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

Abstract The crystallisation kinetics of (Cu 46 Zr 46 Al 8 ) 100–x Gd x ( 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 Cu 10 Zr 7 changes to Cu 10 Zr 7 and Cu 2 Gd 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 Cu 46 Zr 46 Al 8 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 (Cu 46 Zr 46 Al 8 ) 98 Gd 2 and (Cu 46 Zr 46 Al 8 ) 96 Gd 4 is 1.5 < n < 2.5, which suggests that the crystallisation is mainly determined by diffusion-controlled three-dimensional growth with decreasing nucleation rate.