Atomistic characterization of the dispersed liquid droplet in immiscible Al–Pb alloy

This study develops an atomistic simulation-based methodology for studying the dispersed droplet phase in immiscible alloy. The methodology is applied to the immiscible Al–Pb alloy liquid droplet system to study the temperature and curvature effects on the droplet radial distributions of thermodynamic properties, the mutual miscibilities within the spherical droplets, and the pressure differences across the curved liquid–liquid interfaces. The pressure tensor components profiles along radial direction are computed by the Irving–Kirkwood method coupling the spherical coordination and providing the inner droplet pressure data with sufficient statistical precision to validate the generalized Laplace equation in a liquid immiscible alloy system (both Al-rich convex droplet interface and Pb-rich concave droplet interface). Noticeable changes in mutual miscibilities in the droplet phases are seen, which correspond to the shifts of the solvus lines toward lower solubilities as temperature increases or the droplet size decreases. Compared with spherical droplets under the same temperature, cylindrical droplets with the same radii own the same Laplace pressure dependence of the mutual miscibilities but a weaker capability to tune the nano-alloy droplet phase diagram. Current findings contradict the miscibility changes in the two-complexion equilibria within the monoatomic layer at the Al(111)–Pb(liquid) interface [Acta Mater 2018;143:329]. The combined simulation-characterization methodology proposed in this study applies to broader types of immiscible alloy. The calculated data could provide guides to design well-dispersed droplet phases in the immiscible alloys and their manufacturing processes, facilitate the development of the thermodynamic theory/modeling of the nano-sized alloy phase diagram.