Effect of modified AA4043 filler on partially melted zone cracking of Al-alloy gas tungsten arc welds

Abstract

The effect of grain refiners (zirconium, Tibor and scandium) added to the fusion zone through AA4043 filler on the partially melted zone (PMZ) cracking in gas tungsten arc (GTA) welded AA6061 alloy was investigated. Welds of AA6061 in thermal tempers of artificially aged condition (T6) were made with continuous current and pulsed current techniques. Varestraint testing was carried out to study PMZ cracking in welds, and optical SEM examination performed to evaluate it. Addition of grain refiners to the fusion zone improved the PMZ cracking resistance very significantly. Pulsed current technique was also found to improve the resistance to PMZ cracking, as a result of the possible reduction in the strain in the PMZ owing to the ductile fine grained fusion zone. Severe PMZ cracking in the welds of AA4043 filler without grain refiners was attributed to a greater amount of silicon rich eutectic at the grain boundaries of the PMZ.