Regensburg 2025 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 20: Topical Session: Thermophysical Properties of Bulk Metallic Glasses and Bulk Metallic Glass-forming Liquids

MM 20.7: Topical Talk

Wednesday, March 19, 2025, 18:00–18:30, H10

The effect of composition on the thermodynamics, structure, mechanical properties and atomic motion of (Pd-Pt)42.5Cu27Ni9.5P21 alloys — •Ralf Busch — Saarland University, Saarbrücken, Germany

According to basic hard sphere models Pt should replace Pd in the Pd42.5Cu27Ni9.5P21 alloy. But Pt42.5Cu27Ni9.5P21 shows significant structural differences compared to the Pd based alloy. To study the differences, we prepared a series of (Pd-Pt)42.5Cu27Ni9.5P21 alloys replacing Pd with Pt. We assess the thermodynamic functions revealing that the driving force for crystallization increases with the increase of the Pt content, which is in line with the decreasing critical casting thickness. The Pt-richer alloys are thermodynamically more fragile than the Pd-rich alloys, which is revealed by a larger specific heat capacity and a faster drop of the configurational entropy in the Pt-richer alloys. High energy XRD (HEXRD) studies reveal that the structure of the Pt rich alloys is dominated by its change in medium range order whereas the Pd-rich alloy is dominated by extraordinary short range order. The mechanical properties change drastically from a ductile behavior on the Pt-rich side to an embrittlement with increasing Pd content and decreasing Pt concentration. Nano-indentation investigations together with the HEXRD studies reveal that the embrittlement with increasing Pd-content can be connected to the structural changes. We used XPCS to study the atomic dynamics of the alloys as a function of temperature and wave vector.

Keywords: Metallic Glasses; Thermodynamics; Structure; Mechanical Properties; Dynamics