Yb:Fiber Laser Joining of Ti-6Al-4V and AA6013 Dissimilar Metals

Titanium and aluminum alloys have been considered to applications involving structural components of aircrafts. The use of laser beam in the joining of dissimilar metals can reduce or generates acceptable limits of brittle intermetallic compounds in the junction interface. In the present work, Ti-6Al-4V and AA6013 sheets (thicknesses of 1.0 mm and 1.6 mm, respectively) were joined by a Yb:fiber laser welding system. Butt joints were conducted by varying the laser offset toward Al alloy, 0 to 0.5 mm, and maintaining fixed the welding speed and the laser average power, 3.0 m/min and 1000 W, respectively. Helium with a flow rate of 45 l/min was used as shielding gas. Metallographic analyses were performed on the joint cross-section by optical microscopy. The laser offset has great influence on the formation of the joints. Between 0.2 and 0.4 mm, the titanium alloy side is not melted, promoting a smooth joint with no severe defects. On other hand, when the laser offset was nearly of gap between sheets, a mixed region of titanium and aluminum were formed developing a brittle weld region with the presence of pores and cracks. The microhardness profiles of cross-section of the joints with 0.2 to 0.4 laser offset were evaluated. The results show that the hardness in the zone affected zone (HAZ) adjacent to the interface at titanium alloy side is higher than of the titanium base metal. As expected, the melted aluminum region presets a decreasing of the hardness value when compared to aluminum alloy base metal. The hardness of intermetallic metal compound layer is not measured due to its thin thickness, of order 10 µm.