Characterization of Zr-Containing Dispersoids in Al-Zn-Mg-Cu Alloys by Small-Angle Scattering

The characterization of Zr-containing dispersoids in aluminum alloys is challenging due to their broad size distribution, low volume fraction, and heterogeneous distribution within the grains. In this work, small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) were compared to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) regarding their capability to characterize Zr-containing dispersoids in aluminum alloys. It was demonstrated that both scattering techniques are suitable tools to characterize dispersoids in a multi-phase industrial 7xxx series aluminum alloy. While SAXS is more sensitive than SANS due to the high electron density of Zr-containing dispersoids, SANS has the advantage of being able to probe a much larger sample volume. The combination of both scattering techniques allows for the verification that the contribution from dispersoids can be separated from that of other precipitate phases such as the S-phase or GP-zones. The size distributions obtained from SAXS, SANS and TEM showed good agreement. The SEM-derived size distributions were, however, found to significantly deviate from those of the other techniques, which can be explained by considering the resolution-limited restrictions of the different techniques.

Automated summary

Characterizing Zr-containing dispersoids in aluminum alloys is challenging due to their diverse size distribution, low volume fraction, and uneven distribution within the grains. This study compared small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) in characterizing Zr-containing dispersoids. Both scattering techniques were found suitable for characterizing dispersoids in a multi-phase industrial 7xxx series aluminum alloy. SAXS was more sensitive than SANS due to the high electron density of Zr-containing dispersoids, while SANS had the advantage of probing a larger sample volume. The combination of both techniques allowed for distinguishing the contribution of dispersoids from other precipitate phases.