In this study, high-temperature tensile tests were carried out on a Gleeble-3500 thermal simulator under a strain rate of ε = 1 × 10−3 s−1 in the temperature range of 600–1310 °C. The hot deformation process of Fe–15.3Mn–0.58C–2.3Al TWIP/TRIP at different temperatures was studied. In the whole tested temperature range, the reduction of area ranged from 47.3 to 89.4% and reached the maximum value of 89.4% at 1275 °C. Assuming that 60% reduction of area is relative ductility trough, the high-temperature ductility trough was from 1275 °C to the melting point temperature, the medium-temperature ductility trough was 1000–1250 °C, and the low-temperature ductility trough was around 600 °C. The phase transformation process of the steel was analyzed by Thermo-Calc thermodynamics software. It was found that ferrite transformation occurred at 646 °C, and the austenite was softened by a small amount of ferrite, resulting in the reduction of thermoplastic and formation of the low-temperature ductility trough. However, the small difference in thermoplasticity in the low-temperature ductility trough was attributed to the small amount of ferrite and the low transformation temperature of ferrite. The tensile fracture at different temperatures was characterized by means of optical microscopy and scanning electron microscopy. It was found that there were Al2O3, AlN, MnO, and MnS(Se) impurities in the fracture. The abnormal points of thermoplasticity showed that the inclusions had a significant effect on the high-temperature mechanical properties. The results of EBSD local orientation difference analysis showed that the temperature range with good plasticity was around 1275 °C. Under large deformation extent, the phase difference in the internal position of the grain was larger than that in the grain boundary. The defect density in the grain was large, and the high dislocation density was the main deformation mechanism in the high-temperature tensile process.

The effect of Ce treatment on nonmetallic inclusions in Fe–Mn–C–Al twinning‐induced plasticity steel is studied by adding different content of rare‐earth cerium. scanning electron microscopy, energy‐dispersive spectroscopy, and electron probe X‐ray microanalyzer analysis show that the main inclusions in Ce‐treated steel change from Al2O3–MnS to CeAlO3–Ce2S3. With the increase of Ce content, the number, size, and density of inclusions in steel decrease, and the morphology of irregular inclusions is closer to the spindle. In this experiment, the size of inclusions in the test sample with 0.0048% Ce addition is the smallest and the distribution of inclusions is the most uniform. Based on the classical thermodynamics and Factsage thermodynamics software, the evolution rule of Ce addition on inclusions is calculated. The thermodynamic calculation results are in good agreement with the experimental results. In addition, combining the experimental phenomena and thermodynamic calculation results, it is revealed that the transformation path of the main inclusions Al2O3–MnS to CeAlO3–Ce2S3 in the Ce‐treated steel is as follows: the outer layer of MnS → CeS → Ce3S4 → Ce2S3; inner layer Al2O3 → CeAlO3 +Ce2O2S. The anisotropy difference between inclusions and iron matrix after Ce treatment is reduced, which reduces the damage of inclusions to steel.

In the smelting process of high manganese steel, the volatilization of manganese will be accompanied. In this article, the volatilization of manganese in high manganese steel was studied by simultaneous thermal analyzer. The results show that the volatilization rate of manganese in high manganese steel increases with increasing temperature and holding time. It is proved by experimental study and data analysis that manganese volatilization follows the first-order kinetics model, and the empirical formula of manganese evaporation is derived. The volatile products of manganese were analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the volatile components of manganese mainly consisted of MnO, Mn3O4, Mn2O3, and MnO2. Combined with thermodynamics, the mechanism of manganese volatilization is further analyzed, and two forms of manganese volatilization in high manganese steel are revealed. One is that manganese atoms on the surface of high manganese steel and oxygen atoms in the gas form different types of manganese oxides and then volatilize at high temperature. The other way is that Mn atoms vaporize into Mn vapor and evaporate in high temperature environment, and then are oxidized into different types of manganese oxides. The results of theoretical calculation and experiment show that manganese volatilization is mainly in the first form.

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