Microstructural evolution of aluminium-magnesium alloys during thermomechanical processing

During thermomechanical processing, local region within the stock undergo changes in strain path, which have systematic effects on deformed microstructure and subsequent recrystallisation behaviour. Only limited quantitative data are presently available. This paper presents results for the cumulative effects of repeated strain reversals on the dislocation structures, static recrystallisation kinetics and grain size of a series of high purity aluminium-magnesium alloys. The results show that dislocation density and local lattice curvature develop more slowly with strain reversals than with monotonic deformation, but essentially the same characteristics are observed. The slower development of the deformed structure is reflected by slower static recrystallisation kinetics and coarser recrystallised grain size. All the alloys show similar trends, which are discussed in terms of the role of geometrically necessary dislocations.