Diffusion in bulk metallic glasses

Using the radiotracer technique we performed a study of self-diffusion in bulk metallic glasses of the nominal composition Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_{27. 5} and Zr₆₅Cu_17.5Ni₁₀Al_7.5 around the calorimetric glass transition temperature. Self-diffusion of the major component Zr in Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_{27. 5} was studied as well as self-diffusion of Ni in both alloys. The diffusivity of Zr is much slower than that of Ni. The temperature dependence of Ni in Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_{27. 5} and Zr₆₅Cu_17.5Ni₁₀Al_7.5 reveals a non-linear Arrhenius behaviour. In each alloy two sets of Arrhenius parameters are necessary to describe the temperature dependence over the whole investigated temperature range. The break in the Arrhenius function is related to the transition from the glassy to the supercooled liquid state. Furthermore, we present data on pressure dependence of Ni diffusion in the supercooled liquid state of Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_{27. 5} for different temperatures. Diffusion exhibits a non-vanishing pressure dependence and activation volumes average to about 0.52 mean atomic volume.

Drittmittelgeber:

Deutsche Forschungsgemeinschaft (Schwerpunktprogramm "Unterkühlte Metallschmelzen")

Beteiligte Wissenschaftler:

Dr. K. Freitag (Universität Bonn), Dr. K. Knorr (bis März 2000), Dr. M.-P. Macht (HMI Berlin), Prof. Dr. H. Mehrer (Leiter)

Veröffentlichungen:

Knorr, K., M.-P. Macht, K. Freitag, H. Mehrer: Self-diffusion in the amorphous and the supercooled liquid state of the bulk metallic glass Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_{27. 5}, J. of Noncrystalline Solids 250 - 252, 669 - 673 (1999)

Knorr, K., M.-P. Macht, H. Mehrer: Self-diffusion in bulk metallic glasses, Mat. Res. Symp. Proc. Vol. 554, 269 - 274 (1999), (Eds.: W. L. Johnson, A. Inoue, C. T. Liu)

Knorr, K., M.-P. Macht, H. Mehrer: Self-diffusion in bulk metallic glasses, Materials Development and Processing - Bulk Amorphous Materials, Undercooling and Powder Metallurgy (Eds.: J. V. Wood, L. Schultz, D. M. Herlach), EUROMAT 99 - Vol. 8, 22 - 29, Wiley-VCH, Weinheim (2000)

Dissertation:

Kathrin Knorr: "Selbstdiffusion in metallischen Massivgläsern" (2000)