Dislocations and Plastic Flow in NaCl Single Crystals. I

Abstract

Dislocation multiplication and motion in NaCl was studied using etch pit and birefringence techniques. The observations show that dislocations in glide bands of NaCl are in the form of large concentric loops with sources staggered in the center of the bands. They propagate and multiply by cross-slip and are braked through intersection jogs. The slip distance parallel to b is estimated to be 2–3 mm and that normal to b 0.5–1 mm, at a stress of 30 g/mm2 in crystals having 5×104 dislocations/cm2. ``Deformation bands'' form normal to the operating system during the latter part of stage I by ``glide polygonization'' of edge dislocations on closely spaced slip planes. These limit dislocation motion to shorter distances in stage II. Stage III appears when significant flow occurs on a secondary system oblique to the primary operating one.