Origin of enhanced room temperature ductility in TiAl alloys: Reducing activation difference of deformation mechanism of gamma phase

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TiAl alloys have been studied widely as promising candidates for high-temperature applications, while the application has been hindered due to the lack of room temperature ductility. Herein, we systematically investigated the effect of tensile loading direction and additional elements (Cr and Nb) on the initial deformation mechanism in the gamma phase of TiAl alloys, which is one of the crucial factors to decide room temperature ductility. First, we carefully chose two different TiAl alloys with limited and enhanced ductility. Second, by synthesizing the sample with a single gamma phase via extracting the composition of gamma phase in both TiAl alloy composed of gamma and alpha(2) phases, the initial deformation mechanism of gamma phase is confirmed depending on alloy composition as well as loading direction using an in situ transmission electron microscopy. Third, using the first principle density functional theory calculation, we carefully calculate the change in activation factors of deformation mechanism according to each additional element (Cr and Nb) in TiAl alloy. As a result, it can be understood that the deformation mechanism of the gamma phase in TiAl alloys changes depending on the additional element as well as loading direction. In particular, by comparing the experimental and theoretical study, it was revealed that the activation difference of three deformation mechanisms in the gamma phase of TiAl alloy decreases as Nb is added, which leads to the activation of all deformation mechanisms in the gamma phase during deformation, and hence obtains the enhanced room temperature ductility in TiAl alloys. Our results provide an effective strategy for enhancing room temperature ductility of TiAl alloys via reduction of activation difference of deformation mechanisms in gamma phase of TiAl alloys, which will open a new era to develop TiAl alloys with enhanced ductility for various structural parts in automotive and aerospace industries. (C) 2021 Elsevier B.V. All rights reserved.
Publisher
ELSEVIER SCIENCE SA
Issue Date
2022-04
Language
English
Article Type
Article
Citation

JOURNAL OF ALLOYS AND COMPOUNDS, v.899

ISSN
0925-8388
DOI
10.1016/j.jallcom.2021.163307
URI
http://hdl.handle.net/10203/292241
Appears in Collection
ME-Journal Papers(저널논문)
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