Effect of Laser Spot Welding Variables on Microstructure and Mechanical Properties of the Ti-6AL-4V to AISI304 Dissimilar Joint

In this project, joining Ti-6Al-4V and AISI 304 dissimilar plates by laser-spot-welding method has been studied. In this regard, Ti-6Al-4V and AISI 304 plates, with a thickness of 0.7 and 0.5 respectively, were lap-welded using an interlayer of 0.2 & 0.3 mm copper and silver (pure silver). The process was done by 400Watt pulsed laser (Nd:YAG) using oncentric spot welding with 4mm diameter circles as lap welding. Once the spots were created, they got studied and surveyed first by eye inspection, then by optic metallography inspection and finally, by tensile strength and SEM; of course, if cracks were not detected on joining. The results proved copper a better interlayer compared to silver: no joining occurred while using silver as an interlayer for 3 milliseconds, and replacing the upper metal didn’t change the outcome. The best joining result was observed when AISI 304 was placed above (near the laser), copper plate interlayer was used in 7 milliseconds, with 15 Hz frequency, 10.7 J heat input and 1.5 KW peak-power. This way, sheer strength equaled 160 MPa and micro hardness equaled 504 HV.