Stability of ultrafine lamellar structures during aging in two-phase γ-TiAl alloys [electronic resource]
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| Online Access: |
Online Access |
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| Format: | Government Document Electronic eBook |
| Language: | English |
| Published: |
Washington, D.C. : Oak Ridge, Tenn. :
United States. Dept. of Energy ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy,
1997.
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| Abstract: | Two-phase γ-tail alloys such as PM Ti-47Al-2Cr-2Nb or Ti-47Al- 2Cr-1Nb-Ta hot extruded above the α-transus temperature have unique refined-colony/ultrafine lamellar structures. These lamellar microstructures consist of very fine laths of the γ and α₂ phases, with average interlamellar spacings of 100 nm and α₂-α₂ spacings of 200 nm, and are dominated by γ/α₂ interfaces. This ultrafine lamellar structure remains stable during 900 C heat treatment for 2 h, but becomes unstable after 4 h at 982 C. This structure remains stable in both alloys after aging for >5000 h at 800 C but disappears completely at 1000 C. Continuous coarsening begins with dissolution of fine α₂ lamellea. The aged Ta-modified alloy shows similar lamellar coarsening behavior within the colonies but has more discontinuous coarsening of the intercolony γ with new precipitation of coarse α₂ and β phase particles. Analytical electron microscopy show that changes in α₂ phase composition correlate with microstructural instability. |
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| Item Description: | Published through the Information Bridge: DOE Scientific and Technical Information. 08/01/1997. "CONF-970909--4" "DE97008243" 2. international symposium on structural intermetallics, Champion, PA (United States), 21-26 Sep 1997. Wright, J.L.; Liu, C.T.; Maziasz, P.J. |
| Physical Description: | 15 p. |