Development of Texture from the HAZ to Weldmetal Across the Fusion Boundary

Abstract

The textures and grain sizes within the heat affected zone (HAZ) andweldmetal regions of single phase bcc (Fe-3 wt% Si; 430 stainlesssteel) and fcc (AA5182 and 5251) alloys in spot and metal inert gas(MIG) welds have been determined using electron back-scattereddiffraction (EBSD); optical and scanning electron microscopy (SEM)techniques. In all the situations studied, the grains that developedinto the columnar weldmetal grains from the HAZ had a misorientation ofless than 100 between < 100 > and the maximum thermal gradient (delT(max)). The initial weldmetal columnar grain width can be related tothe HAZ grain diameter at the fusion boundary by a simple relationshipinvolving the proportion of grains with the favourable lowmisorientation texture in weldmetal and HAZ. This relationship does nothold throughout the whole weldmetal region due to competitive growthbetween columnar grains (steel) and a columnar-to-equiaxed transition(CET; Al-based alloys).