PhD Yindong Fang honored with poster prize at LI CALPHAD conference in 2024 for his work on „Phase equilibria, microsegregations and mechanical properties of Inconel 718 alloy samples processed in electromagnetic levitation facility”
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PhD Yindong Fang honored with poster prize at LI CALPHAD conference in 2024 for his work on „Phase equilibria, microsegregations and mechanical properties of Inconel 718 alloy samples processed in electromagnetic levitation facility”
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  1. Near-Surface Microstructure and Properties of High-Carbon Metastable Austenitic Steels Subjected to Abrasive Wear

    Authors
    J. Ingber, J. Maier, S. Lippmann, K. Freiberg, T. Studecky, M. Kunert
    Year of publication
    Published in:
    Metallography, microstructure, and analysis: application and innovation for metals, alloys, and engineered materials
    The microstructure and properties in the near-surface region of two high-carbon metastable austenitic steels after two-body abrasive wear were studied. The samples were subjected to wear loads in a range of 8–32 N (corresponding to approximately 0.1–0.4 MPa). Vickers hardness measurements on the worn surface as well as nanoindentation measurements on the cross section present a significant hardness increase from the bulk toward the surface of up to 400%. Electron channeling contrast imaging was utilized to assign the indents from the nanoindentation measurements to the martensitic or austenitic phase. Within a subsurface layer with a thickness of a few microns, it was impossible to distinguish a phase via these images. Magnetic force microscopy revealed a few microns thick martensitic layer, which is the main cause of the significant hardness increase in the near-surface region. No considerable influence of the wear load (within the tested load range) on the resulting microstructure and mechanical properties was found. Transmission electron microscopy images reveal a grain size of several nanometers within the martensitic subsurface layer, which accounts for the observed ductility on the worn surfaces, despite the inherent brittleness typically associated with high-carbon martensite.
    University Bibliography Jena:
    fsu_mods_00036070External link

  3. Soft X-ray imaging with coherence tomography in the water window spectral range using high-harmonic generation

    Authors
    J. Reinhard, F. Wiesner, M. Hennecke, T. Sidiropoulos, S. Kaleta, J. Späthe, J. Abel, M. Wünsche, G. Schmidl, J. Plentz, U. Hübner, K. Freiberg, J. Apell, S. Lippmann, M. Schnürer, S. Eisebitt, G. Paulus, S. Fuchs
    Year of publication
    Published in:
    Light: Science and Applications
    High-harmonic generation (HHG) is used as a source for various imaging applications in the extreme ultraviolet spectral range. It offers spatially coherent radiation and unique elemental contrast with the potential for attosecond time resolution. The unfavorable efficiency scaling to higher photon energies prevented the imaging application in the soft X-ray range so far. In this work we demonstrate the feasibility of using harmonics for imaging in the water window spectral region (284 eV to 532 eV). We achieve nondestructive depth profile imaging in a heterostructure by utilizing a broadband and noise-resistant technique called soft X-ray Coherence Tomography (SXCT) at a high-flux lab-scale HHG source. SXCT is derived from Optical Coherence Tomography, a Fourier based technique that can use the full bandwidth of the source to reach an axial resolution of 12 nm in this demonstration. The employed source covers the entire water window, with a photon flux exceeding 10 ⁶ photons/eV/s at a photon energy of 500 eV. We show local cross sections of a sample consisting of Aluminium oxide and Platinum layers of varying thickness on a Zinc oxide substrate. We validate the findings with scanning and transmission electron microscopy after preparation with focused ion beam milling.
    University Bibliography Jena:
    fsu_mods_00030098External link

  4. Reassessment of Al-Cu System Considering Metastable Extensions of Solid/Liquid Phase Equilibria

    Authors
    Y. Fang, K. Hack, S. Lippmann
    Year of publication
    Published in:
    Journal of phase equilibria and diffusion
    The thermodynamic description of the Al-Cu system is reassessed considering metastable states of Al based alloys in rapid solidification. In previous work, only an improved thermodynamic description of the FCC phase was presented based on experimental results from electromagnetic levitation and simulation results for free dendritic growth to be in accordance with existing thermodynamic descriptions of the liquid phase. The phase diagram thus obtained enabled the correction of the artificial miscibility gap when calculating metastable extensions of the FCC/liquid phase equilibria, the unphysical change of the slope of the solidus line on the Al-rich side and the artificial maximum on the Cu-rich side. However, the description did not well align with the most recent experimental results on the Cu-rich side. The new description reassessing FCC, liquid and the α′-phase demonstrates high consistency with these recent experimental results, reproducing all invariant reactions (temperatures) with an accuracy of ± 4 K and the experimental liquidus line with an accuracy of ± 10 K, all well within the experimental error. The results provide a robust framework for predicting phase behavior under metastable conditions, as confirmed by our experimental data.
    University Bibliography Jena:
    fsu_mods_00027653External link

