MB8形变镁合金疲劳性能研究

Investigation on Fatigue Properties of MB8 Deformed Magnesium Alloy

采用EHF-EM200K2-070-1A型液压伺服疲劳试验机对轧制变形MB8镁合金室温高周疲劳性能进行了研究。结果表明在拉-拉疲劳应力比为R=0.1,循环基数为1×107条件下,MB8镁合金的疲劳强度为69.41 MPa,相当于其抗拉强度的30%左右;MB8镁合金的疲劳裂纹萌生于试样表面,裂纹扩展区由小的平面状断面组成,并有少量二次裂纹。疲劳断口上没有明显的疲劳辉纹,MB8镁合金疲劳断口在裂纹萌生区塑性变形很小,在裂纹扩展区呈现出多个小平面以及撕裂棱组成的准解理断裂特征。在最终断裂区断口上可观察到韧窝存在,呈现出韧性断裂特征。

The high cycle fatigue behavior of MB8 deformed alloy at room temperature was investigated by using EHF-EM200K2-070-1A fatigue testing machine. The test results indicate that the fatigue strength of MB8 is 69.41MPa under stress ratio of R =0.1 and cycles of N= 1 ~ 107 conditions. The fatigue strength is about 30% of its tensile strength. The fatigue cracks initiate at the surface of the samples. The fatigue crack propagation regions of MB8 are composed of some facets. There are small numbers of secondary cracks on the fracture surface, and no obvious fatigue striations appear at fatigue fracture. There is a little plastic deformation in the crack initiation region, and there are many small facets and torn edges in the crack propagation area, it shows quasi-cleavage fracture characteristic. Dimples can be found on the fatigue fracture surface in the last fracture area, which presents the ductile fracture characteristic.