Deformation characteristics in Β phase Ti-Nb alloys

Deformation modes in Β-phase Ti-Nb alloys containing from 36 to 52 wt pct Nb have been investigated as a function of composition, crystallographic orientation, or deformation temperature using both two surface trace analysis and transmission electron microscopy. 332 (113) twinning occurs in the low niobium content alloys independent of orientation and temperature. With increasing niobium content, 332<113> twinning or (111) slip occurs dependent on orientation and temperature. The operative twinning systems are explained by considering both the polarization of twinning shear and the Schmid factor. The 332 (113) twinning is suppressed in the high niobium content alloys and also suppressed by aging or oxygen addition in the low niobium content alloy. These characteristics have previously been observed in Β phase Ti-V and Ti-Mo alloys. The occurrence of 332 (113) twinning in Β-phase Ti alloys is related to the instability of Β phase. Formerly Graduate Student of Tohoku University