Evidence of Large Magnetostructural Effects in Austenitic Stainless Steels

The surprisingly low magnetic transition temperatures in austenitic stainless steels indicate that in these Fe-based alloys magnetic disorder might be present at room temperature. Using a first-principles approach, we have obtained a theoretical description of the stacking fault energy in ${\mathrm{Fe}}_{100-c-n}{\mathrm{Cr}}_c{\mathrm{Ni}}_n$ alloys as a function of composition and temperature. Comparison of our results with experimental databases provides a strong evidence for large magnetic fluctuations in these materials. We demonstrate that the effects of alloying additions on the structural properties of steels contain a dominant magnetic contribution, which stabilizes the most common austenitic steels at normal service conditions.

Figure 1

Comparison between the theoretical and experimental stacking fault energies for austenitic steels. (a) The room-temperature experimental (${\gamma }_{\mathrm{expt}}$) and theoretical (${\gamma }_{\mathrm{theo}}$) SFE for alloys with different chemical compositions. The actual makeup of the alloys can be found in references listed in legend [15, 16, 17, 18, 19, 20]. The dashed lines indicate that most of the experimental data are situated within $\pm 10\mathrm{mJ}/{\mathrm{m}}^2$ around ${\gamma }_{\mathrm{theo}}$. (b) Temperature dependence of the SFE. Lines stand for the theoretical results for ${\mathrm{Fe}}_{70}{\mathrm{Cr}}_{18}{\mathrm{Ni}}_{12}$ (solid line) and ${\mathrm{Fe}}_{74}{\mathrm{Cr}}_{18}{\mathrm{Ni}}_8$ (dashed line). Symbols are the experimental values for ${\mathrm{Fe}}_{70}{\mathrm{Cr}}_{18}{\mathrm{Ni}}_{12}$ [22], ${\mathrm{Fe}}_{71}{\mathrm{Cr}}_{18}{\mathrm{Ni}}_{11}$ and ${\mathrm{Fe}}_{65}{\mathrm{Cr}}_{19}{\mathrm{Ni}}_{16}$ [21], and the average experimental values for ${\mathrm{Fe}}_{75}{\mathrm{Cr}}_{18}{\mathrm{Ni}}_7$ [23] with errors of $20\mathrm{mJ}/{\mathrm{m}}^2$.

Figure 2

Stacking fault energy maps of Fe-Cr-Ni random alloys. The calculated SFE is shown as a function of the chemical composition and temperature.

Figure 3

The magnetic fluctuation contribution to the stacking fault energy. ${\gamma }^{\mathrm{mag}}$ is plotted for $T=300\mathrm{K}$ as a function of the chemical composition.