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采用光学金相、扫描电镜、能谱分析以及疲劳寿命测试等方法,研究了495℃/1h和8h固溶处理对2E12-T4铝合金微观组织和疲劳性能的影响。实验结果表明,延长固溶处理时间可显著减少基体中可溶的Al2CuMg残留相数量,提高合金元素的过饱和固溶度,因而,自然时效后合金强度相应增加。试样自由表面上的大尺寸残留相在疲劳加载过程中,通过自身断裂或与基体脱粘的两种方式优先诱发疲劳裂纹萌生;并且,这些大尺寸残留相还起到促进疲劳裂纹扩展和连接的作用,导致疲劳辉纹形成时发生开裂形成二次裂纹,因而,延长固溶处理时间减少大尺寸残留相数量可提高2E12铝合金的疲劳寿命。
The effects of solution heat treatment at 495 ℃ / 1h and 8h on the microstructure and fatigue properties of 2E12-T4 aluminum alloy were investigated by optical metallography, scanning electron microscopy, energy spectrum analysis and fatigue life test. Experimental results show that prolonging the solution treatment time can significantly reduce the amount of residual Al2CuMg phase in the matrix and increase the supersaturated solid solubility of the alloying elements. Therefore, the alloy strength increases after natural aging. Large residual phases on the free surface of the specimen preferentially induce fatigue crack initiation during fatigue loading by either self-breaking or debonding from the matrix, and these large residual phases also act to promote fatigue crack propagation and attachment , Which leads to the formation of secondary cracks during the formation of fatigue crest. Therefore, prolonging the solution treatment time and reducing the number of large size residual phase can improve the fatigue life of 2E12 aluminum alloy.