Preparation of α'- Fe(N)/α'-Fe8N by γ'-Fe4N precursor

An approach by using the gamma'-Fe4N precursor was proposed to prepare a bulk magnet with high alpha''-Fe16N2 content, and the feasibility for high N content alpha'-Fe(N)/alpha'-Fe8N was demonstrated in ribbon samples. gamma'-Fe4N decomposed when it was heated to a high temperature, and then, a supersaturated gamma-Fe(N) phase formed because of N atoms diffusing out from the gamma'-Fe4N lattice. The short-lived supersaturated gamma-Fe(N) had the face-centered cubic lattice, and its nitrogen content is beyond 3.0 wt. %. The supersaturated gamma-Fe(N) acts as a precursor of the martensite transformation for a body-centered tetragonal phase. After the cryo-treatment, which was essential to complete the martensite transformation, a mixture of alpha'-Fe(N) and alpha'-Fe8N was obtained. The N content of more than 2.5 wt.% in the samples was achieved. (c) 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).