Effect of Nb minor addition on the crystallization kinetic of a Zr-Cu-Al-Ni bulk metallic glassy alloy

Non-isothermal crystallization kinetic of (Zr۵۵Cu۳۰Al۱۰Ni۵)۹۹Nb۱ bulk metallic glass (BMG) was studied by x-ray diffraction (XRD), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The crystallization behavior of (Zr۵۵Cu۳۰Al۱۰Ni۵)۹۹Nb۱ BMG at different heating rates (۵ to ۸۰ K.min-۱) from room temperature to ۸۷۳ K was investigated, so that by increasing the heating rate, the crystallization pathway was changed. The apparent activation energy at characteristic temperatures (a.u. Eg, Ex۱, Ep۱ at Tg, Tx۱, Tp۱, respectively) was calculated using Kissinger, and Ozawa models. Increase of the Eg, Ex۱, Ep۱ for (Zr۵۵Cu۳۰Al۱۰Ni۵)۹۹Nb۱ compared to the base alloy without Nb was observed, demonstrating higher thermal stability and higher barrier for crystallization by minor addition of Nb. Local activation energy variations by crystallized volume fraction (α) (a.u. Ec(α)) was extracted using Ozawa-Flynn-Wall (OFW) method. Decrease of Ec(α) by increasing α was observed. Crystallization reaction function (f(α)) at different heating rate was extracted by means of Johnson-Mehl-Avrami (JMA) model.

کلیدواژه ها:

Zr-based bulk metallic glass (BMG) ، Crystallization kinetics ، Activation energy ، Reaction function.