Solidification regularity of highly undercooled Fe-Co alloy

Fe-Co melts with different Co contents were highly undercooled using fluxing purification method. With increasing the initial melt undercooling (AT), grain refinement occurred twice in Fe_100-x-Co_x(x=10-40) alloy, except Fe₉₀Co₁₀. When undercooling of the melt exceeds the critical undercooling, the microstructure is no longer single phase and metastable phase appears. Except transition at low undercooling, both of the exact undercooling for microstructure transition and the critical undercooling for formation of metastable phase increase with the content of Co. Furthermore, B-C-T model and transient nucleation theory were applied to analyze the microstructure evolutions of Fe-Co alloy.