Influence of phase transformations on the mechanical properties of high-strength austenitic Fe-Mn-Cr steel

Abstract

The influence of Cr and N additions on the mechanical properties of a Fe-Mn-C steel was investigated. The chemical composition was found to have a pronounced effect on the strain-hardening behavior, due to the strain-induced sequence of the ␥ : : ␣Ј martensitic transformations. It was found that Cr and N suppress this transformation sequence. At Cr levels higher than 7.5 mass pct, no ␣Ј martensite was formed, which led to a pronounced improvement of the ductility. The differences in transformation behavior can be attributed to the change in the intrinsic stacking-fault energy (ISFE): in the compositional range studied, Cr and N additions cause an increase of the ISFE.

The Influence of Cr and N Additions on the Mechanical Properties of FeMnC Steels

“…In a previous article, [44] it was illustrated that the low Cr in the hotrolled and annealed condition does not show a beneficial transformation induced plasticity (TRIP) effect, contrary to what is commonly observed in Fe-Cr-Ni-based austenitic steels, e.g., AISI 301. The latter have a sudden increase of strain hardening at a tensile strain of about 15 pct as a result of the strain-induced c fi a¢ martensitic transformation.…”

“…[35,45] In the low Cr alloy in the hot-rolled and annealed condition, the kinetics is very fast, especially for the c fi e-martensite transformation. [44] This is also reflected in the high strain-hardening value at low strains, n 1-5 . Reducing the amount of e-martensite formed in the early stages of the deformation is expected to result in a better TRIP effect.…”

“…The ISFE, therefore, also plays a role, albeit indirectly, in the transformation of austenite into a¢-martensite in these alloys. [41,43,44] The low strength of the austenite matrix implies that the strain-induced transformation will be easier, because, for the same stress level in the material, a higher strain is achieved. The grain size also influences the transformation, because a smaller grain size geometrically restricts the possibilities for the transformation to occur.…”

Cracking in a Fe–25Mn–3Si–3Al Steel

“…[13] TWIP steels presented a dimpled and ductile fracture surface under scanning electron microscopy investigation. [14] The evolution of ductile damage was investigated by three-dimensional X-ray tomography in situ tensile test. It was found that the ductile damage process of TWIP steels involved intense nucleation of small voids combined with the significant growth of the biggest cavities.…”

Powder metallurgy and mechanical alloying effects on the formation of thermally induced martensite in an FeMnSiCrNi SMA

“…At low Mn content or at high deformation degrees, besides ε-hcp, α' (body centre cubic, bcc) martensite can be additionally induced by cooling or deformation [14].…”