The as-cast microstructure of 7150 aluminum alloy was observed by OM（optical microscope） and SEM（scanning electron microscope）

XRD（X-ray diffractometer）

in which the second phase was analyzed by EDS（energy dispersive spectrometer）.The results reveal that the as-cast microstructure of 7150 aluminum alloy is composed of MgZn2（η phase）

Al2CuMg（S phase）

Al2Mg3Zn3（T phase）

primary Al phase

Mg2Si phase and Al6（FeCu） phase.The EDS observation shows that the η phase and T phase is dissolved into Cu element

while S phase is dissolved into Zn element.In addition

the Zn and Mg element content in T phase are slightly higher than that of in S phase.