Beryllium diffusion in the supercooled liquid and glassy state of the Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy

The self diffusivity of Be in the bulk metallic amorphous Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy is investigated by high energy elastic backscattering of 4He2+ ions in the temperature range between 433 K and 663 K. Below the glass transition temperature, the data suggest a single atomic jump diffusion behavior of Be with a migration enthalpy of 1.05 eV/atom and a pre-exponential factor of 1.8.10-11m2/s. Above the glass transition, the diffusivity of Be increases by two orders of magnitude over a temperature interval of 40 K. By taking into account the change in configurational entropy due to the glass transition, we can explain the mechanism for diffusion of Be in the supercooled liquid state of Zr41.2Ti13.8Ni10Cu12.5Be22.5 by single atomic jumps in a slowly changing configuration of neighboring atoms. The corresponding migration enthalpy is the same as in the solid glass, and the number of neighboring atoms which influence the diffusion of Be is about 22. (orig.)