Study of texture in a TiTaNb alloy using electron back scattered diffraction technique

The development of texture during the β → α transformation of a deformed and β-annealed alloy of Ti–5Ta–1.8Nb has been studied using electron back scattered diffraction (EBSD) technique. The microstructures that develop during the above transformation have been characterized and correlated to their mechanism of formation. The X-ray diffraction studies of the wire-drawn alloy suggested a development of characteristic (1 0.0) type of deformation texture. Diffusion controlled slow transformation of the alloy from above the β-transus resulted in a completely different type of texture. The microstructure of this transformation product consisted of colonies of alternate lamella of coarse-α and fine-β together with α along the prior-β grain boundary. EBSD results show that the crystallographic orientation of α lamellae within a colony remains same and changes across the colonies. The observation of a high full width at half maximum (FWHM) due to scatter of the α poles suggests a deviation from an exact Burgers relation. Comparison of experimentally measured misorientation angle between different α-colonies with calculated values based on Burgers relation enabled the identification of orientation of the parent-β grain. Thus a method to characterise the diffusion controlled β → α + β transformation in the Ti–5Ta–1.8Nb alloy has been developed combining microscopy with EBSD studies.