Microstructure and residual stresses in Ti-6Al-4V alloy pulsed and unpulsed TIG welds

Increasing the pulse frequency in pulsed Tungsten Inert Gas arc welding refines the prior-β grain size in the fusion zone of Ti-6Al-4V alloy compared to unpulsed process. The microhardness increases in the fusion zones (FZs) obtained with pulsed welding process with respect to their microstructural evolution. The increase of the pulse frequency contributes to the formation of a significant amount of residual β phase in the FZ which is accompanied by a decrease of its microhardness. The tensile residual stresses (RSs) level in the pulsed process is lower than the one of the unpulsed one. The tensile RSs induced by both welding processes in the heat affected zone (HAZ) are found to decrease when increasing the pulse frequency. In the FZ, the transversal RSs are of compressive type for both processes whereas the longitudinal ones change from tensile to compressive type when increasing the pulse frequency.