The orientation relationship between the α- and ω-phases of titanium and zirconium

High-pressure treated titanium and zirconium have been investigated by means of transmission electron microscopy. The specimens consisted mainly of retained ω-phase, while in some regions α-phase platelets were observed. Two crystallographically nonequivalent sets of matrices of correspondence between the α- and ω-phase were calculated using known matrices for the α- and β-phases and for the β- and ω-phases. It is shown that one of the two sets of matrices is valid for description of mutually parallel directions in the atomic and reciprocal lattices. The orientation relationship as defined by this set of matrices may be given in the form (001)α ∥︁ (011)ω, [100]α ∥︁ [211]ω. A possible mechanism of the α ⇄ ω transformation is proposed.