多级时效对7055铝合金组织及力学性能的影响

Effects of multistage aging on microstructure and mechanical properties of 7055 aluminum alloy

采用光学显微镜、扫描电镜、X射线衍射仪和显微硬度计等研究了多级不同时效处理对7055铝合金经三级固溶处理后的组织和力学性能的影响。结果表明,三级固溶处理后7055铝合金的组织主要存在MgZn2和Al2CuMg相,时效处理并未改变合金的相组成,但三级时效处理组织中MgZn2相显著增多;同时,时效处理可以改善7055铝合金的各向异性,提高合金的力学性能。合金的最佳热处理工艺方案为:三级固溶(450℃×2 h)+(465℃×1 h)+(475℃×1.5 h)和三级时效处理(120℃×24 h)+(175℃×1.5 h)+(120℃×24 h),此时合金的硬度、抗拉强度、屈服强度和伸长率分别为195.2 HV0.5、673 MPa、621 MPa和10.24%。

The effects of multistage aging treatment on microstructure and mechanical properties of 7055 aluminum alloy after three-stage solution treatment were studied by means of optical microscope,scanning electron microscopy,X-ray diffractometer and microhardness tester.The results show that the microstructure of the 7055 aluminum alloy after three-stage solution treatment is mainly composed of MgZn2 and Al2CuMg phases,and the aging treatment does not change the phase composition of the alloy,but the content of the MgZn2 phase increases significantly after the three-stage aging treatment.The aging treatment can improve the anisotropy and mechanical properties of the 7055 aluminum alloy.The optimum heat treatment process of the alloy are as follows:three-stage solid solution(first solid solution at 450℃for 2 h and then solid solution at 465℃for 1 h and last solid solution at 475℃for 1.5 h)and three-stage aging(first aging at 120℃for 24 h plus aging at 175℃for 1.5 h and last aging at 120℃for 24 h).After these treatments,the hardness,the tensile strength,the yield strength and the elongation of the alloy are 195.2 HV0.5,673 MPa,621 MPa and 10.24%,respectively.