Trace elements Sc and Zr were added into the Al-Zn-Mg-Cu alloys

and the differences of the microstructures and properties of the alloy prepared were compared in gravity casting and in squeeze casting.The results show that through the addition of trace elements Sc and Zr

as-cast microstructure of the Al-Zn-Mg-Cu alloys is refined effectively

and dendrite segregation is relieved

so the mechanical properties of alloy are improved.Through squeeze casting

the compactness of the alloys is improved

and the probability of occurrence of shrinkage porosity（holes）and segregation are decreased.In addition

the grain can be refined by the pressure on the alloy melt.Combined the element Sc-Zr microalloying with squeeze casting

Al-Zn-Mg-Cu alloy with uniform

compact

little defect microstructures can be obtained

which provides a new way to the Al-Zn-Mg-Cu alloy forming.