Hydride or martensite? Identification of a new phase in cold-rolled hexagonal close-packed Ti

Two types of lamellar gamma-phases are observed in cold-rolled pure alpha-Ti: the P-type adopting [0001](alpha)//[001](gamma) and (10 (1) over bar0)(alpha)//(110)(gamma), and the B-type adopting [2 (1) over bar(1) over bar0](alpha)//[101](gamma) and (0001)(alpha)//((1) over bar(1) over bar1)(gamma). By using high-resolution transmission electron microscopy, selected area electron diffraction and stereographic projection, the gamma-phase is identified to have a face-centered tetragonal (fct) structure. In situ heating experiment further confirms the yphase to be hydride (TiH) precipitate in alpha-Ti. This work provides convincing evidences that the so-called stress-induced face-centered cubic (fcc) martensite in deformed alpha-Ti reported previously could be mistakenly identified. Available approaches to distinguish the fcc-Ti martensite from the fct-hydride are also discussed.