STUDIES ON THE MECHANICAL PROPERTIES AND MICROSTRUCTURE OF PULSED TIG WELDED JOINTS OF Al-Mg-Si ALLOYS

Abstract

Pulsed TIG in its simplest form is a system in which the arc current alternates between two levels, heating and fusion take place during the periods of higher current, with cooling and solidification during the periods of low current. PGTAW process optimizes the heat input with proper heat distribution while maintaining stable arc characteristics. The heat-treatable 6000 series Al Mg Si alloys, with medium to high strength, excellent formability and good corrosion resistance, possess great application potential in industries. These alloys are principally used in automotive, pipe, structural, railings and extruded parts. In this work, Al-Mg-Si alloys were welded by Pulsed TIG welding process to investigate the influence of pulse frequency, peak current, pulse duration and duty cycle on microstructure and mechanical properties such as hardness and tensile strength. It was observed that pulse TIG welding produced finer grain structure of weld metal than conventional TIG. welding. Hardness was found higher for shorter pulse duration. High tensile strength was also observed with shorter duty cycles than longer duty cycles.