Effect of pulsed welding current on the solidification structures in Al-Li-Cu and Al-Zn-Mg alloy welds

The refinement of weld fusion zone microstructures helps in reducing hot cr acking and improving the weld metal mechanical properties. Pulsing of the w elding current is one technique that could provide such grain size reductio n. In the current work, gas tungsten-arc welding was used to deposit welds in Al-Li-Cu and Al-Zn-Mg alloys both in the pulsed and unpulsed modes. Curr ent pulsation was found to induce grain refinement in three ways: by reduci ng the columnar grain size towards the weld centre, widening of the chill z one adjacent to the fusion boundary and producing a number of fine-grained bands across the length of the weld. While the reduction in average grain s ize improved tensile elongation, the strength was not much affected. The hi gher ductility of the pulsed welds was maintained in the peak-aged conditio n also.