A genome dependence of metastable phase selection on atomic structure for undercooled liquid Nb₉₀Si₁₀ hypoeutectic alloy

The phase selection mechanism within undercooled liquid Nb₉₀Si₁₀ hypoeutectic alloy was investigated by electrostatic levitation technique combined with deep neural network molecular dynamics. A stepwise-solidification procedure was conducted, where the primary phase and eutectic microstructure successively solidified from undercooled liquid alloy and undercooled residual liquid, respectively. The intermetallic phase of the eutectic structure transfers from Nb₃Si to βNb₅Si₃ and finally into αNb₅Si₃ compound with the increase in liquid undercooling. The deep neural network molecular dynamic simulations have shown that the phase selection between Nb₃Si and Nb₅Si₃ is mainly controlled by the short-range order of residual liquid, considering that the predominant short-range configuration transforms from Nb₃Si-like to Nb₅Si₃-like structures. The αNb₅Si₃-like medium-range order, which is characterized by vertex-connected ⟨0,2,8,4⟩ clusters, is shown to significantly influence the competitive nucleation of the αNb₅Si₃ and βNb₅Si₃ phases.