Berlin 2018 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 41: Liquid and Amorphous Metals
MM 41.4: Talk
Wednesday, March 14, 2018, 16:00–16:15, TC 010
The role of the Ga addition to the thermodynamics, kinetics, and tarnishing properties of the Au-Pd-Cu-Ag-Si bulk metallic glass forming system — •Nico Neuber1, Oliver Gross1, Miriam Eisenbart2, Ulrich Klotz2, Isabella Gallino1, and Ralf Busch1 — 1Chair of Metallic Materials, Saarland University, Campus C6.3, 66123 Saarbrücken, Germany — 2FEM, Research Institute for Precious Metals & Metals Chemistry, Katharinenstrasse 17, 73525 Schwäbisch Gmünd, Germany
In the last decade, the 18-karat gold Au-Ag-Pd-Cu-Si bulk metallic glass (BMG) system has received considerable attention as jewelry material due to its extraordinary premium-white gold color, the absence of allergen constituents such as Ni, Cr, and Co, twice the hardness of cold worked or age hardened conventional white gold alloys, melting temperatures below 700 K, less than 0.5% solidification shrinkage and a good processing ability. However, this system is affected by non-uniform tarnishing that is detrimental to its application. This behaviour is typical for a mixture of elements with very different nobility, where preferential oxidation and partitioning are common processes observed upon reaction with the environment. Based on thermodynamic considerations we have judiciously added Ga to the aforementioned system and developed novel 18-karat premium-white gold BMG compositions with improved tarnishing resistance. We report here upon the strategy applied to develop the novel compositions and the influence of the added Ga on the thermodynamics and kinetics of the system is assessed and possible further solutions are reviewed.