Hot-pressed 3 mol% Y 2O 3 partially stabilized ZrO 2 was reacted with titanium at 1550°C/30 min. The interface was characterized by analytical transmission microscopy (transmission electron microscopy/energy-dispersive spectroscopy). The lamellar and the spherical Ti 2ZrO as well as the orthorhombic β′-Ti were found to exist in the titanium side after cooling down to room temperature. The crystal structures of the lamellar and the spherical Ti 2ZrO were orthorhombic and hexagonal, respectively. On heating, the dissolution of a large amount of zirconium and oxygen into titanium gave rise to the metastably supersaturated disordered α-Ti(Zr, O) solid solution where two different Ti 2ZrO phases subsequently precipitated, while the β-Ti coexisting with α-Ti at high temperatures was transformed to the orthorhombic β′-Ti during cooling. The spherical hexagonal Ti 2ZrO was an ordered structure, with Zr and O occupying substitutional and interstitial sites, respectively. The orientation relations between α-Ti and the lamellae orthorhombic Ti 2ZrO were determined to be  α-Ti// Ti2ZrO and (101̄0) α-Ti// (11̄0) Ti2ZrO; meanwhile, those between the α-Ti and the spherical hexagonal Ti 2ZrO were  α-Ti// Ti2ZrO and (101̄0) α-Ti// (101̄0) Ti2ZrO.