STP110: The Tetragonality of the Sigma Phase in the Iron-Chromium System

    Menezes, L.
    Graduate Student, Instructor in Metallurgy, and Associate Professor of Metallurgy, Columbia University, New York, N. Y.

    Roros, J. K.
    Graduate Student, Instructor in Metallurgy, and Associate Professor of Metallurgy, Columbia University, New York, N. Y.

    Read, T. A.
    Graduate Student, Instructor in Metallurgy, and Associate Professor of Metallurgy, Columbia University, New York, N. Y.

    Pages: 4    Published: Jan 1950


    Abstract

    Single crystal specimens of the 50 per cent iron-50 per cent chromium sigma phase were prepared by isothermal transformation of coarse-grained ferrite of this composition at 775 C. In some cases, single grains of ferrite transformed to single crystals of sigma phase, which could then be isolated by careful fragmentation of the brittle sample. Back-reflection Laue diffraction patterns were prepared, and the specimen fragments selected which yielded the best patterns. These patterns revealed a four-fold symmetry axis and two two-fold axes orthogonal to it and to each other, characteristic of tetragonal crystals with the Laue symmetry 4/mmm. Even in the best samples, crystal imperfections existed which led to diffuseness and multiplicity of the Laue pattern spots.


    Paper ID: STP46105S

    Committee/Subcommittee: E04.11

    DOI: 10.1520/STP46105S


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