PULSED CURRENT GMAW OF AI-Li ALLOY SHEET

Abstract

Welds are replacing rivets in a variety of components in both military and commercial airplanes, to improve both cost and structural integrity. Aluminum-lithium alloys are the most recently developed high performance wrought aluminum alloys, primarily intended for aircraft and aerospace structures, they are also known to have excellent fatigue and cryogenic toughness. Welding of Al-Li alloys using gas metal arc welding (GMAW), GTAW, variable polarity plasma arc welding, electron beam welding, laser beam welding, resistance welding and friction stir welding has been reported in the literature. Even though the power beam welding processes yield better weldment strengths compared to that of are welding processes, for wider application, investigations on thicker sections using rather inexpensive processes need to be carried out. Pulsed welding is a controlled method of spray transfer, in which. the arc is maintained at a value high enough to permit spray transfer and for long enough to initiate detachment of a molten droplet. Once the droplet is transferred the current is reduced to a relatively low value to maintain the arc. It has been reported in the literature that weld penetration in these alloys increased with increasing lithium content, perhaps owing to a decrease in thermal conductivity with addition of lithium. This motivates usage of lower energy density processes like GMAW for these alloys. The present investigation is carried out on an Al-Li alloy, AA8090, by continuous current GMA welding and Pulsed current GMA welding process. By varying the 0 parameter indirectly controlling the pulse parameters, and obtaining the lowest heat input and checking the metallurgical properties and mechanical properties of weld joints is been studied.