Dislocation Motion in Copper under Small Stress

Abstract

Dislocation motion in copper was studied by dislocation-etching before and under loading, and also after unloading.
Copper single crystals (nominally 99.999%Cu) were first grown in vacuum by the Bridgman technique and parallelepipeds were cut out and polished by an acid saw and an acid polisher. The parallelepipeds were then subjected to thermal cyclic annealing. Final dimensions and dislocation density of the specimen crystals were approximately 5×4×50 mm³ and 1×10³/cm², respectively. Small tensile stress was applied by hanging a small weight.
Principal results were as follows;
(1) Dislocation locking force due to impurity atoms and lattice frictional force were estimated to be less than 0.46 g/mm² and 0.20 g/mm², respectively.
(2) Both grown-in and multiplied dislocations were observed to move backward after unloading; multiplied dislocations more frequently.
(3) Main obstacles to moving dislocations are probably forest dislocations.