A generic analysis for high-temperature power-law deformation: the case of linear In (strain rate)-In(stress) relationship

Abstract

Isostructural low-stress high-temperature deformation of different classes of materials is often represented by a power law that connects the strain rate to the flow stress through a stress exponent. The temperature dependence of the rate of deformation is assumed to be exponential. In Mukherjee et al's popular approach the temperature dependence of the stress exponent is ignored by assuming a mean value for the stress exponent for the temperature range of interest and the stress is normalized with respect to the elastic constant. In the approach adopted by the engineers the stress is normalized with respect to a reference stress and it is possible to take into account the temperature dependence of the stress exponent while evaluating the activation energy for the rate-controlling process. Experimental data pertaining to 27 systems drawn from metals and alloys, superalloys, ceramics, glass ceramics, metal-matrix composites and an intermetallic, have been analysed using the latter approach to determine an activation energy for the rate-controlling process. It is demonstrated that this is an accurate description of high-temperature power-law deformation and that it involves less numbers of empirical constants than the former approach.