Time-resolved study of the crystallization dynamics in a metallic glass

We report a study of the atomic-scale dynamics in a metallic glass of composition Zr65Ni10Cu17.5Al7.5 by x-ray photon correlation spectroscopy. Our results show a continuous slowing down of the dynamics from the pristine state of the sample until crystallization. We propose a phenomenological model in a framework of thermally activated dynamics with a decreasing attempt rate dependent on the sample state that quantitatively describes our results, giving an activation energy of E-A = 1.95 +/- 0.10 eV. This allows us to conclude that atomic motion and crystallization are manifestations of the same process, with the time scale of crystallization on the order of 100 local atomic rearrangements. This rules out the notion of equilibrium diffusion in a relaxed glassy state in this system.