TY - CONF A1 - Manzoni, Anna Maria T1 - Two decades of cuboids in high entropy alloys N2 - One of the original concepts of high entropy alloys was the use of single-phase alloys that were strengthened by the presence of many different main elements. After some years of research, it was found that this strengthening could be enhanced further by the introduction of a carefully chosen second phase that has a connection to the matrix phase. A most suitable combination is the combination of a ductile matrix phase with a disordered structure and an intermetallic precipitation phase that is coherent to the matrix. The most well-known example is the gamma-gammaprime morphology that is known from Ni-base superalloys, but it is not the only one. Combination of fcc-B2 or bcc-B2 have been discovered and optimized in several alloys and they lead the materials to beautiful microstructures with admirable properties. This talk presents the different types of cuboid formations in HEAs that have been presented in the last two decades. T2 - 32nd International Materials Research Congress - IMRC 2024 CY - Cancun, Mexico DA - 18.08.2024 KW - High entropy alloys KW - Chemically complex materials KW - Transmission electron microscopy PY - 2024 AN - OPUS4-60935 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fantin, Andrea A1 - Cakir, Cafer Tufan A1 - Kasatikov, S. A1 - Schumacher, G. A1 - Manzoni, Anna Maria T1 - Effects of heat treatment on microstructure, hardness and local structure in a compositionally complex alloy N2 - Unlike conventional alloys, high entropy alloys are characterized by one or more solid solution phase(s) without a clearly defined solvent, all element contribute to the matrix in a way that is still not entirely understood. In addition, it is not known to what extent classic thermodynamic rules can be applied to these multi-element alloys, especially concerning the question about what factor incites the matrix to undergo a phase transformation. This work tackles directly some of these aspects on a chosen alloy, Al8Cr17Co17Cu8Fe17Ni33 (at.%), which presents a high temperature single-phase γ state and a two-phase state with γ′ precipitates, above and below 900 ◦C, respectively. A combined investigation via microstructural observations, hardness testing, X-ray absorption and photoelectron spectroscopy was carried out above the γ′ formation temperature. Hardness values are independent of the annealing temperatures, microstructural analysis shows no phase formation and X-ray absorption spectroscopy does not reveal observable changes in neither local atomic nor electronic structure, indicating that approaching γ′ formation temperature is not influenced by atomic or electronic rearrangements. Interestingly, short-range chemical order remains quantitatively compatible at any annealing temperature in the single-phase γ state, and the observed preferred pairs Al–Cu and Al–Ni in the γ state match with the γ’ precipitates composition below 900 ◦C. KW - High entropy alloys KW - EXAFS KW - Short range order KW - Vickers hardness PY - 2022 DO - https://doi.org/10.1016/j.matchemphys.2021.125432 SN - 0254-0584 VL - 276 SP - 125432 PB - Elsevier B.V. AN - OPUS4-53760 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Manzoni, Anna Maria T1 - Tuning high entropy alloys towards superalloy applications N2 - The discovery of the high entropy concept at the beginning of the 3rd millennium lead to a worldwide increase in metallurgical research, as the possible element combinations seemed nearly endless and the range of applications wide. In the early years of research, one of the main goals was the discovery of a single-phase high entropy alloy. As research evolved, it was found that properties could be enhanced by opening the HE-concept towards multiphase alloys, and from the wide area of possibilities our group chose a tuning of the properties towards high temperature application. Compositionally complex Al10Co25Cr8Fe15Ni36Ti6 alloy, which is single-phase at high temperature, around 1200°C, shows a three phase morphology at intermediate temperatures, around 800°C. A high temperature homogenization procedure has to be applied in order to decrease the segregation induced by the dendritic growth. Subsequent annealing promotes the formation of the strengthening γ' precipitates. The alloy shows a positive lattice misfit between the γ and the γ' phase, which can be an indicator for good creep properties. The microstructure can be optimized by adding trace elements such as Mo and Hf, known as γ and γ' strengtheners in Ni-based superalloys, respectively. Atom probe measurements show that Mo segregates into the γ matrix, and Hf prefers the γ' precipitates, where it increases the lattice parameter and thus also the lattice misfit, by about 50%. The alloy family shows interesting mechanical properties, especially the Al9.5Co25Cr8Fe15Ni36Ti6Hf0,5 alloy – its tensile properties are better than those of commercial Alloy 800H and IN617 at temperatures up to 700°C. T2 - BAM Abteilungsseminar CY - Online meeting DA - 21.01.2021 KW - High entropy alloys KW - Compositionally complex alloys KW - Superalloys KW - Hochentropie-Legierung KW - Legierung mit komplexer Zusammensetzung KW - Superlegierung PY - 2021 AN - OPUS4-52442 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Manzoni, Anna Maria T1 - Combining trace elements for microstructural optimization in the Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy N2 - Trace elements W and Hf have different influence on the microstructure and the mechanical properties when added to the Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy. The addition of both can thus merge both element’s beneficial influences when combined with the appropriate heat treatment: Hf enhances the cubicity of the γ’ particles in the γ matrix while the W reduces the negative influence of the Heusler phase: this phase can be completely dissolved when W is present in the alloy. T2 - ICHEM 2020 CY - Berlin, Germany DA - 27.09.2020 KW - High entropy alloys KW - Transmission electron microscopy KW - Lattice misfit KW - X-ray diffraction KW - Scanning electron microscopy PY - 2020 AN - OPUS4-51370 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -