Small atom diffusion and breakdown of the Stokes–Einstein relation in the supercooled liquid state of the Zr46.7Ti8.3Cu7.5Ni10Be27.5 alloy

Abstract

Be diffusivity data in the bulk metallic glass forming alloy Zr_46.7Ti_8.3Cu_7.5Ni₁₀Be_27.5 are reported for temperatures between 530 and 710 K, extending 85 K into the supercooled liquid state of the alloy. At the glass transition temperature T_g, a change in temperature dependence of the data is observed, and above T_g the diffusivity increases more quickly with temperature than below. The data in the supercooled liquid can be described by a modified Arrhenius expression based on a diffusion mechanism suggested earlier. The comparison with viscosity data in the supercooled liquid state of Zr_46.7Ti_8.3Cu_7.5Ni₁₀Be_27.5 reveals a breakdown of the Stokes–Einstein relation, indicating a cooperative diffusion mechanism in the supercooled liquid state of Zr_46.7Ti_8.3Cu_7.5Ni₁₀Be_27.5.