Microstructure and mechanical properties of AA7075(T6) hybrid laser/GMA welds

The weldability of AA7075 using a hybrid laser/gas metal arc (GMA) welding process was examined. After welding process optimisation, the influence of filler wire composition, natural ageing, artificial ageing and a short duration solution heat treatment was investigated to enhance weld microstructural and mechanical properties. Results show that after a short solution heat treatment, a large fraction of the dendrite boundaries in the weld fusion zone dissolved in the primary phase. Tensile tests and micro-hardness tests show that the weld has a comparable strength to the T6 base alloy when welding with an AA2319 consumable. Fracture surfaces observed under a scanning electron microscope indicate a large number of fine ductile type voids and larger sized dimples. The improved ductility of the weld together with the strength comparable to the base alloy make the weld more formable than none solution heat-treated welds.