TY - CONF A1 - Suárez Ocaño, Patricia A1 - Agudo Jácome, Leonardo T1 - Oxidation Behavior of the AlMo0.5NbTa0.5TiZr Chemically Complex Alloy N2 - The chemically complex alloys that contain mostly refractory elements (rCCAs), may be highly resistant to heat and load, which makes them attractive candidates for use at extremely high temperatures associated with technological applications such as aeroengine turbines. However, the oxidation behavior remains an emerging field within the CCA community. The fully heat treated AlMo0.5NbTa0.5TiZr rCCA contains a dual-phase microstructure that resembles the γ/ γ’ pattern of the well-known Ni-base superalloys, however with a continuous Al-Zr-Ti-rich B2 ordered matrix embedding Mo-Nb-Ta-rach bcc precipitates. The question thus arises what is the oxidation behavior of this rCCA alloy? In this study, this question is addressed via in situ and ex situ X-ray diffraction (XRD) in dry and humid air in the 800–1000 °C regime. Electron microscopic investigations complement the findings. In situ synchrotron experiments were carried out at the KMC2 beamline of the Helmholtz Zentrum Berlin (HZB), with a wavelength of 1.5418 Å at 800 and 950 °C under dry and humid (≈ 40% rH, laboratory air) air for 12 h. Scanning and transmission electron microscopy was performed before and after exposure to spatially resolve the scale development ex situ. In general, 12 h exposure led to an oxide scale which internal oxidation reaches several tens of microns, and which is dominated by Zr-, Ti- and Mo-containing oxides although aluminum oxide was also always present. Main differences are observed between temperatures, while the humidity played a lesser role. T2 - International Conference on High Entropy Materials (ICHEM) 2023 CY - Knoxville, TN, USA DA - 18.06.2023 KW - High entropy superalloy KW - High temperature oxidation KW - In situ synchrotron diffraction KW - Electron microscopy PY - 2023 AN - OPUS4-63857 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suárez Ocaño, Patricia A1 - Agudo Jácome, Leonardo T1 - Creep degradation of the high entropy superalloy AlMo0.5NbTa0.5TiZr N2 - The refractory high entropy superalloy (RSA) AlMo0.5NbTa0.5TiZr was the first of a class, with a dual-phase microstructure that resembles that of γ/γ’ in Ni-base superalloys), and the open question whether it performs better as structural alloy under high temperature (HT) applications. Here, we address the HT creep behavior and its associated microstructural degradation of this RSA. The material was produced by arc-melting, heat treatment in argon (24 h @ 1400 °C + 4 h hot isostatic pressure @ 1370 °C & 170 MPa). Interrupted vacuum creep tests were performed at 900-1100 °C and 30-120 MPa. Scanning (S) and transmission (T) electron microscopy (EM) were used to reveal degradation mechanisms. At 1100 °C (Fig.1, middle), the dual A2/B2 microstructure coarsens and partially transforms into a Zr-Al-rich phase (red arrow). An additional external load pronounces directional coarsening. Results are further discussed on the base dislocation and additional damage mechanisms. T2 - International Conferende on Strength of Materials (ICSMA) 2022 CY - Metz, France DA - 26.06.2022 KW - High entropy superalloy KW - Rrafting KW - Dislocation creep KW - Phase transformation PY - 2022 AN - OPUS4-63856 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Evans, Alexander A1 - Schröder, Jakob A1 - Pirling, T. A1 - Ulbricht, Alexander A1 - Suárez Ocaño, Patricia A1 - Bruno, Giovanni T1 - Resolving the Subsurface Residual Stress Maximum in Laser Powder Bed-Fused 316L Stainless Steel by Diffraction-Based Analysis N2 - Laser powder bed fusion (PBF-LB/M) is a metal additive manufacturing process. Due to the complex nature of the layer-wise, repeated heating and cooling cycles, it tends to generate high-magnitude residual stresses. If not correctly understood and mitigated through in- or post-process approaches, these residual stresses can be detrimental as they are often tensile at the surface. However, determining the magnitude and location of peak tensile residual stresses is not trivial as they are often located subsurface. This work focuses on determining the magnitude and location of these deleterious tensile residual stresses in a PBF-LB/316L specimen. Two diffraction-based Methods are used to reveal the relationship between the residual stresses and the underlying microstructure. On the one hand, high spatial resolution Neutron diffraction is used to determine triaxial stresses from the bulk to a depth of 0.15 mm. On the other hand, laboratory X-ray diffraction coupled with electrolytical layer removal allows the biaxial residual stress depth profile to be probed from the surface to a depth of about 0.6 mm. The results show a good agreement between the two methods. The peak residual stress is shown to be 500 MPa, which appears as a plateau between 0.08 and 0.35 mm in depth. KW - Residual stress KW - Diffraction KW - Laser Powder Bed Fusion KW - 316L KW - Additive manufacturing KW - Microstructure KW - AGIL PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-652138 DO - https://doi.org/10.1007/s11837-025-07719-y SN - 1543-1851 VL - 77 IS - 12 SP - 9726 EP - 9737 PB - Springer Nature AN - OPUS4-65213 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Suárez Ocaño, Patricia A1 - Ávila Calderón, Luis A1 - Agudo Jácome, Leonardo A1 - Rehmer, Birgit A1 - Mohr, Gunther A1 - Evans, Alexander A1 - Skrotzki, Birgit T1 - Effect of 700–900 °C heat treatments and room and high temperature tensile deformation on the microstructure of laser powder bed fused 316L stainless steel N2 - The effect of post-processing heat treatments on the hierarchical microstructure evolution and mechanical strength of the austenitic stainless steel 316L produced by laser powder bed fusion has been investigated. Heat treatments between 700 and 900 ◦C and 0.5 to 3 h, were applied to samples treated at 450 ◦C for 4 h. The results showed a stable microstructure at all studied temperatures and times in terms of grain size, morphology, aspect ratio, density of low-angle grain boundaries, and texture. However, temperature and time promoted the diffusion of segregated elements together with a reduction in dislocation density and disappearance of the cellular structure. This was associated with a reduction in hardness and tensile proof strength at both room and high temperature. In addition, microstructural characterization coupled with thermodynamic CALPHAD-based equilibrium calculations showed that the formation of carbides and intermetallic phases was already visible after annealing at 800 ◦C for 3 hours, although these intermetallics did not affect the tensile properties at this level. Analysis of the microstructure evolution after tensile deformation showed differences in the deformation mechanisms at room and high temperature, with twinning and martensitic transformation occurring at room temperature, the latter not widely reported for additively manufactured 316L. Finally, comparisons with similar materials produced under comparable conditions showed differences in the tensile properties, attributed to differences in chemical composition and the associated presence of stacking faults in the undeformed state. KW - Additive manufacturing KW - 316L stainless steel KW - Heat treatments KW - Tensile properties KW - Microstructure PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-632471 DO - https://doi.org/10.1016/j.msea.2025.148469 SN - 0921-5093 VL - 939 SP - 1 EP - 24 PB - Elsevier CY - Amsterdam AN - OPUS4-63247 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -