THE DEVELOPMENT OF TEXTURES AND MICROSTRUCTURES IN ALPHA/BETA TITANIUM ALLOYS

The preferred orientation of crystals, or texture, is a very important phenomenon in Ti alloys, as the hexagonal close packed (hcp) α phase is highly anisotropic, which makes the properties of the alloys extremely sensitive to the orientation distribution of this phase. Moreover, since there is an orientation relationship (OR) – the so called Burgers OR-between the low temperature α phase and the high temperature body centered cubic (bcc) β phase in microstructures directly developed from the β phase by cooling, the texture of the β phase also becomes important. Additionally, the distribution of strains between the two phases during deformation is also dependent to an extent on the texture of these phases. In this study, the relationship between the texture and the microstructure of both β processed and α/β processed Ti alloys has been examined. In the β-processed microstructures, the α phase appears in a lath morphology, in which there is generally a major growth direction, a broad face, a side face and an edge face. It has been observed that there are twelve possible variants of these α laths in a single prior β grain. These comprise of six pairs, the members of which share a common {0001} plane