TY - THES A1 - Suárez Ocano, Patricia T1 - Thermodynamic and microstructural stabilities at high temperatures and their effects on mechanical properties in an AlMo0.5NbTa0.5TiZr refractory high entropy superalloy N2 - Today’s industrial demands challenge the research and development sector to make advances in the design and properties of materials that can withstand harsh environments. The AlMo0.5NbTa0.5TiZr refractory high-entropy superalloy (RSA), with a remarkable morphological similarity to the γ/γ' microstructure of Ni-based superalloys and promising high-temperature compressive properties, has been considered as a candidate for structural applications. However, additional properties need to be investigated in order to assess the suitability of this alloy for high temperature applications. Therefore, this work investigates the thermodynamic and microstructural stabilities of the RSA at room temperature and between 900 and 1100 °C, and their influence on the mechanical properties. Although it is possible to improve the mechanical properties at 20 °C by tuning the cooling rate, long-term high temperature exposures lead to phase instabilities that negatively influence the creep behavior. N2 - Die heutigen industriellen Anforderungen erfordern Fortschritte bei Werkstoffdesign und -entwicklung, insbesondere für raue Umgebungen. Die hochentropische Refraktärsuperlegierung (RSA) AlMo0.5NbTa0.5TiZr, die eine bemerkenswerte morphologische Ähnlichkeit mit der γ/γ'-Mikrostruktur von Ni-Basis-Superlegierungen und vielversprechende Hochtemperatur-Druckeigenschaften aufweist, wurde als Kandidat für strukturelle Anwendungen erwägt. Weitere Eigenschaften müssen untersucht werden, um die Eignung dieser Legierung für Hochtemperaturanwendungen zu beurteilen. In dieser Arbeit werden die thermodynamischen und mikrostrukturellen Stabilitäten von RSA bei Raumtemperatur und zwischen 900 und 1100°C sowie deren Einfluss auf die mechanischen Eigenschaften untersucht. Obwohl es möglich ist, die mechanischen Eigenschaften bei 20 °C durch Abstimmung der Abkühlrate zu verbessern, führen langfristige Hochtemperaturexpositionen zu Phaseninstabilitäten, die das Kriechverhalten negativ beeinflussen. KW - Hochentropielegierung KW - Gefüge (Werkstoffkunde) KW - Mikrostruktur KW - Kriechen KW - Thermodynamische Stabilität KW - High entropy alloys KW - Microstructure KW - Creep KW - Thermodynamic stability PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:hbz:294-108415 DO - https://doi.org/10.13154/294-10841 SP - 1 EP - 170 CY - Bochum AN - OPUS4-59929 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suárez Ocano, Patricia T1 - Effect of heat treatment on the hierarchical microstructure and properties of 316L stainless steel produced by Laser Powder Bed Fusion (PBF-LB/M). N2 - Laser Powder Bed Fusion (PBF-LB/M) of AISI 316L stainless steel has gained popularity due to its exceptional capacity to produce complex geometries and hierarchical microstructures, which can increase the yield strength while maintaining good ductility. Nevertheless, owing to high thermal gradients encountered during the process, the as printed 316L stainless steel often exhibit microstructural heterogeneities and residual stresses, which can limit its performance in demanding environments. Hence, employing heat treatments which balance the reduction of residual stresses while retaining improved static strength may be beneficial in various scenarios and applications. This study investigates the impact of post-processing heat treatments on the microstructure of 316L stainless steel manufactured via PBF-LB/M, along with its correlation with micro-hardness properties. To this end, 6 different heat treatments, i.e., 450 °C for 4h, 700 °C for 1h, 700 °C for 3h, 800 °C for 1h, 800 °C for 3h, and 900 °C for 1h, were applied to different specimens and Vickers hardness measurements (HV1) were performed in all states. At 800 °C, although the cellular structure appears to be retained, there is an observable increase in cellular size. However, while treatments exceeding 900 °C indicate no significant grain growth compared to other conditions, the cellular structure is entirely dissolved, which leads to a reduced Vickers hardness. The effect of the heat treatments on other microstructural features such as grain size and morphology, melt pool boundaries (MPB), crystallographic texture, chemical segregation, dispersoids and phase