Microstructures: The Hidden World of Watercolour

While metals generally possess a monochromatic silver or grey colour palette to the naked eye, a quick trip under the microscope can reveal a world of colour one would not expect. These two images are not simply colourful, but present a narrative, without using words. Each colour tells the story of each grain within the metal's microstructure. Electron Backscatter Diffraction (EBSD) imaging is used to determine the grain orientation within a microstructure when compared along a specified axis. In image (a), you can see areas in which the grain sizes seem to converge into nothingness, while in image (b), the grains present a more randomized appearance. Both samples shown here were subjected to compressive deformation at elevated temperatures. The major microstructural phenomena which take place in image (a) and (b) are disintegration and dynamic recrystallization respectively. The first occurs when the stress concentration is increased significantly within the grains, and the latter occurs when the metal is deformed at a high temperature, which releases the stress within the existing grains, forming new grains.