Core-shell nanoscale precipitates in Al-0.06 at. Sc microalloyed with Tb, Ho, Tm or Lu

摘要

The age-hardening response at 300 °C of Al-0.06Sc-0.02RE (at., with RE = Tb, Ho, Tm or Lu) is found to be similar to that of binary Al-0.08Sc (at.), except that a shorter incubation period for hardening is observed, which is associated with nanoscale RE-rich Al_3(RE_(1-x)Sc_x) precipitates. In addition, Al-0.06Sc-0.02Tb (at.) has a much lower peak microhardness than that of Al-0.08Sc (at.) due to the small solubility of Tb in alpha-Al(Sc). Peak-age hardening occurs after 24 h, and is associated with a high number density of nano-scale Sc-rich Al_3(Sc_(1-x)RE_x) precipitates. Analysis by three-dimensional local-electrode atom-probe tomography shows that x increases with increasing atomic number, and that the REs partition to the core of the precipitates.