High-Temperature Approaches to Synthesize Fe ₁₆ N ₂ through 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 (M_s) 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.