Comparison of joint performance between spot weld bonding and resistance spot welding of titanium alloy

The technology of spot weld bonding and resistance spot welding was applied to 1.5 mm titanium alloy sheet. The spot weld bonding and resistance spot welding joints were acquired under different welding current. The joint strength and failure feature between spot weld bonding and resistance spot welding (RSW) were compared by C-scan images of nuggets, the failure load of joints and fracture morphology. Results show that the change A-scan signals and the characteristics of C-scan images can divide heat affected zone, melting area, nugget zone. It can detect nugget diameters and weld defects of joints, too. The nugget diameters of joints increase with the increase of welding current. When the welding process parameters are the same, the nugget diameters of spot weld bonding is generally larger than the nugget diameters of resistance spot welding. But their strength is similar. When the welding current is changed from 7.0 kA to 8.5 kA, there are many different size dimples of the fracture surface, which present ductile fracture. When the welding current is 10.0 kA, the joints are mainly ductile fracture and quasi-cleavage fracture.