TY - JOUR A1 - Beyer, Katrin A1 - Kannengießer, Thomas A1 - Griesche, Axel A1 - Schillinger, B. T1 - Neutron radiography study of hydrogen desorption in technical iron N2 - The purpose of the present study is to show the feasibility of examining hydrogen desorption in technical iron samples using neutron radiography at the ANTARES facility of the FRM II research reactor, Technische Universität München. It has been shown that this method is appropriate for in situ determination of hydrogen Desorption for concentrations as low as 20 ppmH. Experiments were carried out in the temperature range from room temperature up to 260 °C. Measurement was based on direct comparison between electrochemically hydrogen-loaded iron samples and hydrogen-free reference samples at the same temperature. This enables the determination of hydrogen concentration as a function of time and temperature. Ex situ carrier gas hot extraction experiments using the same temperature–time profiles as the neutron radiography experiments have been used to calibrate the greyscale values of the radiographs to defined hydrogen concentrations. It can be stated that hydrogen desorption correlates with sample temperature. KW - Neutron radiography KW - Hydrogen PY - 2011 U6 - https://doi.org/10.1007/s10853-011-5450-7 SN - 0022-2461 SN - 1573-4803 VL - 46 IS - 15 SP - 5171 EP - 5175 PB - Springer Science + Business Media B.V. CY - Norwell, Mass. AN - OPUS4-25150 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Beyer, Katrin A1 - Kannengießer, Thomas A1 - Griesche, Axel A1 - Schillinger, B. T1 - Study of hydrogen effusion in austenitic stainless steel by time-resolved in-situ measurements using neutron radiography N2 - The purpose of the present study was to show the feasibility of measuring hydrogen effusion in austenitic stainless steel (1.4301) using neutron radiography at the facility ANTARES of the research reactor FRM II of the Technische Universität München. This method is appropriate to measure in-situ hydrogen effusion for hydrogen concentrations as small as 20 ppmH. Experiments were carried out in the temperature range from room temperature up to 533 K. The measurement principle is based on the parallel comparison of electrochemically hydrogen charged specimen with hydrogen-free reference specimen at the same temperature. This allows the determination of the hydrogen concentration in the specimens as a function of time and temperature. Separate hot carrier gas extraction experiments using the same temperature–time profiles as the radiography experiments have been used to calibrate the grey values of the neutron transmission images into hydrogen concentrations. It can be stated that the hydrogen effusion correlates with the specimen temperature. KW - Hydrogen effusion KW - Austenitic stainless steels KW - Neutron radiography PY - 2011 U6 - https://doi.org/10.1016/j.nima.2011.02.010 SN - 0168-9002 SN - 0167-5087 VL - 651 IS - 1 SP - 211 EP - 215 PB - North-Holland CY - Amsterdam AN - OPUS4-23401 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Boateng, Francis Twumasi A1 - Ewert, Uwe A1 - Kannengießer, Thomas A1 - Zscherpel, Uwe A1 - Griesche, Axel A1 - Kromm, Arne A1 - Hohendorf, Stephan A1 - Redmer, Bernard T1 - Real-time radiography for observation of crack growth during GTA (Gas Tungsten Arc) welding N2 - In situ crack detection in the mushy zone and the solid weld of a gas tungsten arc (GTA) weld using X-ray imaging during welding is a new research area for NDT inspection. Usually, NDT flaw detection is done after the complete solidification of the weld seam. In this paper, we present the use of real-time radiography with a minifocus X-ray source (YXLON X-ray tube Y.TU 225-D04) and a 75μm pixel size digital detector array (Dexela 1512) for the acquisition of 2D radiographic images by a sequence of exposures with time intervals of 80 ms for hot crack detection during single pass bead-on-plate GTA welding of 3 mm thick plates of aluminium alloy AlMgSi (6060). An analysis of the crack distribution in the weld sample is conducted from the acquired 2D radiographs and its corresponding 3D volumetric reconstruction achieved by linear coplanar digital laminography. This in situ approach opens new possibilities in the field of hot crack research by having the direct information of both the crack initiation and