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Metallographic, X ray diffraction, and microhardness studies on an alloy of 2.35 wt pct nitrogen, balance iron are reported. This alloy is analogous to the eutectoid iron-carbon alloy with respect to transformation to “pearlitic” and “martensitic” structures. Isothermal transformation at all temperatures is slower in the nitrogen alloy, and the nitrogen austenite is far more stable with respect to transformation to martensite.

Changes in hardness, tensile properties, microstructure, electrical resistance, and X-ray diffraction effects indicate that lattice strains are necessary for the embrittlement of ferritic stainless steels when heated for relatively short times at 475°C (885°F). It is suggested that 475°C (885°F) embrittlement is due to the accelerated formation of an intermediate stage in the formation of σ under the influence of these strains.