Non-isothermal Crystallization Kinetics and Isothermal Crystallization Kinetics in Supercooled Liquid Region of Cu–Zr–Al–Y Bulk Metallic Glass

Abstract

The crystallization kinetics of Cu43Zr48Al9 and (Cu43Zr48Al9)98Y2 bulk metallic glasses in non-isothermal and isothermal conditions was studied by differential scanning calorimetry. In the non-isothermal and isothermal modes, the average activation energy of (Cu43Zr48Al9)98Y2 is larger than that of Cu43Zr48Al9, meaning the higher stability against crystallization of (Cu43Zr48Al9)98Y2. In addition, the average activation energies for Cu43Zr48Al9 and (Cu43Zr48Al9)98Y2 calculated using Arrhenius equation in isothermal mode are larger than the values calculated by Kissinger–Akahira–Sunose method in non-isothermal mode, indicating that the energy barrier is higher in isothermal mode. The Johnson–Mehl–Avrami model was used to analyze the crystallization kinetics in the non-isothermal and isothermal modes. The Avrami exponent n for Cu43Zr48Al9 is above 2.5, indicating that the crystallization is mainly determined by a diffusion-controlled three-dimensional growth with an increasing nucleation rate, while the Avrami exponent n for (Cu43Zr48Al9)98Y2 is in the range of 1.5–2.5 in the non-isothermal mode, implying that the crystallization is mainly governed by diffusion-controlled three-dimensional growth with decreasing nucleation rate. Finally, the Avrami exponents n for Cu43Zr48Al9 and (Cu43Zr48Al9)98Y2 are different in the non-isothermal and isothermal conditions, which imply different nucleation and growth behaviors during the crystallization processes.