Aleksander Amble Larsen

• Poulia, Anthoula; Larsen, Aleksander Amble; Graff, Joachim Seland; Diplas, Spyridon; Gunnæs, Anette Eleonora & Mikheenko, Pavlo (2022). Imaging Magnetic Domain Structure of a High Entropy Alloy: Effect of Applied Magnetic Field, 2022 IEEE 12th International Conference Nanomaterials: Applications & Properties (NAP). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-6654-8982-9. p. NMM01-1–NMM01-5. doi: 10.1109/NAP55339.2022.9934250. Show summary

  High-Entropy Alloys (HEAs) are recently introduced materials consisting of numerous—at least five—elements in nearly equal-atomic concentrations. Studying them, previously unexplored phase fields in multidimensional phase diagrams are now being explored. The HEA concept is based on a thermodynamic balance between mixing entropy and enthalpy, which defines values of several critical parameters that determine the formation of simple or complicated phases. Physical properties, like magnetism, are of great interest for these materials, even though they have not been extensively analyzed so far. Particularly, the exploration of the magnetic domain structure and its correlation with the micro- and nano-structural features of the materials is of high scientific value. In this work, we study the influence of the magnetic history on the alteration of the magnetic domain patterns in polycrystalline FeCoNiAl0.9Mn0.9 High Entropy Alloy (HEA). For the study, we introduce a combinatorial method of Electron Backscatter Diffraction and Magnetic Force Microscopy imaging, which reveals specific magnetic domain structures in the grains of different crystallographic orientations. It is found that in the HEA polycrystal, an increase of the applied magnetic field affects the formation of magnetic domains and leads to a transition from a labyrinth-like pattern to a dotted domain configuration, which is expressed differently in the differently oriented grains.

• Larsen, Aleksander Amble; Poulia, Anthoula; S. Azar, Amin; Bazioti, Kalliopi; Almeida Carvalho, Patricia & Gunnæs, Anette Eleonora [Show all 9 contributors for this article] (2021). Identifying Magnetic Phases in Additively Manufactured High-Entropy Alloy FeCoNiAlxMnx, 2021 IEEE 10th International Conference on “Nanomaterials: Applications & Properties” (NAP – 2021). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-6654-3907-7. p. NMM03-1–NMM03-4. doi: 10.1109/NAP51885.2021.9568591. Full text in Research Archive Show summary

  High-Entropy Alloys are advanced technological materials composed of several (typically five) elements in nearly equal atomic concentration. By forming these alloys, previously unknown phase fields of multidimensional phase diagrams are explored. The large number of possible substitutions of constituent elements on crystal lattice sites justifies the dominant contribution of mixing entropy over enthalpy to the free energy reduction. This leads to the formation of phases, which otherwise could not be formed in alloys with fewer main alloying elements. Here we explore magnetic and compositional properties of a High-Entropy Alloy, namely FeCoNiAl x Mn x (0.05 ≤ x ≤ 3.08), composed of magnetic (Fe, Co, Ni) and non-magnetic elements (Al, Mn). By magnetic force microscopy of a selected area, it is observed that for intermediate to low Al and Mn contents, the alloy splits in two major crystallographic phases with different magnetic properties. Elemental maps of the same area were recorded with energy dispersive spectroscopy and scanning electron microscopy. Counterintuitively, it was found that the phase rich in non-magnetic Al has stronger magnetism than the phase rich in Fe. This work showcases possible applications of the here presented HEAs as soft magnetic materials in functional magnetic elements.

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• Løvvik, Ole Martin; Carvalho, Patricia A.; Stange, Marit Synnøve Sæverud; Sunding, Martin Fleissner; Rajput, Kalpna & Larsen, Aleksander Amble [Show all 9 contributors for this article] (2022). Elastocaloric cooling with TiNiCuZr alloys?
• Larsen, Aleksander Amble & Gunnæs, Anette Eleonora (2021). A Correlated Study of FeNiCoMnxAlx - Magnetic, structural, and compositional properties of additive manufactured high-entropy alloy. Universitetet i Oslo.

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