Isothermal and non-isothermal crystallization kinetics of novel metalloid-bearing light rare-earth-based La64Al26Ga4C6 metallic glass with high thermal stability

Abstract

The crystallization kinetics of a novel metalloid-bearing light rare-earth (RE)-based La64Al26Ga4C6 metallic glass (MG) under isothermal and non-isothermal conditions were systematically researched by Johnson-Mehl-Avrami (JMA), Arrhenius, Kissinger, Ozawa, Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall approaches using differential scanning calorimeter. The present MG possesses higher thermal stability than other light RE-based MGs without metalloid. As the isothermal crystallization temperature increases, the Avrami exponent estimated by JMA equation ranges from 2.36 to 2.94, implying that the isothermal crystallization mechanism varies from a three-dimensional diffusion-governed growth with a decreasing nucleation rate to a three-dimensional diffusion-governed growth with an increasing nucleation rate. Meanwhile, the apparent activation energy determined by Kissinger and Ozawa methods for characteristic temperatures indicates that glass transition is more difficult than crystallization process. Additionally, the local Avrami exponents show various trends, implying a transformable crystallization mechanism with crystallization proceeding. Furthermore, the crystallization process becomes easier due to the decrease of local activation energy.