Interfacial Microstructure of TC4 /5A06 Al Joint Using High Speed Force Arc MIG Welding

High speed force arc MIG welding of TC4 Ti to 5A06 Al was carried out using SAl5183 filler. The effect of welding heat input E on the joint microstructures and properties was analyzed by SEM, XRD and tensile test. The results showed that E has a significant influence on the microstructure and mechanical properties under the test process conditions: lack of fusion occurred at the root part with the E lower than 0.93 kJ/cm, a single TiAl₃ layer with the thickness of less than 1 μm was formed at the Ti/Al interface. Burn through occurred with the E exceeded 1.20 kJ/cm, a TiAl₃ + Ti₃Al double-layered structure with the thickness of 2.5 ~ 6 μm was formed at the top and middle parts, while a single TiAl₃ layer with the thickness of about 1 μm was formed at other parts. When E is in the range of 1.02 − 1.11 kJ/cm, the joint was well formed and a TiAl₃ layer with the thickness of about 0.7 − 1.5 μm was formed at the Ti/Al interface. In the selected processing range, the average tensile strength of the joint increases gradually with the increase of E, the ultimate tensile strength for the joints absent of forming defects can reach 232 MPa.