Improved Magnetic Performance of Near-Stoichiometric Pr-Fe-B Alloys with Hf Addition

This manuscript reports the influence of Hf substitution for Fe on the magnetic properties and microstructure of near-stoichiometric Pr-Fe-B alloys. Melt-spun ribbons with nominal compositions of Pr26.7Fe72.3B1, Pr26.7Fe71.8Hf0.5B1, and Pr26.7Fe71.3Hf1B1 (wt%) are synthesized with optimized wheel speed. Transmission electron microscopy analysis reveals that Hf addition effectively refines the grain structure in terms of grain size. Magnetic characterization at 300 K demonstrates that the partial Hf addition significantly enhances the hard magnetic performance. The pristine alloy (Pr26.7Fe72.3B1) exhibits an intrinsic coercivity (Hcj) of 11.95 kOe, a remanence (Br) of 8.23 kG, and a maximum energy product ((BH)max) of 12.6 MGOe. With 0.5% Hf addition, the properties improve to Hcj of 11.47 kOe, Br of 8.5 kG, and (BH)max of 15.33 MGOe. A further increase to 1.0% Hf leads to a slight reduction in properties, with Hcj of 11.66 kOe, Br of 8.37 kG, and (BH)max of 13.32 MGOe, though they remain superior to the pristine alloy. Furthermore, Hf addition improves the high-temperature magnetic stability. The results indicate that optimal Hf addition is a promising strategy for enhancing the magnetic properties of near-stoichiometric Pr-Fe-B ribbons through microstructural refinement and reducing the volume fraction of the soft magnetic phase.