The effects of Na modification on the morphology of Si phase and tensile properties of ZL101 alloy at low temperature were investigated.The results show that the Na modification can improve the morphology of the Si phase in the alloy.The Si phase is changed from a coarse lamellar structure to a fine fiber one

which reduces the Si splitting effect on the aluminum matrix.After Na modification

the size of Si phase is decreased.The critical shearing stress required for fracture is increased at low temperature

resulting in smaller microcracks.The mechanical properties

such as tensile strength

yield strength and elongation

of the alloy are improved at low temperature

which reach 186 MPa

161 MPa and 6.60%

respectively.