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Appl. Sci. 2017, 7(11), 1193; https://doi.org/10.3390/app7111193

Impact of Alloying on Stacking Fault Energies in γ-TiAl

Chair of Physical Metallurgy and Metallic Materials, Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Leoben A-8700, Austria
Current address: Chair of Nonferrous Metallurgy, Department of Metallurgy, Montanuniversität Leoben, Franz-Josef-Str. 18, Leoben 8700, Austria.
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Author to whom correspondence should be addressed.
Received: 21 October 2017 / Revised: 13 November 2017 / Accepted: 15 November 2017 / Published: 21 November 2017
(This article belongs to the Special Issue Mechanical Behaviour of Aluminium Alloys)
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Abstract

Microstructure and mechanical properties are key parameters influencing the performance of structural multi-phase alloys such as those based on intermetallic TiAl compounds. There, the main constituent, a γ -TiAl phase, is derived from a face-centered cubic structure. Consequently, the dissociation of dislocations and generation of stacking faults (SFs) are important factors contributing to the overall deformation behavior, as well as mechanical properties, such as tensile/creep strength and, most importantly, fracture elongation below the brittle-to-ductile transition temperature. In this work, SFs on the { 111 ) plane in γ -TiAl are revisited by means of ab initio calculations, finding their energies in agreement with previous reports. Subsequently, stacking fault energies are evaluated for eight ternary additions, namely group IVB–VIB elements, together with Ti off-stoichiometry. It is found that the energies of superlattice intrinsic SFs, anti-phase boundaries (APBs), as well as complex SFs decrease by 20–40% with respect to values in stoichiometric γ -TiAl once an alloying element X is present in the fault plane having thus a composition of Ti-50Al-12.5X. In addition, Mo, Ti and V stabilize the APB on the (111) plane, which is intrinsically unstable at 0 K in stoichiometric γ -TiAl. View Full-Text
Keywords: titanium aluminides; stacking fault energies; density functional theory titanium aluminides; stacking fault energies; density functional theory
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Dumitraschkewitz, P.; Clemens, H.; Mayer, S.; Holec, D. Impact of Alloying on Stacking Fault Energies in γ-TiAl. Appl. Sci. 2017, 7, 1193.

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