SYMPOSIA PAPER Published: 01 January 1950

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


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.

Author Information

Menezes, L.
Columbia University, New York, N. Y.
Roros, J., K.
Columbia University, New York, N. Y.
Read, T., A.
Columbia University, New York, N. Y.
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Developed by Committee: E04
Pages: 71–74
DOI: 10.1520/STP46105S
ISBN-EB: 978-0-8031-6741-4
ISBN-13: 978-0-8031-6506-9