Abstract
Dislocation structures introduced by deformation at various temperatures in the anomalous strengthening region in Ni3Al single crystals have been examined using high voltage electron microscopy with special care in preserving the bulk structure after deformation. The three-dimensional dislocation structures found by stereo microscopy have been analysed and correlated with the high-temperature strengthening. It is shown that the rapid work hardening leading to the anomalous strengthening is essentially controlled by the Kear-Wilsdorf locking or the (010) cross slip and is not affected by the secondary slip. The origin of the transition in the strain-rate sensitivity has also been considered and is attributed to the transition in the hardening mechanism due to (010) cross slip.