High resolution EBSD analysis of severely deformed submicron grained aluminium alloys

There is currently much interest in the use of severe plastic deformation techniques for the production of submicron grained Al-alloys. Because of their small grain sizes, previous investigations have relied on the TEM to study the grain structures after processing. However, the TEM is not that well suited to obtaining statistically significant data on the misorientations of the boundaries present in the deformed state. Recent improvements in the resolution of SEM-EBSD systems means that this powerful technique can now be used to quantitatively analyse severely deformed structures more reliably than was previously possible. Results using this method have shown that the deformation structure is very sensitive to the strain path, material, and processing conditions. With a constant strain path fibrous grain structures tend to be formed and homogeneous submicron grain structures can only be produced at very high plastic strains, of greater than ten. Materials deformed with cyclic strain paths are more isotropic, but generally have bimodal grain structures and contain a lower density of high angle boundaries and only bands of submicron grains.