Properties study on Ti/Al butt joining by GMAW/GTAW hybrid welding-brazing

Abstract

For adjusting the distribution of welding heat to obtain sound Ti/Al butt joints, Gas Metal Arc Welding (GMAW)/Gas Tungsten Arc Welding (GTAW) hybrid welding-brazing was introduced to join 5A06 to TC4. Then two kinds of tensile strength was tested. And the weld microstructure was observed by Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and Energy Dispersive Spectrometer (EDS). Effects of welding parameters on weld reinforcement and interface characteristics were investigated. Results revealed TiAl3 IMCs layer was formed in the weld area of the titanium alloy side. The other area of weld was composed of α-Al matrix and Mg2Si+Al+Si eutectic. The back welding reinforcement was improved with the welding heat of the joint back increasing. But this may lead to a large number of molten metal flowing to the back of weld, the face reinforcement of the weld became poor. However, effects of welding parameters on the interface bonding strength was different. It was depended on the thickness and morphology of IMCs. When serrated IMCs of 2–6μm thickness were formed, the highest tensile strength without reinforcement was 240.3 MPa. Through comprehensive analyzing, when the welding parameters were welding speed of 15 mm s−1, GTAW current of 80–90 A and GMAW/GTAW position of −1 mm, the weld reinforcement and interface bonding strength were also high. So the excellent butt joints of TC4/5A06 were achieved. The maximum average value of TC4/5A06 joints tensile strength with reinforcement was 265 MPa with fracture inside the weld far from IMCs layer.