Microstructural evolution during solidification is an important phenomenon that determines several properties of materials and hence their performance. Solidification microstructures, in general, consist of features spanning multiple length scales and understanding the microstructural evolution at each every length scale is important. In this thesis, primarily, molecular dynamics (MD) simulations have been employed to study solidification at the atomistic scale. MD simulations have been performed using an open source software LAMMPS, to obtain various thermophysical and kinetic properties. The calculated parameters include melting/liquidus temperature, molar volume, latent heat of fusion, specific heat,crystal-melt interface energy, kinetic coefficient and its anisotropy, Gibbs energy of phases and diffusion coefficient.
Ni-Al and Ni-Zr systems have been considered for the study. A systematic study of Ni-Al at the atomistic scale, could explain different growth mechanisms in metals, ordered and disordered intermetallic alloys. In Ni-Zr system, effect of solute atoms on the growth kinetics has been studied. It has been demonstrated that the calculated material parameters can be used in Phase Field simulations, to study morphological evolution of microstructures during solidification in the mesoscopic length-scale.
Interatomic potential is a major input to MD simulations. In this work, a sensitivity analysis has been performed on the Modified Embedded Atom Method (MEAM) potentials of Ni and Al, to understand the effect of potential parameters on the ground state and thermal properties. The investigated properties include lattice parameter, cohesive energy, elastic constants, vacancy formation energy, structural energy differences, melting temperature and latent heat. Among the parameters, Cmin, Cmax (screening parameters) and t(3) (weighing factor for the angular contribution for electron density) are identified to have profound impact on melting temperature and latent heat. Among these parameters, tuning t(3) has been found to affect only the melting temperature and latent heat without disturbing other fit properties such as lattice parameter, elastic constants and cohesive energy. Based on the results, a methodology to refine MEAM potential for tuning properties related to solidification/melting has been arrived at. In summary, this thesis (a) provides recipes for tuning interatomic potentials, and calculation of material properties using MD, and (b) addresses an important aspect of linking across length-scales through a demonstration of interfacing between MD and phase field simulations.