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 Pr_26.7Fe_72.3B₁, Pr_26.7Fe_71.8Hf_0.5B₁, and Pr_26.7Fe_71.3Hf₁B₁ (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 (Pr_26.7Fe_72.3B₁) exhibits an intrinsic coercivity (H_cj) of 11.95 kOe, a remanence (B_r) of 8.23 kG, and a maximum energy product ((BH)_max) of 12.6 MGOe. With 0.5% Hf addition, the properties improve to H_cj of 11.47 kOe, B_r 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 H_cj of 11.66 kOe, B_r 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.