Liquid Structure and Thermophysical Properties of Ternary Ni-Fe-Co Alloys Explored by Molecular Dynamics Simulations and Electrostatic Levitation Experiments

The structure, thermodynamic and dynamic properties of normal and metastable liquid Ni_2xFe_50−xCo_50−x alloys were systematically investigated by combining electrostatic levitation (ESL) experiments and molecular dynamics (MD) simulations. Their composition dependence and mutual interaction were explored in detail. The actual densities of liquid Ni₉₀Fe₅Co₅, Ni₈₀Fe₁₀Co₁₀, Ni₇₀Fe₁₅Co₁₅ and Ni₆₀Fe₂₀Co₂₀ alloys were measured by ESL experiments in a wide temperature range. The simulated densities of these liquid alloys are in good agreement with the corresponding experimental data. The thermodynamic properties show that all these alloys exhibit a negative excess volume and mixing enthalpy. Meanwhile, their pair distribution functions indicate that Fe and Co atoms easily bond with Ni atoms and have a similar characteristic to each other if compared with Ni atoms. Furthermore, the structure factors validate that there exist icosahedral short-range and medium-range orders of Ni-Ni, Fe-Fe, Fe-Co and Co-Co bonds in these liquid alloys. Additionally, the solute diffusion properties reveal that the correlation between dynamic behavior and alloy composition is determined by the diffusion of Fe and Ni atoms.