Elektronenmikroskopische untersuchung der versetzungsanordnung verformter kupfereinkristalle im belasteten zustand

Abstract

Copper single crystals orientated for single glide were deformed in tension at 78°K and irradiated before load-removal with fast neutrons at 4°K or 20°K. The dislocation arrangement which was thus stabilized in the stress-applied state was investigated extensively by transmission electron microscopy and compared with the results of corresponding investigations on unloaded crystals. In stage II dislocation braids and dislocation grids (sheets) are observed both in the stress-removed and the stress-applied states. Groups of primary dislocations of the same sign, however, are a representative feature of the dislocation arrangement in the stress-applied state only. It is concluded from the observations that the grids are formed by secondary slip at the head of piled-up groups and are capable of growth. The observed spatial change in the curvature of free primary dislocations in the stress-applied state points directly to the existence of a quasi-periodic long-range internal stress field whose amplitude is of the order of the applied stress and whose wavelength is closely correlated to the number of dislocation groups. A quantitative analysis of the observed dislocation groups is in fair agreement with the long-range stress theory of work-hardening in stage II.