Microstructure and properties of Mg/Ti joint welded by resistance spot welding with asymmetric electrodes
Resistance spot welding was carried out on 2 mm thick AZ31B magnesium alloy and TA2 titanium plate using asymmetric electrodes.The effects of welding current and welding time on weld nugget diameter and tensile shear load of the joint were studied,and microstructure of the joint welding zone was analyzed.The results show that with the increase of welding current and welding time,the nugget diameter of the AZ31B/Ti joint increases,and the tensile shear load shows a trend of first increasing and then slightly decreasing.When the welding time is 180 ms,the welding current is 16 kA and the electrode pressure is 3 kN,the maximum tensile shear load of the joint is about 5.9 kN.An Al-rich layer is formed near the interface in the nugget at the magnesium alloy side,and many crystalline cracks are formed inside this layer.The formation process of the AZ31B/Ti joint welded by resistance spot welding with asymmetric electrodes is a fusion brazing process,and the Al-rich layer near the interface in the nugget is the main factor restricting the performance of the joint.
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