growth and its correlation to the welding parameters. KW - Hot cracking KW - Radiography KW - GTA welding KW - Aluminium alloys KW - Real-time operation PY - 2016 U6 - https://doi.org/10.1007/s40194-016-0351-7 SN - 0043-2288 SN - 1878-6669 VL - 60 IS - 5 SP - 931 EP - 937 AN - OPUS4-37128 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Browne, D. A1 - García-Moreno, F. A1 - Nguyen-Thi, H. A1 - Zimmermann, G. A1 - Kargl, F. A1 - Mathiesen, R. H. A1 - Griesche, Axel A1 - Minster, O. ED - Solanki, K. N. ED - Orlov, D. ED - Singh, A. ED - Neelameggham, N. R. T1 - Overview of In situ X-ray studies of light alloy solidification in microgravity N2 - Gravity has significant effects on alloy solidification, primarily due to thermosolutal convection and solid phase buoyancy. Since 2004, the European Space Agency has been supporting investigation of these effects by promoting in situ X-ray monitoring of the solidification of aluminium alloys on microgravity platforms, on earth, and in periodically varying g conditions. The first microgravity experiment-investigating foaming of liquid metals - was performed on board a sounding rocket, in 2008. In 2012 the first ever X-ray-monitored solidification of a fully dense metallic alloy in space was achieved: the focus was columnar solidification of an Al-Cu alloy. This was followed in 2015 by a similar experiment, investigating equiaxed solidification. Ground reference experiments were completed in all cases. In addition, experiments have been performed on board parabolic flights-where the effects of varying gravity have been studied. We review here the technical and scientific progress to date, and outline future perspectives. KW - Dendritic growth KW - Materials in space KW - Columnar and equiaxed structures PY - 2017 SN - 978-3-319-52392-7 SN - 978-3-319-52391-0 U6 - https://doi.org/10.1007/978-3-319-52392-7_80 SN - 2367-1181 SP - 581 EP - 590 PB - Springer CY - Berlin, Heidelberg AN - OPUS4-39442 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Dabah, Eitan A1 - Griesche, Axel A1 - Beyer, Katrin A1 - Solórzano, E. A1 - Kannengießer, Thomas ED - Kannengießer, Thomas ED - Babu, S. S. ED - Komizo, Y. ED - Ramirez, A.J. T1 - In situ measurements of hydrogen diffusion in duplex stainless steels by neutron radiography N2 - Hydrogen embrittlement (HE) is a widely known phenomenon and under investigation already for more than a century. This phenomenon, though thoroughly studied, is not yet completely understood, and so far, there are several suggested mechanisms that try to explain the occurrence of HE. One important factor of understanding the HE phenomenon and predicting hydrogen-assisted failure is the descent knowledge about the hydrogen transport behaviour in the material. Neutron radiography is a proven method for tracking hydrogen diffusion and it was applied successfully in various research studies. In the presented study, we examined the hydrogen effusion behaviour in duplex stainless steel by means of neutron radiography and calculated the effective diffusion coefficient from the obtained transmission images. KW - Neutron radiography KW - Hydrogen diffusion KW - Duplex stainless steels KW - Hydrogen embrittlement PY - 2014 SN - 978-3-319-06144-3 SN - 978-3-319-06145-0 U6 - https://doi.org/10.1007/978-3-319-06145-0_9 SP - 155 EP - 163 PB - Springer AN - OPUS4-31357 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dabah, Eitan A1 - Pfretzschner, Beate A1 - Schaupp, Thomas A1 - Kardjilov, N. A1 - Manke, I. A1 - Boin, M. A1 - Woracek, R. A1 - Griesche, Axel T1 - Time-resolved Bragg-edge neutron radiography for observing martensitic phase transformation from austenitized super martensitic steel N2 - Neutron Bragg-edge imaging was applied for the visualization of a γ-Austenite to α'-martensite phase transformation. In the present study, a super martensitic stainless steel sample was heated until complete austenitization and was subsequently cooled down to room temperature. The martensitic phase Transformation started at Ms = 190 °C. Using a monochromatic neutron beam with λ = 0.390 nm, the transmitted intensity was significantly reduced during cooling below Ms, since the emerging martensitic phase has a higher attenuation coefficient than the austenitic phase at this wavelength. The phase Transformation process was visualized by filming