Abstract Scope |
The interconnected ligament network of npg may be seen as put together by torus-like rings. Similar to the reduction of the number of structural elements in other coarsening phenomena, npg reduces its number of rings during coarsening. Two basic mechanisms appear conceivable, ring collapse and ligament pinch-offs, both being fundamentally different topological transitions. To better understand this aspect of npg microstructure evolution, isothermally annealed samples were decomposed into their relevant rings, applying results and algorithms from graph theory to skeletonized 3D reconstructions from focused ion beam tomography. This approach enabled to analyze distributions of topological classes, referring to number of ring edges, and their evolution over isothermal annealing. The results from five samples show a broadening of these distributions, suggesting an increasing relative dominance of pinch-offs over time. One consequence is a slow but steady increase of the average number of ring edges, that speaks against a self-similar evolution. |