Vertical-Up Gas Tungsten Arc Welding of Ti6Al4V Alloy and Characterization

Abstract

Gas tungsten arc (GTA) welding of Ti alloy Ti6Al4V is carried out in vertical-up direction. Weld parameters for the Ti6Al4V alloy were developed using Ti6Al4V (ELI) alloy filler wire and following two pass welding process. X-ray radiography was carried out to ensure the soundness of the weld. Tensile strength of the weldment was evaluated and microstructure characterization was carried out. It is observed that specimens mostly failed in heat affected zone (HAZ) area toward parent material with occasional failure at the weld. Microhardness mapping and microstructural analysis revealed HAZ as the weaker zone, where dissolution of α and formation of β have initiated. Due to moderate cooling rate at this zone, microstructure remained α–β, whereas weld microstructure is found to have martensitic α′ resulting in an increase in the microhardness. Yield strength (YS) of weldment is found to be more than 90% of parent metal (PM) and also reduction in elongation is noted. Fractography observations of failed specimen away from the weld show mainly ductile failure. Weldment failure fractography shows the presence of dendrite indicating failure near the fusion line.