stability are also discussed in the present work T2 - 4th Symposium on Materials and Additive Manufacturing CY - Berlin, Germany DA - 12.06.2024 KW - Additive manufacturing KW - Heat treatment KW - Microstructure PY - 2024 AN - OPUS4-60304 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Suárez Ocano, Patricia A1 - Fries, S. G. A1 - Lopez-Galilea, I. A1 - Darvishi Kamachali, Reza A1 - Roik, J. A1 - Agudo Jácome, Leonardo T1 - The AlMo0.5NbTa0.5TiZr refractory high entropy superalloy: Experimental findings and comparison with calculations using the CALPHAD method N2 - Detailed microstructural characterization of the AlMo0.5NbTa0.5TiZr refractory high entropy superalloy in the as-cast state is reported for first time and compared with the state annealed at 1400 oC for 24 h. The former shows a dendritic structure, with a mixture of A2/B2 phases < 20 nm in both the dendritic and interdendritic regions. A mostly amorphous phase, rich in Al and Zr, is found within the interdendritic region. The annealed state reproduced the combination of A2/B2/Al-Zr-rich phases reported previously. Calculations from two relevant ThermoCalc databases were compared with the experimental results. Equilibrium calculations were compared with results for the annealed alloy, whereas solidification paths calculated using Scheil-Gulliver model were used for comparison with the as-cast alloy. A previously hypothesized spinodal decomposition during cooling as the mechanism responsible for the patterned A2/B2 microstructure is confirmed via the CALPHAD calculations, pointing to its use as an efficient design tool for such alloys. Finally, the comparison between the experimental and computational findings allowed better understanding the solidification path and equilibrium stability of this alloy, giving a base to make better decisions on the field of new refractory superalloy design. KW - CALPHAD database analysis KW - Refractory superalloys KW - Chemically complex alloy KW - Characterization KW - Microstructure PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-545906 DO - https://doi.org/10.1016/j.matdes.2022.110593 SN - 1873-4197 VL - 217 SP - 1 EP - 13 PB - Elsevier CY - Amsterdam AN - OPUS4-54590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suárez Ocano, Patricia T1 - Creep Properties of the Refractory Chemically Complex AlMo 0.5 NbTa 0.5 TiZr Alloy N2 - The development of refractory CCAs has been explored for potential use in high temperature applications. An example of this is the AlMo0.5NbTa0.5TiZr alloy, which resembles the well-known γ/γ’ microstructure in Ni-Base superalloys with cuboidal particles embedded in a continuous matrix. The aim of this work is to evaluate the alloy’s mechanical behavior under tension in the temperature range 800-1000°C, by applying creep tests under vacuum (excluding oxidation effects). Some little temperature influence on minimum creep rate @ 1000 and 1100 °C was found and at a first glance, and Norton plots shows that deformation is probably both diffusion and dislocation controlled. However, further work is needed to stablish deformation and degradation micro mechanisms in the studied creep regime. T2 - SPP Kick-Off Meeting 2nd Phase CY - Online meeting DA - 14.04.2021 KW - Creep behavior KW - Chemically complex alloy KW - Microstructure PY - 2021 AN - OPUS4-53389 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suárez Ocano, Patricia T1 - Effect of the heat treatment in the microstructure of a refractory chemically complex alloy N2 - A set of some unexpected and interesting microstructures has put the so-called complex concentrated alloys (CCAs) in the eye of the scientific community. The AlMo0.5NbTa0.5TiZr refractory (r)CCA, aimed at substituting Ni-base superalloys in gas turbine applications, belongs to this alloy family. After a two-stage heat treatment, this rCCA morphologically resembles the typical a two-phase microstructure of the latter. The objective of this work consists in determining the effect of the two stages of the heat treatment on the microstructure of the AlMo0.5NbTa0.5TiZr alloy to eventually improve it in terms of homogeneity and porosity. T2 - Third International Conference on High Entropy Materials (2020) CY - Berlin, Germany DA - 27.09.2020 KW - Annealing KW - Hot isostatic pressing KW - Refractory chemically complex alloy KW - Microstructure PY - 2020 AN - OPUS4-53386 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -