Fatique life and twinning in alphazirconium

M.R. Warren, C.J. Beevers

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    Abstract

    Two grades of polycrystalline α-Zr containing ~0.003 and ~0.0775 wt pct O have been fatigued in tension-compression about a zero mean load at a frequency of 100 cps at room-temperature. A combined metallographic and microbeam X-ray pole-loci analysis has revealed the presence of {10•12}, {11−21}, and {11•22} twins and {1O−10} slip. In grains completely enclosed by surrounding material fatigue damage has been found in association with 11•21 twins and very occasionally with {11−22} twins but not with 10•12 twins. A further quantitative interpretation has shown that there is a critical resolved shear stress for {11−21} twinning of ~0.5 kg mm−2 in zirconium containing 0.003 wt pct O. During observations confined to internal grains it was found that increasing grain size and decreasing oxygen content favored the formation of fatigue damage in association with these {11−21} twins. In external grains the fatigue damage was mainly in the form of edge cracks emanating from the specimen surface. The most appropriate criterion for the formation of damage in {11−2l} twin-matrix interfaces appears to be the attainment of a critical resolved shear stress in the {11−21} twinning plane in the (11−26) twinning direction.
    Formerly with the Department of Physical Metallurgy and Science of Materials, The University, Birmingham, England
    Original languageEnglish
    JournalMETALLURGICAL TRANSACTIONS
    Volume1
    Issue number6
    Pages (from-to)1657-1661
    ISSN0026-086X
    DOIs
    Publication statusPublished - 1970

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