Kinetics of heterogenous nucleation and growth

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Utilizing the stochastic nature of nucleation, nucleation kinetics parameters, specifically the nucleation barrier heights and the nucleation rates are determined experimentally. Thus, measurements are conducted that allow statistically analyzing the experimental data concerning the nucleation rate without applying a specific nucleation model. These data shall be obtained for large undercooling intervals corresponding to several orders of magnitude variations in the nucleation rates. For this reason, conventional and micro-chip calorimetry shall be employed. With a recently established combination of repeated solidification cycling using an interrupted melting procedure, heterogeneous nucleation can be studied for defined and known nucleant phases where the nucleant phase consists of the same elements as the binary alloy. Additionally, this method allows investigating the impact of the shape and the morphology of the nucleant phases or of their abundance on nucleation and growth. Thus, systematic variations of the structure of the intrinsic heterogeneous phase, of its volume fraction and of the morphology of its interface with the melt will be used for comparing the experimentally obtained data with atomistic – and phase field simulations performed in collaborative projects.