Transmission electron microscopy of plastically deformed [001]-orientated NaCl single crystals

Abstract

The dislocation arrangement of [001]-orientated NaCl single crystals which were deformed into Stage II of the work-hardening curve at room temperature is studied by transmission electron microscopy. Dislocation layers lying approximately parallel to the primary glide plane and several μm thick are observed. These layers contain mutually interacting primary and secondary dislocations. Primary edge dislocations are polygonized into kink walls having a dense core or are arranged in multipole bundles, which generally contain a large number of fragmented loops, and a few secondary dislocations. The observed primary dislocations are only slightly bowed out. This indicates small internal stresses, in accordance with the low energy structure deduced for the kink walls and the dislocation layers. The dislocation forest seen by the primary dislocations may account for the major part of the (essentially athermal) flow stress. This is corroborated by an estimation of Saada-type and source-type contributions to the flow stress.