Interpretation of the morphology and crystallography of precipitate γ1-Ti4Nb3Al9 in L10-TiAl(Nb)-based intermetallics by invariant line theory |
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| Affiliation: | 1. College of Mechanical Engineering, Guangxi University, Nanning 530004, PR China;2. School of Mechanic Engineering, South China University of Technology, Guangzhou 510640, PR China;3. Institute of Solid State Physics, Chinese Academy of Science, Hefei 230031, PR China;4. National Key Laboratory of Solid State Microstructure, Nanjing University, Nanjing 210093, PR China |
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| Abstract: | The coherent precipitate γ1-Ti4Nb3Al9 in the Nb-modified TiAl-based intermetallic compound with a nominal composition of Ti–48 at% Al–10 at% Nb was investigated by transmission electron microscopy. The crystallographic and morphologic characteristics of the precipitating phase have been calculated based on invariant line theory. It is revealed that in the γ-TiAl(Nb)/γ1-Ti4Nb3Al9 couples, both the morphological and crystallographical characteristics of the precipitate γ1-Ti4Nb3Al9 could be predicted by the three-dimensional phase transformation invariant line model. The needle direction of [001] at the early stage for coherent precipitate γ1-Ti4Nb3Al9 and [111] for equilibrium phase γ1-Ti4Nb3Al9 have both been explained well. The characterization of morphology and crystallography of the precipitate reaction in γ-TiAl/γ1-Ti4Nb3Al9 system sustain the postulate that precipitates are bounded by unrotated planes (eigenplanes) when three real eigenvalues exist. |
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