Microstructure, creep, and tensile behaviour of a Ti-15Al-33Nb (at.%) beta+orthorhombic alloy

C. J. Cowen, C. J. Boehlert

    Research output: Research - peer-reviewArticle

    • 14 Citations

    Abstract

    The microstructural evolution, creep and tensile deformation behaviour of a Ti-15Al-33Nb (at.%) alloy was studied. Monolithic sheet material was produced through conventional thermomechanical processing techniques comprising non-isothermal forging and pack rolling. Electron microscopy studies showed that depending on the heat-treatment schedule, this alloy may contain three constituent phases including:β(disordered body-centred cubic), 2 (ordered hexagonal close-packed based on Ti3Al) and O (ordered orthorhombic based on Ti2AlNb). Heat treatments at all temperatures above 990°C, followed by water quenching, resulted in fully-β microstructures. Below 990°C, Widmanstätten O-phase or 2-phase precipitated within theβgrains. The fine-grained as-processed microstructure, which exhibited 90vol.% β-phase, exhibited excellent strength (UTS=916MPa) and ductility (f>12%). After heat treatment, greater volume fractions of the orthorhombic phase precipitated and resulted in lower f values with UTS values ranging between 836-920MPa. However, RT elongations of more than 2% were recorded for microstructures containing up to 63vol.% O-phase. Specimens subjected to 650°C tensile experiments tended to exhibit lower strength values while maintaining higher elongation-to-failure. Tensile creep tests were conducted in the temperature range 650-710°C and stress range 49-275MPa. The measured creep exponents and activation energies suggested that grain boundary sliding operates at intermediate stress levels and dislocation climb is active at high stresses. Microstructural effects on the tensile properties and creep behaviour are discussed in comparison to a Ti-12Al-38Nb O+β alloy.

    LanguageEnglish (US)
    Pages99-124
    Number of pages26
    JournalPhilosophical Magazine
    Volume86
    Issue number1
    DOIs
    StatePublished - Jan 1 2006

    Profile

    heat treatment
    microstructure
    Microstructure
    Creep
    tensile creep
    elongation
    temperature
    Heat Treatment
    creep tests
    tensile deformation
    forging
    tensile properties
    schedules
    ductility
    sliding
    electron microscopy
    grain boundaries
    quenching
    exponents
    activation energy

    ASJC Scopus subject areas

    • Philosophy

    Cite this

    Microstructure, creep, and tensile behaviour of a Ti-15Al-33Nb (at.%) beta+orthorhombic alloy. / Cowen, C. J.; Boehlert, C. J.

    In: Philosophical Magazine, Vol. 86, No. 1, 01.01.2006, p. 99-124.

    Research output: Research - peer-reviewArticle

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