Study on isothermal crystallization kinetics of Zr55.7Cu22.4Ni7.2Al14.7 bulk amorphous alloy

Abstract

Zr55.7Cu22.4Ni7.2Al14.7 alloy bars were prepared by copper mold suction casting, and the structure and thermodynamic properties of the prepared specimens were characterized by X-ray diffractometer and differential scanning calorimeter. Furthermore, isothermal crystallization mechanism and crystallization activation energy were investigated by Johnson–Mehl–Avrami model and Arrhenius equation. The results show that the structure of the specimen is amorphous. The glass transition temperature (Tg), onset crystallization temperature (Tx) and crystallization peak temperature (Tp) are 713 K, 779 K, and 781 K, respectively, and supercooled liquid region (ΔT=Tx-Tg) is 66 K. The crystallization incubation times are shortened and the crystallization transformation rates increase with temperature rising. As the crystallization volume fraction increases, the crystallization nucleation rate shows a trend of first increasing and subsequently decreasing, while the activation energy decreases monotonously, in the same time, the crystallization behavior transforms from interface-controlled to diffusion-controlled growth. The thermal stability of amorphous alloy is also discussed.