Interface reactions between mild steel and liquid Mg–Mn alloys

Chemical interaction was investigated experimentally between solid mild steel and liquid Mg–Mn alloys at 1000 K. In half-saturated Mg–Mn melts (0.6–0.7 at.% Mn), a transition zone with a gradient in Mn concentration consisting of an inner layer of αFe(Mn) and an outer one of γ(Fe, Mn) grows at a slow rate by solid state diffusion. When the Mg–Mn melt is fully saturated in Mn (1.3 at.%), a continuous reaction layer of βMn(Fe) with an Mn content ranging from 65 to 93 at.% is rapidly formed at the steel surface. Growth of this layer proceeds by solid state diffusion of Fe and Mn atoms according to a parabolic law e2=kt, with k=2.4×10−12 m2 s−1. The effects of silicon dissolved as impurity in the melt and of carbon dissolved in Fe base substrate are pointed out.