焊后热处理对Al-Zn-Mg-Cu合金MIG焊接接头组织与性能的影响

采用ER5356焊丝对Al-4.6Zn-1.5Mg-0.15Cu合金板材进行熔化极钨极氩弧焊试验,并对焊接接头进行了不同的焊后热处理。借助光学显微镜(OM)、扫描电镜(SEM)研究不同焊后热处理试样的组织变化规律,并进行了显微硬度测试与拉伸试验。结果表明:经固溶加时效处理后,焊接接头抗拉强度与显微硬度得到明显提升,抗拉强度与焊缝硬度均值分别提高至304 MPa与85 HV,相比焊后未处理的263 MPa与66 HV,增幅分别达15.6%与28.8%。焊接接头经时效处理后,组织的不均匀性及强化相的分布得到改善;而经重新固溶后,第二相发生回溶,再经时效处理将使得一部分不稳定的过饱和固溶体重新析出且弥散分布。

Influence of post weld heat treatment on microstructure and properties of MIG welded joint of Al-Zn-Mg-Cu alloy

Al-4.6Zn-1.5Mg-0.15Cu alloy plate was welded by using metal inert-gas welding (MIG) with ER5356 welding wire as filler metal. And different post weld heat treatments were carried out on the welded joints.The microstructure evolution of the welded joints after different post weld heat treatments was investigated using optical microscopy (OM) and scanning electron microscope (SEM). In addition, the microhardness measurements and tensile tests were conducted. The results show that after solution and aging treatments, the tensile strength and microhardness of the welded joints are significantly improved. The microhardness of the welded joint is increased from 66 HV before heat treatment to 85 HV after solution and aging treatments, increasing by 28.8%. The tensile strength is increased from 263 MPa before heat treatment to 304 MPa after solution and aging treatments, increasing by 15.6%.After aging treatment, the inhomogeneity of microstructure and the distribution of strengthening phase are improved.After solution treatment, the second phase of the welded joint can be re-dissolved, and then aging treatment makes some unstable supersaturated solid solution re-precipitated and diffusely drstributed.