STUDIES ON HEAT TREATABLE ALUMINUM WELD JOINTS PRODUCED BY PULSE TIG WELDING

Abstract

Pulsed Tungsten Inert Gas welding is a process 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. Pulse TIG welding optimizes the heat input with proper heat distribution while maintaining stable arc. Al- Zn-Mg, Al- Cu alloys are high strength heat treatable aluminum alloys used in aircraft industry, automobile industry and for high strength applications. Al-Si alloys are mainly used in wear resistance applications and used as filler wire for welding Al- Mg-Si, Al- Cu alloys. The good flow characteristics of these alloys render them for casting of complex designs. In this investigation two Al- Cu alloys, two Al- Si alloys and one Al- Zn-Mg alloy were welded using pulse TIG welding_ The effect of pulse parameters on micro structure and mechanical properties of weld joints like tensile strength and hardness was observed. It was found that pulse parameters have a significant effect on micro structure and mechanical properties of the weld joint. Short pulse duration produced higher weld bead hardness. High strength was found with lower frequency weld joints. Partial melting of grains and grain boundaries increases with increase in peak current and pulse duration. iii