Tensile properties of two 7-9Cr ferritic/martensitic steels have been inves
tigated over the temperature range 77-293 K. Along with the temperature dep
endence, the strain rate sensitivity of the yield stress has been studied b
y performing strain rate jump tests. Activation volume and activation energ
y 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 op
erate, replacing the Peierls mechanism. At static strain rates, the atherma
l regime is reached slightly above room temperature. (C) 1999 Elsevier Scie
nce B.V. All rights reserved.