STUDIES ON WELD PROPERTIES OF PULSED CURRENT MIG WELDED ALUMINIUM

Abstract

The influence of pulse parameters (mean current, pulse duration and pulse frequency) on the microstructure, hardness and tensile properties on the pulsed MIG welded aluminium were investigated. Continuous current (0 Hz) MIG welds were also prepared to compare itself in microstructure, hardness and tensile properties with that of the pulsed MIG welds. The microstructure close to fusion line has been found to have significant recrystallization and grain growth. The recrystallization and grain growth of HAZ are found to be comparatively less at the pulse frequencies at around 33 Hz and 50 Hz and comparatively high at the pulse frequency 100 Hz. The coarsening of HAZ microstructure has been found to be comparatively reduced during welding by pulsed current process when compared with that of continuous current process. The fracture surfaces of the tensile specimens were found to have significant amount of porosity. The porosity content of this area, has been found to vary with the pulse parameters. The tensile strength and elongaiton of the pulse current MIG welds has been found to be comparable with those of the conventional MIG welds when it is prepared at the mean current and pulse frequency of 220 A and 50 Hz respectively. The hardness behaviour of weldmetal and HAZ at different process parameters has also been investigated