In situ TEM observations of dislocation dynamics in alpha titanium: Effect of the oxygen content

Plastic deformation micro-mechanisms, dislocation structures and glide kinetics in two titanium batches with moderate and high oxygen contents (450 and 3200 wppm, respectively) are investigated by in situ tensile tests in a transmission electron microscope, at room temperature. In both materials, plastic deformation is accommodated with < a > type screw dislocations gliding mainly in prismatic planes. The movement of screw segments is jerky, oxygen-dependent and strongly controlled by pinning on localized obstacles if the oxygen content is high. Dislocation multiplication is mainly controlled by the opening of loops produced by a double-cross slip mechanism at super-jogs. Evidences of composite glide between prismatic, first order pyramidal and basal planes are pointed out, proving the existence of intensive cross slip.