Microstructures and mechanical properties of ADC12 alloy with different Sm additions were investigated by optical microscopy（OM）

scanning electron microscopy（SEM）

energy dispersive spectrometry（EDS）.With the increase of the Sm in the range of 0

1

.0%

the secondary dendrite arm spacing and the size of primary α-Al phase as well as the size of silicon phase are decreased

while the tensile strength and elongation are increased.With 1% Sm addition

the secondary dendrite arm spacing and the average size of primary α-Al cell are about 15 μm and 30

4

0 μm

respectively

and most of the Si phases exhibit spherical structure or rod-like shape with high aspect ratio.The tensile strength and elongation reach 220 MPa and 3.1%

respectively

increased by 22% and 210%

respectively

compared with those of ADC12 alloy.However

with Sm addition more than 1%

the mechanical properties are decreased as a result of coarseness of the microstructures.