STP110: Sigma Phase in Chromium-Molybdenum Alloys with Iron or Nickel

    Putman, John W.
    Research Assistant, Massachusetts Institute of Technology, Cambridge, Mass.

    Grant, N. J.
    Associate Professor, Massachusetts Institute of Technology, Cambridge, Mass.

    Bloom, D. S.
    Research Assistant, Massachusetts Institute of Technology, Cambridge, Mass.

    Pages: 10    Published: Jan 1950


    Abstract

    Because the brittleness of chromium-base alloys for high-temperature duty was believed to be due in part to sigma formation, research was undertaken to study the formation of sigma in simple alloys of chromium, molybdenum, and iron. The extent of the sigma phase in the chromium-molybdenum-iron ternary diagram has been determined, and some of the properties of the sigma occurring in this system have been described. The experiments indicate that molybdenum increases the high-temperature stability of sigma in iron-chromium alloys, and that the sigma phase in the 60Cr-25Mo-15Fe alloy is stable at 1100 C. With regard to this alloy, the temperature effect is such that at lower temperatures the tendency for the formation of sigma is increased provided that sufficient time be allowed for the transformation. The sigma phase has been found to occur in the chromium-molybdenum-nickel ternary alloys, although its occurrence has not been reported in any of the three constituent binaries. X-ray diffraction data on chromium-molybdenum-nickel sigma are included.


    Paper ID: STP46104S

    Committee/Subcommittee: E04.11

    DOI: 10.1520/STP46104S


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