Plentiful sodium was introduced into the alloy using salt fluxes as medium, then the existing form and influence of sodium on the microstructure and tensile properties of Al?4.5%Cu (mass fraction) alloy were investigated. It is proved that the elemental sodium segregates at the grain boundaries of Al?4.5%Cu alloy and weakens the bond between the matrix and CuAl2-phase. After T6 heat treatment, sodium results in micro-fracture and induces the residual of CuAl2-phase in Al?4.5%Cu alloy. The tensile test results show that the sodium causes a transition from dimple fracture to intergranular fracture, which makes the mechanical performance of Al?4.5%Cu decrease dramatically.
