Microstructure and magnetocaloric properties of partially crystallized Gd₆₀Co₃₀Fe₁₀ amorphous alloy prepared by different solidification cooling rates

The Gd₆₀Co₃₀Fe₁₀ alloy ribbons with different solidification cooling rates were prepared by modifying the melt-spinning speed of 6.0, 12.5, 25.0 and 50.0 m·s⁻¹. With cooling rate decreasing, the (Fe,Co)₅Gd and hcp-Gd nanocrystalline was in situ precipitated among the amorphous matrix, which resulted in the composition change of the amorphous phase. Because of the only slight amount of crystalline phase in Gd₆₀Co₃₀Fe₁₀ alloys, the magnetic and magnetocaloric properties mainly depend on the amorphous phase, and all the magnetic entropy change versus temperature (|ΔS_M|–T) curves are table-like, indicating the suitability for Ericsson cycle. The magnetic transition temperature of the Gd₆₀Co₃₀Fe₁₀ alloy at a melt-spinning speed of 6.0 m·s⁻¹ shifted obviously to the lower value with the applied magnetic fields increasing. The peak value of magnetic entropy change (|ΔS_M^pk|) is 2.19 J·kg⁻¹·K⁻¹ at 217 K under the magnetic field change of 0–2 T, and the table-like region is 200–230 K. It was proved that the moderate reduction of the cooling rate will not deteriorate the magnetocaloric performance of the Gd₆₀Co₃₀Fe₁₀ ribbons seriously.

使用熔体旋淬法, 通过调节辊轮转速为6.0, 12.5, 25.0 和 50.0 m·s⁻¹, 制备了不同冷却速度的Gd₆₀Co₃₀Fe₁₀合金条带。随着冷却速度的降低, (Fe,Co)₅Gd和hcp-Gd纳米晶从非晶基体中原位析出, 使非晶相的成分发生变化。由于析出的晶相含量较低, 因此整个样品的磁性能和磁热性能主要取决于非晶相, 磁熵变温变 (|ΔS_M|-T) 曲线均呈平台型, 表明其适用于Ericsson循环。辊轮转速为6.0 m·s⁻¹时制备的Gd₆₀Co₃₀Fe₁₀合金的磁转变温度随着外加磁场的增加明显向低温偏移, 在磁场变化为0-2 T的条件下, 217 K时磁熵变峰值 (|ΔS_M^pk|) 为2.19 J·kg⁻¹·K⁻¹, 平台区为200-230 K。本研究证明适度的降低冷却速度, 不会使Gd₆₀Co₃₀Fe₁₀合金条带的磁热性能表现严重恶化。