Low temperature yield properties of two 7-9Cr ferritic/martensitic steels

Tensile properties of two 7-9Cr ferritic/martensitic steels have been investigated over the temperature range 77-293 K. Along with the temperature dependence, the strain rate sensitivity of the yield stress has been studied by performing strain rate jump tests. Activation volume and activation energy have been determined and used to identify the rate controlling mechanism of dislocation motion. It has been observed that the temperature and stress dependence of the activation parameters are both consistent with a Peierls mechanism below 190 K. Between 190 and 293 K, other mechanisms begin to operate, replacing the Peierls mechanism. At static strain rates, the athermal regime is reached slightly above room temperature. (C) 1999 Elsevier Science B.V. All rights reserved.