Effect of Yb addition on precipitation and microstructure of Al-Cu-Mg-Ag alloys

Al-Cu-Mg-Ag alloys with different Yb contents were prepared by ingot metallurgy and thermomechanical treatment. The effect of Yb addition on the precipitation and microstructure of the alloys was investigated using mechanical properties testing, optical microscopy, differential scanning calorimetry(DSC), scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results show that adding 0.10%-0.35% Yb accelerates the aging hardening process, increases the maximum hardness and the tensile strength of the extruded alloys from room temperature to 300 °C. Trace Yb element addition refines the grains of the casting alloys from 85 μm to 30 μm, decreases the precipitation temperature of Ω phase. Moreover, the addition of Yb into Al-Cu-Mg-Ag alloy decreases the precipitates size, and improves the density and the thermal stability of Ω phase between 200 °C and 300 °C.