Deformation behavior and microstructure evolution of 300M ultrahigh strength steel subjected to high strain rate: an analytical approach

In this paper, the deformation behavior and microstructure evolution of 300M steel are comprehensively studied by using the split-Hopkinson pressure bar technology, with an emphasis on the analytical estimate of material flow and microstructure distribution subjected to high strain rate. It is found that the grains have been significantly refined due to dynamic recrystallization (DRX) and major continuous DRX supplemented by few discontinuous ones governs the microstructure evolution. The dislocation activities associated with the angle change of grain boundaries and mechanical twinning dominate the deformation mechanism of 300M steel under high strain rate. Besides, nanoparticles in the form of carbide precipitation are uniformly distributed in the deformed zone, which strengthens the material by pinning the dislocations. A thermo-mechanical coupled analytical model considering dynamic recovery and dynamic recrystallization was innovatively developed, based on which the distribution of grain size and microhardness was predicted. The results indicated that the flow behavior described by the models and the calculated grain size as well as microhardness are proven to agree well with the results of experimental analysis.