Mechanisms of equiaxed grain formation in ferritic stainless steel gas tungsten arc welds

Mechanisms of providing nuclei for equiaxed grains in gas tungsten arc welds in ferritic stainless steel were examined. Tin-quenching of the solid-liquid interface revealed that TiN particles in commercial steels could act as heterogeneous nucleation sites. Direct additions of TiN also promoted an equiaxed region. However, no evidence for equiaxed grain formation by dendrite fragmentation was observed, despite the fact that titanium additions did produce a more branched dendritic structure.