Finemet型铁基多元合金是目前应用极广泛的纳米晶软磁材料之一.深入认识其形成过程的晶化动力学特性,对更好地调控制备工艺以获得稳定且软磁性能更优的目标纳米晶具有重要意义.为此,通过差示扫描量热仪(Differential scanning calorimeter,DSC)在不同升温速率的条件下研究了 Fe74Si14.5B7.5Nb3Cu1(原子分数,%)非晶的非等温晶化行为,首先利用 Kissinger-Akahira-Sinose(KAS)、Flyn-Wall-Ozawa(FWO)、Starik 和Boswell这几种典型的等转化率法求得Fe74Si14.5B7.5Nb3Cu1合金的晶化过程激活能Eα,之后采用补偿效应法得出指前因子 A,从而实现了反应模型f(α)的数值重建和Avrami指数n(α)的求解.结果表明,Fe74Si14.5B7.5Nb3Cu1非晶合金的晶化仅较接近维度扩散的反应机理模型,但不完全符合现有任何理论模型,是一个涉及多个反应模型的复杂反应.晶体形核速率在晶化初期(α<0.2)由增长阶段快速达到降低阶段(n(α)=2.3),而在0.2<α<0.5时缓慢降至零(n(α)=1.5),之后在晶化末期(α>0.5),晶体在已有晶粒的基础上继续长大(n(α)<1.5),整个晶化过程为形核速率持续降低的三维生长.Fe74Si14.5B7.5Nb3Cu1非晶合金的晶化是一个由三维扩散主导的多个晶化机制共同控制、多个反应模型协同参与的复杂过程.
The Finemet-type multi-component alloy is one of the most commonly used nanocrystalline soft magnetic materials.In-depth understanding of its crystallization mechanism is essential for better modification of the preparation process,which is of great importance for obtaining target nanocrystalline alloys with stable and excellent soft magnetic properties.Therefore,the non-isothermal crystallization behavior of Fe74Si14 5B7 5Nb3Cu1(at%)amorphous system was studied by differential scanning calorimeter(DSC)under different heating rates in this study.Firstly,the activation energy Eα for the crystallization process of Fe74Si14.5B7.5Nb3Cu1 amorphous system was obtained by the typical iso-conver-sional methods of Kissinger-Akahira-Sinose(KAS),Flyn-Wall-Ozawa(FWO),Starik and Boswell.After that,the preexponential factor A was de-rived by the compensation effect method,which led to the numerical reconstruction of the reaction model f(α)and the Avrami index n(α).The results showed that the crystallization of Fe74Si14 5B7 5Nb3Cu1 amorphous alloy was only relatively consistent with the reaction mechanism model of dimensional diffusion,but did not fully close to any present theoretical models,indicating that the crystallization process was a complex reaction involving multiple reaction models.The nucleation rate of crystals rapidly reached a decreasing stage(n(α)=2.3)from the increasing stage at the beginning of crystallization(α<0.2)and slowly decreased to 0(n(α)=1.5)at 0.2<α<0.5.Finally,the crystals continued to grow on the basis of existing grains(n(α)<1.5)at the end of crystallization(α>0.5),which was manifested as the three-dimensional growth with a conti-nuously decreasing nucleation rate during the entire crystallization process.The crystallization of Fe74Si14.5B7.5Nb3Cu1 amorphous alloy was a complex process dominated by three-dimensional diffusion,which was jointly controlled by multiple crystallization mechanisms and coordinated by multiple reaction models.