Effects of Oxygen Concentration and Grain Size on Twinning Deformation Behavior in Commercially Pure Titanium

To obtain the fundamental knowledge for the improvement of strength-ductility relationship in commercially pure titanium, effects of O concentration and grain size on tensile properties were investigated with emphasizing on twinning deformation, using titanium sheets with different O content and grain size. Twinning deformation occurs in the materials with 0.11mass% or lower O contents and 23 μm or larger grain size, and the larger grain size enhances twinning deformation. Materials with 0.11 mass % O and grain size larger than 70 μm show the excellent balance of uniform elongation and 0.2% proof stress, due to solid solution strengthening by O and active twinning deformation.