Investigation of Oxygen-Free Wetting Behavior of Aluminum on Copper via Molecular Dynamics Simulations and Experiments

The wettability of aluminum droplets (Al) on different copper substrates (Cu), where liquid Al spreads on solid Cu surfaces to form a liquid–solid interface, is studied numerically and experimentally. The molecular dynamics (MD) method is employed to investigate the Al/Cu wetting system at the atomistic level. Wetting experiments in an oxygen-free atmosphere, limited to the fast spreading regime, are used for validation in this study and show good agreement. Several key parameters, including the size of the Al droplet, the temperature of the Al/Cu system, and the crystal orientation of the Cu substrate, are analyzed in detail. The contact angle and equilibrium spreading radius of the Al droplet are used to characterize its wettability and spreading kinetics. The results reveal that: (1) the size of the Al droplet has almost no influence on the equilibrium contact angle once it exceeds a critical value; (2) Higher temperatures promote the wettability of the Al/Cu system, leading to a better droplet spreading; (3) The Al droplet exhibits superior wettability on the Cu(111) surface due to its lowest energy barrier, i.e., the minimum energy an atom must overcome to move. The spreading of Al droplets on all Cu substrates primarily follows a two-stage process, with an initial fast regime driven by inertia and a subsequent slow regime governed by surface tension (on Cu(100) and Cu(110)) or diffusion (on Cu(111)).