Macrosegregation mechanisms in arc welds made with dissimilar filler metals

More often than not, filler metals differ from the workpiece in composition. To study macrosegregation in a single alloy system, alloy Cu-30Ni was arc welded with seven different filler metals, including Cu, Cu-12Ni, Cu-22Ni, Cu-30Ni, Cu-45Ni, Cu-67Ni and Ni. It was explained that liquid 1 flowing into liquid 2 of a different composition can cause macrosegregation if liquid 2 is below the liquidus temperature of liquid 1 to make liquid 1 freeze quickly. The liquidus temperatures of the base metal T-LB and the bulk weld metal T-LW were compared. All four mechanisms proposed recently by the authors were identified: mechanisms I (T-LW<T-LB and quick freezing along pool boundary), II (T-LW>T-LB and quick freezing along pool boundary), III (T-LW<T-LB and quick freezing near pool bottom) and IV (T-LW>T-LB and quick freezing near pool bottom).