Post-weld heat treatment of 2195 Al-Li alloy electron beam welded joint

doi:10.13251/j.issn.0254-6051.2020.01.017

Abstract

Abstract: Post-weld heat treatment (PWHT) was carried out for the electron beam welded joint of 2195 Al-Li alloy. The microstructure evolution of weld zone under the different heat treatments was investigated by using optical microscope (OM), scanning electron microscopy (SEM) combined with energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD), respectively. And the strengthening mechanism of the welded joint during PWHT process was discussed. The results show that the microstructure of welded joint is greatly improved after PWHT, and the strengthening phases precipitate in weld zone, which is advantageous to the mechanical properties of welded joint. After solution and double aging treatment, the fine equiaxed grain zone (EQZ) near fusion line in as-welded condition disappears, and the strengthening phases such as β′, θ′ and T ₁, are generated in weld zone. Compared with the single aging treatment, the effect of precipitation strengthening is more obvious during double aging treatment. Tests of joint mechanical properties show that, after double aging treatment, the tensile strength of welded joint reaches to 492.5 MPa, which is 90.4% of that of the base metal. There are many small dimples on the fracture surface, as well as the cleavage facets exist, and the joint presents the mixed mode of ductile-brittle fracture.

Key words: Al-Li alloy, electron beam welding, post-weld heat treatment, microstructure, mechanical properties

CLC Number:

TG457.14

Zhao Li, Zhu Ruican, Xie Meirong, Wang Shaogang. Post-weld heat treatment of 2195 Al-Li alloy electron beam welded joint[J]. HTM, 2020, 45(1): 84-90.

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