中文摘要：

研究AZ31镁合金不同方向的力学性能、疲劳裂纹扩展行为和单峰过载效应以及载荷比对疲劳裂纹扩展速率的影响。结果表明：不同方向材料的抗拉强度相当，而屈服强度差别较大：不同方向疲劳裂纹扩展行为存在差异，是由于屈服强度不同所致，归一化后差别消失：当应力强度因子范围相同时，疲劳裂纹扩展速率随载荷比的降低而降低；单峰过载时，疲劳裂纹向前扩展一段距离并偏离原扩展方向，导致随后裂纹扩展迟滞，这是由于过载增大残余压应力和裂纹出现偏折的结果。

英文摘要：

The tensile property, fatigue crack growth behavior and the effect of single overload ofAZ31 magnesium alloy and load on fatigue crock growth rate were investigated under different directions. The results show that the ultimate strength has little difference, while the yield strength diverges under various directions, and the difference of fatigue crack growth behavior attributes to the yield strength, which disappears after unification. Under identical AK, the fatigue crack growth rate decreases with the decrease of stress ratios. During single overloading, the fatigue crack continues to the propagate and deflects from its original path, and it induces subsequent crock growth retardation due to the increase of compressive residual stress and crock deflection.