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 1650.    HAHN, H., AND MÜHLBERG, H.  [Metal Amides and Metal Nitrides.  XX.  The System Iron-Nickel-Nitrogen.]  Ztschr. Anorg. Chem., vol. 259, 1949, pp. 121-134; Chem. Abs., vol. 44, 1950, p. 992.

       Alloys of Fe and Ni containing 10, 20, 30, 40, 50, 60, 70, 80, 90, and 95 at.  % Fe were nitrided at 300°-1,000° in a stream of NH3.  The optimum temperature range for uptake of N was 350°-600°.  The weight % N in the nitrided alloys varies linearly with the atomic % Fe.  The uptake of N can be increased further by pretreatment of the alloy with NH3 at 600°-800°, quenching to room temperature, and finally prolonged nitriding at 400°-500°. For alloys treated this way which contain 50% Fe or more, the % N again varies linearly with the % Fe; with alloys containing less Fe, the % N approximates that for Fe4N.  Debye-Scherrer diagrams were made of the pure and nitrided alloys.  There were 2 alloy and 2 nitride phases found.  A cubic face-centered alloy (I) occurs in alloys containing 10-70% Fe and is the only phase if the % N is below 5.  This phase resembles γ-Fe in dissolving N with an increase in the lattice constant a.  A cubic body-centered alloy phase (II) is stable for Fe above 70%, N up to 3%, and at nitriding temperatures up to 450°; above 450° it changes to (I) with a greatly enlarged lattice.  Like a-Fe, (II) takes up only very little N in solid solution.  A cubic face-centered nitride phase (III) is stable up to 70% Fe, while above this a hexagonal nitride phase (IV) also occurs.  (III) corresponds to Fe4N with some of the Fe replaced by Ni.  The constant a increases with % N and its increase with the % Fe parallels that for the pure alloys.  (IV) resembles Fe2N except that a little of the Fe is replaced by Ni.  The decomposition temperatures of the nitrided alloys are low, ranging 360°-500° with increase in the % Fe.

                   KADOTA, N.  See abs. 2205.