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

Abstract

The textures and grain sizes within the heat affected zone (HAZ) and weldmetal regions of single phase bcc (Fe-3 wt% Si; 430 stainless steel) and fcc (AA5182 and 5251) alloys in spot and metal inert gas (MIG) welds have been determined using electron back-scattered diffraction (EBSD); optical and scanning electron microscopy (SEM) techniques. In all the situations studied, the grains that developed into the columnar weldmetal grains from the HAZ had a misorientation of less than 10° between and the maximum thermal gradient (∇Tmax). The initial weldmetal columnar grain width can be related to the HAZ grain diameter at the fusion boundary by a simple relationship involving the proportion of grains with the favourable low misorientation texture in weldmetal and HAZ. This relationship does not hold throughout the whole weldmetal region due to competitive growth between columnar grains (steel) and a columnar-to-equiaxed transition (CET; Al-based alloys).