Improved soft magnetic properties and thermal stability for Fe_82·65Cu_1·35Si₂B₁₄ alloys with Nb, Zr, Ta or Co addition

Abstract

Nanocrystalline Fe_81·65Cu_1·35Si₂B₁₄M (M = Ta, Nb or Zr) alloys were obtained by melt spinning followed by annealing. The addition of Ta, Nb or Zr not only significantly increased the ΔT_x of the Fe_82·65Cu_1·35Si₂B₁₄ alloy, which is defined as the temperature interval between the first and second crystallisation temperatures, but also had advantages in reducing grain size. In particular, Zr doping increased ΔT_x from 91 to 155·2°C, and the Fe_81·65Cu_1·35Si₂B₁₄Zr alloy had good soft magnetic properties even after annealing at 500°C. Ta added alloy can still maintain fine grain size below 35 nm after annealing at 450°C. The effects of partial replacement of Fe with Co in the (Fe_1−xCo_x)_82·65Cu_1·35Si₂B₁₄ alloys (x = 0, 0·3, 0·5 and 0·7) on the structure and magnetic properties were also investigated. Increasing the Co content reduced the first crystallisation temperature, and 30%Co substituted alloy had the highest saturation magnetisation. Co improved the thermal stability through increasing both Curie temperature T_c of the amorphous phase and ΔT_x.

Keywords:

• Nanocrystalline alloys
• Soft magnets
• Thermal stability

This work is partly supported by the Natural Science Foundation of China (grant no. 51174094) and the Program for New Century Excellent Talents in University (grant no. NCET-11-0156).