The average velocities of dislocations on octahedral and cube planes in single crystals were measured as a function of the resolved shear stress, at temperatures ranging from 293 to 1133K, by using the etch-pit technique. In all cases, the stress-dependence of the velocity could be expressed by a power-law equation. In the case of octahedral slip, the exponent lay between 20 and 31 and the activation area was between 81b2 and 99b2. In the case of cube slip, the exponent was between 12 and 16 and the activation area was between 56b2 and 84b2. Three temperature domains were identified; in which differing glide systems operated. In the first domain, the dislocations could move only on the octahedral plane. In the second domain, they could move on both octahedral and cube planes. In the third domain, they could move only on the cube plane. It was found that the velocity of the dislocations moving on the octahedral planes exhibited an anomalous behavior which involved a positive temperature dependence of the resolved shear stress for a constant dislocation velocity, and a tension-compression velocity asymmetry. No obviously anomalous velocity behavior was observed for the cube glide system. All of the results suggested that a positive temperature dependence of the critical resolved shear stress, and the tension-compression flow asymmetry, could be directly related to the behavior of individual dislocation velocities.

Dislocation Velocities in Ni3Al Single Crystals C.B.Jiang, S.Patu, Q.Z.Lei, C.X.Shi: Philosophical Magazine Letters, 1998, 78[1], 1-8