Decoupled alpha and beta relaxation kinetics in a thermally cycled bulk Pd40Ni40P20 glass
Stringe, Mark 1Spangenberg, Katharina 1Pinto, Manoel Wilker da Silva 1Peterlechner, Martin 1Wilde, Gerhard1
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作者信息
1. Westfal Wilhelms Univ Munster
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Abstract
Reproducible thermodynamic sample states of a Pd40Ni40P20 bulk metallic glass are realized via differential scanning calorimetry by repeated quenching from the supercooled liquid state to temperatures well below the glass transition. Annealing treatments at 0.81 Tg and 0.96 Tg are embedded in the calorimetric method, changing the energetical state of the system. Varying the annealing times, a detailed and reproducible picture of the reversible relaxation dynamics with separated alpha- and beta-relaxation is obtained. An endothermic signature before Tg can either be provoked or depressed depending on the annealing temperature. The activation energy related to this process is obtained via Kissinger analyses yielding about 30 RTg. A large number of annealing cycles at 0.96 Tg irreversibly alters the response of the alpha-relaxation, while the mechanism of beta-relaxation is interestingly not influenced by this alternation. In order to extend the calorimetric response of the relaxation spectra to spatial resolution, the sample states were additionally analyzed using electron correlation microscopy providing information on the glass dynamics on an atomistic scale. The thus obtained kinetic parameters of local dynamics do not show an alteration of room temperature dynamics for different levels of alpha-relaxation, which is consistent with the results obtained via kinetic analyses of calorimetric data.
NSTL
Elsevier