Serrated Flow in 9-11Cr Ferritic/Martensitic Steels

9–12%Cr ferritic/martensitic steels have been suggested for structural applications in Generation-IV reactors. Because of the high temperatures approaching 823–973 K envisioned in the designs of Generation IV reactors, mechanical behavior of the 9–12%Cr steels at temperatures up to 823–973 K require investigations. Serrated flow in P92 and 11Cr ferritic/martensitic steels was investigated through tensile tests at initial strain rates of 2×10−5−10−3 s-1 at temperatures ranging from 298 to 973 K. Serrated flow occurred at three temperature regions of 298 K, 548–623 K and 773–973 K when tensile tests were conducted at strain rates of 2×10−5−10−3 s−1. There appear to have no previous reports on the serrated flow found in 9–12%Cr ferritic/martensitic steels at temperatures higher than 823 K. Activation energy for the occurrence of serrated flow at temperatures around 573 K (558–623 K) and around 923 K (873–973 K) was determined to be about 126.5 and 43.44 KJ/mol, respectively. The mechanism of serrated flow in the steels was discussed.