A study was made of the effect of O and Al upon the deformation behavior of ultra-high purity Ti-(48, 50 or 52)at%Al alloys; using ultra-high purity Ti containing 30ppm[wt]O. It was shown that the yield strength increased with increasing O content. Stoichiometric Ti-50at%Al alloys exhibited the lowest yield strength and the highest ductility when the O content was sufficiently low. It was suggested that the deformation mechanism of ultra-high purity binary Ti-Al was strongly related to the Al concentration. The deformation sub-structure of ultra-high purity Ti-48at%Al was dominated by ordinary dislocation, as well as deformation, twinning; and to a small extent by super-dislocations. The deformation sub-structure of ultra-high purity Ti-50at%Al was similar to that of Ti-48at%Al, but no deformation twinning was observed. Most of dislocation structures of ultra-high purity Ti-52at%Al consisted of faulted dipoles. The major deformation mode of ultra-high purity Ti-48at%Al and ultra-high purity Ti-50at%Al was ordinary dislocations in deformation orientation; which took advantage of ordinary dislocation slip. The major deformation mode in this orientation, for ultra-high purity Ti-52at%Al, was super-dislocation slip.

Compositional Dependence of the Deformation Behaviour of Ultrahigh-Purity Ti-Al Alloys. S.G.Pyo, J.K.Oh, M.S.Yoo, N.J.Kim, M.Yamaguchi: Philosophical Magazine, 2004, 84[28], 3001-17