Theoretical equation for steady-state dislocation creep in a material having a threshold stress

Abstract A model of the dislocation creep process has been developed and shown to give reasonable predictions for the thermal and in-reactor creep rates of some pure crystalline materials. Its application to solid solutions has also been described and in the present paper the model is further developed for materials (such as those hardened by a dispersion) in which, arguably, dislocation creep only occurs when a threshold stress is exceeded. The predictions of the resultant creep equation are compared with the results of experiment and reasonable agreement is found. In particular the absolute rate of creep for a 'SAP' type material is forecast with reasonable accuracy while the dependence of the stress and temperature sensitivity (of the creep rate) upon the absolute magnitudes of stress and temperature are correctly mirrored by the theoretical equation.