TY - CONF A1 - Agudo Jácome, Leonardo A1 - Göbenli, Gülcan A1 - Eggeler, Gunther T1 - High Temperature and Low Stress (011)<01-1> Shear Creep Deformation of the Single Crystal Ni-Based Superalloy LEK 94 - elementary softening and deformation processes T2 - 17th International Conference on the Strength of Materials (ICSMA17) CY - Brno, Czech Republic DA - 2015-10-01 PY - 2015 AN - OPUS4-34516 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo A1 - Eggeler, Gunther A1 - Pöthkow, Kai A1 - Pätsch, Olaf A1 - Hege, H. C. T1 - Three-Dimensional Characterization of Superdislocation Interactions in the High Temperture and Low Stress Creep Regime of Ni-Base Superalloy Single Crystals T2 - 13th International Conference on Creep and Fracture of Engineering Materials and Structures (CREEP 2015) CY - Toulouse, France DA - 2015-05-31 PY - 2015 AN - OPUS4-34517 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo T1 - Diffraction Contrast in Scanning Transmission Electron Microscopy (STEM) as a Powerful Tool for Quantitative Dislocation Analysis T2 - Institutskolloquium, Institut für Materialphysik der westfälischen Wilhelms-Universität Münster CY - Münster, Germany DA - 2014-06-24 PY - 2014 AN - OPUS4-32949 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo T1 - Diffraction Contrast in Scanning Transmission Electron Microscopy (STEM) as a Powerful Tool for Quantitative Dislocation Analysis T2 - Symposium "Recent prograss in transmission electron microscopy and atom probe analysis of advanced high temperatur materials" vom SFB/TR 103 CY - Bochum, Germany DA - 2014-03-06 PY - 2014 AN - OPUS4-32950 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo A1 - Dlouhý, Antonin A1 - Otto, Frederik A1 - Somsen, Christoph A1 - George, Easo P. A1 - Eggeler, Gunther T1 - Structural Defects in Advanced Alloys and Intermetallics T2 - Microscopy Conference (MC) 2013 CY - Regensburg, Germany DA - 2013-08-25 PY - 2013 AN - OPUS4-32951 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo A1 - Dlouhý, Antonin A1 - Otto, Frederik A1 - Somsen, Christoph A1 - George, Easo P. A1 - Eggeler, Gunther T1 - Structural Defects in Advanced Alloys and Intermetallics T2 - DGM-Arbeitskreis (AK) Mechanisches Werkstoffverhalten bei hoher Temperatur CY - Mülheim an der Ruhr, Germany DA - 2013-10-09 PY - 2013 AN - OPUS4-32952 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo T1 - Characterization of dislocation networks N2 - The presentation shows how the three-dimensional quantification of dislocations and their characteristic features, e.g. Burgers vector, line direction, dislocation density, is carried out at the transmission electron microscope in scanning mode (STEM) at Division 5.1 at BAM. Exemplarily, the methods are shown for Ni-base superalloy single crystals, for which a short introduction is given using further TEM techniques. Additional examples on low angle grain boundaries, nucleation of oxides at dislocations and interaction of dislocations and carbides are shown. The content of the presentation was addapted, aiming at scientists who work within the DFG Priority Programme 1713 "Strong coupling of thermo-chemical and thermo-mechanical states in applied materials". T2 - SPP 1713: Focus Group Meeting Experiments CY - Berlin, Germany DA - 27.06.2016 KW - Dislocation KW - Transmission electron microscopy KW - Three-dimensional (3D) characterization KW - Ni-base superalloy KW - Creep PY - 2016 AN - OPUS4-40278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo T1 - Dislocation analysis in Ni-base superalloy single crystals N2 - The LEK94 is a Ni-base superalloy single crystal (SX) of the second generation, a materials class which is important for its high temperature creep resistance (>1000°C) in first stage blades of low-to-medium pressure gas turbines. Monocrystalline Ni-base superalloy SXs have a two-phase microstructure consisting of small cubes (' phase with the ordered L12 crystal structure, cube edge length: 500 nm), separated by thin channels (γ phase with fcc solid solution structure, channel width: 20 nm). The microstructural evolution during high temperature and low stress tensile creep has been thoroughly investigated previously, mainly for [001] loading, both in terms of dislocation activity (filling of γ channels, formation of dislocation networks, cutting of the γ’ phase) as well as phase coarsening (rafting, topological inversion). Other loading geometries have received less attention. The present work studies high temperature and low stress creep deformation of the superalloy LEK 94 at temperatures around 1000°C, where rafting