Substitutional-Interstitial Interaction and the Anomalous Snoek Peak in Fe-V-N Alloys

It has been shown that the anomalous Snoek internal friction peaks observed in Fe-V-N alloys by Fast and Meijering2 can be interpreted as being made up of three distinct contributions. From a study of the manner in which these contributions vary with the free nitrogen level in the alloy, a model is proposed and considered in detail in which between one and three nitrogen atoms reside in the six octahedral sites co-ordinated with a vanadium atom. The three contributions then correspond to jumps by the nitrogen atoms for the cases when one, two, and three interstitials are present. The model allows the evaluation of the interaction energy between a nitrogen atom and either a vanadium atom, a vanadium-nitrogen pair, or a vanadium-di-nitrogen group as about 0.3 eV. The calculated variation of the filling of sites with the free nitrogen level in the alloy is in fair agreement with the resolved contributions to the anomalous peak.