Aleksander Amble Larsen

• Larsen, Aleksander Amble; Gorantla, Sandeep; Nguyen, Phuong Dan; Rosnes, Andreas; Xu, Yijiang & Iordanidou, Konstantina [Vis alle 10 forfattere av denne artikkelen] (2026). Atomic-Resolution EDS Characterization of Ordering in a β–Cu–Zn–Al Alloy. Metallurgical and Materials Transactions A. ISSN 1073-5623. doi: 10.1007/s11661-025-08093-9. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Atomic ordering in single-crystal β –Cu–Zn–Al, relevant to the martensitic transformation and functional properties, is investigated using analytical STEM. Atomic-resolution EDS along the [110] zone axis, where all Wyckoff positions are spatially resolved, reveals three chemically distinct site occupancies. Correlation with HAADF-STEM contrast provides real-space evidence consistent with L2 1 ordering. In agreement with experiments, first-principles calculations show a slight energetic preference for L2 1 over D0 3 , with finite-temperature free-energy calculations indicating that this preference persists at elevated temperatures.

• 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 9781665489829. s. NMM01-1–NMM01-5. doi: 10.1109/NAP55339.2022.9934250. Fulltekst i vitenarkiv Vis sammendrag

  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; Azar, Amin S.; Bazioti, Kalliopi; Carvalho, Patricia Almeida & Gunnæs, Anette Eleonora [Vis alle 9 forfattere av denne artikkelen] (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 9781665439077. s. NMM03-1–NMM03-4. doi: 10.1109/NAP51885.2021.9568591. Fulltekst i vitenarkiv Vis sammendrag

  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; Stange, Marit Synnøve Sæverud; Bumke, Lars; Quandt, Eckhard; Kušnír, Jakub & Grabek, Tomas [Vis alle 11 forfattere av denne artikkelen] (2025). Phase change materials for elastocaloric cooling. Fulltekst i vitenarkiv
• Larsen, Aleksander Amble; Huang, Xinyue; Carvalho, Patricia A.; Gunnæs, Anette Eleonora; Løvvik, Ole Martin & Chen, Xian (2025). Size and Orientation Effects in Cu-Zn-Al Shape Memory Micropillars. Fulltekst i vitenarkiv Vis sammendrag

  Introduction and objective Martensitic phase transformations in Cu-Zn-Al alloys give rise to functional behaviors such as superelasticity, the shape memory effect, and elastocaloric responses, making them attractive for various applications, including solid-state cooling. While the bulk behavior of these alloys is well-characterized, their response under small-scale mechanical loading is complex and remains an area of ongoing research. This study explores the effects of pillar size and crystallographic orientation on stress-induced martensitic transformation in Cu-Zn-Al single crystals using nanomechanical compression testing. Methods Two compositions of β-phase Cu-Zn-Al single crystals were selected for nanomechanical studies. Samples were cut and prepared with surface orientations corresponding to the (001), (011), and (111) planes of the austenitic phase, as confirmed by electron backscatter diffraction (EBSD). Micropillars with diameters ranging from 0.2 to 3 µm were fabricated using focused ion beam (FIB) milling. Mechanical uniaxial compression tests were performed at room temperature using a nanoindenter to induce martensitic transformation in the pillars. Results Micropillar compression experiments revealed a clear size effect on the martensitic phase transformation. Smaller pillars showed diminished or incomplete transformation compared to larger ones. In addition, crystal orientation significantly influenced the nature and extent of the transformation, with certain orientations exhibiting more substantial transformation strains during compression. For some orientations, no transformation was observed, indicating a strong dependence on crystallographic alignment. These observations highlight how geometric confinement and crystal orientation affect martensitic phase transformation behavior in Cu-Zn-Al.

• Løvvik, Ole Martin; Carvalho, Patricia A.; Stange, Marit Synnøve Sæverud; Sunding, Martin Fleissner; Rajput, Kalpna & Larsen, Aleksander Amble [Vis alle 9 forfattere av denne artikkelen] (2022). Elastocaloric cooling with TiNiCuZr alloys? Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv

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