自然时效效应及预时效处理对7A20铝合金组织性能的影响

研究了中强度7A20铝合金的自然时效硬化效应及预时效处理对组织和性能的影响。采用光学显微镜和透射电镜表征了其微观组织结构,采用维氏硬度计和万能拉伸试验机测试了其硬度和力学性能。结果表明:固溶态7A20试验铝合金的自然时效硬化效应明显,12天后硬度由56 HV0.5提高到122 HV0.5,提高了117.86%。经120 ℃×10 min预时效处理后,自然时效硬化增量最低,相比于固溶态降低了16 HV0.5,有效抑制自然时效硬化效应;同时,预时效处理提升了烘烤硬化效应,烘烤硬化后屈服强度提升了166 MPa,抗拉强度提高了51 MPa,伸长率降低了7%。烘烤处理前,其晶内的强化主要来自于与基体共格的GP区,烘烤处理后为尺寸小于5 nm、弥散分布的η′强化相。

Effect of natural aging effect and pre-aging treatment on microstructure and properties of 7A20 aluminum alloy

Natural aging effect and effect of pre-aging treatment on the microstructure and mechanical properties of 7A20 aluminum alloy were investigated by means of OM, TEM, Vickers hardness tester and multifunctional tensile testing machine. The results indicate that the solution treated 7A20 aluminum alloy has obvious natural aging hardening effect, and the microhardness increases by 117.86% after natural aging for 12 days, from 56 HV0.5 to 122 HV0.5. After the pre-aging treatment at 120 ℃×10 min, the natural aging hardening increment is the lowest, reduced by 16 HV0.5 compared to the solution treated alloy. Simultaneously, this pre-aging treatment improves the baking hardening effect, the yield strength and tensile strength increase by 166 MPa and 51 MPa respectively, while the elongation decreases by 7%. Before the bake hardening process, the strengthening effect in the grains comes mainly from GP zones coherent with the matrix; and after the baking treatment, it comes from dispersed strengthening phase η′ with a size of less than 5 nm.