Optimisation of Bead Geometry of Pulsed GTAW Process for Aluminium Alloy 7039 Using Ar + He Gas Mixtures

The present paper depicts the application of pulsed gas tungsten arc welding (pulsed GTAW) for aluminium alloy (AA7039) using various Ar + He (Argon + Helium) mixtures as a shielding gas with sinusoidal AC wave. In this investigation, Taguchi method is used to formulate the experimental layout, to analyse the effect of each process parameter on the bead geometry, and to predict the optimum setting for each welding process parameter. The pulsed GTAW process is employed for a high rate of current rise and decay at a high pulse repetitive rate, which is widely used in the joining of precision parts. Zinc is usually added to improve mechanical properties through formation of hard intermediate phase, such as Mg₂Zn. The main aim of pulsing is to achieve maximum penetration without excessive heat built-up. The use of high current pulses is to penetrate deeply and allow the weld pool to dissipate some of the heat during a proportionately of longer arc period at a lower current. AA7039 is employed in aircraft, automobiles, high-speed trains and high-speed ships due to their low density, high specific strength and excellent corrosion resistance.