中文摘要：

通过开展正负交变电脉冲辅助时效实验，采用TEM分析以及电导率、维氏硬度和力学性能等测试手段，研究不同频率的正负交变电脉冲对7075铝合金组织和性能的影响。结果表明：频率为10和700 Hz的正负交变电脉冲可加速时效析出进程，显著提高铝合金硬度；同时，经过正负交变电脉冲时效热处理后，试样的强度较常规时效热处理后试样的强度提高了10.3%，伸长率提高了3.1%；通过TEM对7075铝合金的显微组织进行观察，发现与常规时效热处理相比，在正负交变电脉冲时效热处理条件下，晶内析出相η′的数量增多，弥散度增高；晶界析出相由细小连续分布向断续分布的粗化沉淀相转变。可见，正负交变电脉冲辅助时效热处理比常规时效热处理工艺对铝合金组织和性能的改善效果更加明显。

英文摘要：

The positive and negative alternating electrical impulse aging experiments were conducted to study the influence of positive and negative alternating electrical impulse on the microstructure and mechanical properties of 7075 aluminum alloy by TEM analysis, conductivity, Vickers hardness and mechanical properties measurement. The results show that the positive and negative alternating electrical impulse with frequencies of 10 and 700 Hz can accelerate the aging precipitation process and obviously increase the hardness of aluminum alloy. Compared with conventional aging heat treatment, the positive and negative alternating electrical impulse aging heat treatment can improve the strength of the specimen by 10.3% and the elongation of the specimen by 3.1%. Meanwhile, the observation of the microstructure of 7075 aluminum alloy by TEM indicates that positive and negative alternating electrical impulse aging heat treatment can multiply the number and improve the dispersion degree of precipitate η′ compared with conventional aging heat treatment; grain boundary precipitate transforms from small continuous distribution to coarsening discontinuous distribution. As a result, the positive and negative alternating electrical impulse aging heat treatment is better than conventional aging heat treatment on the aluminum alloy in improving the microstructure and properties.