The average velocities of screw dislocations in Ni3Al single crystals were directly measured as a function of resolved shear stress and orientation in the temperature domain of the flow stress anomaly using the etch-pit technique. The velocity was found to be extremely sensitive to the resolved shear stress in all cases. In contrast with ordinary metals, the screw dislocation velocities in Ni3Al show anomalous behaviour; under a constant resolved shear stress, the velocities decreased dramatically with increasing temperature. Furthermore, the velocities and the tension-compression asymmetry of the velocities depend on the orientation of applied stress.

The Orientation and Temperature Dependences of Dislocation Velocity in Ni3Al Single Crystals. Zhang, Z.F., Jiang, C.B., Wu, S.D., Patu, S.: Philosophical Magazine Letters, 2003, 83[9], 563-8