Austenitic Fe-Mn-Al-C low-density steels have been considered structural materials for cryogenic applications due to the attractive combination of mechanical properties such as mechanical strength (yield strength of ~0.5–1.0 GPa; ultimate tensile strength of ∼1.2–1.5 GPa), tensile elongation (30–70%) and Charpy impact energy (40–140 J), which are comparable to that of conventional stainless steels [1]. The austenitic structure is the most promising crystal structure for cryogenic applications as the ε(hcp)- and α’ (bcc)-martensitic phases are detrimental to the Charpy impact energy. However, the deformation mechanisms of these steels at cryogenic temperatures are still unclear. In this presentation, we present the main characteristics of the deformation behavior of two Fe-30Mnx-Al-yC low-density steels in the temperature range of 23°C to -196°C investigated by EBSD, ECCI, and TEM. Aspects such as grain orientation dependence, crystallographic alignment, and strain dependence of the deformation structures are analyzed. In particular, the contribution of the deformation structures to the distribution of plasticity (homogeneous vs. inhomogeneous [2]) is discussed. These effects have a profound influence on the distribution of plasticity, microtexture, and mechanical behavior.

References

[1] I. Gutierrez-Urrutia; ISIJ, 2021, 61, 16-25

[2] I. Gutierrez-Urrutia et al.; Acta Materialia, 2022, 233, 118053