Model for kink-like deformation in CoTi single crystals

Single crystals of the B2 CoTi intermetallic compound were deformed in compression at temperatures between room temperature and 1000 K. The orientation was about 10° off the [001] cube axis. For B2 compounds with `strong’ AB bonding, the slip dislocations are often $\langle 100\rangle$ type gliding on $\{110\}$ planes although $\langle 110\rangle$ and $\langle 111\rangle$ slip cannot be ruled out especially when, as in this case, the Schmid factors for $\langle 100\rangle$ glide are very small. In the lower half of the temperature range, deformation progressed by a series of load drops which manifests itself as coarse bands formed at intervals along the gauge length. The bands are roughly parallel to the (001) plane but it is concluded that the slip planes are $\{110\}$ and that the kink-like behaviour is due to the formation of twist boundaries. A model for this behaviour is presented which is based on a pole mechanism and the glide of $\langle 100\rangle$ dislocations.