Space manufacturing-oriented prediction and control strategy of solidification shrinkage for ultrahigh temperature alloys

Freezing shrinkage is an inherent phenomenon for liquid alloys and becomes particularly critical in a space microgravity environment, where the suppression of natural convection and the absence of container walls fundamentally alter the solidification process. To clarify the governing mechanisms, containerless rapid solidification experiments are conducted aboard the China Space Station under controlled undercooling conditions. By combining measured thermophysical properties with calculated internal flow velocities, both the phase-transition volume contraction and the liquid feeding capability are quantified during solidification. A new dimensionless shrinkage criterion is established by comparing these two competing effects, enabling the evaluation of local shrinkage risk. The criterion successfully predicts shrinkage risk across different undercooling levels and shows strong agreement with experimental observations. This work provides a practical framework for assessing shrinkage behavior in microgravity and supports the development of defect control in future space-manufactured materials.