Effect of Gd addition on non-isothermal and isothermal crystallisation of Cu–Zr–Al bulk metallic glass

Abstract

Abstract The crystallisation kinetics of (Cu46Zr46Al8)100–xGdx (x = 0, 2 and 4 at.%) bulk metallic glasses in non-isothermal and isothermal conditions were studied by differential scanning calorimetry and X-ray diffraction. X-ray diffraction analysis shows that the crystallisation product Cu10Zr7 changes to Cu10Zr7 and Cu2Gd in the presence of Gd in non-isothermal and isothermal conditions. Crystallisation activation energy was calculated using the Kissinger and Ozawa methods in non-isothermal conditions and using the Arrhenius model in isothermal conditions. The results show that Gd addition triggers an increase in the energy barrier during crystallisation. The Johnson–Mehl–Avrami model was employed to analyse the crystallisation kinetics in the isothermal condition. The Avrami exponent, n, for Cu46Zr46Al8 is more than 2.5, which demonstrates that the crystallisation is mainly governed by diffusion-controlled three-dimensional growth with increasing nucleation rate. Comparably, n for (Cu46Zr46Al8)98Gd2 and (Cu46Zr46Al8)96Gd4 is 1.5 < n < 2.5, which suggests that the crystallisation is mainly determined by diffusion-controlled three-dimensional growth with decreasing nucleation rate.