2D and 3D orientation mapping in nanostructured metals: A review

Nanostructured metals possess various excellent properties and offer the potential for a wide range of applications.Improvements in the properties and performance of nanostructured metal components motivate a complete characterization of the microstructures and crystallographic orientations of nanostructured metals with nanoscale spatial resolution.Two well developed orientation mapping techniques for such characterization are electron backscatter diffraction(EBSD)in the scanning electron microscope and precession electron diffraction(PED)using diffraction spots in the transmission electron microscope.However,these methods can only characterize the structure in two dimensions.It is still a great challenge to characterize grains in three dimensions,i.e.from the interior of the nanostructured metals.Recently,three-dimensional orientation mapping in the transmission electron microscope(3 D-OMi TEM)was developed and further improvements of this technique are introduced in this paper.Utilization of these orientation mapping techniques for structural and orientational characterizations are demonstrated by examples of surface-deformed metals with gradient nanostructures,and a sputtered gold film of nano-islands containing nanograins.The merits and challenges of each of these techniques are discussed and suggestions for further developments are proposed.

3D characterization of abnormal grain growth in nanocrystalline nickel

Abnormal grain growth,a pervasive phenomenon witnessed during the annealing of nanocrystalline metals,precipitates a swift diminution of the distinctive prop-erties inherent to such materials.Historically,conventional transmission electron microscopy has struggled to efficiently procure comprehensive five-parameter crystallographic information from a substantial number of grain boundaries in nanocrystalline metals,thus inhibiting a deeper understanding of abnormal grain growth behavior within nanocrystalline materials.In this study,we utilize a high-throughput characterization method-three-dimensional orientation mapping in the TEM(3D-OMiTEM)to characterize the crystallographic five-parameter character of grain boundaries with an area of over 3.4×10^(6)nm^(2)in an abnormally grown nanocrystalline nickel sample.When coupled with existing theoretical simulation results,it is discerned that the grain boundary population shows a relatively large scatter when it is correlated to the calculated grain boundary energy;the grain boundaries of abnormally grown grains exhibit lower grain boundary energy compared to those that have not undergone abnormal growth.Merging highthroughput grain boundary information obtained from three-dimensional orientation mapping data with grain boundary properties derived from high-throughput theoretical calculations following the concept of materials genome engineering will undoubtedly facilitate further advancements in comprehending and discerning the interfacial behaviors of crystalline materials.