First-Principles prediction of the deformation modes in austenitic Fe-Cr-Ni alloys

TL;DR

This study uses first-principles calculations to predict deformation modes in Fe-Cr-Ni alloys by analyzing the gamma-surface and stacking fault energy, aligning well with experimental data and plasticity theory.

Contribution

It introduces a first-principles approach to predict deformation mechanisms in Fe-Cr-Ni alloys based on gamma-surface and stacking fault energy calculations.

Findings

Stacking fault energy trends match experimental data.

Deformation mode prediction based on SFE thresholds.

Twinning remains a possible deformation mode at high temperatures.

Abstract

First-principles alloy theory is used to establish the $\gamma$-surface of Fe-Cr-Ni alloys as function of chemical composition and temperature. The theoretical stacking fault energy (SFE) versus chemistry and temperature trends agree well with experiments. Combining our results with the recent plasticity theory based on the $\gamma$-surface, the stacking fault formation is predicted to be the leading deformation mechanism for alloys with effective stacking fault energy below about 18 mJ m$^{-2}$. Alloys with SFE above this critical value show both twinning and full slip at room temperature and twinning remains a possible deformation mode even at elevated temperatures, in line with observations.