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Fe–Mn–Al–C low-density steels are regarded as promising materials applied in the automotive industry to achieve the minimization of vehicular emissions and fuel consumption. This study investigates the high-temperature strength and hot ductility of Fe–22Mn–9Al–0.6C low-density steel through high-temperature tensile tests at 800–950 °C. The high-temperature strength decreases with an increasing deformation temperature. This indicates that the precipitation of B2 reduces the hot ductility during the hot deformation of steel, where the results are consistent with those during the solid-solution treatment at 800–950 °C with a holding time of 0.5 h. Furthermore, at 800 °C the γ transforms into a mixture of α + DO3 and κ-carbide precipitates. A transformation of κ + DO3→B2 occurs in the temperature range of 850–900 °C, and at this point the κ-carbide dissolves into the matrix and B2 is generated, resulting in a significant decrease in hot ductility. As the temperature increases up to 950 °C, B2 emerges and transforms into the δ phase, and the κ-carbide precipitates along the γ/γ grain boundaries. The precipitation of B2 during high-temperature treatments in Fe-Mn-Al-C low-density steels is the critical factor affecting hot ductility, leading to crack generation; therefore, it is extremely essential to prevent the temperature interval of B2 precipitation during hot deformation processes. [ABSTRACT FROM AUTHOR]

The impact behaviors of N‐bearing QN1803 and 304 stainless steels are studied using instrumented Charpy impact test in the range of −192–100 °C. The fracture and deformation substructures are systematically investigated by scanning electron microscopy and transmission electron microscopy. The results show that QN1803 presents ductile–brittle transition temperature (DBTT) and 304 shows ductile fracture. With increasing temperature, the stacking fault energy (SFE) of QN1803 and 304 increases, but the former is always lower than the latter. QN1803 presents low impact toughness with low‐density dislocation at −192 °C. At high temperature, QN1803 and 304 show good impact toughness and the deformation substructures are dominated by high‐density dislocations and deformation twinning. [ABSTRACT FROM AUTHOR]