Scale-bridging phase-field simulations of microstructure responses on nucleation in metals and colloids

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Phase-field simulations from atomic to mesoscopic length scales are used to analyse the microstructure responses on heterogeneous nucleation, both in metallic as well as in colloidal systems. The scale-bridging from 1 nm to 10 μm in metals is achieved either by combining Molecular Dynamics (MD) and Phase-field (PF) simulations or by hybrid PF modelling. Essential for three dimensional numerical computations is the employment of performance optimized simulation techniques and adaptive grids. Thermodynamic parameters for Ni, Ni-Cu, Ti, Al-Cu, Al-Ni and Al-Ti are provided from experimental measurements as well as from MD simulations of cooperating groups. The microstructure responses on the parameter sets, on the shape of the nuclei and on the characteristic properties of the substrate are systematically investigated in PF simulations. Large-scale simulations of microstructure formations are compared with experimental observations. Extensions of the PF model cover a method to incorporate volume constraints, a line tension energy formulation and specific boundary conditions at the surface of the substrate. The new model is applied to sessile drop simulations to precisely analyse equilibrium shapes and diffusion processes. In particular, the formalism with higher order potentials is used to investigate the length-scale dependent effect of the line tension on the Young’s force balance at triple lines in 3D. A new PF model for colloidal systems of hard spheres will be formulated on the basis of the recently designed PF crystal model. The Ginzburg-Landau functional will be derived from Dynamical Density Functional Theory (DDFT) taking the results from identification of the order parameter of relevance from Forware Flux Sampling (FFS) into account.