Abstract
Interstitial alloying has become an important pillar in tuning and improving the materials properties of high-entropy alloys, e.g., enabling interstitial solid-solution hardening and for tuning the stacking fault energies. In this work we performed ab initio calculations to evaluate the impact of interstitial alloying with nitrogen on the fcc–hcp phase stability for the prototypical CrMnFeCoNi alloy. The N solution energies are broadly distributed and reveal a clear correlation with the local environments. We show that N addition stabilizes the fcc phase of CrMnFeCoNi and increases the stacking fault energy.
Highlights
High-entropy alloys (HEAs) or complex concentrated alloys (CCAs) based on 3d transition metals have attracted enormous attention, due to their outstanding mechanical properties
An important quantity which can be sensitive to the interstitial alloying elements and which is linked to the mechanical properties is the stacking-fault energy (SFE), which is directly related to the face-centered cubic and the hexagonal close-packed phase stability
A small fraction of 13% and 17% for the fcc and the hcp phases, respectively, remained at the tetrahedral sites. This indicates that the vast majority of tetrahedral sites of CrMnFeCoNi tend to be dynamically unstable for N atoms
Summary
High-entropy alloys (HEAs) or complex concentrated alloys (CCAs) based on 3d transition metals have attracted enormous attention, due to their outstanding mechanical properties. For MnFeCoNi alloyed with Al, even the improvements of both strength and ductility are observed when adding C.[28] A recent experimental study[29] revealed that N-alloyed CrFeCoNi with a bimodal grain structure shows improved strength and ductility, overcoming their trade-off relation This all highlights the potential of interstitial alloying for improving the materials properties of 3d-transition-metal HEAs. An important quantity which can be sensitive to the interstitial alloying elements and which is linked to the mechanical properties is the stacking-fault energy (SFE), which is directly related to the face-centered cubic (fcc) and the hexagonal close-packed (hcp) phase stability. We utilize ab initio calculations to close the previous simulation gap and investigate the impact of interstitial N atoms on the fcc–hcp phase stability and SFE for CrMnFeCoNi, similar as previously performed for C[52]. Solution energies of interstitial N atoms are computed for both phases and a large number of interstitial sites is considered to explore the dependence on the local environments around N atoms
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