Fe-B非晶合金的等温晶化动力学研究

Isothermal Crystallization Kinetic Study of a Fe-B Amorphous Alloy

为研究Fe_(85)B_(15)非晶合金等温条件下晶化的形核、长大及碰撞等动力学机制,采用差热扫描量热仪(DSC)对未经过和经过预热处理的该非晶合金在不同温度下进行等温实验,用X射线衍射仪和透射电子显微镜分析其晶化前后的物相组成和显微结构。该合金等温晶化后为层片状分布的αFe和Fe 3B两相。运用解析相变模型结合碰撞模式判断,对所有DSC实验数据进行拟合得到晶化动力学参数。等温晶化的形核和生长激活能分别为355 kJ·mol-1和279 kJ·mol-1。未预热处理等温晶化有效激活能约311 kJ·mol-1,生长指数为2.2~2.3;预热处理等温晶化有效激活能为280~308 kJ·mol-1,生长指数为1.3~2.2。预热处理形成预存晶核,影响晶化过程。Fe_(85)B_(15)非晶合金等温晶化遵循混合形核,三维扩散生长及晶核非随机分布碰撞。

The study is aimed to study the kinetics of nucleation,growth and impingement during isothermal crystallization of the Fe 85 B 15 amorphous alloy.The crystallization process of samples with and without pre annealing was recorded by using the differential scanning calorimetry(DSC).X ray diffraction and transmission electron microscopy(TEM)were employed to investigate the phase composition and microstructure of the material.The modular kinetic model considering impingement mode was utilized to fit all the curves with and without pre annealing obtained experimentally by DSC simultaneously.The result show that the Fe 85 B 15 amorphous alloy crystallized into two phases,αFe and Fe 3B with lamellar growth.The separate activation energy for nucleation and growth amounts to 355 kJ·mol-1 and 279 kJ·mol-1,respectively.For crystallization without pre annealing,an activation energy of about 311 kJ·mol-1 and a growth exponent of 2.2~2.3 are obtained.With pre annealing,the activation energy decreases to 280~308 kJ·mol-1 and the growth exponent to 1.3~2.2.The number of pre existing nuclei increases during the treatment,which affects the process of crystallization.The crystallization of Fe 85 B 15 amorphous alloy follows mixed nucleation,three dimension diffusion controlled growth and impingement according to non random nuclei dispersion.