Stability of ultrafine lamellar structures during aging in two-phase {gamma}-TiAl alloys

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Two-phase {gamma}-tail alloys such as PM Ti-47Al-2Cr-2Nb or Ti-47Al- 2Cr-1Nb-Ta hot extruded above the {alpha}-transus temperature have unique refined-colony/ultrafine lamellar structures. These lamellar microstructures consist of very fine laths of the {gamma} and {alpha}{sub 2} phases, with average interlamellar spacings of 100 nm and {alpha}{sub 2}-{alpha}{sub 2} spacings of 200 nm, and are dominated by {gamma}/{alpha}{sub 2} 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 ... continued below

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15 p.

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Maziasz, P.J.; Liu, C.T. & Wright, J.L. August 1, 1997.

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Two-phase {gamma}-tail alloys such as PM Ti-47Al-2Cr-2Nb or Ti-47Al- 2Cr-1Nb-Ta hot extruded above the {alpha}-transus temperature have unique refined-colony/ultrafine lamellar structures. These lamellar microstructures consist of very fine laths of the {gamma} and {alpha}{sub 2} phases, with average interlamellar spacings of 100 nm and {alpha}{sub 2}-{alpha}{sub 2} spacings of 200 nm, and are dominated by {gamma}/{alpha}{sub 2} 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 {alpha}{sub 2} lamellea. The aged Ta-modified alloy shows similar lamellar coarsening behavior within the colonies but has more discontinuous coarsening of the intercolony {gamma} with new precipitation of coarse {alpha}{sub 2} and {beta} phase particles. Analytical electron microscopy show that changes in {alpha}{sub 2} phase composition correlate with microstructural instability.

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15 p.

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OSTI as DE97008243

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  • 2. international symposium on structural intermetallics, Champion, PA (United States), 21-26 Sep 1997

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  • Other: DE97008243
  • Report No.: CONF-970909--4
  • Grant Number: AC05-96OR22464
  • Office of Scientific & Technical Information Report Number: 516994
  • Archival Resource Key: ark:/67531/metadc690096

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  • August 1, 1997

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  • Aug. 14, 2015, 8:43 a.m.

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  • Jan. 21, 2016, 12:32 p.m.

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Maziasz, P.J.; Liu, C.T. & Wright, J.L. Stability of ultrafine lamellar structures during aging in two-phase {gamma}-TiAl alloys, article, August 1, 1997; Tennessee. (digital.library.unt.edu/ark:/67531/metadc690096/: accessed October 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.