Refractory metals can be used to design alloys for high-temperature structural applications due to their high melting temperatures. The three-phase V_ss-V₃Si-V₅SiB₂ alloys are a class of vanadium-based alloys. To produce the three-phase V_ss-V₃Si-V₅SiB₂ alloys via a casting process, a precisely determined liquidus projection would be useful for the choice of alloy compositions. Thus, the solidification behavior close to the ternary V_ss-V₃Si-V₅SiB₂ eutectic reaction in the V-Si-B system has been experimentally investigated in this work.
     Alloys near the ternary eutectic reaction were produced via arc-melting. Their microstructures were characterized using scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD) measurements and X-ray diffraction (XRD) analysis. The composition of the ternary eutectic reaction has been determined as V-9Si-6.5B (at%). Different microstructures were observed in two different sample parts in the ternary eutectic alloy V-9Si-6.5B corresponding to different cooling rates indicating a competitive solidification behavior between the two-phase V_ss-V₅SiB₂ and three-phase V_ss-V₃Si-V₅SiB₂ eutectic growth. To investigate this phenomenon, a eutectic growth model based on the Jackson-Hunt theory was developed and applied to both the two-phase V_ss-V₅SiB₂ and the three-phase V_ss-V₃Si-V₅SiB₂ eutectics. The calculated results agree well with the experimental observations.
     As a result, the liquidus projection around the ternary eutectic reaction has been modified and the cross section of the ternary V_ss-V₃Si-V₅SiB₂ eutectic coupled zone along the monovariant V_ss-V₅SiB₂ and V₃Si-V₅SiB₂ reaction lines proposed. The modified liquidus projection can be used to design as-cast V-Si-B alloys with different microstructures close to the ternary eutectic reaction. Some of them having representative microstructures, e.g. two-phase V_ss-V₅SiB₂ and three-phase V_ss-V₃Si-V₅SiB₂ eutectic microstructures, will be mechanically tested in the future.