Nitrogen-Induced Phase Separation in Equiatomic FeNiCo Medium Entropy Alloy

We report the first observation of isothermal phase separation triggered by inwardly diffusing interstitial nitrogen atoms during nitriding of an equiatomic FeNiCo medium entropy alloy. Detailed microstructural characterization revealed a phase-separated microstructure within the nitrided region containing two FCC solid solution phases with one enriched in Fe and N while other enriched in Co and Ni. This demonstrates the potential utilization of interstitial N alloying to tailor the microstructure of multi-principal element alloys. Graphical Abstract