Application of orientation mapping in TEM and SEM for the study of inhomogeneous microstructural evolution during annealing of aluminum alloy with bimodal particle distribution
|Krzysztof Sztwiertnia , Magdalena M. Bieda , Anna Korneva , Grzegorz Sawina|
Polish Academy of Sciences, Institute of Metallurgy and Materials Sciences (IMIM PAN), Reymonta 25, Kraków 30-059, Poland
In recent years, orientation mapping (OM), i.e. determination of topography of crystallite orientations, has become a well established technique of examining and quantifying microstructures of any mono- and polycrystalline material. The OM technique, performed in the TEM and SEM, covers a spatial resolution range from several to hundreds of nanometers, respectively.
Examination of recrystallization process in aluminum alloy 6013 have been selected to show the application of the OM in microstructure analysis. The alloy contains both large (>1 μm) and small (<<1 μm) second-phase particles. During deformation, the laminar structure and zones of localized strain around large particles (both with characteristic local textures) are formed. In situ investigations in TEM as well as calorimetric measurements, combined with OM in TEM and SEM, demonstrate, that recrystallization can be considered as a number of partly overlapping processes, proceeding in two stages. In the initial stage, there occurs particle stimulated nucleation and migration of high angle grain boundaries (HAGB) limited to the areas of deformation zones (DZ) around particles. A certain enlargement of newly-created grains was also observed outside the DZs. Here, however, it appears due to the annihilation of low-angle grain boundaries (LAGB) between the chains of subgrains lying in layers parallel to the sheet plane. As a consequence, new grains often have a plate-like habit, with the shorter axis parallel to the sheet plane normal direction (ND). In the second stage, HAGBs were observed to migrate in the direction of high orientation gradient. This migration, mostly in the ND, was limited to "free areas" of the deformed matrix between bands of the new grains formed in the zones of localized strain in the initial stage of recrystallization.
Presentation: Invited at E-MRS Fall Meeting 2007, Symposium J, by Krzysztof Sztwiertnia
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-08 11:23 Revised: 2009-06-07 00:44