Metastable dodecagonal-atomic-column state related to the formation of the σ structure in the Cr-Co alloy system

Toshihiro Doi, Makoto Tanimura, Yasumasa Koyama

    Research output: Contribution to journalArticle

    5 Citations (Scopus)

    Abstract

    The σ phase in transition-metal alloy systems such as the Fe-Cr and Cr-Co systems has a very complicated crystal structure consisting of complex coordination polyhedra including polyhedra with coordination number 14. To understand the structural unit of the σ structure, we have examined the crystallographic features of the (bcc→bcc+σ) reaction in the Cr-Co alloy system by transmission electron microscopy. It was, as a result, found that there existed a metastable state consisting of dodecagonal atomic columns, which are entirely different from atomic columns produced by a one-dimensional connection of polyhedra with coordination number 14. The (bcc→σ) structural change, in fact, occurred via the metastable dodecagonal-atomic- column lattice (DACL) state. In an ideal case, the DACL state is characterized by a periodic array of dodecagonal atomic columns. The interesting features of the structural change are that dodecagonal atomic columns are already present in the bcc matrix, and that the change from the DACL state to the σ structure is associated with the formation of polyhedra with coordination number 12 in a metastable precipitate, which are also involved in the σ structure. A polyhedron with coordination number 12 is obviously an icosahedral atomic cluster. It is thus understood that an icosahedral atomic cluster is identified as a structural unit of the σ structure.

    Original languageEnglish
    Article number134204
    JournalPhysical Review B - Condensed Matter and Materials Physics
    Volume79
    Issue number13
    DOIs
    Publication statusPublished - 2009 Apr 1

    Fingerprint

    Transition metal alloys
    Coordination Complexes
    Precipitates
    Crystal structure
    polyhedrons
    Transmission electron microscopy
    coordination number
    atomic clusters
    metastable state
    precipitates
    transition metals
    transmission electron microscopy
    crystal structure
    matrices

    ASJC Scopus subject areas

    • Condensed Matter Physics
    • Electronic, Optical and Magnetic Materials

    Cite this

    Metastable dodecagonal-atomic-column state related to the formation of the σ structure in the Cr-Co alloy system. / Doi, Toshihiro; Tanimura, Makoto; Koyama, Yasumasa.

    In: Physical Review B - Condensed Matter and Materials Physics, Vol. 79, No. 13, 134204, 01.04.2009.

    Research output: Contribution to journalArticle

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