Austenite Grain Refinement of Ductile Iron Castings (Published)
Austenite is the strong phase that contributes most to the strength of an iron alloy. Therefore, for a ductile iron to be strengthened the austenite phase must be strengthened, and one main approach is by controlling its nucleation and growth during solidification. The effect of a selected amounts of titanium addition on austenite grain refinement in ductile iron will be determined in this study using three methods: secondary dendrite arm spacing measurement, measurement of the nodule count of graphite particles and liquidus undercooling and recalescence measurement. Titanium addition in the amount of 0.02wt.% was tested. The results showed that addition of titanium did have an impact on the fineness of the dendrite arms closer to the casting wall but the result was quite similar to the addition without titanium at the thin section of the casting. Farther away from the casting wall, the titanium modified heat grew coarser and sparse. The nodule count result showed that generally, the nodule count dropped due to the addition of titanium and this can reduce the material’s ductility. The results from the liquidus recalescence measurement needs to be reviewed with a higher sample rate to obtain a better understanding of the recalescence at the liquidus temperature at the thin section of the casting.
Keywords: austenite nucleation, ductile iron, grain refinement, titanium