  5. Experimentelle Untersuchungen zur Identifikation einer Lotlegierung auf Cu-Basis zum Hartlöten mit Schmelztemperaturen unter 800°C

    Author
    M. Salge
    Year of publication
    Die Kombination von unterschiedlichen Materialien mit deutlich voneinander abweichenden physikalischen Eigenschaften, wie Metall-Metall (z. B. Stahl-Aluminium), Metall-Keramik oder Metall-Glas, kann Verbessungen in bestehenden Anwendungen ermöglichen oder sogar vollkommen neue Einsatzgebiete erschließen. Ein wichtiges Verfahren zur Herstellung solcher Verbindungen ist das Hartlöten. Diese Technik ermöglicht stoffschlüssige, widerstandsfähige Fügeverbindungen zwischen verschiedenen Grundmaterialien ohne deren Eigenschaften nennenswert zu beeinträchtigen. Innerhalb des Legierungssystems Ag-Cu-Zn-Sn wurde über die Jahre eine Reihe von Lotlegierungen entwickelt, welche heute kommerziell zum Fügen verschiedenster Materialien verwendet werden und deren Eigenschaften bereits intensiv untersucht worden sind. Wesentliche Verbesserungen hinsichtlich Schmelztemperatur, Benetzung- bzw. Fließverhalten oder mechanischer Eigenschaften dieser Legierungen sind innerhalb des quaternären Ag-Cu-Zn-Sn-Systems nicht mehr möglich. In der vorliegenden Arbeit werden verschiedene Legierungssysteme mit zu herkömmlichen Ag-Cu-Zn-Sn-Legierungen vergleichbaren Eigenschaften hinsichtlich ihrer Phasenbildung untersucht und bewertet, inwieweit sich diese als Alternative zu standardisierten Hartloten eignen. Es werden Cu-Basislegierungen sowohl mit als auch ohne Ag hergestellt und die Auswirkung zusätzlicher Legierungselemente, insbesondere Lithium, auf Gefüge und Eigenschaften wie Schmelztemperatur, Verformbarkeit und Fließverhalten untersucht. Mit dem Ziel, die Entwicklungszeit zu verkürzen, werden für die Untersuchung der Cu-reichen Ecke des Cu-Ga-Sn-Systems Methoden der gerichteten Erstarrung genutzt. So können mit Hilfe von Temperaturgradienten hergestellten Proben in einem großen Zusammensetzungsbereich hinsichtlich des vorliegenden Gefüges, der Härte und des Schmelzbereiches untersucht werden. Zusätzlich werden mit Hilfe der CALPHAD-Methode Solidus- und Liquidusprojektionen optimiert.
    University Bibliography Jena:
    fsu_mods_00025462External link

  7. Fabrication of shallow EUV gratings on silicon by irradiation with helium ions

    Authors
    J. Kaufmann, R. Ciesielski, K. Freiberg, M. Walther, A. Fernández Herrero, S. Lippmann, V. Soltwisch, T. Siefke, U. Zeitner
    Year of publication
    Published in:
    Nanotechnology
    To accurately achieve structure height differences in the range of single digit nanometres is of great importance for the fabrication of diffraction gratings for the extreme ultraviolet range (EUV). Here, structuring of silicon irradiated through a mask by a broad beam of helium ions with an energy of 30 keV was investigated as an alternative to conventional etching, which offers only limited controllability for shallow structures due to the higher rate of material removal. Utilising a broad ion beam allows for quick and cost effective fabrication. Ion fluence of the irradiations was varied in the range of 10¹⁶ ... 10¹⁷ ions · cm⁻². This enabled a fine tuning of structure height in the range of 1.00 ± 0.05 to 20 ± 1 nm, which is suitable for shallow gratings used in EUV applications. According to transmission electron microscopy investigations the observed structure shape is attributed to the formation of point defects and bubbles/cavities within the silicon. Diffraction capabilities of fabricated elements are experimentally shown at the SX700 beamline of BESSY II. Rigorous Maxwell solver simulation based on the finite-element method and rigorous coupled wave analysis are utilised to describe the experimental obtained diffraction pattern.
    University Bibliography Jena:
    fsu_mods_00023928External link

