Structure of the B2 phase in the Ti-25Al-25Zr alloy: a density functional study

We report a first-principles density functional theory study of the B2 phase structure in the Ti-25Al-25Zr alloy. Several structural models with different site occupancies have been investigated. In the ideal B2 phase, the Zr atom is found to preferentially occupy the Ti site. However, if the atoms are allowed to relax, Zr occupies both Ti and Al sites, leading to local positional disorder in the structure due to the large size differences of the constituent elements. Further, this alloy is predicted to have better room temperature ductility, enhancing its utility in several technological applications.