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| EBSD map of a fully impinged AGG Ni sample |
This electron backscatter diffraction (EBSD) map came from an annealed nanocrystalline nickel (Ni) sample that featured abnormal grain growth (AGG). I have shown some pictures in the past where the AGG remained as individual islands from one another. This sample was annealed further such that all the abnormal grains are impinging upon one another and completely fill up the space of whatever remaining matrix grains were there. As a result, there are some extremely planar facets on certain grains, but also some interesting grain morphology not seen in your typical sample, especially the twin related grains that exist within the their parent grain.
Of major point of curiosity was how the how the twin content of this material compared to traditional FCC Ni. What we knew before from some previous scans is that some of these AGG featured bi-grain clusters, which were very often twin related. However, these twins were very often just single boundaries which could be continuous, but also sometimes jagged. We suspected that if we allowed this microstructure to grow out completely, the twin statistics should be very different because this wasn't the traditional twinning mechanism.
The interesting point was when the fraction of twin boundaries in both type of observed materials were approximately the same. That being said, one of my advisers had predicted this even though I adamantly thought it would be otherwise.
In my head I lost this little science bet, but nonetheless excited for some of the upcoming future work.
