Main and secondary relaxations in an Au-based bulk metallic glass investigated by mechanical spectroscopy
Résumé
The dynamic mechanical relaxation behavior of an Au49Cu26.9Si16.3Ag5.5Pd2.3 (at.%) bulk metallic glass was investigated by mechanical spectroscopy as a function of temperature or driving frequency. The mechanical spectra show the evidence of a secondary relaxation (or β) process at low temperature or high driving frequency. The main relaxation (α) is clearly evident at higher temperature or lower frequency. Crystallization induces an increase in elastic modulus, in two steps, which correspond to the formation of two different crystalline phases, as determined by in-situ X-ray diffraction experiments. Master curves could be obtained based on the time-temperature superposition principle. From these curves the apparent activation energies for the two relaxation phenomena were determined: Eβ = 1.10 eV and Eα = 3.65 eV, respectively. These values indicate that the secondary relaxation may be attributed to local atomic movements, while the α relaxation corresponds to correlated movements. © 2016 Elsevier B.V.
Mots clés
Activation energy
Crystallization
Glass
Palladium
Temperature
X ray diffraction
Apparent activation energy
Bulk metallic glass
Dynamic mechanical relaxation
In-situ X-ray diffraction
Main relaxation
Mechanical spectroscopy
Secondary relaxations
Time-temperature superposition principles
Metallic glass