一种新的Cu基大块非晶合金非等温晶化动力学研究

Kinetic Analysis of the Non-isothermal Crystallization of a New Cu-Based Bulk Metallic Glass

摘要:

采用铜模吸铸法制备了Cu56.4Zr31.02Ti6.58Al6大块非晶合金（BMGs），并利用X射线衍射仪（XRD）、透射电子显微镜（TEM）和同步示差扫描量热仪（DSC）等手段对其晶体结构、晶化激活能和晶化机制进行了研究。利用y(a)和z(a)判据检测了不同晶化模型对于该BMGs初始晶化相晶化过程的适用性。结果显示：该BMGs初晶晶化产物为Cu10Zr7相，Starink-Zahra模型可以很好地描述其晶化机制。拟合参数λi不为零，故晶化过程中软碰撞作用不可忽视；Avrami指数n由2.5减小为2.3，其晶化过程为连续形核过程中伴随着晶核受扩散控制的三维方式长大，且形核速率不断减小。

Abstract:

Copper-mold suction casting was employed to prepare the Cu56.4Zr31.02Ti6.58Al6 bulk metallic glass (BMGs). X-ray diffraction (XRD), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) were used to analyze their microstructure, activation energy and crystallization mechanism. The criterions y(a) and z(a) were applied to test the validity of different nucleation-growth models for the first crystallization stage of the BMGs. Results show that the primary crystallization product of Cu56.4Zr31.02Ti6.58Al6 is Cu10Zr7 and the Starink-Zahra model can describe the crystallization mechanism well. Fitting parameters show that impingement effect factor λi≠0, indicating that impingement effect can't be ignored. Avrami exponent n decreases to 2.3 from 2.5, suggesting that the BMG experienced a continuous nucleation process and diffusion controlled growth process. Furthermore, the nucleation rate has a decrease trend.