Liquid state properties and amorphous solidification kinetics of quinary Zr-Ni-Al-Cu-Nb alloy explored under electrostatic and electromagnetic levitation states

The thermophysical properties and amorphous solidification kinetics of liquid Zr₅₆Ni₂₀Al₁₅Cu₅Nb₄ alloy were investigated through both electrostatic levitation (ESL) and electromagnetic levitation (EML) techniques. The liquid density, surface tension, and viscosity were measured under the ESL state as 6.64 g cm⁻³, 1.46 N m⁻¹, and 106.73 mPa s at liquidus temperature, respectively. The incubation time required for crystallization was found to first decrease and then increase with liquid undercooling. This indicated a shift in the crystallization mechanism from nucleation-controlled at small undercoolings to growth-controlled solidification under large undercoolings. As a result, a mixed solidification microstructure composed of primary Zr₆Al₂Ni compound, pseudobinary (Zr₆Al₂Ni + Zr₅Ni₄Al) eutectic, and amorphous phase was observed at undercoolings beyond 110 K. The volume fraction of amorphous phase gradually increased and approached nearly 100% at 342 K undercooling under the EML state. Isothermal crystallization kinetics analysis further revealed a progressive increase in activation energy from 225 to 397 kJ mol⁻¹ during crystallization. This was directly correlated with the observed suppression of crystalline growth under great undercoolings, which strongly facilitates the formation of amorphous phase.