Crystallographic preferred orientation and microstructure of experimentally deformed Braubach galena ore with emphasis on the relation to diffusional processes

Abstract

Sample cylinders of two galena ore hand specimens from Braubach, Germany were axially shortened in the strain rate range 5 × 10-5 s-1-5 × 10-7 s-1 at a confining pressure of 200 (300) MPa and at temperatures of 20°C-600°C. Neutron diffraction analyses of the crystallographic preferred orientation (texture) were carried out before and after experimental deformation on the same sample cylinder. Up to a deformation temperature of 300°C and a strain rate of 5 × 10-6 s-1 a more or less complete 〈110〉 fiber texture develops, the strength of the fiber texture only depending on strain and the strength of the original preferred orientation. At slower strain rate and higher temperature, there is a distinct decrease of the fiber texture development. Diffusional mass transfer starts to become a significant deformation mechanism. Deformation at 500°C changes the original texture only slightly, which indicates a rapid increase of importance of diffusional flow processes. The alteration of the accompanying sulfosalts indicates that the temperature is high enough for the movement of atoms. The micro structure only reveals remarkable deformation structures at higher strains and in areas of locally higher stresses. © Springer-Verlag 1998.