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MM: Fachverband Metall- und Materialphysik

MM 5: Liquid and Amorphous Metals - Kinetics and Modelling

MM 5.1: Vortrag

Montag, 16. März 2020, 10:15–10:30, IFW D

Nucleation rates of crystallization of a bulk metallic glass-former — •Mark Stringe, Martin Peterlechner, and Gerhard Wilde — Institute of Materials Physics, University of Münster, 48149 Münster, Germany

Crystallization plays a crucial role not only regarding the production of metallic glasses via melt quenching, but also concerning the stability of the resulting metastable systems. High scanning rates in calorimetric measurements are realized using a custom-built fast differential scanning calorimeter. With this fast scanning calorimetry (FSC), samples with a mass of the order of micrograms are measured with scanning rates up to the order of 10.000 K/s. This vast range of scanning rates enables an analysis of crystallization for different levels of undercooling. An AuCuAgSi bulk metallic glass with low melting point is analyzed. In FSC it is possible to reach cooling rates to quench a glass in-situ. Hence, the critical cooling rate can be determined directly. Thus, using FSC it is possible to obtain large datasets of measurement cycles. Statistical variations of the undercooling of the glass-forming alloy can be extracted from these datasets. Applying a Poisson process to the stochastic nature of nucleation, the activation barriers for nucleation of the crystalline phase are determined. Low activation barriers indicate a heterogeneous nucleation mechanism for crystallization of the FSC samples.