INFLUENCE OF THE TIG WELDING PROCESS PARAMETERS ON THE PERFORMANCE OF DISSIMILAR ALUMINUM ALLOY WELD JOINTS

Abstract

Pulsed TIG in its simplest form is a system in which the arc current alternates between two levels, heating and fusion takes 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 2xx.x series Al-Cu alloys have high strength at room and elevated temperatures and have high toughness. These alloys are principally used in aircraft, automotive applications (engines). The non- heat treatable 4xx.x series Al-Si alloys have good castability and weldability. These alloys have been using extensively in dental equipment, marine and architectural parts. The _nonheat treatable 5xx.x series Al-Mg alloys have reasonably high strength, good resistance to corrosion. These alloys are principally used in aircraft and high way fittings. In the present investigation, pulsed TIG welding for two dissimilar combinations of Aluminum alloys has been done. First dissimilar combination is a heat treatable and non heat treatable Al alloy combination AA206-AA443. Second dissimilar combination is A1-5%Mg-Al-3.6%Mg. Attempts have been done to improve the mechanical properties of first dissimilar combination (AA206-AA443) by two different methods • Post weld heat treatment [T6 condition] • Work hardening by warm rolling [hot rolling + cold rolling] And only post weld heat treatment (T6 condition) has been done to improve the mechanical properties of second dissimilar combination (Al-5%Mg — Al-3.6%Mg). The effect of pulse parameters and strengthening processes on the microstructure and mechanical properties of weld joints like tensile strength and hardness was observed for both dissimilar combinations. It was found that pulse parameters have a significant effect on micro structure and mechanical properties of the pulsed TIG weld joint. Hardness and tensile strength was found higher for low frequencies and shorter duty cycles. It was also observed that warm rolling process improves the mechanical properties of the dissimilar weld combination AA206-AA443 more effectively than post weld heat treatment (T6) process.