5th International High Manganese Steel Conference - HMNS 2022

Understanding the deformation behavior of metals over a wide range of strain rates is of critical importance in a variety of engineering applications, such as vehicle collision, projectile penetration, explosion shock, and so on. Decades ago, studies on the strain rate dependent deformation behavior of various metals, including bcc metals (e.g. pure iron), fcc metals (e.g. Cu, Ni), and hcp metals (e.g. Ti), were reported, and the results show that all of these metals exhibit positive strain rate sensitivity (SRS). In the present study, we investigated the strain rate dependent mechanical behavior of a medium Mn steel fabricated by a room-temperature quenching and partitioning (RT-Q&P) processing. We found that the RT-Q&P medium Mn steel exhibits abnormally negative SRS. The underlying mechanism has been comprehensively investigated by interrupted tensile tests, synchrotron XRD, TEM and APT. We found that the interstitial carbon is the reason for the negative SRS, but not the TRIP effect. Our finding implies that we have to be extremely cautious when using high-carbon high-strength steels that are subjected to high-strain-rate deformation, such as automobile anti-collision components (e.g. A, B pillars, crash-box etc).