7xxx series aluminum alloys containing Zr (Al-Zn-Mg-Cu-Zr) are among high strength alloys widely used in the aerospace industry. Zr is added to the alloy to form precipitates, so-called dispersoids, during homogenization treatment to retard/inhibit recrystallization. However, to optimize the production route, we need to know how these dispersoids behave and they can be characterized throughout the production processes. Therefore, the current thesis answered 3 questions:
1.Is it possible to characterize Al3Zr dispersoids with Small angle scattering techniques?
In the first section, we showed that small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) are suitable operative techniques to characterize the dispersoids' size (distribution), and their results correlated well with the ones derived from transmission electron microscopy (TEM). However, scanning electron microscopy (SEM), due to its limitations, is not feasible.
2.How can we use SAXS to examine the effect of homogenization parameters on the dispersoids?
We showed that the evolution of the dispersoids could be tracked by employing in-situ SAXS during the homogenization treatments and investigating the effect of homogenization parameters on the dispersoids’ features. In-situ SAXS results showed that decreasing the heating rate from room temperature to the first step, prolonging the first step period, and increasing the number of steps lead to increasing the number density of the dispersoids.
3.How does hot deformation (hot rolling) affect the dispersoids?
In this section of the thesis, using the in-situ SAXS measurements at a high temperature (375oC), we showed that the hot rolling process did not affect the dispersoids’ size, and they essentially have the same size as they had before the hot rolling process. In this part of the work, we also revealed that choosing the correct approach for data evaluation is vital since it profoundly impacts the final results.