Effect of interstitial-driven lattice expansion on the stacking fault energy in austenitic steels

TL;DR

This study uses first-principles calculations to show that interstitial elements like carbon and nitrogen influence the stacking fault energy in austenitic steels primarily through lattice expansion, aiding the design of better TWIP steels.

Contribution

It demonstrates that lattice expansion caused by interstitials is the main factor affecting SFE, providing a new understanding of alloying effects in TWIP steels.

Findings

Interstitials increase lattice volume significantly.

Lattice expansion correlates strongly with SFE changes.

Predictions match experimental measurements for C and N alloys.

Abstract

Interstitials (carbon and nitrogen) are crucial alloying elements for optimizing the mechanical performance of the twinning-induced plasticity (TWIP) steels in terms of the stacking fault energy (SFE). First-principles calculations have been performed to study the effect of interstitial-induced lattice expansion on the SFE. Comparing the predictions with the SFEs measured for alloys containing C and N, our results suggest that the dominant effect of these interstitials on the SFE is due to the lattice expansion effect.