中文摘要：

研究了恒变幅疲劳载荷作用下Al-Si-Mg合金的疲劳行为及微结构对其疲劳性能的影响。对恒变疲劳载荷作用下Al-Si-Mg合金的单轴疲劳寿命以及疲劳行为进行了研究。利用透射透射电子显微镜观察在恒变幅载荷条件下Al-Si-Mg合金中位错以及位错带的演变情况。结果表明，Al-Si-Mg合金的疲劳寿命随变幅载荷的变化而变化；位错结构在Al-Si-Mg合金中的运动具有一定的规律性。变幅加载条件会引起材料微结构发生变化，使得材料的硬化效果和变形行为表现出明显的差异，从而影响了损伤的演化进程，材料的疲劳寿命强烈地依赖于加载历史所导致的材料微观结构变化。

英文摘要：

The effects of microstructural characteristics on the fatigue behavior in Al-Mg-Si alloy were researched. Fatigue tests were conducted to determine the influence of constant loading and variable amplitude loadings. The dislocation substructures of Al-Mg-Si alloy were observed by transmission electron microscopy （TEM）. The fatigue life exhibits a variable behaviour with variable amplitude loading. Results show that the dislocation structures of Al-Mg-Si alloy have certain regularity in the movement. Additionally, the change of material＇s microstructure is caused by loading conditions; in this way hardening effect and deformation behavior of material show significant differences, thus affecting the damage evolution process. The fatigue behavior and uniaxial fatigue life are strongly dependent on material＇s microstructure which is caused by the loading history.