Browsing by Author "Gerling, R"

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    In and ex situ investigations of the β-phase in a Nb and Mo containing gamma-TiAl based alloy.
    (Elsevier, 2008-06) Clemens, H; Chladil, HF; Wallgram, W; Zickler, GA; Gerling, R; Liss, KD; Kremmer, S; Guther, V; Smarsly, W
    In β-stabilized Ti-43Al-4Nb-1Mo-0.1B alloy (composition in atomic percent) the correlation between the occurrence of β-phase and temperature was analyzed experimentally and compared to thermodynamic calculations. Results from in situ high-energy X-ray diffraction, texture measurements, heat treatments, scanning electron microscopy, and temperature-dependent flow stress measurements were used to study the evolution of the β-phase with temperature. Thermodynamic calculations based on the CALPHAD method were applied to correlate the phases developed in the β-solidifying TiAl based alloy under investigation. This alloy is characterized by an adjustable β-phase volume fraction at temperatures where hot-work processes such as forging and rolling are conducted. Due to a high volume fraction of β-phase at elevated temperatures the hot-extruded alloy can be forged under near conventional conditions. © 2008, Elsevier Ltd.
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    In situ high-energy X-ray diffraction study and quantitative phase analysis in the α+γ phase field of titanium aluminides
    (Elsevier, 2007-12) Yeoh, LA; Liss, KD; Bartels, A; Chladil, HF; Avdeev, M; Clemens, H; Gerling, R; Buslaps, T
    Quantitative atomic structure and phase analysis in the titanium aluminide intermetallic system of composition Ti–45Al–7.5Nb–0.5C (at.%) was conducted in situ by use of high-energy X-ray diffraction from a synchrotron and evaluated using the Rietveld method, implementing a model for atomic order in the α-phase which describes the order to disorder transition α2→α at the eutectoid temperature. The order parameter exhibits unexpected behavior and is entangled with the competition of different kinetic processes. © 2007, Elsevier Ltd.
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    Precipitation, recovery, phase transition and recrystallization processes of massively transformed TiAI scrutinized by ex- and in-situ high-energy X-ray diffraction
    (Australian Institute of Physics, 2005-01-31) Liss, KD; Bystrzanowski, S; Bartels, A; Buslaps, T; Clemens, H; Gerling, R; Schimansky, FP; Stark, A
    High-energy synchrotron radiation above 100 keV is a novel and sophisticated probe to access the volume properties of materials. A Debye-Scherrer method is shortly presented for the measurements of textures, strain and composition. Low density, high specific yield strength, good oxidation resistance and good creep properties at elevated temperatures make intermetallic γ-TiAl-based alloys top candidates as structural materials for advanced jet and automotive engines as well as for future hypersonic vehicles. The mechanical properties depend strongly on composition, thermo mechanical processing and subsequent heat treatments. The present study examines the recrystallization processes of a massively transformed specimen of Ti45AI46Nb9 upon a heat ramp from room temperature to 1400 deg C. The registered Debye-Scherrer rings are rich of features relating to thermal expansion, phase changes, domain and phase coherences, chemical separation and much more which will be regarded in detail.