Aluminium deformation. High-resolution orientation map, created using transmission Kikuchi diffraction (TKD) in a scanning electron microscope (SEM), showing a severely deformed aluminium alloy with nanocrystalline shear bands (diagonal) cutting across large, deformed original grains. The colours indicate the orientation of the crystal lattice at each point in the map. Black lines show high-angle grain boundaries, where adjacent grains have a very different orientation from each other; grey lines show low-angle sub-grain boundaries, across which there are only small lattice orientation changes. The development of nanocrystalline microstructures in such alloys produces desirable physical properties such as enhanced strength and hardness, and as such, is an area of significant materials research.