Co添加對熔體快淬Fe55Pt15B30合金的組織結構與磁性能的影響Co添加對熔體快淬Fe55Pt15B30合金的組織結構與磁性能的影響Effect of Co Addition on the Structure and Magnetic Properties of Melt-spun Fe55Pt15B30 Alloy 研究了熔體快淬Fe55-xCoxPt15B30 (x = 0~45，原子分數，%)合金熱處理前后的組織結構和磁性能。結果表明，添加Co可提高Fe55Pt15B30合金的非晶形成能力，使x = 15~45的快淬合金形成非晶態。經適當熱處理后，合金中形成了由有序面心四方結構的永磁(Fe, Co)-Pt(L10)相和軟磁(Fe, Co)2B相及(Fe, Co)B相組成的納米復相組織，而顯示出永磁性；添加Co合金的組織得到明顯細化，x = 15~45合金平均晶粒尺寸均約為18 nm；其中x = 15合金具有最佳的永磁性能，磁能積達到94.4 kJ/m3。合金的矯頑力隨Co含量的增加而增大，在x = 30時達到最大值413.7 kA/m后，隨Co含量的進一步增加而減小。通過解析合金的組織結構，解釋了Co含量變化對磁性能的影響機理。 Fe-Pt-B nanocomposite magnets have attracted much attention because of their excellent hard magnetic properties, in which the face-centered-tetragonal FePt (L10) phase ensures high coercivity (iHc) and the Fe2B phase provides high magnetic saturation. A high iHc, however, is hard to reach at low Pt concentrations in these nanocomposite magnets. It is known that a high concentration of B favors formation of the L10 phase in the Fe-Pt-B alloys with low Pt concentration, but the annealed microstructure is usually coarse-grained due to their low amorphous-forming abilities, and the magnetic properties get deteriorated. Replacement of Fe with Co is expected to enhance the amorphous-forming ability of Fe-Pt-B alloys with low Pt and high B concentrations, and to improve their magnetic properties. In the present work, the structure and magnetic properties of as-quenched and annealed Fe55-xCoxPt15B30 (x = 0~45, atomic fraction, %) alloys have been investigated. Melt-spun ribbons were prepared by melt spinning, followed by vacuum annealing at different temperatures. The structure of the samples were examined by XRD and TEM. The magnetic properties were measured by using a vibrating sample magnetometer (VSM). The results indicate that single amorphous phase is formed in the alloys with x = 15~45. After appropriate annealing, a nanocomposite structure consisting of L10 and (Fe, Co)2B phases is obtained at x = 0 and 15, and an additional (Fe, Co)B phase gets formed at x = 30 and 45. A fine microstructure with mean grain size of ~18 nm has been obtained in the annealed alloys with x = 15~45. In these nanocomposite alloys, the best hard magnetic property with an energy product of 94.4 kJ/m3 is reached at x = 15. It is also found that with increasing Co concentration, the iHc gradually increases to a maximum value of 413.7 kA/m at x = 30, and then decreases at higher Co concentrations. The effect of Co addition on the magnetic properties is discussed in terms of the microstructural characteristic of these alloys.
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