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First-Principles Study on the Impact of Antisite Defects on the Mechanical Properties of TiAl-Based Alloys
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.ORCID iD: 0000-0001-6482-1404
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2019 (English)In: Acta Metallurgica Sinica, ISSN 0412-1961, Vol. 55, no 5, p. 673-682Article in journal (Refereed) Published
Abstract [en]

Microalloying is an effective approach to improve the mechanical properties of TiAl-based alloys which have been applied as high-temperature structure materials. The antisite defects may be regarded as special alloying elements. However, the detailed information about the effect of antisite defects on mechanical behavior (full slip and twinning), which may be described theoretically by generalized stacking fault energy (GSFE), of TiAl-based alloys are scarce. In this work, the composition dependent GSFEs of off-stoichiometric gamma- TiAl were calculated by using the first-principles exact muffin-tin orbitals method in combination with coherent potential approximation. With the calculated GSFE, the energy barriers for various deformation modes including twin (TW), ordinary dislocation (OD), and superlattice dislocation (SDI and SDII) were determined. The selection of the deformation mode under external shear stress with various directions was analyzed. The effects of the Ti-Al and Al(Ti )antisite defects on the mechanical properties of gamma-TiAl were then discussed. The results showed that the Ti-Al antisite defect decreases the energy barrier for the TW deformation leading by the superlattice intrinsic stacking fault (SISF) partial dislocation and increases the angle window of the applied shear stress within which TW deformation may be activated. Therefore, Ti-Al antisite defect is expected to improve the plasticity of gamma-TiAl. The effect of Al-Ti antisite defect is opposite. The Al-Ti antisite defect decreases the energy barriers for the OD and SDII deformations leading by complex stacking fault (CSF) partial dislocation and increases their operating angle window, indicating that Al-Ti facilitates the slip of OD and SDII. Considering that the energy barrier for CSF is much higher than that for SISF, the plasticity induced by OD and SDII should be lower than that induced by TW. Calculations in this work explain the experimental finding that Ti-Al antisite defect improves the plasticity of gamma-TiAl more significantly than Al-Ti antisite defect.

Place, publisher, year, edition, pages
SCIENCE PRESS , 2019. Vol. 55, no 5, p. 673-682
Keywords [en]
antisite defect, TiAl-based alloy, generalized stacking fault energy, plastic deformation
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Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-251470DOI: 10.11900/0412.1961.2018.00349ISI: 000464751100014OAI: oai:DiVA.org:kth-251470DiVA, id: diva2:1317365
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QC 20190522

Available from: 2019-05-22 Created: 2019-05-22 Last updated: 2019-05-22Bibliographically approved

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Ji, Zong-WeiLu, SongVitos, Levente

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