Research on the Influence Law of Ultrasonic Rolling Passes on the Tension-Tension Fatigue Properties of AZ31B Magnesium Alloy

In order to improve the fatigue performance of AZ31B magnesium alloy under high-stress levels and reveal the related mechanism，ultrasonic rolling process was used to roll it for different passes (2/4/6).Subsequently， the fatigue life， surface roughness， microstructure and microhardness of AZ31B magnesium alloy before and after rolling treatment were tested and analyzed.Results showed that the fatigue life of AZ31B magnesium alloy was the best after two passes of rolling treatment， which was 53.6%longer than that of the original sample.The improvement of fatigue performance was related to the reduction of surface roughness， but it was not the dominant factor.The surface grains of the magnesium alloy treated by ultrasonic rolling were significantly refined， and a plastic deformation layer with a thickness of 235～315 μm was formed.Additionally， the microhardness showed a trend of first increasing and then decreasing.Grain refinement and severe plastic deformation had important contributions to the improvement of fatigue properties of magnesium alloys.Overall，the research results provided theoretical basis and experimental basis for the anti-fatigue manufacturing of magnesium alloys.