Effects of strain rate on the hot deformation behavior and dynamic recrystallization in China low activation martensitic steel

• Average grain sizes of 1.8 μm are observed at strain rate of 10 s−1.
• Peak stress value increased, but strain decreased with increasing of strain rate.
• A catenuliform recrystallized occurred at a strain rate of 5 s−1.
• DRX effect improved with increasing of deformation amounts.

To investigate the effects of strain rate on dynamic recrystallization (DRX) behavior on China low activation martensitic steel, hot uniaxial compression tests with strain rates ranging from 0.1 s−1 to 10 s−1 and deformations amounts of 40% and 70% where conducted. The true stress–true strain curves were analyzed for the occurrence of DRX under the different strain rates and compressive deformation amounts. The steel microstructures were examined and linked to the observed stress-strain diagrams to study DRX. Results show that DRX was responsible for refining the grain structure over a wide range of strain rates under 70% deformation. However, significant DRX occurred only at the relatively low strain rate of 0.1 s−1 under 40% deformation. The original elongated microstructure of the rolled plate from which the specimens were taken was replaced by dynamic recrystallization grains. At 70% deformation, the average grain size was 4.2 μm at a strain rate of 0.1 s−1, 2.5 μm at a strain rate of 5 s−1, 1.8 μm at a strain rate of 10 s−1. In conclusion, with increasing strain rate, the recrystallized grain size decreased and the peak stress increased.

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