Nucleation in polycrystalline metallic structures: classical theory and recent extensions
Channel: bhadeshia123
Date: 15/04/2021

Lecture by Professor Ernst Kozeschnik, in a series entitled "Metallic Microstructures", organised by KTH Stockholm, Gent University and Delft University of Technology.


Nucleation is the initiating mechanism by which new phases occur in supersaturated solutions. In poly-crystalline materials, heterogeneous nucleation sites can substantially facilitate the appearance of new phases. This lecture will introduce the main aspects of Classical Nucleation Theory (CNT), first, and discuss, which mechanisms need to be accounted for in the particular situation of metallic microstructures. The impact of nucleus size, chemical composition of the nucleus and diffuse interfaces will be reviewed, as well as some aspects of heterogeneous site energies and how they influence the nucleation barrier. Finally, the model is used to demonstrate that nucleation at grain boundaries can occur with minimum or even without nucleation barrier, as observed experimentally in continuous cooling DSC experiments in Al alloys.