Structural Mechanisms of Dilatometric Processes

Temperature actions on metals and alloys usually stimulate the development of irreversible processes of structural evolution. Dilatometric hysteresis can be considered as the total effect of such processes. The elementary mechanisms affecting the sample size upon heating are known to be the thermal expansion of materials, the phase and structural transformations, the ductile flow under its own weight, and the creep stimulated by internal stresses. Each of these mechanisms has specific features, which are unavoidably reflected by the shape of the dilatometric curves in the corresponding temperature ranges. The thermal activation parameters of the mechanisms controlling the kinetics of the change in structural parameters and the development of the corresponding size effects have been determined by photometric analysis of structural images and directly from the dilatometric curves, and the results are discussed in this paper.