The refinement of weld fusion zone microstructures helps in reducing hot cracking and improving the weld metal mechanical properties. Pulsing of the welding current is one technique that could provide such grain size reduction. 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. Current pulsation was found to induce grain refinement in three ways: by reducing the columnar grain size towards the weld centre, widening of the chill zone 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 size improved tensile elongation, the strength was not much affected. The higher ductility of the pulsed welds was maintained in the peak-aged condition also.