Influence of bevel angle and wire offset on the microstructure and mechanical properties of Ti/Al joint by cold arc MIG welding

Cold arc MIG welding of TA2 titanium and 5A05 aluminum alloy was conducted with SAl 5183 wire. The influence of bevel angle in titanium and wire offset on joint forming and the Ti/Al interfacial microstructure was studied. Partial melting of top titanium and poor bonding of the root appeared in the same joint when the bevel angle is too small. However, Weld sag was observed with too large bevel angles. With the bevel angle is in the range of 30° ~ 45°, good joint forming and sound interfacial combination along the thickness direction were observed. Partial melting of top titanium and poor bonding of the root appeared in the same joint when the welding wire was point to titanium side. Weld sag was observed with too large wire offset towards aluminum. Good joint forming and sound interfacial combination were observed with the wire offset towards aluminum was in the range of 0 ~ 1 mm. The optimal parameters obtained were that the bevel angle was 35° in titanium and the wire offset was 0.5 mm towards aluminum, the average tensile strength reached up to 198 MPa. The titanium and the weld metal were brazed by the formation of a Ti_3.3Al layer and a TiAl₃ layer in the upper region of the joint. While only a TiAl₃ layer was formed between titanium and weld metal in the bottom region of the joint.