Eleventh International Conference on Internal Friction and Ultrasonic Attenuation in Solids
J. Phys. IV France 06 (1996) C8-175-C8-178
Dislocation Relaxation Processes due to Kink MigrationE.B. Hermida1, A. Seeger2 and W. Ulfert2
1 Unidad Act. Materiales, Comisión Nacional de Energía Atómica, Av. del Libertador 8250, 1429 Buenos Aires and Dto. de Física, Fac. de Ciencias Exactas y Naturales (UBA), Pabellón I, Ciudad Universitaria, 1428 Buenos Aires, Argentina
2 Max-Planck Institut für Metallforschung, Institut für Physik and Universität Stuttgart, Institut für Theoretische und Angewandte Physik, 70569 Stuttgart, Germany
The interpretation of the Bordoni relaxation and of related relaxation phenomena in terms of the thermally activated, stress-assisted formation of kink pairs on dislocation lines is well established on assuming that the migration of kinks along dislocation lines is described by a high kink mobility µk. This assumption, however, is not valid if the activation enthalpy for kink migration, Hm, is comparable with or even larger than the formation enthalpy of kink pairs or if even when small compared with the formation energy of kinks, Hm is larger than the lowest thermal energies accessible in internal friction experiments. In those cases not only migration but also annihilation and trapping of thermal kink pairs may produce internal friction peaks. The difference-differential equations governing the thermal kink pairs evolution along dislocation lines under the action of a homogeneous applied shear stress are set up and their time-dependent solutions characterized by a set of relaxation times. It is shown how to obtain, from these solutions, the internal friction spectrum under conditions that are experimentally realized. Quantitative descriptions of geometrical kink migration and kink pair evolution are compared with selected experimental results.
© EDP Sciences 1996