Characterisation of laser welded dissimilar Ti/steel joint using Mg interlayer

Abstract

Fibre laser welding of Ti–6Al–4V alloy to AISI 304L stainless steel (SS) using an Mg interlayer was developed. The microstructure and fracture behaviour of the joints were analysed by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Accepted joints could be obtained under the optimised welding parameters. The cross-weld tensile strength of the joints was up to 221 MPa, recovering 94% of commercial AZ31B Mg alloy. The intermetallic compound of Mg₁₇Al₁₂ was observed in the Ti/weld interface, while no intermetallic compound was found in the SS/weld interface. The joints all fractured at the interfaces, but the fracture location changed from the SS/weld interface to the Ti/weld interface as the laser power was >2·5 kW. Furthermore, the strong links between laser power and joining mechanism were found and discussed by the experimental results.

Keywords:

• Laser welding
• Dissimilar metal
• Titanium alloy
• Stainless steel