Precipitation evolution and coarsening resistance at 400 °C of Al microalloyed with Zr and Er

The hardening effect and coarsening resistance of precipitates were studied in Al–Zr, Al–Er and Al–Zr–Er alloys during aging at 400 °C. Joint addition of 0.06 Zr and 0.03 Er (at.%) in Al gives a maximum microhardness of 380 MPa, which is higher than the summation of individual contributions. The precipitates in Al–0.06 Zr–0.03 Er (at.%) continue to offer excellent coarsening resistance at 400 °C. The results indicate that in Al–0.06 Zr–0.03 Er, Er stimulates the decomposition of Al–Zr, while Zr retards the coarsening of precipitates.