The modification effect of ZL115 aluminum alloy with different Sb contents at different holding time was investigated by rapid thermal analysis technology. The results indicate that the growth temperature(T

eg

) of the eutectic silicon is decreased by Sb addition of 0.1%～0.3%

which has 3.6～8.3 ℃ difference before modification

and a good corresponding relationship with the modification effect can be obtained. Desirable modification effect and the optimal mechanical properties of the ZL115 alloy were obtained with addition of 0.3%Sb

where the as-cast tensile strength and elongation are increased

reaching 208 MPa and 5.65%

respectively. The length of the eutectic silicon can be shortened with increasing in the holding time

while the longer holding time leads to the excessive Mg

3

Sb

2

intermetallic

reducing the mechanical properties. Therefore

the desirable holding time is 60～90 min. The excessive eutectic silicon modification occurs when the Sb content exceeds 0.3%

and Mg

3

Sb

2

is generated under fast cooling rate.