The Effect of Hf Substituting for Cu on the Glass-Forming Ability, Crystallization Behavior, and Saturation Magnetization in Fe₈₅Si₂B₈P₄Cu_1−xHf_x Alloys

Abstract

The effect of Hf substituting for Cu on the glass-forming ability (GFA), crystallization behavior, and saturation magnetization (M_s) in Fe-rich Fe₈₅Si₂B₈P₄Cu_1−xHf_x alloys has been investigated. The result shows that the addition of Hf plays a positive role in improving GFA, and the Fe₈₅Si₂B₈P₄Cu_0.5Hf_0.5 alloy ribbon shows an entirely amorphous structure. Both the ribbons of Fe₈₅Si₂B₈P₄Cu₁ and Fe₈₅Si₂B₈P₄Cu_0.5Hf_0.5 have two obviously exothermic crystallization peaks, and the addition of Hf improves the onset temperatures of both first and second crystallization peaks, and leads to the improvement of the thermal stability of the amorphous alloys. For the Fe₈₅Si₂B₈P₄Cu_0.5Hf_0.5 ribbon, after annealing at 623 K, crystallization seeds with sizes of 2–4 nm are found and the initial crystallization has occurred; as the annealing temperature is increased to 723 and 823 K, the size distribution of most of the grains is about 20 nm and bigger than 20 nm, respectively. The M_s of the Fe₈₅Si₂B₈P₄Cu_0.5Hf_0.5 ribbon is about 154 emu/g, which is obviously lower than 205 emu/g of the Fe₈₅Si₂B₈P₄Cu₁ ribbon. However, after annealing at 723 K, the M_s increases to 212 emu/g for the former alloy. The newly developed amorphous/nanocrystalline Fe-Si-B-P-Cu-Hf alloy with excellent soft magnetic properties shows a potential application for substituting partial Si steels.