Synchrotron X-ray diffraction analysis of the microstructure of the Ti-6Al-V-Mo-Zr/Al-Cu-Li dissimilar joints produced by CO2 laser welding

The paper presents the results of both microscopic and synchrotron X-ray diffraction analysis of the microstructure of the dissimilar Ti-6Al-V-Mo-Zr/Al-Cu-Li butt laser welds, as well as their mechanical properties. While the thickness of the welded plates (2 mm), the power (1.2 kW) and velocity (1 m/min) were constant, the variable parameter has been the laser beam offset towards the titanium alloy plate (from 0 to 1 mm). The offset has replaced a conventional joining process (via mixing both molten base metals) into a welding-brazing. The conventional joints have consisted of a separate aluminium melting zone (Al FZ) and a mixing zone (MZ). The Al FZ has contained typical secondary aluminium alloy phases and the TiAl3 intermetallic particles, while the α2Ti3Al, β2-Ti and γTiAl compounds have been found in the MZs. With rising the beam offset value, mechanical tests have shown an increase in the ultimate tensile strength of the welded joints from 74 up to 168 MPa.