating was about 50 μm after 10 min of impact time, which was approximately 15 μm higher than that of the MAO coating. The elemental composition of the composite coating was mainly Mg, O, and Si elements, and the phase structure of the coating, mainly MgO and Mg 2SiO 4, was the same before and after UI. The microhardness value gradually decreased in a gradient with the increasing distance from the sample surface. The coating had a lower average coefficient of friction (0.18) and lower wear loss (1.56 mg) for the 15 min impact time. Moreover, a small amount of abrasive and adhesive wear served as the primary modes of wear. Keywords: AZ31B magnesium alloy; ultrasonic impact; micro-arc oxidation; composite coating; friction wear performance To enhance the frictional wear performance of AZ31B magnesium alloy, a nanocrystalline layer was prepared by ultrasonic impact (UI) treatment on magnesium alloy samples, and the effects of different ultrasonic impact times (5 min, 10 min, and 15 min) on the organization and wear resistance of the composite coating were studied. The findings revealed that the maximum thickness of the composite coating was about 50 μm after 10 min of impact time, which was approximately 15 μm higher than that of the MAO coating. The elemental composition of the composite coating was mainly Mg, O, and Si elements, and the phase structure of the coating, mainly MgO and Mg 2SiO 4, was the same before and after UI. The microhardness value gradually decreased in a gradient with the increasing distance from the sample surface. The coating had a lower average coefficient of friction (0.18) and lower wear loss (1.56 mg) for the 15 min impact time. Moreover, a small amount of abrasive and adhesive wear served as the primary modes of wear. Keywords: AZ31B magnesium alloy; ultrasonic impact; micro-arc oxidation; composite coating; friction wear performance Keywords: AZ31B magnesium alloy; ultrasonic impact; micro-arc oxidation; composite coating; friction wear performance Keywords: