PLASTIC-DEFORMATION OF CALCITE SINGLE-CRYSTALS DEFORMED IN COMPRESSION PARALLEL TO [111]

Natural calcite single crystals were plastically deformed by compression along [111] between 373 and 823 K. Thermal activation analysis of the deformation and TEM observation of the resulting dislocation structure indicate that two mechanisms control the dislocations motion. At low temperatures (T < 600 K), the deformation by slip on {100} planes is controled by dislocation‐impurity mechanisms and the resulting dislocation structure consists of edge dipoles. At higher temperatures, creep behaviour is observed with a power law n ≈ 3.5 of the applied stress. The dislocation dipoles transform into dislocation loops by pipe‐diffusion. This process is investigated on the basis of dissociation of each perfect dislocation into two partials with Burgers vector ± 1/2 〈110〉. Copyright © 1978 WILEY‐VCH Verlag GmbH & Co. KGaA