Elimination of pores and microstructural characterization in Ti-6Al-4V alloy welds using fast-frequency double pulse TIG welding

This study utilizes a fast-frequency double pulse tungsten inert gas (FFDP TIG) process to weld 2 mm thick Ti6Al-4V alloy, with the objective of investigating the influence of a large fast-frequency current amplitude on porosity, microstructure, and tensile properties of the weld joint. Unlike conventional TIG welding, the FFDP TIG welding process led to a reduction and elimination of porosity, and refined the prior (3 grain and alpha phase by 34.3 % and 33.3 %, respectively, while also refining the martensitic alpha ' structure. Stirring of the molten pool resulted in improved uniformity of grain orientation distribution, accompanied by decreased variant selection of the alpha phase and reduced texture strength of the alpha phases. Moreover, three-variant clusters of alpha/alpha ' phases with triangular morphology and micro- and nanoscale recrystallized alpha grains appear in the FFDP TIG weld. Concurrently, the FFDP TIG process significantly enhanced the tensile strength and ductility by 14.5 % and 114 %, respectively, compared to the conventional TIG process.