Chemical composition and microstructure in pulsed MIG welded Al-Zn-Mg alloy

Abstract

Pulsed MIG welding of Al-Zn-Mg alloy has been carried out by using extruded sections of base material and Al-Mg (5183) filler wire. During welding the pulse parameters such as the mean current and pulse frequency are varied and their effect on the chemical composition, susceptibility to precipitation, morphology and hardness of weld bead have been studied. For a comparative study weldments are also prepared by using conventional continuous current MIG welding process, where the welding currents equivalent to that of mean currents of pulsed process are used. The characteristics of weld bead concerning the aspects mentioned above are found to be affected by the mean current and pulse frequency. The hardness of weld bead has been found to be governed by the precipitation as well as the morphology of weld bead, where the presence of a higher amount of zinc in it results in enhancement in the precipitate ((Al, Zn)49Mg32) content and the coaxial growth of dendrite favours the increase in hardness of weld bead.