High-Temperature Approaches to Synthesize Fe₁₆N₂through the Heat Treatment of As-Nitride Fe-Cu-B Ribbon

Fe16N2 is one of the promising candidates for rare-earth free magnets. It possesses a giant saturation magnetization (Ms) and reasonably high magnetocrystalline anisotropy. Past efforts made in synthesizing Fe16N2 were mostly on thin films, foils, and fine powders through different processes including sputtering, ion implantation, chemical reactions, and ball milling; this could cause a challenge of scaling up into massive production. The limitation in massive production of Fe16N2 requires intensive investigations to conquer. Compared with our previous endeavor of the low-temperature synthesizing process of Fe16N2 in bulk form, this paper proposes a method of gaseous nitridation with a high-temperature approach that can improve the process efficiency by applying the quenching and tempering treatment to address the challenge. An Fe-Cu-B ribbon was selected in this paper as the raw material to go through the gaseous nitriding using the high-temperature approach to form austenite with a high nitrogen content. The consequent quenching and tempering activate the martensite transformation and finally lead to the formation of the ordered Fe16N2 phase. The effect of microstructure on the magnetic performances are also investigated. The distribution of copper under different nitriding potentials, ribbon thicknesses, and manufacturing processes are investigated. A further discussion about the strain and magnetic field amid quenching and temperature changes is included to make the endeavor of maximum volume a fraction of Fe16N2.