中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 29 No. 12 December 2019 |
（1. College of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620, China;
2. Shandong Provincial Key Laboratory of Special Welding Technology, Harbin Institute of Technology at Weihai, Weihai 264209, China;
3. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China;
4. National Key Laboratory for Remanufacturing, Beijing 100072, China）
Abstract:The microstructure and mechanical properties of multi-layer multi-pass TIG welded joints of Al-Zn-Mg alloy plates were studied. The phase constituent and microstructure of different regions of the welded joints were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy disperse spectrum (EDS), while the mechanical properties were evaluated according to the impact test. A dispersively distributed spherical and needle-like η(MgZn2) phase was obtained in the welding seam. The phase composition of the heat-affected zone (HAZ) was α(Al)+η(MgZn2)+Al6Mn, and there were a large number of dispersively precipitated nanoscale particles. The welded joint zone had the highest impact toughness as compared with the other parts of the joint. The MgZn2 phase in the weld zone contributed to the improved toughness of the joint. Al2MgCu phase in HAZ was proven to act as a crack source during fracture.
Key words: Al-Zn-Mg alloy; thick plates; multi-layer TIG welding; microstructure; impact mechanical property
