On the transitions of deformation modes of fully austenitic steels at room temperature

Abstract

The present study was undertaken to provide a more comprehensive understanding of the deformation modes of advanced fully austenitic steels exhibiting an enhanced combination of strength and ductility. For this purpose, a new plasticity, called microband induced plasticity (MBIP), was introduced. In addition, the origin of its superb combination of strength and ductility over the well-known transformation induced plasticity (TRIP) and twin induced plasticity (TWIP) was elucidated. With the aids of previously developed models, we focused on predicting the transitions among TRIP, TWIP, and MBIP, primarily in terms of the stacking fault energy. The analysis revealed that the TRIP-TWIP transition can be reasonably predicted by the energy balance for FCC austenite -HCP ε martensite transformation. The TWIP-MBIP transition can be addressed by the critical stress for mechanical twinning, which causes the infinite divergence of the Shockley partials. Lastly, the TWIP-MBIP transition model was validated by comparing it with the experimental data.

Strain hardening by dynamic slip band refinement in a high-Mn lightweight steel

“…The origin of pronounced planar glide in the FeMnAlC system was controversially discussed in the literature [24,46,61]. Three main reasons for pronounced planar glide in fcc metals were proposed:…”

“…The recently discussed MBIP hardening mechanism, reported in high-SFE alloys (~90 mJ m À2 ), is described by the formation of thin planar shear zones that are confined by a dislocation wall on either side. These features are called microbands [2,23,24]. All the above mentioned hardening mechanisms result in strong refinement of the respective microstructures during straining enabling high strain hardening rates.…”

The Role of κ-Carbides as Hydrogen Traps in High-Mn Steels

“…In particular, so-called high-Mn steels, comprising a broad spectrum of Fe-based alloys with Mn contents in the range of 20-30 wt % and Al and C contents in the ranges of 0-10 wt % and 0-2 wt %, respectively, have attracted attention [1]. These steels exhibit particular deformation mechanisms, such as transformation-induced plasticity (TRIP), twinning-induced plasticity (TWIP), or microband-induced plasticity (MBIP) [2], thereby yielding extraordinarily high strength and ductility. Steels containing considerable amounts of Al in addition to Mn have raised recent interest due to the precipitation of ordered carbides, both from A critical aspect with respect to the application of high-Mn steels is their large susceptibility to hydrogen-induced delayed fracture (HIDF) [6].…”

The effect of Ti precipitates on hydrogen embrittlement of Fe–18Mn–0.6C–2Al–xTi twinning-induced plasticity steel

“…Fe-high Mn-C twinning-induced plasticity (TWIP) steel has received much attention as an advanced automotive steel due to its good tensile strength and uniform ductility [1][2][3][4]. In addition, because the TWIP steel has a single fcc austenite phase with a large solubility and a slow diffusivity of hydrogen [5], the resistance to hydrogen embrittlement (HE) of the TWIP steel is higher than that of high strength martensitic C steel [6,7].…”