A Comparative Analysis of the Influence of Welding Current on Microstructure and Mechanical Properties in TIG Welded Ti5Al2.5Sn Alloy

Abstract

Tungsten inert gas (TIG) welding was performed on a 1.6 mm thick Ti5Al2.5Sn alloy sheet to analyze the influence of welding current on the resultant microstructure and mechanical properties in the weldments. Fusion zone (FZ) width was observed to increase with increasing the welding current. The heat-affected zone (HAZ) showed acicular α, primary α and α' martensite phases depending upon the cooling rate. FZ was comprised of α´ martensite at the high cooling rate, acicular α at a low cooling rate and some retained β. The ultimate tensile strength (UTS), notch tensile strength (NTS) and impact toughness in all the weldments increased from 754 MPa to 810 MPa, 703 MPa to 785 MPa, and 2.3 J to 3.3 J, respectively, by increasing the welding current. However, percentage elongation decreased from 10% to 6.5% by increasing the welding current from 12 A to 18 A. Moreover, the impact toughness value was observed to increase by increasing welding current owing to the formation of a higher proportion in acicular α, α' martensite phases within the FZ. Furthermore, higher microhardness was achieved at higher currents.