The effects of single or compound addition of La and Ce on thermal conductivity

microstructure and mechanical properties of Al-3 Si-0.5 Cu-0.7 Fe casting alloys were investigated by optical microscope

SEM and tensile testing. The results indicate that the microstructure of alloys is gradually refined

and the thermal conductivity and mechanical properties of the alloy are improved with the increase of rare earth content. After compound addition of 0.3%（La+Ce）

the coarse dendritic of primary α-Al phases become fine

and the morphology of eutectic silicon is transformed from bulk-like shape and strip-like shape into particle-like shape

where secondary dendrite arm spacing（SDAS） of α-Al phases reach the minimum（27.32 μm）. The thermal conductivity

tensile strength and elongation of the alloy reach up to 170.67 W/（m·K）

245.4 MPa and 19.8%

respectively

increased by 7.72%

31.74% and 74.24%

compared with those of ones without rare earth addition.