Les dislocations dans la forsté rite déformée à haute Tempé rature

Abstract

Abstract Dislocations in forsterite deformed at a high temperature Creep experiments have been performed at high temperatures on forsterite single crystals at moderate stress (8–100 MPa, 1400–1650°C). Samples have been deformed by compression in three simple orientations. Dislocation microstructures are reported here for these three groups of samples. Previous observations were made using a very efficient decoration technique. TEM results confirm the reliability of this technique. Moreover they give a complete identification of Burgers vectors and activated slip systems. For the first orientation, most of the dislocations are ‘a’ edges in glide bands. Tilt walls are also present. The ‘a’ edges are not very straight. For the third orientation, most of the dislocations are ‘c’ screws. Twist walls are numerous. The ‘c’ screws are very straight. The second orientation is intermediate between the first and the third ones. It shows the two types of microstructures in highly variable proportions. These facts she...