Pure titanium-oxygen alloys with different oxygen contents were tensile-tested to investigate the effect of oxygen on work hardening rate and deformation behavior. Yield and ultimate tensile strengths markedly increased with increasing oxygen contents, although the elongations were decreased. Work hardening rate was also enhanced with increasing oxygen contents resulting in increase in the uniform elongation. The improved work hardening rate was ascribed to transition of primary deformation mode from twin deformation to dislocation slip by oxygen addition. When twin deformation is suppressed by oxygen addition, however, the 〈. c+. a〉 dislocation must function as a substitute for twinning to permit the homogeneous plastic deformation. It contributed that the improved work hardening rate without deformation twinning is thought to be a restriction of dislocation slips to a certain special plane by oxygen addition.
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