Microstructural Evolution and Age Hardening in Aluminium Alloys: Atom Probe Field-Ion Microscopy and Transmission Electron Microscopy Studies

This paper examines the microstructural evolution in selected aluminium alloys based on commercial age hardenable 2000, 6000, and 7000 series alloys. Atom probe field-ion microscopy and transmission electron microscopy have been used to examine the effects of microalloying and the origins of hardening. The combined application of these techniques is particularly important in the study of nanoscale precipitation processes. It is shown that the nature and kinetics of the precipitation process depend on the solute–solute interactions that produce solute clusters. The solute clusters precede the formation of GP zones or precipitation, and have a defining role on the nature and kinetics of the subsequent precipitation processes. Moreover, interactions between solute clustering and dislocations can have a significant hardening effect, the origins of which seem to be distinctly different from the conventional notion of precipitation hardening.