Coupling effect of strain rate and temperature on deformation mechanism of reduced activation ferritic/martensitic steel

The tensile properties and deformation mechanisms of the reduced activation ferritic/martensitic steel—China low activation martensitic (CLAM) steel are determined from tests carried out over a wider range of strain rate and temperature. During high-temperature deformation, the plastic deformation modes involve dynamic recrystallization (DRX) and dynamic recovery (DRV) processes, which govern the mechanical behaviors of CLAM steel under different loading conditions. This work systematically explored the effects of increasing strain rates and temperatures, finding that the microstructure evolution process is facilitated by nano-sized M₂₃C₆ precipitates and the grain boundaries of the initial microstructure. Under quasi-static loading conditions, DRX grains preferentially nucleate around M₂₃C₆ precipitates, and the dominant deformation mechanism is DRX. However, under dynamic loading conditions, the number of DRX grains decreases significantly, and the dominant deformation mechanism converts to DRV. It was concluded that the coupling effects of strain rates and temperatures strongly influence DRX and DRV processes, which ultimately determine the mechanical properties and microstructure evolution. Moreover, dynamic deformation at elevated temperatures achieves much finer grain sizes, offering a novel method for grain refinement through dynamic straining processes.