The influence of temperature and strain rate on the flow stress of α-iron single crystals

Abstract

The reversible contribution to the flow stress in α-iron single crystals was investigated by temperature and strain rate changes between −72°c and + 22°c and over several orders of magnitude of strain rate. The corresponding flow-stress changes were, compared with f.c.c. metals, quite large and increased with increasing deformation. The results were quantitatively evaluated using the assumption that the activation volume decreased with increasing stress. The initial distance between obstacles was found to be ∼5 × 10⁻⁶ cm and the activation energy 0.55 ev. Impurities are considered most likely to form the obstacles responsible for the thermally activated flow-stress contribution in the temperature range studied.