Non-isothermal nano-crystallization kinetics in amorphous Ni_(55)Nb_(35)Si_(10) alloy

非晶态Ni_(55)Nb_(35)Si_(10)合金的非等温纳米结晶动力学（英文）

The non-isothermal crystallization kinetics of Ni55Nb35Si10 amorphous alloy,prepared by mechanical alloying,was studied using differential scanning calorimetry.The amorphous alloy showed one-stage crystallization on heating,which led to the formation of nano-intermetallic crystals in amorphous matrix.The apparent activation energy for the crystallization of the alloy,determined by the Kissinger equation,was relatively high(468 kJ/mol),indicating that this amorphous alloy has high thermal stability.Changes in the activation energy during the crystallization process,were also evaluated by iso-conversional methods.The results showed that it decreases slowly from the beginning to crystallized fractionα=0.35 and it remains almost constant to the end of the process.The nano-crystallization mechanism for the non-isothermal crystallization of the amorphous alloy was explained by determining Avrami exponents.Transmission electron microscopy studies revealed the microstructural modification of amorphous alloy via nanocrystallization during annealing.The results suggest that the nucleation rate decreases with increasing time and the crystallization mechanism is governed dominantly by a three-dimensional diffusion-controlled growth.A predictive equation was obtained based on the Sestak-Berggren autocatalytic model to describe quantitatively the non-isothermal crystallization kinetics.

采用差示扫描量热法(DSC)研究机械合金化制备的Ni_(55)Nb_(35)Si_(10)非晶合金的非等温结晶动力学。结果表明,该非晶合金在加热过程中表现出单级结晶,导致非晶态基体中形成金属间化合物纳米晶体。由基辛格方程确定的合金结晶表观活化能较高(468 k J/mol),说明该非晶合金具有较高的热稳定性。采用等转换法对结晶过程中活化能的变化进行研究,活化能从结晶开始一直缓慢降低至结晶分数α=0.35,然后几乎保持不变直至结晶结束。通过测定Avrami指数,解释非晶合金非等温结晶的纳米结晶机理。透射电镜研究表明,在退火过程中通过纳米结晶可对非晶态合金进行微观结构调控。成核速率随时间的延长而减小,结晶机理主要受三维扩散控制生长支配。在Sestak-Berggren自催化模型的基础上,得到定量描述非等温结晶动力学的预测方程。