Dynamic measurements of the tensile storage and loss moduli of a bulk glass-forming metallic alloy, Pd48Ni32P20, have been performed below and close to the calorimetric glass transition temperature. These results were compared with the previously measured tensile relaxation behaviour in Pt60Ni15P25 which is a non-bulk metallic glass former. The measurements for the Pd-alloy indicate a higher tensile viscosity and a more gradual change of relaxation times with temperature near the glass transition compared to the Pt-alloy. This is consistent with the fact that Pd48Ni32P20 has a lower fragility parameter than Pt60Ni15P25. From the master curve of the elastic moduli obtained by time-temperature superposition, a discrete spectrum of relaxation frequencies have been computed for both alloys. Unlike the distribution for Pt60Ni15P25 which has the more common features of a single broad and asymmetric peak that is skewed towards high frequencies, the relaxation spectrum for Pd48Ni32P20 exhibits a secondary low amplitude peak on the high frequency side of a main maximum. This suggests that there is a separate concentration of some intrinsic relaxation processes in a finite region of the relaxation spectrum at higher frequencies than the microscopic processes governing the main relaxation event. The fairly wide relaxation frequency distributions for both alloys indicate a dynamically heterogeneous environment near the glass transition.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Acoustics and Ultrasonics
- Surfaces, Coatings and Films