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Titel: The role of Ga addition on the thermodynamics, kinetics, and tarnishing properties of the Au-Ag-Pd-Cu-Si bulk metallic glass forming system
VerfasserIn: Neuber, Nico
Gross, Oliver
Eisenbart, Miriam
Heiss, Alexander
Klotz, Ulrich E.
Best, James P.
Polyakov, Mikhail N.
Michler, Johann
Busch, Ralf
Gallino, Isabella
Sprache: Englisch
Titel: Acta Materialia
Bandnummer: 165 (2019)
Seiten: 315-326
Verlag/Plattform: Elsevier
Erscheinungsjahr: 2018
Freie Schlagwörter: Thermodynamics
Kinetics
Bulk metallic glasses
Gold
Jewelry application
Ion implantation
DDC-Sachgruppe: 500 Naturwissenschaften
Dokumenttyp: Journalartikel / Zeitschriftenartikel
Abstract: Effective strategies to improve the tarnishing resistance of the 18 K (karat) gold-based bulk glass-forming composition Au49Ag5.5Pd2.3Cu26.9Si16.3 were recently found, with the addition of Ga at the expense of Cu and a sufficient reduction of Si. However, the modification of the alloy is accompanied by a reduction of the glass-forming ability (GFA) from 5 to 2 mm in terms of the critical casting thickness, and eventually collapses for Ga contents higher than about 9 at%. In this work, thermodynamic and kinetic studies of the newly discovered 18 K Au-Ag-Pd-Cu-Ga-Si system shed light on the reason for the loss in GFA with increasing Ga content. Investigations of the liquid kinetics in terms of viscosity and transition time, assessed by three-point beam bending and the Tg-shift method, reveal an unexpected change of the fragility to stronger liquid kinetics with increasing Ga concentration, which is usually attributed to an increase in the GFA. Thermodynamic considerations based on specific heat capacity measurements reveal, in contrast, an ascending driving force for crystallization with an increasing Ga-content, accountable for the drop in GFA. Therefore, a Ga-rich melt beyond the threshold concentration of 9 at% is not desirable for the production of bulk metallic glasses (BMGs) from the liquid state. With the intention to outrun this barrier, while preserving the amorphous structure, Ga-ion implantation with a liquid metal focused ion beam source is used as a post-processing routine for a cast Ga-containing 18 K Au-BMG. Hence, the thermodynamic borderline concentration is successfully crossed with additional tremendous improvement of the tarnishing resistance in the Ga-enriched areas.
DOI der Erstveröffentlichung: 10.1016/j.actamat.2018.11.052
URL der Erstveröffentlichung: https://www.sciencedirect.com/science/article/abs/pii/S1359645418309285
Link zu diesem Datensatz: urn:nbn:de:bsz:291--ds-396598
hdl:20.500.11880/35736
http://dx.doi.org/10.22028/D291-39659
ISSN: 1359-6454
Datum des Eintrags: 4-Mai-2023
Fakultät: NT - Naturwissenschaftlich- Technische Fakultät
Fachrichtung: NT - Materialwissenschaft und Werkstofftechnik
Professur: NT - Prof. Dr. Ralf Busch
Sammlung:SciDok - Der Wissenschaftsserver der Universität des Saarlandes

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