Effect of homogenization and alloying elements on recrystallization resistance of Al-Zr-Mn alloys

One of the main problems of using Al3Zr in order to stabilize the microstructure in aluminium alloys, i.e. to inhibit recrystallization, is that these dispersoids usually are heterogeneously distributed. The areas of low dispersoid number density makes such alloys prone to recrystallization, and in this work it was therefore attempted to generate a homogeneous distribution of Al3Zr by subjecting two Al-Zr-Mn alloys to a homogenization treatment at 630°C in order to remove the microsegregation of Zr, i.e. to ensure that the driving force for dispersoid formation was equal throughout the microstructure prior to precipitation annealing. Homogenized variants were then compared with unhomogenized variants with respect to recrystallization resistance after cold rolling. The results showed, however, that the homogenization treatment led to a reduced structural stability. This was mainly caused by particle stimulated nucleation (PSN) of recrystallized grains in the deformation zones around coarse Mn-bearing phases that developed during the homogenization, and also by a reduced number density of Al3Zr dispersoids.