The effects of the mixture of MgAl

2

O

4

and MgO on the grain size and the morphology of second phase in 8079aluminum alloy were investigated systematically by XRD（X-ray diffraction）

OM（optical microscopy）

SEM（scanning electron microscopy）and EDS（energy dispersive spectrometer）.The results show that MgAl

2

O

4

and MgO have obvious refinement effect on the microstructure of 8079aluminum alloy

and they can modify the morphology of needle-like Al

3

Fe.With the increase of the mixture of MgAl

2

O

4

and MgO

the grain size of the 8079aluminum alloy is decreased gradually

and the needle-like phase becomes smaller with the shape modified to particle.With adding a mixture of 0.05%MgAl

2

O

4

and MgO

the grain size of 8079aluminum alloy can be decreased effectively from more than100μm to about 30μm

and the shape of need-like Al

3

Fe phase is converted into particle structure.