Gestaltung von fortgeschrittenen Ti-Basis Dendriten - nanoskaligen/ultrafeinen eutektischen Matrix Kompositen durch die kontrollierte Erstarrung
Final Report Abstract
The project was aimed to gain better understanding of the solidification peculiarities of Ti-rich binary Ti-Fe and ternary Ti-Fe-Nb alloys. Representing the family of the β-Ti in situ composites, these alloys are highly potential for commercial applications due to high strength of ultrafine eutectic matrix, toughened by the ductile dendrites of the primary phase. The possibility to achieve deliberate morphology and distribution of the primary phase via semi-solid processing has been tested. To conduct these experiments a substantial development of the cold-finger facility was carried out within the project. The modifications proved to be particularly important in order to assure the reproducibility of the methods. A precise control over the processing parameters and enhanced cooling rate have a potential in successful application of this facility to many systems. Elaborated experimental work proved its potential for Ti-based multicomponent composite systems, providing guidelines for the future application of this method. To support the experiments on semi-solid processing, the high-temperature phase equilibria in Ti-rich corner of the Ti-Fe-Nb system was studied. The liquidus and solidus surfaces, as well as isothermal section at 1000°C were determined for the composition range up to 50 at.% Fe and 7.5 at.% Nb. These experimental data have been reasonably described by the thermodynamic modeling of the β-(Ti,Fe,Nb), FeTi, and liquid phases, which was done via extrapolation of the published assessments for binary terminal systems. Further particulars of the solidification in the hypo and hypereutectic alloys of binary Ti-Fe and ternary Ti-Fe-Nb systems have been studied by in situ high-energy X-ray diffraction combined with electrostatic levitation technique. The method provided a unique possibility to measure lattice parameters at elevated temperatures, otherwise not accessible for reactive materials, such as Ti-based alloys. In combination with the conventional dilatometry measurements the thermal expansion coefficients are found to be undistinguishable for β-(Ti,Fe) and FeTi phases (at least for the compositions, falling within the eutectic plateau) and show a quadratic temperature dependence, anticipated from recent ab initio calculations. Tracing the positions and intensity of the Bragg’s reflections, the time evolution of the composition and volume fraction of the constituent phases were deduced for binary alloys solidified from different undercooling levels. It was observed, that coarse microstructure formed at low undercoolings leads to the limited solid-stated diffusion below approx. 1000°C, resulting in the residual oversaturation of the β-(Ti,Fe) phase with iron. In contrast, fine microstructure, formed at deep undercoolings, signifies solidstated diffusion down to approx. 800°C and consequently attains the saturation level closer to equilibrium. These findings vividly illustrate crucial interconnection between the solidification conditions and resulting microstructure and may serve as a guide in how to obtain deliberate saturation of the constituent phases.
Publications
- Metastable solidification in undercooled liquid droplets of Fe-Ni based soft-magnetic alloys under terrestrial and microgravity conditions. Journal of Physics: Conference Series, 327 (2011) 012005
W. Löser, T.G. Woodcock, O. Shuleshova, R. Hermann, H.-G. Lindenkreuz, B. Gehrmann, S. Schneider, T. Volkmann
(See online at https://dx.doi.org/10.1088/1742-6596/327/1/012005) - Does an icosahedral short-range order prevail in glass-forming Zr-Cu melts? EPL (Europhysics Letters) 100 (2012) 56002
D. Holland-Moritz, F. Yang, T. Kordel,S. Klein, F. Kargl, J. Gegner, T. Hansen, J. Bednarcik, I. Kaban, O. Shuleshova, N. Mattern, A. Meyer
(See online at https://dx.doi.org/10.1209/0295-5075/100/56002) - Experimental and thermodynamic assessment of the Gd– Zr system, CALPHAD 39 (2012) 27–32
N. Mattern, J.H. Han, M. Zinkevich, O. Shuleshova, I. Kaban, D. Holland-Moritz, J. Gegner, F. Yang, J. Bednarcik, W. Löser, J. Eckert
(See online at https://doi.org/10.1016/j.calphad.2012.08.001) - Sessile drop study of Gd–Ti monotectic alloys on ceramic substrates : phase transformations, wetting, and reactivity, Journal of Material Science 47 (2012) 8381–8386
I. Kaban, R. Nowak, O. Shuleshova, B. Korpala, G. Bruzda, A. Siewiorek, J.H. Han, N. Sobczak, N. Mattern, J. Eckert
(See online at https://doi.org/10.1007/s10853-012-6775-6) - Solidification and melting of high temperature materials: in situ observations by synchrotron radiation, Journal of Materials Science 47 (2012) 4497–4513
O. Shuleshova, W. Löser, D.M. Herlach, J. Eckert
(See online at https://dx.doi.org/10.1007/s10853-011-6184-2) - In situ observation of the phase selection from the undercooled melt in Cu–Zr, Journal of Alloys and Compounds 576 (2013) 232–235
J. Gegner, O. Shuleshova, R. Kobold, D. Holland-Moritz, F. Yanga, W. Hornfeck, J. Bednarcik, D.M. Herlach
(See online at https://doi.org/10.1016/j.jallcom.2013.04.035) - Liquid - liquid transition in a strong bulk metallic glass-forming liquid, Nature communications 4 (2013) 1-17
S. Wei, F. Yang, J. Bednarcik, I. Kaban, O. Shuleshova, A. Meyer, R. Busch
(See online at https://dx.doi.org/10.1038/ncomms3083) - Local atomic arrangements and their topology in Ni–Zr and Cu–Zr glassy and crystalline alloys, Acta Materialia 61 (2013) 2509–2520
I. Kaban, P. Jóvári, V. Kokotin, O. Shuleshova, B. Beuneu, K. Saksl, N. Mattern, J. Eckert, L. Greer
(See online at https://doi.org/10.1016/j.actamat.2013.01.027) - Effect of Nb addition on microstructure evolution and nanomechanical properties of a glass-forming Ti–Zr–Si alloy, Intermetallics, 46 (2014) 156–163
S. Abdi, M.S. Khoshkhoo, O. Shuleshova, M. Bönisch, M. Calin, L. Schultz, J. Eckert, M.D. Baró, J. Sort, A.Gebert
(See online at https://doi.org/10.1016/j.intermet.2013.11.010) - In situ studies of temperature-dependent behaviour and crystallisation of Ni36.5Pd36.5P27 metallic glass, Journal of Alloys and Compounds 615 (2014) 208-212
I. Kaban, K. Khalouk, F. Gasser, J.-G. Gasser, J. Bednarcik, O. Shuleshova, I. Okulov, T. Gemming, N. Mattern, J. Eckert
(See online at https://doi.org/10.1016/j.jallcom.2013.12.259)
