Microstructure and properties of Mg/Ti resistance spot welded joint using TiFeCrCoNi high entropy alloy as intermediate layer
Using TiFeCoCrNi high entropy alloy powder as the intermediate layer,resistance spot welding was carried out on magnesium/titanium dissimilar materials.Microstructure,phase and mechanical properties of the joint were studied using scanning electron microscopy,X-ray diffraction and electronic universal testing machine.The interfacial reaction diffusion behavior of the joint was analyzed.The results show that the joint is sequentially composed of magnesium alloy base material,α-Mg+Al2FeCo,FCC+η,Ti3Al+FCC+η and TC4 base material.The Al element in the magnesium alloy diffuses into the middle layer of high entropy alloy to generate Al2FeCo,while the Ti and Al elements in the titanium alloy diffuse into the middle layer of high entropy alloy to form Ti3Al.Both interface regions are composed of a mixed structure of solid solution and compound,which improves the joint performance.Within the process range of welding current of 18.8-24.5 kA,welding pressure of 4.06-7.83 kN,and welding time of 6-24 cycles,the joint strength is above 2.4 kN.When the welding pressure is 5.13 kN,the welding current is 21.7 kA,and the welding time is 20 cycles,the maximum tensile shear load of the joint is 5.368 kN.
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