Research On Optimization Of Arc Welding-brazing Parameters And Connection Mechanism Of Ti/Al Dissimilar Alloy

The composite connection of Ti/Al dissimilar materials has good application prospects,but due to the large differences in the thermophysical properties of the two,it is difficult to obtain a reliable connection of Ti/Al dissimilar materials by traditional welding methods.In this paper,based on MIG arc welding-brazing process,through numerical simulation and experimental analysis,the effects of process parameters and filler materials on weld forming and joint performance are explored.In this paper,based on the finite element theory of welding process,the transient temperature and stress changes in the whole welding process are simulated and analyzed.The results show that the brazing process of Ti/Al dissimilar metals is a non-uniform heating and cooling process,and the temperature field presents non-uniform distribution in transverse direction and plate thickness direction.By adjusting the heat input and arc offset position during the welding process,the temperature field distribution of the welding process can be effectively controlled:when the welding current is 110A,the welding voltage is 15V,the welding speed is10mm/s,that is,the heat input is 1.32k J/cm,and the arc shifts to the aluminum alloy side by 0.3mm,the weld temperature remains at a higher temperature below the melting temperature of the titanium alloy,and the temperature gradient of titanium alloy brazing interface is small,which is an effective welding parameter.The generation of residual stress after welding is related to the higher cooling rate during the cooling process.The results show that the transverse residual stress near the weld on one side of aluminum alloy shows the phenomenon of"compression at both ends and tension in the middle",while the longitudinal residual stress is larger tensile stress.The transverse residual stress in the area near the weld seam on one side of the titanium alloy shows higher tensile stress,and the longitudinal residual compressive stress.The welding parameters optimized used to conduct welding-brazing process tests on 2.5mm thick TC4 titanium alloy and 2A12 aluminum alloy.The results show that the titanium alloy in the direct arc heating zone of the fusion brazed joint obtained by welding wires with different alloy elements is slightly melted,the middle and lower part is serrated brazing interface,and there are some rod and block precipitates in the welding seams around the brazing interface.The upper fusion zone on the titanium alloy side of the joint obtained by Al-Si welding wire is narrower and the brazing interface is wider and the overall thickness is uniform.The element distribution and phase composition analysis of the titanium-aluminum transition zone of the fusion brazed joint obtained by using Al-Si welding wire are carried out.The fusion zone of the multilayer structure formed on the upper part of the joint is composed of Ti(Al,Si)₃layer,Ti(Al,Si)and Ti-Si mixed layer,Ti₃Al layer,the middle and lower brazing area of the joint is composed of Ti(Al,Si)₃layer,Ti(Al,Si)₃and Ti-Si mixed layer Layer,?-Ti layer composition.The results show that the microhardness of the welded joint with different element filler wire shows obvious regional distribution.Using Al-Cu welding wire,the highest hardness of the joint is 450HV_0.1.The tensile test shows that the tensile strength of the joint filled with Al Si welding wire is the highest,reaching227MPa.