Effect of welding techniques on microstructure and mechanical properties of aluminium-lithium alloy welds

The tensile properties and fatigue crack growth behaviour of sheets of an Al-1.9Li-1.8Cu-1.0 Mg-0.1Zr alloy welded under different conditions were evaluated. The basic welding technique was constant current (CC) gas tungsten arc (GTA) welding. Two modifications viz. pulsed current (PC) and magnetic arc oscillation (AO) were introduced to study effects on microstructure and properties. Both PC and AO resulted in microstructural refinement in the fusion zone. The tensile residual stresses present in CC welds reduced when either PC or AO welding was used. The tensile strength and ductility increased, and fatigue crack growth rates lowered when PC or AO conditions replaced CC welding.