The Mg-Ni-Y alloys were prepared by conventional gravity casting

and effects of Ni additions on microstructure and mechanical properties of the alloys were investigated.The results show that the Mg-0.5Ni-3.5Yalloy is composed ofα-Mg matrix and Mg24Y5 phases

while

in the Mg-1.2Ni-3.5Y

Mg24Y5 phases disappear with the generation of lamellar long period stacking ordered（LPSO）phases.Besides ofα-Mg matrix and LPSO phases

eutectic structures can be obserevd at the grain boundaries in Mg-1.9Ni-3.5Yand Mg-3.5Ni-3.5Yalloy.LPSO phase can enhance the strength of alloys

so the Mg-1.2Ni-3.5Yalloy with lots of fine and dense LPSO lamellar structure exhibits the desirable mechanical properties

where the ultimate tensile strength and elongation reach 210 MPa and 8.8%

respectively.