Stress-Velocity Relations for Dislocations in Niobium.

The stress-velocity relations for screw and mixed dislocations in high purity niobium were studied at 298K and 196K. Etch pitting methods were used to reveal the dislocation positions after stress pulses in tension and compression. Attention was particularly directed towards establishing any asymmetry in the motion of dislocations on the 112. No asymmetry was observed for either screw or mixed dislocations moving on the 112. The motion at 298K at low stresses was limited by extrinsic barriers while that at 196K and high stresses seemed limited by intrinsic dislocation drag. Author