Phase Transformations During Solidification of a Laser-Beam-Welded TiAl Alloy—An In Situ Synchrotron Study
An in situ highly time-resolved, high-energy X-ray diffraction investigation was carried out to observe the phase transformations of a TiAl alloy during laser beam welding. The diffraction patterns are recorded every 0.1 seconds by a fast area two-dimensional detector and plotted according to time, yielding the solidification pathway, the solid phase volume fraction, and the lattice parameter variation of different phases during the solidification and cooling process. Moreover, it is the first study that can demonstrate that the α phase without any Burgers orientation relationship, the so-called non-Burgers α, precipitates appear earlier than the Burgers α. The non-Burgers α grains are found to nucleate on the primary borides.
KeywordsBoride Orientation Relationship TiAl Alloy Total Free Energy Laser Beam Welding
The authors thank John Hedde, René Kirchhof, Gerhard Kozik, René Dinse, Jürgen Buhrz, Andreas Beldowski, Jörg Burmester, and Dennis Heims for the kind support in the design and construction of the experimental setup. Moreover, the authors are very grateful to Professor Florian Pyczak, Dr. Michael Oehring, and Dr. Jonathan Paul for the discussion about the results. Finally, the authors appreciate the specimen preparation work of Falk Dorn.
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