Influence of welding techniques on microstructure and pitting corrosion behaviour of 1441 grade Al–Li alloy gas tungsten arc welds

Abstract

The effects of changing the welding technique on the weld bead solidification structure and resistance to pitting corrosion of an aeronautical grade Al-Li based alloy have been studied. Russian alloy 1441, with a nominal composition Al-1.9Li-1.8Cu-1.0Mg-0.1Zr (wt-%) and in the form of sheet, was welded using constant current, pulsed current and arc oscillation gas tungsten arc welding techniques. Under the optimum conditions of welding, the solidification structure was coarse columnar in constant current welds, fine equiaxed in pulsed current welds and fine equiaxed intermixed with fine cellular grains in arc oscillation welds. The distribution of interdendritic (and intergranular) non-equilibrium solidification products became increasing discrete on changing from constant current to pulsed current and arc oscillation welding. Resitance to pitting corrosion was found to be greatest in welds having a discrete second phase distribution, i.e. those produced using the pulsed current and arc oscillation methods.