Interpretation of creep behaviour of dispersion-strengthened Al–Fe–V–Si alloys in terms of detachment mechanisms: an overview

Creep data for different Al–Fe–V–Si alloys and composites were analysed using the detachment model. Between 673 and 723 K, the materials exhibited a typical threshold-like behaviour but the magnitude of the threshold stress was found to change from one material to another. The threshold stress was ascribed to the particle-dislocation interaction; in particular, the Rösler–Arzt model for athermal detachment of dislocations from interacting particles was considered. The different values of the threshold stress and its dependence on temperature were thus related to the magnitude of the kr parameter and to the initial size of the dispersoids. The disappearance of the threshold stress observed when testing a composite at temperatures above 723 K, as suggested in the literature, was explained in terms of transition from athermal to thermally activated detachment of dislocations from the particles; however, it was concluded that this mechanism becomes rate-controlling only for low applied stresses, i.e. when the applied stress is lower than the athermal-detachment stress, as originally postulated by Rösler and Arzt. When the applied stress exceeds the athermal-detachment stress, the latter becomes rate-controlling, irrespective of the testing temperature.