  8. Comparative Study of Experimental Methods for Measuring Thermal Properties of 100Cr6 Steel Powders

    Authors
    J. Zhuo, H. Kohl, D. Liu, L. Matthäus, A. Bochmann, A. Berger, S. Weber, S. Nolte, S. Lippmann
    Year of publication
    Published in:
    Advanced Engineering Materials
    University Bibliography Jena:
    fsu_mods_00025275External link

  9. Ultra shallow silicon EUV gratings fabricated via ion irradiation

    Authors
    J. Kaufmann, R. Ciesielski, K. Freiberg, M. Walther, A. Fernández Herrero, S. Lippmann, V. Soltwisch, T. Siefke, U. Zeitner
    Year of publication
    Published in:
    EUV and X-Ray Optics: Synergy between Laboratory and Space IX: 7-8 April 2025, Prague, Czech Republic
    University Bibliography Jena:
    fsu_mods_00026647External link

  10. Fabrication of ultra-shallow EUV gratings in silicon via ion irradiation

    Authors
    J. Kaufmann, R. Ciesielski, K. Freiberg, M. Walther, A. Herrero, S. Lippmann, V. Soltwisch, T. Siefke, U. Zeitner
    Year of publication
    Published in:
    Advances in X-ray/EUV sources, optics, and components XX
    University Bibliography Jena:
    fsu_mods_00029436External link

  11. Climate related phase transitions with moving boundaries by virtue of mushy zone investigation in Al–Cu: Experiment and phase-field modeling

    Authors
    I. Nizovtseva, V. Ankudinov, E. Rahner, S. Lippmann
    Year of publication
    Published in:
    Mathematical Methods in the Applied Sciences
    Studying Arctic ice formation stays in the focus of research groups over the past decades in the context of ice cover changes, thermal budget and climate agenda in general. Nevertheless, the phenomenon's underlying mechanisms are still not completely understood and described. The main reason for the lack in understanding is the limited experimental access to the field data when it comes to the processes that occur below the ice floe. Thus, there is a need to build competent analogies between the natural (ocean water–ice) and laboratory (here: binary alloy) conditions of the experiment as a step of data preparation for the verification of the mathematical model. In the current paper, the existing qualitative models describing the process of melting and crystallization were expanded and the experimental method was developed copying the layering of the natural ocean water–ice mixture. The experimental set-up for studying the solidification within the intermediate zone was designed for Al–Cu alloys being the system with appropriate solidus line for creating a sufficient concentration gradient and by that temperature dependent phase fraction under isothermal conditions. The gained experimental data were used for validating a binary phase-field model for solidification considering moving boundaries. The model includes the description of the free energy of both phases and their respective diffusion coefficients. It allows modeling a binary system at a mesoscopic spatial level by including the concentration-driven phase transition and resolidification in the two-phase region. The novel results will help the quantitative understanding of solidification phenomena and are highly-evaluated from interdisciplinary point of view, including glaciology and geosciences, being ultimately significant for the understanding the global climate change landscape.
    University Bibliography Jena:
    fsu_mods_00010512External link

  12. Dendritic Si growth morphologies in highly undercooled Al–Si alloys

    Authors
    D. Liu, Y. Fang, S. Nolte, S. Lippmann
    Year of publication
    Published in:
    Journal of materials research and technology : official publication of the Brazilian Metallurgical, Materials and Mining Association
    The morphology of primarily crystallizing Si in hypereutectic Al-(20, 40, 55) wt%Si alloys during conventional casting (nucleation undercooling ΔT<1 K) and solidification at high undercoolings (ΔT up to 335 K) has been investigated. As expected, at higher undercoolings a higher nucleation frequency and fast growth of primary Si is observed, leading to the formation of multiple microstructural zones. Instead of the well-known plate-like Si in the as-cast microstructure, various morphologies of primary Si such as faceted and non-faceted blocky morphologies as well as dendrites with aligned side branches showing constant spacing features are observed after solidification at high undercoolings. The special Si dendrites only grow in a limited range of melt concentrations and undercoolings. The transition from faceted to non-faceted growth appears to occur in several steps, as Si dendrites with similar features of the secondary arms as in non-faceted metal alloys are also observed.
    University Bibliography Jena:
    fsu_mods_00013946External link
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