固溶处理时间对2E12铝合金组织和疲劳性能的影响

 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 ℃/1 h和8 h固溶处理对2E12T₄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。

Effect of Solution Treatment Time on Microstructures and Fatigue Properties of Aluminum Alloy 2E12

The effect of solution treatment at 495 ℃ for 1 h and 8 h on the microstructures and fatigue properties of aluminum alloy 2E12 is investigated by optical microscopy, scanning electron microscopy, X-ray energy dispersive spectrum and fatigue life testing. The amount of residual Al2CuMg phases is greatly reduced after solution treatment at 495 ℃ for 8h, which enhances the solid solubility of Cu and Mg in the matrix after water quenching. Therefore, the strength of the alloy is increased after T4 temper. The residual phases of larger sizes on the free surfaces of the specimens initiate fatigue crack by two types: self fracture of particles and detachment from the matrix. The presence of larger size particles also accelerates the growth of fatigue crack into the matrix, causes the connection between fatigue cracks with the minimum distance and promoted fatigue striations to form secondary cracks.Therefore,reducing the amount of residue phases by increasing solution treatment time may increase the fatigue life of aluminum alloy 2E12.