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 β grains prime to higher tensile properties, hardness and elongation of joints in the as-welded condition. The post-weld heat treatment (PWHT) at 910 °C resulted in enhancement in elongation and deterioration in tensile strength due to coarsening of α and disintegration of α-martensite into symmetrical α and β. However, pulsed gas tungsten constricted arc welded (P-GTCAW) joints showed greater tensile elongation even in PWHT conditions.