Processing effects on the grain-boundary character distribution of the orthorhombic phase in Ti-Al-Nb alloys

Dingqiang Li, C. J. Boehlert

    Research output: Research - peer-reviewArticle

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    Abstract

    The grain-boundary character distribution of the orthorhombic (O) phase in Ti2AlNb intermetallic alloys was investigated. The alloys were thermomechanically processed either above or below the bcc transus temperature. Using electron backscattered diffraction, the twin-related O-phase variant interfacial planes were identified and quantified. For the subtransus-processed samples, the equiaxed-O/equiaxed-O grain boundaries tended to primarily prefer 65-deg misorientations and secondarily prefer 90-deg boundaries. Of the 65-deg misoriented boundaries, which were preferentially rotated about [001], ∼40 pct contained (110) twin-related interfacial planes. The observations were rationalized by the α2-to-O phase transformation. It is suggested that for subtransus processing within the α 2-containing phase regimes, the resulting heat-treated O + bcc microstructures evolve such that the O/O boundaries tend to exhibit distinct twin-related variants with misorientations between 55 and 65 deg. For a supertransus-processed alloy, it was found that approximately equal distributions of the six resolvable O variants were formed from the dominant parent bcc orientation. The resulting O/O boundaries tended to cluster at near-90-deg misorientations, which can be explained by the bcc/O orientation relationship. It is suggested that whenever the O phase primarily transforms from the bec structure, the resulting O + bcc microstructures evolve such that the O/O boundaries tend to exhibit misorientations near 90 deg.

    LanguageEnglish (US)
    Pages2569-2584
    Number of pages16
    JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
    Volume36
    Issue number10
    StatePublished - Oct 2005

    Profile

    Grain boundaries
    Processing
    titanium-niobium-aluminum alloy
    grain boundaries
    misalignment
    Microstructure
    microstructure
    Electron diffraction
    Intermetallics
    Phase transitions
    Temperature
    Hot Temperature
    phase transformations
    intermetallics
    electron diffraction
    heat
    temperature

    ASJC Scopus subject areas

    • Materials Science(all)
    • Metals and Alloys

    Cite this

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    abstract = "The grain-boundary character distribution of the orthorhombic (O) phase in Ti2AlNb intermetallic alloys was investigated. The alloys were thermomechanically processed either above or below the bcc transus temperature. Using electron backscattered diffraction, the twin-related O-phase variant interfacial planes were identified and quantified. For the subtransus-processed samples, the equiaxed-O/equiaxed-O grain boundaries tended to primarily prefer 65-deg misorientations and secondarily prefer 90-deg boundaries. Of the 65-deg misoriented boundaries, which were preferentially rotated about [001], ∼40 pct contained (110) twin-related interfacial planes. The observations were rationalized by the α2-to-O phase transformation. It is suggested that for subtransus processing within the α 2-containing phase regimes, the resulting heat-treated O + bcc microstructures evolve such that the O/O boundaries tend to exhibit distinct twin-related variants with misorientations between 55 and 65 deg. For a supertransus-processed alloy, it was found that approximately equal distributions of the six resolvable O variants were formed from the dominant parent bcc orientation. The resulting O/O boundaries tended to cluster at near-90-deg misorientations, which can be explained by the bcc/O orientation relationship. It is suggested that whenever the O phase primarily transforms from the bec structure, the resulting O + bcc microstructures evolve such that the O/O boundaries tend to exhibit misorientations near 90 deg.",
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