The self-diffusivity of Be in the bulk amorphous metallic alloy was investigated by studying the high-energy elastic back-scattering of 4He2+ ions at temperatures ranging from 433 to 663K. When below the glass transition temperature, the data suggested the operation of a single atomic jump Be diffusion behavior, with a migration enthalpy of 1.05eV and a pre-exponential factor of 1.8 x 10-11m2/s. When above the glass transition, the Be diffusivity increased by 2 orders of magnitude over a temperature interval of 40K. By taking account of the change in configurational entropy due to the glass transition, it was possible to explain the mechanism of Be diffusion in the supercooled liquid state in terms of single atomic jumps in a slowly changing configuration of neighboring atoms. The corresponding migration enthalpy was the same as in the solid glass, and the number of neighboring atoms which affected Be diffusion was estimated to be equal to about 22.

U.Geyer, S.Schneider, Y.Qui, M.P.Macht, T.A.Tombrello, W.L.Johnson: Materials Science Forum, 1996, 225-227, 89-94

Table 352

Diffusivity of B in Zr41Be22.5Ti14Cu12.5Ni10

Table 353

Diffusivity of Fe in Zr41Be22.5Ti14Cu12.5Ni10