Microstructure and Properties of Tungsten Inert Gas Welded 7075 Aluminium Joints Prepared with Al-5.5Mg-1Zn Filler Containing Trace Element Er
HE Rouyue1,2, HUANG Qibo1,2, CUI Hongbo1,2, TANG Xin1,2
1 School of Materials Science and Engineering, Guilin University of Technology, Guilin 541004, China 2 Key Laboratory of New Processing Technology for Nonferrous Metal & Materials, Ministry of Education, Guilin University of Technology, Guilin 541004, China
Abstract: Optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied to study the microstructure and mechanical properties of 7075 aluminum alloy weld joint prepared with Al-5.5Mg-1Zn weld wires containing different contents of Er. The results showed that the reticulate eutectic T [Mg32(Al,Zn)49] phases in the weld zone was refined due to the addition of Er element, and the refinement of α-Al grain could be attributed to the formation of primary Al3Er phase for the primary Al3Er phase acted as an effective heterogeneous nucleation of α-Al grain, and restricted the growth of recrystallized α-Al grains. And the secondary nano-Al3Er particles have strong interaction with the subgrain boundary and dislocation, as a result, the strength of welded joint was enhanced. With the increase of Er element into the welding wires, the ultimate tensile strength of the welded joint showed a trend of increasing initially and then decreasing. The refinement of α-grain and eutectic T phases and improvement of the mechanical properties of the welded joint could be attributed to the proper addition of Er element in the welding wire. When the content of Er element in the welding wire was 0.6wt%, the ultimate tensile strength of the welded joint value was max. Compared with the weld without Er element, and the increasement of ultimate tensile strength and yield strength were 44 MPa (12.7%) and 68 MPa (36.6%) respectively compared with the weld without Er element.
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2020, Vol. 34 
