The effects of Ni content on the microstructure of Mg

98-x

Er

2

Ni

x

（x=0

0.25

0.5

1

mole fraction）alloy were investigated by means of OM（optical microscope）

XRD（X-ray diffraction）

SEM（scanning electron microscope）and EDS（energy dispersed spectrometer）.The results show that the ascast Mg

98

Er

2

alloy is composed of primary dendriteα-Mg phase with segregation of components.The composition phases of the three alloys of Mg

97.5

Er

2

Ni

0.25

Mg

97.5

Er

2

Ni

0.5

and Mg

97

Er

2

Ni

1

are mainly composed ofα-Mg phase and LPSO phase.The area fraction of the second phase reach 12%

19%and34%

respectively.During solid solution treatment at 540℃

the structure change of Mg

98-x

Er

2

Ni

x

alloy can be ignored

and the second phase is not dissolved obviously.Compared with that of the as-cast alloys

the area fraction of the three alloys of Mg

97.75

Er

2

Ni

0.25

Mg

97.5

Er

2

Ni

0.5

and Mg

97

Er

2

Ni

1

after solution treatment

reach 16%

34%and 42%

respectively.