Crystal growth and time evolution in Zr–Al–Cu–Ni glassy metals in supercooled liquid

Abstract

Crystal nucleation and its time evolution during isothermal annealing in supercooled liquid of glassy metals Zr 55 Al 10 Cu 30 Ni 5 and Zr 55 Al 10 Cu 35 are examined using a technique of differential thermal analysis. Time dependence of the fraction of crystallization in supercooled liquid at several temperatures is analyzed by the Johnson–Mehl–Avrami form. The Avrami number is 2.8 ± 0.4 for the present samples. Since crystallites growing in the supercooled liquid with time are found to be Zr 2 Cu crystals, it is suggested that the crystal growth in supercooled liquid is ruled by a long range diffusion process of elements. Plots of the fraction of crystallized volume versus a scaled time normalized by the half time of full crystallization almost collapse on an almost single curve . The temperature dependence of the half time is discussed using a Williams–Landel–Ferry function. The excitation energy for crystal nuclei with a critical radius is estimated.