ORIENTATION DEPENDENCE OF TWINNING IN COMMERCIALLY PURE TITANIUM

Orientation dependence of twinning in commercially pure titanium was determined in both single crystals deformed in tension or compression and polycrystals deformed in tension. {1̄012} and {112̄2} twins in single crystals, and {1̄012}, {112̄1} and {112̄2} twins in polycrystals occurred depending on the sense and direction of applied stress. It was observed that twinning generally occurred on a highly stressed system with a large Schmid factor for twinning. However, {1̄012} twins which have smaller Schmid factors than those for {112̄1} twins operated predominantly in the region where the angle between the tensile axis and basal pole is about 30 approximately 40°. This suggests that {1̄012} twins are formed more easily than {112̄1} twins. The planar anisotropy of work hardening, which has been reported in tensile deformation of commercially pure titanium sheet, is satisfactorily explained by the orientation dependence of twinning presented in this study.