Determination of α lamellae orientation in a β-Ti alloy using electron backscatter diffraction

The spatial orientation of α lamellae in a metastable β-Ti matrix of Timetal LCB (Ti-6.8 Mo-4.5 Fe-1.5 Al in wt%) was examined and the orientation of the hexagonal close-packed α lattice in the α lamella was determined. For this purpose, a combination of methods of small-angle X-ray scattering, scanning electron microscopy and electron backscatter diffraction was used. The habit planes of α laths are close to {111}_β, which corresponds to (1320)_α in the hexagonal coordinate system of the α phase. The longest α lamella direction lies approximately along one of the 〈110〉_β directions which are parallel to the specific habit plane. Taking into account the average lattice parameters of the β and α phases in aged conditions in Timetal LCB, it was possible to index all main axes and faces of an α lath not only in the cubic coordinate system of the parent β phase but also in the hexagonal system of the α phase.