1170.    GEBHARD, K., HANEMANN, H., AND SCHRADER, A.  [Martensite System.]  Arch. Eisenhüttenw., vol. 2, 1929, pp. 763-771; Chem. Abs., vol. 23, 1929, p. 3648.

        Thermal and photomicrographic investigation of martensite, using electrolytic Fe and steels with C content ranging 0.06-1.75%.  The heterogeneity of martensite is established, as well as the existence of a 2d metastable system of Fe-C alloys.  Photomicrographs and a phase diagram of the martensite system are included.  In the metastable martensite equilibrium only ε-Fe occurs up to about 0.1% C.  0.1-0.37% C, martensite consists of ε-Fe and heynite (θ-phase), while 0.37-0.9% C, heynite and hardenite (η-phase) are the constituents of martensite.  With more than 0.9% C, a quenched steel contains hardenite and austenite, the austenite increasing as C increases.  If the steel contains more than 1.1% C, the η-phase crystallizes from the γ-Fe immediately. If the equilibrium is not completely established, hardened steel contains austenite even with less than 0.9% C, and heynite even with more than 0.9% C.