Effect of Pulsation in Microstructure and Mechanical Properties of Titanium Alloy-Annealed Welded Joints at Different Temperatures

Abstract

Thin sheets of Ti-6Al-4V alloy of thickness 1 mm were butt welded using a pulsed Nd-YAG low-power laser setup. The goal of this research is to explore the influence of pulsation on the microstructure and mechanical properties. In addition to that, annealing at different temperatures has been performed to compare the results of pulsation and heat treatment. The results indicate that after annealing at 980 °C, the structure completely transformed into an equiaxed structure. When annealed at 1010 °C, almost the total area is composed of an equiaxed α phase, and the grains are coarse as compared to the previous. This suggests that the grain size becomes thicker when the annealing temperature is raised above 980 °C. The volume fraction of the equiaxed structure is maximum. It can be deduced that the volume–fraction is dependent on the annealing temperature. The volume fraction of the equiaxed structure increases as the annealing temperature increases. A higher tensile strength value of the sample annealed at 980 °C was found as compared with the overlapped sample (A-2). The fusion zone overlapped sample (A-2) shows high hardness with a value of 397 HV1. In the FZ sample, annealing at 980 °C has a hardness of 386 HV1. The (A-2) sample indicates higher (3–4%) hardness as compared to the annealed sample at the FZ. The β phase is increased by 16% in the XRD analysis of the overlapped samples. Hence, it is evident that the amount of β phase has increased during heating, and a complete transformation has taken place at a temperature of 958 °C.