Regensburg 2010 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 18: Topical Session Glass Dynamics V
MM 18.3: Talk
Tuesday, March 23, 2010, 11:00–11:15, H16
Enthalpy and free volume relaxation in a Zr-Ti-Ni-Cu-Be bulk metallic glass alloy — •Zach Evenson and Ralf Busch — Chair of Metallic Materials, Saarland University, PO Box 151150, 66041 Saarbruecken, Germany
We report on the enthalpy and free volume relaxation kinetics of the Zr44Ti11Ni10Cu10Be25 (Vitreloy 1b) bulk metallic glass as measured with dilatometric and calorimetric methods. Using Differential Scanning Calorimetry (DSC) samples are relaxed into the metastable equilibrium liquid at temperatures below the calorimetric glass transition (Tg); the resulting enthalpy recovery (Δ Hrecov.) is then measured upon re-heating into the supercooled liquid region. It is found that the sample volume also relaxes into a metastable equilibrium liquid state, observed on a long time scale. These volumetric changes are measured isothermally using Thermal Mechanical Analysis (TMA). The total changes in the free volume (Δ vf/vm) from the initially glassy state and the equilibrium liquid are calculated during annealing at the same temperatures as in DSC. The equilibrium free volume change is found to relax with a stretched exponential behavior and is best fitted with a Kohlrausch-Williams-Watts (KWW) function with beta-values approaching unity close to the glass transition. The measured values of Δ Hrecov. and Δ vf/vm correlate well within the framework of free volume theory and a linear relationship is found between the two.