Thermal behavior and non-isothermal crystallization kinetics of (Ti41Zr25Be28Fe6)93Cu7 bulk metallic glass

Abstract

The thermal behavior analysis of (Ti41Zr25Be28Fe6)93Cu7 bulk metallic glass was investigated using the non-isothermal differential scanning calorimetry method. DSC curves at lower heating rates (≤30K·min−1) revealed four exothermic and three endothermic peaks. The middle endothermic peak was characterized as the formation of the CuZr2 Laves phase. The crystallization behavior of the alloy was identified. The first and second exothermic peaks overlapped at all heating rates, therefore the non-isothermal crystallization kinetics of the two peaks were investigated. Using the Kissinger equation the apparent activation energy of the first and second peaks estimated to be 155.6±11.6 and 154.1±4.9kJ·mol−1, respectively. Similar values were also obtained by Ozawa and Boswell methods. The dependence of the local activation energy on the conversion fraction was generalized by the Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW) and Friedman methods. The local activation energy remained constant during the first crystallization event and dramatically decreased during the second crystallization reaction. The validity of the JMA model for both transformations was investigated. An autocatalytic behavior of crystallization was observed and the mathematical description of the crystallization using Šesták-Berggren model has been built for the two crystallization reactions. The validity of the proposed models was investigated using the master plot method.