Outer space cultivated regular eutectic cells with anomalous internal microstructures for rapidly solidifying Zr50V50 hypereutectic alloy

Abstract

The special type of regular eutectic cells with anomalous internal microstructures may improve advanced alloy performances but is difficult to cultivate on the ground because of the coupled effect between cell growth dynamics and strong natural convection. Here, outer space experiments aboard the China Space Station were designed to explore and cultivate this kind of special eutectic cells in the Zr50V50 hypereutectic alloy. It was found that the space environment under 10−5 g0 microgravity brought in much more and smaller eutectic cells on the alloy surface, in particular, the alloy droplet solidified at 160 K undercooling displayed priority growth of eutectic cells with anomalous internal microstructures. This was controlled by the more nuclei within the floating droplet resulting from much lower flow velocity, much weaker convection, and less uniform temperature distribution, as revealed by the thermophysical properties measured via space-based electrostatic technique. Furthermore, a critical anomalous eutectic transition undercooling range of 102–110 K was ascertained by the space interface migration dynamics. Our findings contribute to the method and principle of how to apply the outer space environment to cultivate extraordinary microstructures within eutectic alloys.