2510.     ---------------.  [ÖHMAN, E.]  X-Ray Investigation on the Crystal Structure of Hardened Steel.  Jour. Iron Steel Inst. (London), vol. 123, 1931, p. 445; Chem. Abs., vol. 25, 1931, p. 4502.

        X-ray study of quenched steels confirmed the existence of the tetragonal phase, the axial ratio of which increased with increasing C content.  From a consideration of these data it is concluded that martensite consists of a solid solution of C in body-centered Fe.  On effective quenching, the tetragonal phase has the same composition as the parent austenite, as proved by the direct relationship between C content and space-lattice dimensions.  It appears probable that the C atoms disolved in a-Fe form a complex substitutional group in which 2 C atoms replace 1 Fe atom.  On tempering, the tetragonal phase decomposes continuously with a progressive decrease in axial ratio.  The causes of the hardness of martensite are discussed.  47 refs.