Fragility measurement of Pd-based metallic glass by dynamic mechanical analysis

The measurement of fragility of glass-forming liquids involves either the determination of viscosity at different temperatures above the glass transition or the measurement of the dynamic glass–liquid transition by calorimetry or dilatometry at different heating rates. Significant data dispersion is observed when comparing fragility parameters obtained by different techniques. Dynamic mechanical analysis (DMA) is widely used for characterizing glass transition in polymer science while it is still seldom used in metallic glasses. In this work we determine the relaxation time (τ) vs temperature of a Pd77.5Si16.5Cu6 glass by means of DMA measurements. The measured range of relaxation times cover the whole region from glass transition (τ > 100 s) to times of the order of 10−2 s. The fragility parameter obtained for this alloy is found significantly higher than the values obtained from previous viscosity and calorimetric techniques. The application range, limitations and correctness of the technique are discussed.