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.T1 Hf 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 (D-Er > D-Zr > D-Hf). The peak hardness values for the Al-0.045Er-0.08Zr-0.1Hf are 644 MPa and 662 MPa after isochronal aging to 450 degrees C and isothermal aging at 350 degrees 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 degrees C, about 25 degrees 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. (C) 2015 Elsevier B.V. All rights reserved,