Transverse deformation of a lamellar TiAl alloy at high temperature by in situ microcompression

Thomas Edward James Edwards, Fabio Di Gioacchino, Amy Jane Goodfellow, Gaurav Mohanty, Juri Wehrs, Johann Michler, William John Clegg

    Research output: Contribution to journalArticleScientificpeer-review

    13 Citations (Scopus)


    The distribution of strain in hard mode oriented lamellar stacks of the two-phase γ-TiAl/α2-Ti3Al alloy Ti-45Al-2Nb-2Mn (at.%)-0.8 vol% TiB2 was measured at several temperatures up to 633 °C by in situ micropillar compression, complemented by electron backscatter diffraction orientation mapping and digital image correlation strain mapping of a thermally stable surface Pt speckle pattern. Post-mortem transmission electron microscopy further identified the finest scale deformation structures. It was found that slip and twinning transverse to the lamellae operates within discreet bands that zigzag across the lamellar structure. The shear strain within each band is approximately constant across the pillar width. This is inconsistent with current energetic models for transverse twin formation in γ-TiAl, which assume independent, non-interacting twins. This is explained using a mathematical formulation for the stress required to operate this transverse mechanical twinning as a function of strain. This study has elucidated how the multi-scale combination of several transverse twinning systems on different {111} planes in γ-TiAl lamellae can relieve the elastic stresses generated at a lamellar interface by the primary (highest Schmid factor) twinning system. It is thought that the facilitation of this mechanism will promote the ductilisation of lamellar γ-TiAl alloys. This is crucial for an increased damage tolerance and ease of component manufacture, leading to a more widespread use of γ-TiAl alloys.

    Original languageEnglish
    Pages (from-to)85-99
    Number of pages15
    JournalActa Materialia
    Early online date27 Nov 2018
    Publication statusPublished - 1 Mar 2019
    Publication typeA1 Journal article-refereed


    • Deformation twinning
    • Digital image correlation
    • Electron backscattering diffraction (EBSD)
    • Scanning transmission electron microscopy
    • Titanium aluminide polysynthetically twinned crystal (PST)

    Publication forum classification

    • Publication forum level 3

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Ceramics and Composites
    • Polymers and Plastics
    • Metals and Alloys


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