New Metastable Ternary Fe.sub.7.5MoC.sub.1.5 Phase: Nanosized State and Mn-Like Polymorphism

The Fe-Mo-C spinning ribbons produced by rapid melt cooling at a rate of ~10.sup.6 K/s have been studied by transmission electron microscopy. The metastable ternary phase of stoichiometry close to Fe.sub.7.5MoC.sub.1.5 has been found for the first time. In conditions far from equilibrium, this phase behaves like a metallochemical and structural analogue of elementary Mn in thermodynamic equilibrium conditions, namely: it can appear in crystalline structures that are isostructural to [gamma], [beta], and [alpha] polymorphic modifications of Mn ([gamma], [pi], and [chi] phases, respectively). In addition, the temperature sequence of diffusionless [gamma] [right arrow] [pi] [right arrow] [chi] transformations in the cooling process is similar to the temperature sequence of polymorphic [gamma] [right arrow] [beta] [right arrow] [alpha] transformations of Mn. In this case, the [gamma] [right arrow] [pi] transformation is close to martensitic one, and the temperature of the [pi] [right arrow] [chi] transformation of nanosized metastable phases is close to the temperature of the polymorphic [beta]-Mn â [alpha]-Mn transformation. The crystal lattices of the [pi] and [gamma] phases obey orientation relationships, for example: [Formula omitted]