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1517. HUME-ROTHERY, W., RAYNOR, G. V., AND LITTLE, A. T. Lattice Spacings and Crystal Structure of Cementite. Jour. Iron Steel Inst. (London), vol. 145, 1942, pp. 143P-152P; Iron and Steel (London), vol. 15, 1942, pp. 318-320; Chem. Abs., vol. 36, 1942, p. 3465.
Cementite examined by Lipson and Petch (abs. 2120) was prepared by passing CO over Fe2O3 at 550°. It evidently had been partly decomposed during annealing and had lattice spacings different from the cementite used in the present study, which was extracted from steel by electrolytic attack in HCl. The values obtained by Debye-Scherrer photographs in a 19-cm. camera are: a=4.5155 Å., b=5.0773 Å., c=6.7265 Å. at 25°. Samples from 3 steels of commercial purity gave the same results. Analysis confirmed the composition Fe3C. The structure of cementite can be derived from that of martensite by a simple shearing process. The ready formation of cementite from martensite (compared to formation from austenite) suggests that the relative positions of Fe and C atoms in martensite enable this transformation to take place with small atomic movements at a low temperature. 2 refs.
HUNSMANN, W. See abs. 853.
HUNTER, W. See abs. 409.
HUNTOON, R. T. See abs. 3262.