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E. Kozeschnik, B. Sonderegger:
"TEM characterization and precipitation simulation of secondary phases in Ni-base superalloy Rene 65";
Talk: FIMPART, Bordeaux; 2017-07-09 - 2017-07-12.

In precipitation processes in solid state alloys, nucleation represents the essential step that determines the occurrence or absence of precipitates as well as their distribution and size. Quantification of nucleation can rather successfully be performed within the framework of Classical Nucleation Theory (CNT), which is a continuums-based theory delivering a value for the number of new precipitates that are formed in unit volume and unit time. A main assumption in CNT is that the specific volume and interface energies are independent of size, a simplification that is successfully applied in systems with low supersaturation and relatively large critical nucleus sizes. In most practical situations, these premises are, however, not valid because the critical nuclei contain several tens or less atoms and the size-dependence of volume and interface energy enter significantly into predictions of nucleation rates. In this presentation, two recent approaches addressing this issue are briefly reviewed. A major focus of the talk is then put on the implications of the size dependence of energies on the nucleation rate as a function of nucleation conditions. This is discussed in detail in the form of parameter studies.