Study on the synergistic strengthening mechanism of pre-tension deformation and surface mechanical rolling treatment on the fatigue performance of AZ31B magnesium alloy

AZ31B magnesium alloy is widely used in transportation and aerospace fields due to its light weight and high strength, but it often causes structural failure due to fatigue fracture during service. Fatigue fracture is usually caused by the initiation of cracks on the surface of structural parts and the propagation of cracks to the interior of the specimen in the form of intergranular fracture. In order to improve the fatigue performance, this study proposes a method of pre-tension deformation and surface mechanical rolling treatment of AZ31B magnesium alloy, thereby changing the crack initiation area and increasing the crack propagation resistance. The experimental results show that: As the pre-tension deformation increases, the fatigue limit shows a trend of first rising and then decreasing. The 5PT specimen exhibits the optimal strengthening effect, with a fatigue limit of 115 MPa, which is a 27.78 % improvement. Under surface mechanical rolling treatment, the fatigue limit reaches 140 MPa, which is a 55.56 % improvement. When pre-tension deformation and surface mechanical rolling treatment are combined, the fatigue limit is further improved compared to individual strengthening methods. Among these, the 2PT+SMRT specimen shows the most significant strengthening effect, with a fatigue limit of 150 MPa, which is a 66.67 % improvement. This study proposes a new strategy for improving the fatigue performance of AZ31B magnesium alloy, and reveals the synergistic strengthening mechanism of pre-tension deformation and surface mechanical rolling treatment of AZ31B magnesium alloy, which is of great significance for improving the fatigue performance of metal materials.