Directional Solidification of FeSiMg Alloys

Five FeSiMg alloys were re-melted and directionally solidified. Typical composition of the alloys were around 45 wt.% Fe, around 45 wt.% Si, 5 wt.% Mg with minor additions of rare earth elements as well as calcium and aluminum. It was found that the cooling rate decreases with increasing distance from the cooled end of the cast bars. Chemical analyses performed at different distances from the cooled end of the bars showed segregations in the longitudinal direction of bars. The magnesium concentration goes through a minimum, the iron concentration has a maximum, while the silicon concentration does not change significantly with increasing distance from the cooled end. Image analyses showed that FeSi2 is the dominant phase in the examined alloys (around 60 area. pct.). The amount of this phase decreases with increasing distance from the cooled end. The same tendency is also found for the FeSi phase (around 20 area. pct.). The area fractions of Mg2Si and Si phases increase with increasing distance from the cooled end.