Diffusion in Bulk Glass Forming Alloys– from the Glass to the Equilibrium Melt

Klaus Rätzke; V. Zöllmer; A. Bartsch; Andreas Meyer; Franz Faupel

doi:10.4028/www.scientific.net/DDF.266.109

Paper Titles

A Mathematical Formulation for Interfacial Diffusion, Incorporating Deviation from the Classical Random Walk Theory
p.63

First-Principles Computation of Transition-Metal Diffusion Mobility
p.73

An Examination of Diffusion Paths in Terms of Interdiffusion Fluxes and Interdiffusion Coefficients
p.83

Diffusion in Metallic Melts
p.101

Diffusion in Bulk Glass Forming Alloys– from the Glass to the Equilibrium Melt
p.109

Non-Random Interaction of Vacancies with Atoms during Interdiffusion and Ionic Conductivity in Materials
p.119

Interdiffusion Behavior in γ-Phase U-Mo Alloy versus Al-6061 Alloy Couples Fabricated by Friction Stir Welding
p.131

Growth Kinetics of Intermetallic Phases in U-Mo vs. Al Alloy Diffusion Couples Annealed at 550°C
p.149

The Influence of Solid State Diffusion on Microstructural Development during Solidification
p.157

HomeDefect and Diffusion ForumDefect and Diffusion Forum Vol. 266Diffusion in Bulk Glass Forming Alloys– from the...

Diffusion in Bulk Glass Forming Alloys– from the Glass to the Equilibrium Melt

Abstract:

Since the discovery of bulk metallic glasses there has been considerable research effort on these systems, in particular with respect to mass transport. Now the undercooled melt between the melting temperature and the caloric glass transition temperature, which has not been accessible before due to the rapid onset of crystallization, can be investigated and theories can be tested. Here we report on radiotracer diffusion measurements in metallic bulk-glass-forming Pd-Cu-Ni-P alloys. Serial sectioning was performed by grinding and ion-beam sputtering. The time, temperature as well as the mass dependence, expressed in terms of the isotope effect E, of Co-diffusion were investigated. The Co isotope effect measurements, which have never been carried out near Tc in any material, show atomic transport up to the equilibrium melt to be far away from the hydrodynamic regime of uncorrelated binary collisions. In the glassy state as well as in the deeply supercooled state below the critical temperature Tc, where the mode coupling theory predicts a freezing-in of liquid-like motion, the experimentally determined very small isotope effects indicate a highly collective hopping mechanism involving some ten atoms. Below Tc the temperature dependence shows Arrhenius-type behavior with an effective activation enthalpy of 3.2 eV. Above Tc the onset of liquid-like motion is evidenced by a gradual drop of the effective activation energy and by the validity of the Stokes-Einstein equation, which is found to break down below Tc. Although having strong covalent bonding tendencies, Phosphorous diffusion is only slightly slower than Co diffusion, indicating that it does not determine the overall viscosity below Tc. The Stokes-Einstein equation is presently tested for other constituents of the alloy.