Effect of welding parameters on morphology and mechanical properties of Ti-6Al-4V laser beam welded butt joints

The influence of welding speed and laser power on weld quality of 1.6 mm thick Ti-6Al-4V sheets autogenously laser beam welded in butt configuration using a Nd-YAG laser was studied. The joint quality was characterized in terms of weld morphology, microstructure and mechanical properties. An underfill defect, controlling the whole weld geometry, was observed both at the weld face and root surface. In dependence of the specific heat input, this defect showed a maximum, which separates two different welding regimes: keyhole welding, at low heat input, and a welding regime where heat conduction around the keyhole is predominant, at high heat input. Influence of the underfill radius on the weld fatigue life was also assessed.