The automatic TIG welding on AZ31B alloys was carried out by the six-axis robot in the present work. After post-welded heat treatment (PWHT), the microstructure, precipitates, and mechanical properties of the AZ31B joints were investigated by using the optical microscope (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The experimental results reveal that after PWHT, the microstructure and mechanical properties of the AZ31B joints were both significantly improved. After PWHT, the grains of the AZ31B joint were still fine, whereas the number of the precipitates along with the grain boundaries was dramatically decreased. The ultimate tensile strength (UTS) and the elongation (EL) of the PWHT AZ31B joints were up to the 100 and 96.9% of the base metal (BM), respectively.
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This work is supported by the National Key Research and Development plan of China (Grant No. 2017YFB0103904, 2016YFB0301105), the Shandong Province Key Research and Development Plan, China (Grant No. 2017CXGC0404, 2016ZDJS02A09), and the Youth Foundation of Shandong Academy of Sciences, China (Grant No. 2016QN015).
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