The spreading kinetics and precursor film characteristics of Zr-based alloy melt on W substrate

The wettability and spreading kinetics of Zr-based alloy melt on W substrate were evaluated using the modified sessile drop method under ultrahigh vacuum. The alloy melt wets the substrate well and the spreading kinetics indicates that drop spreading is mainly controlled by the viscous friction. The drop spreads rapidly and the spreading follows the hydrodynamic model and Jiang's empirical formula. The spreading of the drop shows little interaction with the precursor film, which is generated by diffusion. After the initial incubation period, the equilibrium contact angle stabilizes at about 29°, and the precursor film spreads linearly with the square root of time.

► Drop spreading is mainly controlled by the viscous friction.
► The precursor film has little influence on the drop spreading.
► After the incubation period, the precursor film spreading is determined by diffusion.