Atomistic characterization of the chemically heterogeneous Al-Pb solid-liquid interface

The chemically heterogeneous interface between solid Al and liquid Pb at 625 K is examined by using molecular-dynamics simulation. For the interfacial orientations (1 0 0), (1 1 0) and (1 1 1), we characterize the interface by calculating the density, potential energy, stress and diffusion constant profiles as well as a two-dimensional Fourier analysis of the interfacial layers. Our results are consistent with experimental observations [Acta Mater 2001;49:4259], based on the equilibrium shape of liquid Pb inclusions in solid Al just above the melting temperature of Pb, that the (1 1 1) interface is faceted, while the (1 0 0) and (1 1 0) interfaces are rough. We found that Al and Pb form immiscible two-dimensional domains within the interfacial layers, rather than an intermixed interfacial alloy, as was observed in recent simulations of the Cu-Pb interface [Acta Mater 2011;59:3137]. In addition, in contrast to earlier observations on the (1 1 1) Cu-Pb interface at this temperature, no prefreezing layers are found in Al-Pb interfaces for any of the orientations studied.