Stacking Fault Energy Maps of Fe–Mn–Al–C–Si Steels: Effect of Temperature, Grain Size, and Variations in Compositions

Abstract

A subregular solution thermodynamic model was employed to calculate the stacking fault energy (SFE) in Fe–Mn–Al–C–Si steels with contents of carbon 0.2–1.6 wt.%, manganese 1–35 wt.%, aluminum 1–10 wt.%, and silicon 0.5–4 wt.%. Based on these calculations, temperature-dependent and composition-dependent diagrams were developed in the mentioned composition range. Also, the effect of the austenite grain size (from 1 to 300 μm) on SFEs was analyzed. Furthermore, some results of SFE obtained with this model were compared with the experimental results reported in the literature. In summary, the present model introduces new changes that shows a better correlation with the experimental results and also allows to expand the ranges of temperatures, compositions, grain sizes, and also the SFE maps available in the literature to support the design of Fe–Mn–Al–C–Si steels as a function of the SFE.

A general perspective of Fe–Mn–Al–C steels

“…Recently it was concluded, using ab-initio calculations, that the carbon increase the SFE in Fe-C [170] and FCC for pure iron [141,171]. Additionally, the variation of the SFE with the carbon and aluminum content for the Fe-Mn-Al-C system [161] is shows in Figure 20. Figure 19.…”

“…the TRIP and TWIP effects are reduced or suppressed in fine grain sizes [133,174,175] or promoted in coarse grain sizes [172]. The variation of the SFE with the austenitic grain size in the Fe-Mn-Al-C system [161] is shows in Figure 21. Recently, it was reported that Nb additions in Fe-Mn-Al-C steels [176], produced a drastic decrease of the twin activity, mainly caused by the grain size refinement in the microstructure.…”

“…They found with increasing the test temperature the partial dislocation width increases which produce a decrease of the SFE. Recently, the variation of the SFE with temperature was plotted in Figure 18 [161]. Figure 18.…”

“…Influence of alloy elements on the SFE in the Fe-22Mn-0.6C system, reproduced from [132] with permission of Elsevier ® Figure 20. Two-dimensional SFE (unit: mJ/m 2 ) map for Fe-15Mn-XAl-0.5 C alloy system with carbon contents [161] 3. [155] in Fe-Mn alloys in a range of austenitic grain sizes from 5 to 150 µm, confirms that increasing the grain size, the SFE drastically decreases for all manganese contents.…”

“…Variations in SFE map by increasing grain size and manganese and aluminum contents: for 10 wt.% Al[161] …”