为研发具有良好软磁性和工艺性的高饱和磁感应强度(B_s) 铁基纳米晶合金，本工作以高Fe含量的Fe-B-Cu合金体系为对象，研究了B含量对Fe_{98.5 - x} B _x Cu_1.5 (x = 12~18，原子分数，%)系快淬合金带材的微结构、结晶化组织和磁性能的影响，分析了B含量-快淬微结构-结晶化组织-磁性能间的关联。结果表明，快淬合金均为非晶基体中分布着纳米尺度α-Fe晶粒(预存α-Fe晶)的结构；随x由12增加至18，非晶基体中预存α-Fe晶的数密度和晶粒尺寸逐渐降低，结构转变为近非晶态。经低升温速率热处理后，x = 12~17时合金均为非晶/α-Fe纳米晶双相结构，而x = 18时合金形成了非晶/α-Fe/Fe₃B纳米复相组织结构；x = 13~16时合金具有微细的纳米晶组织和较好的软磁性能，α-Fe相的平均晶粒尺寸(\overline{D}_α-Fe)、B_s和矫顽力(H_c)分别在15.8~16.3 nm、1.80~1.91 T和18.9~22.7 A/m的范围内，其中x = 15时合金的\overline{D}_α-Fe、B_s和H_c分别为16.0 nm、1.86 T和18.9 A/m。基于合金热处理前后的组织结构演化，提出了不同B含量快淬合金的结晶化模型，阐明了快淬合金非晶基体中高数密度的细小预存α-Fe晶粒间以及与热处理结晶化新生α-Fe晶粒间的强竞争生长效应，导致均匀、微细纳米晶组织形成的机制。

With the development of electromagnetic devices towards high-frequency, miniaturization, and high efficiency, the demand for the soft magnetic nanocrystalline alloys with high saturation magnetic flux density (B_s), excellent high-frequency performance, as well as good manufacturability is becoming increasingly urgent. In this work, the effects of B content on the melt-spun structure, thermal stability, crystallization structure, and magnetic properties of Fe_{98.5 - x} B _x Cu_1.5 (x = 12-18, atomic fraction, %) alloy ribbons were investigated; and the correlation among B content, melt-spun structure, crystallization structure, and magnetic properties was explored. The results show that the melt-spun structure of all the alloys is a dual-phase composed of α-Fe nanograins distributing in an amorphous matrix. As the x increases from 12 to 18, the number density and grain size of the α-Fe grains gradually decrease, and the structure transforms into a nearly amorphous state. After crystallization annealing under a low heating rate, the alloys with x = 12-17 have the amorphous/nanocrystalline α-Fe dual-phase structure, while the x = 18 alloy forms a amorphous/α-Fe/Fe₃B tri-phase structure. The alloys with x = 13-16 exhibit a fine nanocrystalline structure and good soft magnetic properties with the average α-Fe grain size (\overline{D}_α-Fe) of 15.8-16.3 nm, B_s of 1.80-1.91 T, and coercivity (H_c)of 18.9-22.7 A/m. Among them, the alloywith x = 15 has the \overline{D}_α-Fe, B_s, and H_c of 16.0 nm, 1.86 T, and 18.9 A/m, respectively. Based on the structure of the alloys before and after annealing, a crystallization model for the melt-spun alloys with different B contents was proposed, and the mechanism of which the strong competitive growth effect between the high-number-density pre-existing fine α-Fe nanograins in the amorphous matrix of the melt-spun alloys along with the newly-formed α-Fe grains during crystallization annealing results in the uniform and fine nanocrystalline structure of the alloys was elucidated.