复合热处理对7075铝合金组织和力学性能的影响

采用光学显微镜(OM)、扫描电子显微镜(SEM)、布氏硬度计、室温拉伸测试与Image J图像处理软件等手段,研究了复合热处理对7075铝合金微观组织与力学性能的影响。结果表明,与T6处理相比,固溶+深冷12h+时效复合热处理工艺对7075铝合金组织与性能提高作用明显,在其延伸率基本保持不变的基础上,抗拉强度与硬度分别提升了18.6%与20.43%;深冷过程中温度剧烈变化带来的应力细化了合金的晶粒,同时降低了Al基体的固溶度,促进原子析出形成更多GP区,为时效过程中析出相的孕育提供了更多驱动力,增加了合金的析出相强化效果,进一步提升合金的力学性能。

Effect of Combined-heat Treatment on Microstructure and Properties of 7075 Alloy

The effects of Combined-heat treatment on the microstructure and mechanical properties of 7075 alloy was investigated by means of OM, SEM, brinell hardness tester, tensile test and image processing software. The results show that the microstructure and the mechanical properties were improved obviously after solid solution+12 h cryogenic + aging composite heat treatment. The tensile strength and hardness increase by 18.6% and 20.43% compared with the T6 treatment process while the elongation nearly remains unchanged.The stress caused by the cryogenic process refines the grain of the alloy, while the low temperature reduces the solid solubility of the Al matrix, promotes the precipitation of atoms to form more GP zones, and provides the precipitation of precipitates in the aging process. The cryogenic process increases the effect of precipitation phase strengthening and further improves the mechanical properties of the alloy.