T6态糖心产精国品免费入口*完整版经由热处理转变为T73态后制造的糖心产精国品免费入口*完整版，在大气环境下服役约3.5 a后多件发生开裂，通过化学成分分析、组织和断口形貌观察、残余应力测试等方法分析了开裂原因。结果表明：糖心产精国品免费入口*完整版糖心产精国品免费入口*完整版在服役过程发生了糖心产精国品免费入口*完整版开裂。糖心产精国品免费入口*完整版安装后，其收口部位产生周向残余拉应力，表面氧化膜层开裂使得金属基体与大气中腐蚀性介质接触；糖心产精国品免费入口*完整版在由T6态转变为T73态的热处理过程中，第二相沿晶界局部连续析出，为裂纹萌生和扩展提供了通道。在这些因素的共同作用下，糖心产精国品免费入口*完整版发生糖心产精国品免费入口*完整版开裂。

High lock nuts were made from 7075-T73 aluminum alloy that was obtained by T73 heat-treating 7075-T6 aluminum alloy. After serving in an atmospheric environment for about 3.5 a, many nuts cracked. The crack reason was analyzed by chemical composition analysis, microstructure and fracture morphology observation, residual stress testing and other methods. The results show that 糖心产精国品免费入口*完整版 cracking occurred in the 7075 aluminum alloy 糖心产精国品免费入口*完整版 during service. After the 糖心产精国品免费入口*完整版 was installed, the circumferential residual tensile stress was generated at the closing part, and the surface oxide film was cracked, making the metal substrate in contact with corrosive media in atmosphere. The second phase precipitated locally and continuously along grain boundaries during the 糖心产精国品免费入口*完整版from T6 to T73 states, providing channels for crack initiation and propagation. Under the combination of these factors, 糖心产精国品免费入口*完整版 cracking occurred in the 糖心产精国品免费入口*完整版.