Modeling dissolution and spreading of Bi–Sn alloy drops on a Bi substrate

A dissolutive wetting model is employed to study the dynamics of axisymmetric Bi–Sn alloy drops spreading on Bi. The liquid drop surface is assumed to be a spherical cap, while the isothermal model for solute transport with simplified hydrodynamics computes the evolution of the solid–liquid interface. Simulations are performed on a millimeter scale to model experiments. The evolution of the drop radius, the flow and solute concentration profiles near the triple junction, the contact line mobility relationship, the apparent contact angles and the shape of the dissolution boundary during spreading are investigated as functions of initial Sn concentration, model parameters and initial conditions. Good agreement is obtained when compared with the experiments for the cases where diffusion is the dominant transport mode. The shape of the solid–liquid interface is predicted better when the initial experimentally determined dissolution boundary is implemented as the starting point of the subsequent simulation.