Overview of the atomic relaxation processes in ?-TiAl intermetallics for aeronautic applications

Reference Speaker Authors
Jose San Juan San Juan, J.(Universidad del Pais Vasco); Usategui, L.(Universidad del Pais Vasco); Klein, T.(Montauniversitat Leoben); Mayer, S.(Montauniversitat Leoben); Clemens, H.(Montauniversitat Leoben); Ruano, O.A.(CENIM-CSIC); Nó, M.L.(Universidad del Pais Vasco); In the last decades there has been a growing interest in developing new intermetallic families, which would we able to improve the performances of superalloys at high temperature. In particular a new Ti-Al-Nb-Mo family called TNM is being optimized to fulfil the required performances. In the present work we will present an overview of the studies performed in the last decade on several ?-TiAl intermetallics, with special emphasis on the last generations of Ti-Al-Nb-Mo alloys. As a deep understanding of the atomic mechanisms controlling plastic deformation at high temperature is a key point for a final optimization of these alloys, a new approach by mechanical spectroscopy has been considered. Indeed, mechanical spectroscopy has been used to measure the internal friction and the dynamic modulus evolution from 300ºC up to 1350ºC in the above alloys. Several relaxation processes have been observed in different intermetallic alloys and a complete study has allowed to identify the responsible atomic diffusion mechanisms having place in different phases, ?, ? and ?, constituents of these alloys [1, 2]. In addition, the relaxation processes associated to the high-temperature internal friction background have been directly related to the creep behaviour of these materials and its analysis is allowing design more creep-resistant alloys [2, 3]. The measurement of the activation parameters of these relaxations will be presented along the talk, and the corresponding atomic mechanisms will be also overviewed and discussed. It will be emphasized, along the presentation, the potentiality and the interest of the mechanical spectroscopy as an alternative approach to be used not only for basic research but also to solve technological problems in materials for high temperature applications, as in the present case of ?-TiAl alloys, which are at present flying in the new generation of engines used in the aircrafts of the main aeronautic companies. [1] J. San Juan, P. Simas, T. Schmoelzer, H. Clemens, S. Mayer and M.L. Nó. Acta Materialia 65, 338-350 (2014). [2] T. Klein, L. Usategui, B. Rashkova, M.L. Nó, J. San Juan, H. Clemens, S. Mayer. Acta Materialia 128, 440-450 (2017). [3] M. Castillo-Rodriguez, M.L. Nó, J.A. Jiménez, O.A. Ruano, J. San Juan. Acta Materialia 103, 46-56 (2016).
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