The effects of copper on the microstructure and mechanical properties of ZL114 Aaluminum alloy were investigated by optical microscope

scanning electron microscope and tensile testing experiment.The results reveal that there exist changes-absent in the microstructure or the mechanical properties with copper content less than 0.1%

which indicates that the copper is completely soluted in the matrix.As the increasing in Cu content

the tensile strength of the alloy is increased fast firstly and then declined slightly while the elongation is decreased.With the Cu content of 0.5%

the tensile strength and elongation of the alloy reach 337.21 MPa and 3.4%

respectively.Furthermore

the EDS data verifies that the improvement mechanisms of alloy is attributed to dispersed precipitation of the second phase W（Al2Mg5Si4Cu4）to form second phase strengthening effects with the content of Cu exceeding 0.1%（the limit of the matrix solid solubility）

and there exists also lattice distortion being generated as the second phase to improve the tensile strength of the ZL114 Aaluminum alloy.