Effect of trace Sc and Zr on aging behavior and tensile properties of 2618 alloy

The aging behavior of 2618 (Al-Cu-Mg-Fe-Ni) alloy added trace Sc and Zr was studied by Vicker's hardness measurement at 200 and 300 degrees C, and the tensile properties(yield strength, ultimate tensile strength and elongation) of alloys were measured at 20, 200, 250 and 300 degrees C. The microstructures were observed by using optical microscope, SEM and TEM. It was found that the addition of Sc and Zr to 2618 alloy resulted in a uniform distribution of fine coherent Al-3(Sc, Zr) precipitates which had obvious aging hardening effect and made the S' phase precipitate more homogeneously. The strength of alloy increased at ambient and elevated temperature without a decrease of ductility because of the precipitation strengthening and thermal stability of Al-3(Sc, Zr) particles. The ductile fracture of alloy occurred by microviod nucleation, growth and coalescence, so the microvoid coalescence was the dominant fracture mechanism. Al-3(Sc, Zr) particles could inhabit the recrystallization process of alloy 2618.