Hydrogen absorption/desorption behavior of Ti–22Al–27Nb alloys with β0 single-phase and β/O two-phase microstructures

We investigated multiphase effects on the hydrogen absorption/desorption behavior at 100 °C of a ternary alloy (Ti–22Al–27Nb (at.%)) whose microstructure consists of β0(B2) single-phase and β(bcc)/O(orthorhombic, based on Ti2AlNb) two-phase structures. The β–γ hydride transformation is generally very sluggish in this alloy. However, when the O phase exists in the β matrix phase, the β–γ hydride transformation occurs and the reversible absorption/desorption of hydrogen between β- and γ-hydrides is observed. Roles of the O phase in the reversible hydrogen absorption/desorption behavior are discussed on the basis of a matrix analysis of lattice deformation commonly used for martensitic transformations.