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Correction published on 7 September 2017, see Metals 2017, 7(9), 353.

Open AccessArticle
Metals 2016, 6(7), 165; doi:10.3390/met6070165

Hydrostatic Compression Behavior and High-Pressure Stabilized β-Phase in γ-Based Titanium Aluminide Intermetallics

1
Quantum Beam Science Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
2
Australian Nuclear Science and Technology Organisation, Lucas Heights 2234, Australia
3
School of Mechanical, Materials & Mechatronic Engineering, Faculty of Engineering and Information Sciences, University of Wollongong, Northfields Avenue, Wollongong 2522, Australia
4
Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS-Tokai), Tokai, Ibaraki 319-1106, Japan
5
SPring-8, Japan Synchrotron Radiation Research Institute, Kouto, Sayo, Hyogo 679-5198, Japan
6
Quantum Beam Science Center, Japan Atomic Energy Agency, Kouto, Sayo, Hyogo 679-5148, Japan
Present Address: Quantum Beam Science Research Directorate, National Institute for Quantum and Radiological Science and Technology, Kouto, Sayo, Hyogo 679-5148, Japan
Present Address: Materials Sciences Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan and Kouto, Sayo, Hyogo 679-5148, Japan
*
Author to whom correspondence should be addressed.
Academic Editor: Hugo F. Lopez
Received: 15 April 2016 / Revised: 30 May 2016 / Accepted: 13 June 2016 / Published: 15 July 2016
(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)
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Abstract

Titanium aluminides find application in modern light-weight, high-temperature turbines, such as aircraft engines, but suffer from poor plasticity during manufacturing and processing. Huge forging presses enable materials processing in the 10-GPa range, and hence, it is necessary to investigate the phase diagrams of candidate materials under these extreme conditions. Here, we report on an in situ synchrotron X-ray diffraction study in a large-volume press of a modern (α2 + γ) two-phase material, Ti-45Al-7.5Nb-0.25C, under pressures up to 9.6 GPa and temperatures up to 1686 K. At room temperature, the volume response to pressure is accommodated by the transformation γ → α2, rather than volumetric strain, expressed by the apparently high bulk moduli of both constituent phases. Crystallographic aspects, specifically lattice strain and atomic order, are discussed in detail. It is interesting to note that this transformation takes place despite an increase in atomic volume, which is due to the high ordering energy of γ. Upon heating under high pressure, both the eutectoid and γ-solvus transition temperatures are elevated, and a third, cubic β-phase is stabilized above 1350 K. Earlier research has shown that this β-phase is very ductile during plastic deformation, essential in near-conventional forging processes. Here, we were able to identify an ideal processing window for near-conventional forging, while the presence of the detrimental β-phase is not present under operating conditions. Novel processing routes can be defined from these findings. View Full-Text
Keywords: high pressure; high temperature; phase transformation; equation of states; plasticity; TiAl; intermetallics; synchrotron radiation; multi-anvil press; in situ diffraction high pressure; high temperature; phase transformation; equation of states; plasticity; TiAl; intermetallics; synchrotron radiation; multi-anvil press; in situ diffraction
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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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MDPI and ACS Style

Liss, K.-D.; Funakoshi, K.-I.; Dippenaar, R.J.; Higo, Y.; Shiro, A.; Reid, M.; Suzuki, H.; Shobu, T.; Akita, K. Hydrostatic Compression Behavior and High-Pressure Stabilized β-Phase in γ-Based Titanium Aluminide Intermetallics. Metals 2016, 6, 165.

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