Precipitation evolution in Al–Er–Zr alloys during aging at elevated temperature

Highlights: •We investigate the precipitation evolution of dilute Al–Er–Zr at 450 and 500 °C. •The coarsening is controlled by the diffusion of solute atoms in the outer layer. •Precipitates in Al–Er–Zr have enhanced coarsening resistance compared with Al3Er. •Precipitates in Al–0.04Er–0.08Zr transform to D023 after aging at 500 °C for 100 h. -- Abstract: The temporal evolution of the Al3(ErZr) precipitates is investigated in Al–0.04Er–0.04Zr and Al–0.04Er–0.08Zr alloys during aging at elevated temperature of 450 and 500 °C. The results show that the coarsening behavior of the precipitates in both alloys is similar, due to the core–shell structure with Zr segregated in the shell of the Al3(ErZr) precipitates. With the increase of the amount of Zr addition, the misfit between the precipitate and the Al matrix decreases, consequently the coherency transition size of the precipitates in Al–0.04Er–0.08Zr is larger than that of Al–0.04Er–0.04Zr. After aging at 500 °C for 100 h, some of the precipitates in Al–0.04Er–0.08Zr transform to D023 structure due to the high Zr/Er ratio, while the precipitates in Al–0.04Er–0.04Zr keep the L12 structure