The effect of the nucleation ability on solidified microstructures of gas-atomized Fe–6.5 wt.%Si alloy powder

•We report the effect of nucleation ability on solidified structures of atomized powder.•The number of heterogeneous cores clearly affects structure of larger atomized powders.•The effect of nucleation ability weakens as decreasing size of atomized powders.•Single-crystal particles form when particle size less than a certain critical value.

The Fe–6.5 wt.%Si alloy powders were prepared by high-pressure gas atomization in which the nucleation ability of the melt varied with the different purities of the raw materials and experimental conditions. The results indicated that the number of heterogeneous cores has a substantial effect on the grain size of the larger atomized powder particles, i.e. the more heterogeneous cores that are contained in the melt, the smaller the grain size of the atomized powder particles will be. However, the above effect became less significant when the powder particle size decreased. When the particle size was less than a certain critical value, single-crystal particles were formed. In addition to this, it was seen that the effect of the heterogeneous core number on the secondary dendrite arm spacing was fairly insignificant.

Graphical abstractGrain number of the atomized powder from the melt with more heterogeneous cores was greater than those from the melt with less heterogeneous cores. And the difference of grain size was greater for the larger powder particles prepared under two experiments, which gradually became smaller with decreasing particle diameter.Figure optionsDownload full-size imageDownload as PowerPoint slide