A study of precipitation strengthening and recrystallization behavior in dilute Al-Er-Hf-Zr alloys

A study on the precipitation hardening and recrystallization behavior of dilute Al-Er-Hf and Al-Er-Hf-Zr alloys has been carried out. The results show that both Al-0.045Er-0.18Hf and Al-0.045Er-0.08Zr-0.1Hf alloys can obtain remarkable age strengthening effect and recrystallization resistance. The precipitation hardening rate of Al-0.045Er-0.08Zr-0.1Hf is accelerated compared with that of the Al-0.045Er-0.18Hf alloy due to substituting 0.08 at% Zr for Hf, which can be ascribed to the sequential precipitation of solute elements on the basis of the disparity in their intrinsic diffusivities (DEr>DZr>DHf). The peak hardness values for the Al-0.045Er-0.08Zr-0.1Hf are 644 MPa and 662 MPa after isochronal aging to 450 °C and isothermal aging at 350 °C for 84 h, respectively, which are higher than those of the Al-0.045Er-0.18Hf alloy. The recrystallization temperature of Al-Er-Hf-Zr alloy is 450 °C, about 25 °C higher than that of the Al-Er-Hf alloy due to the larger f/r ratio of precipitates in Al-Er-Hf-Zr alloys.