Directional Growth of Crystals and Orientation of Easy Magnetization Axis in Ce-Fe-Al-B Compounds

Ce element is abundant in rare-earth ore, and it is expected to substitute for Nd in Nd₂Fe14B to prepare permanent magnets. However, the crystal structure stability of Ce₂Fe14B is poor, and both CeFe₂ phase and α- Fe phase exist in Ce14(Fe,M)79.7Al0.5B5.8 strips prepared by rapid solidification. Via increasing the content of Al and reducing the content of B, α-Fe phase is eliminated in Ce14(Fe,M)78.9Al1.6B5.5 strips, and the columnar crystals are formed for the main phase of Ce₂Fe14B crystals. CeFe₂ phase is basically distributed in linear patterns, thinly coating on the surface of columnar cry stals of Ce ₂Fe14B. Owing to Al atoms entering into Ce₂Fe14B crystals, the lattice entropy increases in Ce ₂Fe14B crystals, and the melting point of the main phase increases. From the perspective of thermodynamics, it can enhance the stability of Ce₂Fe14B crystal structure. As the content of Al increases to 2.0 at.%, the columnar crystals are not formed in some areas due to the competitive growth of heterogeneous phases. These experiments indicate that by modifying the chemical composition in the Ce-Fe-Al-B compounds the crystal directional growth could be promoted, which should be beneficial to improve the orientation of easy magnetization axis in sintered magnets.