SKM 2023 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 28: Liquid and Amorphous Metals
MM 28.3: Talk
Wednesday, March 29, 2023, 10:45–11:00, SCH A 118
Unravelling the origin of the anomalous thermal expansion in Fe-based bulk metallic glasses — •Alexander Firlus1, Mihai Stoica1, Gavin Vaughan2, Stefan Michalik3, Robin E. Schäublin1, and Jörg F. Löffler1 — 1Laboratory of Metal Physics and Technology, ETH Zurich, 8093 Zurich, Switzerland — 2European Synchrotron Radiation Facility (ESRF), Grenoble, France — 3Diamond Light Source Ltd., Didcot, UK
Fe-based bulk metallic glasses (BMGs) are known for their soft-magnetic properties but their magnetic interactions also give rise to an anomalous thermal expansion, called the Invar effect. In the ferromagnetic state, their coefficient of thermal expansion is reduced by a factor of four. This phenomenon has been observed in all ferromagnetic Fe-based BMGs at the macroscopic scale, but due to the lack of long-range order the physics of this effect needs to be described at the atomic scale. Although it is now widely accepted to be of magnetic origin, the contributions of the different atomic species to the Invar effect have been unknown. We studied the atomic-scale thermal expansion of multiple quaternary BMGs by in situ X-ray diffraction. The anomalous thermal expansion is visible in all diffraction patterns and can clearly be associated with the disordered Fe network. Through variations of the minor alloying elements, we elucidated the effect of different atomic species and provide a framework in which their respective influence on the Invar effect can be understood.