Eutectic growth kinetics and microscopic mechanical property of refractory Zr57V43 alloy under space and ground conditions

Abstract

The eutectic growth kinetics and solidified microstructures of liquid Zr₅₇V₄₃ refractory alloy were explored aboard the China Space Station (CSS), where long-term microgravity state and confined fluid flow were ensured synchronously. The thermophysical properties were determined at both metastable undercooled liquid and high temperature solid states, which were hard to measure accurately on the ground. The solidified microstructures exhibited eutectic cells with a novel ripple-like characteristic under the effects of 10^–5 g₀ microgravity and 73 K undercooling. The eutectic growth velocity attained 4.59 mm·s^–1 in this case. The ripple-like pattern was formed by the (Zr) and V₂Zr phases developing alternatively from the surface towards the droplet center, resulting from suppressed convection around the nucleation sites. Anomalous eutectic was distributed inside the eutectic cells and the lamellar eutectic outside due to the eutectic growth kinetics change. The anomalous eutectic and finer lamellar eutectic respectively lead to an 11.7 % and 13.2 % increase in micro-indentation hardness of the Zr₅₇V₄₃ alloy compared with the levitationally solidified alloy at a similar undercooling on the ground. The research findings contribute to further understanding of novel microstructure formation and the performance change of eutectic alloys solidified in outer space.