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

doi:10.13251/j.issn.0254-6051.2020.04.037

Abstract

Abstract: 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.

Key words: Al-Zn-Mg-Cu alloy, melt inert-gas welding (MIG), microstructure, mechanical properties

CLC Number:

Zhang Xiang, Chen Bo, Xie Dejie. Influence of post weld heat treatment on microstructure and properties of MIG welded joint of Al-Zn-Mg-Cu alloy[J]. Heat Treatment of Metals, 2020, 45(4): 176-179.

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