坡口角度及焊丝偏移量对钛/铝冷弧MIG焊接头显微组织与力学性能的影响

采用SAl 5183焊丝对TA2钛/5A05铝进行脉冲冷弧MIG焊. 研究钛侧坡口角度θ及焊丝偏移量d对接头成形及显微组织与力学性能的影响. 结果表明，坡口角度过小时，接头上部钛局部熔化而根部结合不良，Ti/Al界面组织差异大；坡口角度过大则出现焊缝下塌；坡口角度在30° ~ 45°范围内，Ti/Al界面组织差异小且结合良好. 焊丝偏向钛侧时，接头上部钛局部熔化而根部结合不良，Ti/Al界面组织差异大；焊丝向铝侧偏移过大则出现焊缝下塌；焊丝偏铝侧0 ~ 1 mm时，Ti/Al界面组织差异小且结合良好. 试验获得的优化工艺为坡口角度θ = 35°，焊丝偏铝d = 0.5 mm. 最佳工艺下，接头上部Ti/Al钎焊界面形成了Ti_3.3Al和TiAl₃两层金属间化合物；接头下部则通过形成一层TiAl₃实现钎焊结合；接头平均抗拉强度达198 MPa.

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.