Influences of Gd content（0

1

2.7%）on the microstructure and mechanical properties of sandcast Mg-Gd-Y alloys were investigated by OM（optical microscopy）

SEM（scanning electron microscopy）and tensile test.Relationships between Gd content and the average grain size ofα-Mg

yield strength and ultimate tensile strength were established.The morphology of the fracture was observed

and the crack behavior was described.The average grain size ofα-Mg is decreased from 112μm to 54μm

and yield strength

tensile strength of the alloy are increased from 64.9 MPa to 174.3 MPa and from 157.5 MPa to 221.2 MPa

while elongation is decreased from 21.3%to 0.9% with Gd content increased from 0 to 12.7%in the alloy.The alloy with 10.2% Gd content possesses the desirable mechanical properties

where yield strength

tensile strength and elongation reach 140.0 MPa

196.1 MPa

3.3%

respectively.