Microstructural investigation of a rapidly solidified Fe-Si-C alloy

An Fe-C-Si alloy treated with a nondularizer, Fe-45 at.%Si-3at.%Mg was melt quenched by single roller melt spinning. Two new metastable phases were found in the as-quenched condition. The major metastable phase is a simple cubic structure with a lattice constant of 0.63 nm. By using the convergent beam electron diffraction technique, the detailed structure was analyzed to be point group 432 and space group P4132 or P4332. The second metastable phase is a body centred cubic (b.c.c.) structure with a lattice constant of 0.89 nm. Decomposition of these two metastable phases was studied by in situ heating in a transmission electron microscope. At around 300°C, graphite particles precipitate out in the simple cubic structured metastable phase. However, no phase transition was noted in the b.c.c. structured metastable phase after heating at around 300°C for 2 h.