Co-Finemet非晶合金晶化动力学及其纳米晶粉芯的磁性

利用单辊熔体快淬法在大气环境中制备了Fe73.5-xCoxSi13.5B9Cu1Nb3(x=10,30,50)非晶薄带,利用差示扫描量热法(DSC)研究了非晶薄带的晶化动力学行为。采用Kissinger和Ozawa方法计算了非晶薄带的晶化表观激活能,计算结果表明:随着Co含量的增加,一次晶化的表观激活能降低而二次晶化的表观激活能升高。利用Johnson-Mehl-Avrami(JMA)模型计算了非晶薄带一次晶化的局域Avrami指数m,计算结果表明非晶薄带一次晶化的机理在不同的晶化阶段是不一样的,晶化初期为扩散控制的三维形核和晶粒生长的整体晶化,晶化中后期为一维形核和晶粒生长的表面晶化,形核率近似为零。研究了Fe63.5Co10Si13.5B9Cu1Nb3纳米晶粉芯的磁性与球磨时间之间的关系,结果表明:纳米晶粉芯的有效磁导率表现出较好的频率稳定性,而且随着球磨时间的增加而减小,品质因子在低频范围内随着频率的增加而增加,在约80 kHz达到峰值,然后随着频率的进一步增加而逐渐减小。

Crystallization Kinetics of Co-Finemet Amorphous Alloys and Magnetic Properties of Nanocrystalline Powder Cores

Amorphous Fe73.5-xCoxSi13.5B9Cu1Nb3(x=10,30,50) ribbons were prepared by the single copper wheel melt spinning technique in the air atmosphere.The nanocrystallization kinetics of amorphous ribbons was investigated by differential scanning calorimetry(DSC).The apparent activation energies of amorphous ribbons were calculated by using Kissinger and Ozawa methods.It was found that the activation energies of the first crystallization reduce and those of the second crystallization rise with increasing Co content.The local Avrami parameter m for primary crystallization was calculated using Johnson-Mehl-Avrami(JMA) model.The values of the Avrami parameter showed that the primary crystallization mechanism of amorphous ribbons varied at different stages.In the initial stage,the crystallization mechanism was bulk crystallization with three dimensional nucleation and grain growth controlled by diffusion.In the following stage,it was surface crystallization with one dimensional nucleation and grain growth at a near zero nucleation rate.The variation of soft magnetic properties of nanocrystalline Fe63.5Co10Si13.5B9Cu1Nb3 powder cores as a function of milling time has been investigated.It was found that the effective permeability of the cores shows high frequency stability and decreases with increasing milling time.The quality factor increases with increasing frequency in the lower frequency range,reaches a maximum at the frequency of 80 kHz,and then decreases gradually with increasing frequency.