Combined Effects of Mn, C, and H on the Stacking Fault Energy in Austenitic Mn Steels

Abstract

Manganese, carbon, and hydrogen are common alloying elements in austenitic Mn steels, which all influence the stacking fault energy (SFE), with Mn and H decreasing while C increasing it. The combined effects of Mn, C, and H on the SFE in austenitic Fe 1Àx Mn x alloys, including pure Fe, Fe 31 Mn, Fe 15 Mn, Fe 7 Mn, and Fe 3 Mn, using first-principles calculations, are investigated. The enhancing effect of C on the SFE is 29 mJ m À2 lower in Fe 3 Mn than in pure Fe, whereas it remains largely unchanged for low Mn concentrations. The noticeable combined MnÀC effect for Fe 3 Mn is mainly due to the formation of MnÀCÀMn trimer. Similarly, the boosting effect of H is weakened with increasing Mn content. As for the ternary MnÀCÀH effect, it is found that it is generally stronger than that of binary effects. All the binary and ternary effects are much smaller than those of individual elements, indicating weak multiatom interactions of Mn, C, and H.