Space station based experimental research on thermophysical properties and solidification mechanisms of Fe-19%Si alloy

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The thermophysical properties and rapid solidification mechanism of Fe-19 ​wt%Si alloy were investigated by electrostatic levitation aboard China Space Station and terrestrial drop tube techniques. All the solidification events neither favour the retention of the metastable Fe 2 Si phase nor induce the decomposition of the Fe 5 Si 3 phase. The density was determined to be a linear decreasing relationship with temperature, in which the liquid density at eutectic temperature was determined to be 6.19 ​g ​cm −3 . The surface tension and viscosity were measured to be 1.44 ​N ​m −1 and 29.8 ​mPa ​s at liquid state. Because space environment suppresses the gravity-driven liquid flow required for solidification feeding, the space shrinkage was significantly higher than the ground condition. The Fe 3 Si and Fe 2 Si phases only displayed a divorced eutectic growth mode in the ground-based experiments, while the coupled growth appears under the space condition due to the suppression of long-range solute transport. The crystal grain size of Fe 3 Si phase in space condition was larger than that on the ground.