Role of Yb and Si on the precipitation hardening and recrystallization of dilute Al–Zr alloys

Abstract

The effect of Yb and Si on precipitation hardening and recrystallization of Al–Zr alloys have been investigated. The results show that Yb is more effective than Si to accelerate the precipitation kinetics and stimulate the precipitation of Al–Zr alloy. The peak hardness values for the Al–Yb–Si–0.08Zr are 510MPa and 515MPa after isochronal aging to 425°C and isothermal at 350°C for 200h, respectively, which are significantly larger than that of the Al–Yb–Zr and Al–Si–Zr alloys. The precipitates in alloys with addition of Zr are more thermally stable than that of the Al–Yb alloy. The recrystallization temperatures of Al–Zr, Al–Si–Zr, Al–Yb–Zr and Al–Yb–Si–Zr alloys are 250, 400, 425 and 450°C, respectively, increase with the increase of the corresponding peak aging hardness. The recrystallization temperature of Al–Yb alloy is 325°C, which is much lower than that of the Al–Yb–Zr alloy due to the coarsening of the Al3Yb at temperature larger than 300°C.