A study on the feasibility of friction stir welding in joining dissimilar metals for SS400 and Ti-6Al-4V

Abstract This study designed friction stir multi-pass welding machine to conduct friction stir welding on carbon steel/titanium alloy clad sheets. The experimental process utilized the pin and pinless tools. The results demonstrate that the two dissimilar materials can be welded using the assembly-embedded rod pinless tool under the following welding conditions: a rotational speed of 1200 rpm, a downward force of 4 kN, a welding speed of 15 mm/min, and tool offset distances of 5 and 10 mm. Furthermore, this study investigated the microstructure and mechanical properties of the weld. In addition, the peak temperature measured at the joint interface exceeded the β phase transition temperature of the titanium alloy and surpassed 1000°C. The shear tensile test shows the weld’s failure load was about 4300 N. The intermetallic compound at the welding interface has a microhardness value of approximately 400 Hv. According to the results of SEM observations and EDS composition element analysis, the elements of low carbon steel and titanium alloy at the interface of the clad sheet diffused and formed Fe-Ti intermetallic compounds.