occurs. Differences between loading under different uniaxial, biaxial and triaxial stress states are discussed. Stereo-microscopy and g∙b analysis in the scanning transmission electron microscopy mode (STEM) are combined for microstructural analysis. The focus is set on the role of dislocation interactions with the aging microstructure. Both development in STEM characterization methods, as well as the roles of phase coarsening, γ channel filling, microstructural heterogeneity and γ’ phase cutting are discussed. T2 - Eingeladener Vortrag CY - US Air Force Research Laboratories, Dayton, OH, USA DA - 19.07.2016 KW - Doslocation KW - Superalloy KW - Microscopy KW - Creep PY - 2016 AN - OPUS4-41945 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo T1 - Quantitative 3D Stereo Microscopy in Diffraction Contrast (S)TEM N2 - The realistic description of plastic deformation caused by dislocations demands the representative measurement of their features, e.g., Burgers vector, slip plane, line direction and density. In the case of bulk deformation of technical alloys, reliable data must be ensured for large regions. Nonetheless, the (thin) filiform nature of dislocations and also the heterogeneity in some microstructures additionally require flexible analysis techniques that resolve the details of their interactions. Strong and clear channeling contrasts, faint extinction contours and the absence of chromatic aberration make scanning transmission electron microscopy (STEM) an ideal imaging mode in wide and thick regions of TEM foils, as opposed to conventional (C)TEM. It is the purpose of this contribution to show how STEM can be applied for quantitative measurement of dislocation features. Furthermore, a new tool will be presented, which enables the three-dimensional (3D) reconstruction, visualization and quantification of dislocation densities and directions from stereo-pairs. The application of these techniques will be shown on a monocrystalline Ni-base superalloy, an important class of structural materials that has been implemented in the first row blades of gas turbines. The examples are extracted from specimens subjected to creep deformation at high temperature and low stress under various macroscopic deformation geometries. The spacial and angular accuracy are discussed as well as possible sources of error. T2 - Symposium on Advanced Mechanical and Microstructural Characterization Methods for SX Ni- and Co-based Superalloys CY - Bochum, Germany DA - 13.09.2017 KW - Dislocation KW - Scanning Transmission Electron Microscopy KW - Microscopy KW - 3D reconstruction PY - 2017 AN - OPUS4-42175 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Agudo Jácome, Leonardo A1 - Mielke, Viola T1 - Mechanisms of M23C6 Carbide Precipitation in Ni-Base Superalloy Single Crystals N2 - The demand for improved castability and low angle grain boundary (LAGB) resistance has led to the addition of low contents of e.g., B, Hf, Zr or C, into large industrial gas turbine components made of Ni-base superalloy single crystals (SXs). Due to the long-term application of Ni-base superalloy SX components in the temperature regime > 1000 °C, the formation of carbides is highly probable, which could jeopardize mechanical properties, such as high cycle fatigue. In the present contribution, the effect of internal and external stresses on the nucleation and growth characteristics of M23C6 carbides is investigated. Creep experiments are performed on the Ni-base superalloy SX LEK 94, which shows a low C concentration (= 0.1 at. %), at 1020 °C under parallel and circularly notched tensile specimens at a nominal stress of 160 MPa in the crystallographic direction [001]. The carbides are then characterized via scanning (S) and transmission (T) electron microscopy (EM). Nucleation is enhanced in the dendritic cores, often as coalesced colonies, extending over micrometers within M-rich (M: Cr, Re, W, Mo) γ channels. Lath shapes with facets on {100} (parallel to growth direction) and {111} are common. These facets exist since early stages (Fig.1a) and later develop misfit dislocations (Fig.1b), preserving the orientation relationship {100}γ || {100}M23C6. Fig. 1c shows a region from the creep gage, where carbides interact with superdislocations in the γ’ phase. Possible mechanisms are discussed. T2 - European Congress and Exhibition on Advanced Materials and Processes (EUROMAT) 2017 CY - Thessaloniki, Greece DA - 17.09.2017 KW - Superalloy KW - TEM KW - Carbide KW - Nucleation KW - Pore KW - Dislocation PY - 2017 AN - OPUS4-42176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -