Abstract
The fully lamellar microstructure of powder metallurgy Ti-48Al-2W after cooling from the α region to 1280 °C, followed by air cooling and aging at 950 °C for up to 96 hours, is presented. Aging times as short as 5 hours result in acicular-shaped precipitates of W-rich β 0 along lamellar interfaces, with the β 0 size increasing with aging time. The β 0 precipitates nucleate and grow in the α 2 lamellae. Concurrently, with the formation of β 0, the α 2 decomposes into discontinuous lamellae. Aging to precipitate β 0 along lamellar interfaces increases the 760 °C tensile strength (with a slight reduction of ductility) and reduces the instantaneous creep strain, since β 0 precipitates at lamellar interfaces hinder interface dislocation mobility. The deformed microstructures from interrupted creep tests at 140 to 276 MPa at 760 °C indicate that the precipitation of β 0 along interfaces substantially reduces the primary creep strain, primarily due to the influence of β 0 on interface dislocation emission and motion. These results are discussed in terms of the influence of lamellar morphology on the instantaneous creep strain and primary creep transient, and the possible creep mechanisms are highlighted.
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This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint Committee of Mechanical Behavior of Materials.
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Seo, D.Y., Zhao, L. & Beddoes, J. Primary creep behavior of Ti-48Al-2W as a function of stress and lamellar morphology. Metall Mater Trans A 34, 2177–2190 (2003). https://doi.org/10.1007/s11661-003-0281-z
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DOI: https://doi.org/10.1007/s11661-003-0281-z