Abstract：The quasi-static and dynamic compression experiments of Mn-Si-Cr quenching-partitioning (Q&P) steel were carried out by universal testing machine and Split Hopkinson Pressure Bar (SHPB), respectively. The true stress-strain curves were obtained at the strain rate of 0.001, 0.01, 0.1 s-1 and 900, 1 500, 2 200, 3 000 s-1, respectively. Scanning electron microscopy (SEM) was employed to observe microstructure and fracture surface after compression. Phase analysis of specimens under the two conditions was conducted by XRD. The results show that under both quasi-static and dynamic deformation conditions, the true stress-strain curves of steel can be roughly divided into two stages, i.e., elastic and plastic deformation, and no obvious yield platform is observed. Under quasi-static condition, the strain rate strengthening effect is not obvious while the strain hardening effect is remarkable. In contrast, under dynamic deformation, the strain hardening effect is not obvious but shows a certain strain rate strengthening effect. After quasi-static deformation, directional arrangement of lath structure occurs along nearly horizontal direction (i.e. perpendicular to compression direction) in the central region of sample. After dynamic deformation, about 1/3 of samples are fractured and 45° shearing band appears in the central region of unfractured sample with twisting lath structure near this region. There is a significant decrease in residual austenite content of specimens after quasi-static deformation, while only small decrease of retained austenite is found after dynamic deformation. Meanwhile, the serious deformation and microcracking are observed in the blocky M/A island, which may be the cause of fracture for some samples. On the damage fracture of dynamic deformation specimens, the whole sample undergoes 45° shearing fracture with microvoid coalescence fracture on one end and shearing fracture on the other end.
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2022, Vol. 32 
