Microstructural evolution and micro-texture in Zr-2.5Nb tubes

Both small experimental extruded tubes and full-size pressure tubes were examined using scanning electron microscope/electron backscattered diffraction (SEM/EBSD) and transmission electron microscope/selected area diffraction (TEM/SAD). The final microstructures and textures vary with billet microstructure, extrusion temperature and extrusion ratio. Three components in {0002} pole figures were determined. The first component (radial) is produced by a and c+a slip in a-grains during extrusion. The second component (transverse) is associated with the elongated alpha-grains with their c-axes parallel to their long dimension. The third component (axial) is produced by beta-alpha phase transformation after extrusion with a preferred variant of the Burgers relationship.