Microgravity solidification behavior of 52 m long drop tube Ag-Ge alloy

drop tube;  microgravity;  microstructure;  Supercooling

Ag-52%Ge (mass fraction) sub-eutectic and Ag-15%Ge (mass fraction) hyper-eutectic alloy microgravity tests were carried out by 21m long drop tube device, and the microstructure of the solidified alloy spheres was analyzed, and the structure of the same composition alloy under conventional solidification conditions was compared. The results show that the down-tube experiment can make the alloy obtain a large subcooling, so that the Ag-15%Ge (mass fraction) subeutectic alloy Ag primary return solution phase is significantly refined, and the dendrite characteristics disappear and change into fine irregular blocks or approximately spherical shapes. The microstructure and quantity of Ge primary phase in Ag-21%Ge (mass fraction) supereutectic alloy were refined and increased, but the lateral growth mechanism of Ge phase of facet crystal was not changed.