The precipitation of γ-deuterides (hydrides) in titanium

Abstract The crystal structure of titanium deutende precipitates in specimens of titanium containing up to 0.64 at.% deuterium was found to be face-centred-tetragonal TiD, c a = 1.12 , isomorphous with γ-ZrH, in agreement with recent findings of Numakura and Koiwa. This deutende phase was observed by transmission electron microscopy to precipitate on prism habit planes, and near-basal habit planes {2027}, about 27.5° from the basal plane. These habit planes can be related to dislocation mechanisms for the formation of γ by a martensitic transformation. In particular, the calculated near-basal habit plane is in reasonable agreement with observation, while the prism habit plane is the result of a plane strain transformation. Complex precipitation was found to be rather common, an example of a prism habit γ-plate consisting of sub-units of near-basal γ-laths is shown. Experimentally, the presence of γ Ti interfacial ledges with effective displacement vectors in the 〈 a 〉-direction is consistent with the proposed mechanism of formation of γ-plates with prism habit planes.