Microstructural and magnetic characterization of hydrogen-decrepitated CeFeB melt-spun ribbons fabricated at various wheel surface speeds

The demand for heavy rare earth-free permanent magnetic alloys has been increasing due to the limited reserves and high costs of critical rare earths such as Nd, Dy, and Pr. In this context, CeFeB alloys are considered a promising alternative because of the abundance and low cost of element Ce. In this study, CeFeB alloys (Ce: 35 wt%, Fe: 64 wt%, B: 1 wt%) were produced by the melt-spinning method at different wheel surface speeds of 3, 5, 15, and 25 m/s. Subsequently, the ribbons were subjected to a hydrogen decrepitation (HD) process to investigate the effects of cooling rate and hydrogen-induced cracking on their microstructural and magnetic properties. According to the X-ray diffraction results, all specimens exhibited a partially crystalline structure containing Ce₂Fe₁₄B as the main hard-magnetic phase, along with minor α-Fe and CeFe₂ phases. Increasing the wheel surface speed led to finer grains and more amorphization in the HD specimens. After the HD process, better microstructure and more homogeneous crack distribution were observed, in the specimen produced at the wheel surface speed of 5 m/s. The magnetic measurements revealed that coercivity (Hc), remanence (Mr), and maximum energy product ((BH)max) were strongly dependent on the cooling rate and the HD process. The highest Hc and (BH)max values were obtained as 4129.9 Oe and 13.62 MGOe, respectively, in the HD5 sample. However, formation of more amorphous regions, and oxidation at the higher cooling rates weakened the exchange-interaction mechanism, leading to a decrease in the Hc and (BH)max values.