Abstract: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.

Key words: Al-Cu alloy; sodium; grain boundaries; fracture; mechanical performance