Berlin 2024 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 55: Liquid and Amorphous Materials II
MM 55.4: Vortrag
Donnerstag, 21. März 2024, 11:00–11:15, C 230
Atomic-scale model of the Invar effect in metallic glasses — •Alexander Firlus1, Mihai Stoica1, Pál Jóvári2, Michalis Charilaou3, Robin E. Schäublin1, and Jörg F. Löffler1 — 1ETH Zurich, Switzerland — 2Wigner Research Centre for Physics, Hungary — 3University of Louisiana at Lafayette, USA
The disordered atomic arrangement of metallic glasses (MGs) provides them with a variety of unique properties such as high hardness, high strength and high elastic limit, and excellent soft-magnetic properties for Fe-based MGs. For all these properties, a microscopic explanation has already been provided, based on the disordered atomic arrangement of MGs. However, Fe-based MGs also universally exhibit the Invar effect, which reduces the coefficient of thermal expansion (CTE) in the ferromagnetic state to almost zero. Despite its universality, there has been no explanation on how the disordered atomic arrangement gives rise to the Invar effect.
We studied the atomic arrangement of quaternary MGs by in situ X-ray diffraction and absorption techniques over all length scales from the atomic to the macroscopic. Based on the experimental data we performed Reverse Monte Carlo modeling to obtain a series of 3D model structures to reveal how the magnetic interactions stabilize the atomic arrangement and lead to a reduced CTE. We find that all Fe atoms contribute to the Invar effect with their magnetic interactions, and that the structural disorder enables a local optimization of the potential energy landscape, which explains the universal occurrence of the Invar effect.
Keywords: Metallic glass; Invar effect; Disorder; Magnetism; Atomic scale