【摘要】 本文对不同时效状态,相同时效状态在不同的环境介质条件下的2091Al-Li合金疲劳裂纹扩展速率进行了研究。同时还用透射电镜及扫描电镜对合金的显微组织与疲劳断口等进行了观察。研究结果表明:在不同时效状态下,欠时效合金的疲劳裂纹扩展速率最慢,门槛值最高。过时效合金的疲劳裂纹扩展速率最快,门槛值最低。峰时效合金介于二者之间。 研究结果还表明,峰时效状态的合金在室温空气介质条件下疲劳裂纹扩展速率比在130℃加热条件下及3.5％NaCl水溶液中的均慢,门槛值均高。而130℃加热时合金的疲劳裂纹扩展速率比3.5％NaCl水溶液中的还快,门槛值也低。 本文还对上述合金的疲劳裂纹扩展速率的变化规律与它的显微组织,断口形貌及疲劳裂纹扩展形态之间的关系进行了探讨。更多还原

【Abstract】 The fatigue crack propagation (FCP) behaviors of Al-Li 2091 alloy in different aging states and in different environments were studied. The microstructures and fatigue fracture surfaces of the alloy were examined by using TEM, SEM and optical microscope. The results showed that in ambient air, under-aged alloy has the lowest FCP rate and the highest FCP threshold, and over-aged alloy has the highest FCP rate and the lowest FCP thres -hold, while peak-aged alloy is between them. It was shown that peak-aged alloy has lower FCP rate and higher threshold in ambient air than in air of 130℃ C or in 3.5 % Nacl agueous solution. The alloy in air of 130℃ has higher FCP rate and lower thersnold than in 3.5% NaCl aqueous solution. The relationship among FCP rate, crack path and microstructure was discussed.更多还原