Influences of Mg-Ce alloy and Ce on the microstructure of Al-5Ti alloy were investigated by SEM and OM.The results show that:Ti-Al phases with strip structure and 50

1

00μm in radial direction and more than 200μm in axial direction are distributed on the substrate of Al-5Ti master alloy.After adding of rare earth 0.3%Ce

the shape of Al-Ti phase nucleation particles is transformed into fine feathery with significant decrease of size to 10

5

0μm and more dispersedly distribution.After adding1% Mg-30 Ce alloy

Al-Ti particles are changed into fine needle particles with axial size and radial dimension of 20μm and 10

2

0μm

respectively.After adding Mg elements

Al-Ti particle size is further reduced and magnesium-rich particles can be observed in interface of Al-Ti phases.Based on the refining effect analysis of Al-5Ti and Al-5Ti-1（Mg-30Ce）

the refining effect of Al-5Ti-1（Mg-30Ce）for Al-Si alloy is significantly superior to that of Al-5Ti alloys.