MOTION OF DISLOCATIONS IN HIGHLY PERFECT COPPER CRYSTALS.

Motion of dislocations after their breakaway from as-annealed positions, is studied in highly perfect copper crystals at stress levels less than the shear stress tau //m needed for dislocation multiplication, using an etch-pit technique. Waiting time t//w required for the edge dislocation to jump over the obstacle by a thermally activated process is experimentally shown to range from 3 to 5 s under effective shear stresses of 5. 4 to 9. 5 multiplied by 10**4Pa at room temperature, whose values correspond to the activation energies of about 6-7 multiplied by 10** minus **2**0J. Forest dislocations are not responsible for this process.