17: Critical review of constitution of carbon-iron-molybdenum system

Abstract

The constitution of the C-Fe-Mo system is reviewed. A liquidus projection with isothermal contours and ten ternary invariant points is proposed. It gives a complete and self-consistent, but speculative rationalization of the liquid-solid equilibria of the ternary γ-phase (τ₁ in this assessment) and of the solid phases derived from the three binary systems. These equilibria are, in part, metastable and alternative interpretations are also discussed. A second ternary phase, Fe₂MoC (τ2) appears to form from a solid-state peritectoid reaction. Solid-state equilibria are reviewed on the basis of three experimental isothermal sections at 1000, 900, and 700°C. A reaction sequence, partly hypothetical, is given which connects known equilibria between the liquid phase and low temperatures. It is emphasized that some of the experimental data refer to metastable conditions and that true equilibria must remain conjectural for the present.