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.