Combined Effect of Gas Tungsten Arc Welding Process Variants and Post-Weld Heat Treatment on Tensile Properties and Microstructural Characteristics of Ti-6Al-4V Alloy Joints

In aerospace and chemical industries, Ti-6Al-4V alloys are mostly used due to outstanding resistance to corrosion and high specific strength. Gas tungsten arc welding (GTAW) process is generally preferred to join Ti-6Al-4V alloy, but width of bead and heat-affected zone are wider in these joints. To overcome these problems, pulsed current gas tungsten arc welding (PC-GTAW), one of the variants of GTAW process, was employed to join Ti-6A-4V alloy. Recently, gas tungsten constricted arc welding (GTCAW) process, a new advanced variant of GTAW process, was developed. It creates high-frequency current level variation in the arc to produce low heat input, narrow fusion zone and heat-affected zone with deeper penetration compared to conventional GTAW and PC-GTAW processes. The present research work is focused to understand the influence of the post-weld heat treatment on tensile properties, microhardness and microstructure of Ti-6Al-4V alloy joints welded by GTAW, PC-GTAW and GTCAW processes. High frequency resulted in appreciable refinements of prior beta grains prime to higher tensile properties, hardness and elongation of joints in the as-welded condition. The post-weld heat treatment (PWHT) at 910 degrees C resulted in enhancement in elongation and deterioration in tensile strength due to coarsening of alpha and disintegration of alpha-martensite into symmetrical alpha and beta. However, pulsed gas tungsten constricted arc welded (P-GTCAW) joints showed greater tensile elongation even in PWHT conditions.