Solid-State Amorphization Observed in the Cu–Zr System by Molecular Dynamics Simulation

概要

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An n-body potential of the Cu–Zr system is constructed under the formalism of the second moment approximation of tight-binding. Applying the proven relevant Cu–Zr potential, solid-state amorphization has been observed in the Cu–Zr system by molecular dynamics simulations using the solid solution and sandwich models. Simulations using the solid solution models not only reproduce the experimentally observed crystal-to-amorphous transition in the system, but also clarify that the physical origin of the transition is the crystalline lattice collapsing while the solute atoms are exceeding the critical solid solubilities, 8 at. % of Cu and 10 at. % of Zr in the hcp Zr-based and fcc Cu-based solid solutions, respectively, which matches well with that observed in experiments. Simulations using the Cu/Zr/Cu sandwich models indicate that the amorphization is initiated by the mutual diffusion of the atoms and that the Cu–Zr amorphous layer grows in a layer-by-layer kinetics featuring a so-called asymmetric-growth behavior. The growth of the amorphous interlayer can be divided into three stages: the fast nucleating stage, the diffusion-growing stage and the steady finishing stage.
2008-10-15