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.