the transmission images from a scintillator screen with a CCD camera with a temporal resolution of 30 s and a spatial resolution of 100 µm. KW - Neutron imaging KW - Bragg-edge imaging KW - Phase transformation PY - 2017 U6 - https://doi.org/10.1007/s10853-016-0642-9 SN - 0022-2461 SN - 1573-4803 VL - 52 IS - 6 SP - 3490 EP - 3496 AN - OPUS4-38574 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gollnow, C. A1 - Griesche, Axel A1 - Weidemann, Jens A1 - Kannengießer, Thomas T1 - Influence of external loads on a characteristic angle between grains and solidus line as an indicator for hot cracking susceptibility during GTA welding N2 - A long list of criteria determining the hot cracking susceptibility already exists. A main influence on solidification cracking can result from the design of the welded construction, i.e. from the influence of external loads. Using the Controlled Tensile Weldability (CTW) test, an external load hot cracking test, the influence of constant pre-load and different extension rates on the solidification cracking behavior of GTA (Gas Tungsten Arc) welds in an austenitic (AISI 309) and a ferritic (AISI 441) steel were investigated. Compared to specimens welded allowing free shrinkage and welded with an applied constant tensile pre-load, the specimens welded during the application of increasing tensile load show solidification cracks. In the weld seams, a characteristic angle α between the predominantly columnar grains and the fusion line can be observed. Specimens showing solidification cracks show a significantly larger angle α compared to the crack-free specimens. Based on these observations, the characteristic angle α is proposed as a new hot cracking criterion. KW - Hot cracking KW - External load test KW - Component design KW - Crack criterion KW - Grain growth PY - 2017 U6 - https://doi.org/10.1016/j.jmatprotec.2016.08.013 VL - 239 SP - 172 EP - 177 PB - Elsevier AN - OPUS4-37278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel A1 - Altenkirch, J. A1 - Gibmeier, J. A1 - Beyer, Katrin A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Welding problems - Investigations with neutrons of residual stress and of hydrogen diffusion in steels N2 - We report about investigations of typical material problems in steels. First, residual stresses in and around weld seams with low martensite transition temperature filler material were analyzed w/ and w/o additional transverse tensile load. The investigation was accompanied by x-ray diffraction measurements to track stress-induced phase transitions. Martensite formation during welding under external load yield strain gradients near the surface that improve the integrity of the weld. Further, the residual stress distribution close to laser-treated steel surfaces was analyzed. The method could be improved to reduce analysis artifacts. Finally, hydrogen diffusion in different steels was measured using neutron radiography and subsequent image analysis. Diffusion coefficients were derived by analyzing the time-dependent mass flux. In an outlook we describe the optimal ESS instrumentation from a metallurgist’s point of view. T2 - ESS Workshop "Science Vision for the European Spallation Source - German Perspectives" CY - Bad Reichenhall, Germany DA - 2011-10-10 PY - 2011 UR - http://www.fz-juelich.de/cae/servlet/contentblob/1058986/publicationFile/24649/Griesche_pdf.pdf UR - http://www.fz-juelich.de/sid_BD693DF17F42B3018726EE5C2558C56C/jcns/EN/Leistungen/ConferencesAndWorkshops/ESS/_node.html AN - OPUS4-24464 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel A1 - Horbach, Jürgen A1 - Meyer, Andreas T1 - Thermodynamics and Correlation Effects on Diffusion in Al-Ni Melts T2 - NIST Diffusion Workshop Series: Multicomponen Diffusion Data and Its Impact on the Materials Design Process: Data Needed; Daa Acquisition; and Data Application CY - Gaithersburg, MD, USA DA - 2012-05-03 PY - 2012 AN - OPUS4-25895 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel T1 - World Materials Research Institute Forum - An Introduction T2 - NIST Diffusion Workshop Series: Multicomponen Diffusion Data and Its Impact on the Materials Design Process: Data Needed; Data Acquisition; and Data Application CY - Gaithersburg, MD, USA DA - 2012-05-03 PY - 2012 AN - OPUS4-25896 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -