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1600. ---------------. [JACK, K. H.] [X-Ray Structural Investigations of the Iron-Carbon and Iron-Nitrogen Systems and of Related Interstitial Alloys.] Acta Cryst., vol. 3, 1950, pp. 392-393; British Abs., 1951, I, A, p. 41.
Three tempering stages of C martensite are discussed. The loss of tetragonality of martensite during the 1st tempering stage is due to the precipitation of a close-packed hexagonal Fe carbide, structurally similar to ε-Fe3N. The unit-cell dimensions are a 2.73 Å, c 4.33 Å. The behavior of N martensite on tempering is quite different from that of the corresponding C alloys. At temperature <250° a new phase, a”, is formed as an intermediate in the decomposition a’-γ’. This a” phase is relatively stable, with a 5.72Å, c 6.29 Å. The structures of ε-Fe nitrides and the ε-ζ transitions are discussed. The hexagonal structure of Ni3N is confirmed, the unit-cell dimensions being a 2.6677 Å±0.0005 Å, c 4.3122 Å±0.0005 Å. There appears to be no evidence as yet for the existence of a hexagonal allotrope of Ni.
See abs. 578a, 1218.
JACOB, K. See abs. 2434.
JACOBS, J. See abs. 1255.