Microstructure of semi-solid Al-20Sn-lCu bearing alloy was observed by OM（optical microscope） and SEM（scanning electron microscope）.The results indicate that the semi-solid Al-20Sn-lCu alloy possesses uniformly distributed fine microstructure

in which the absence of coarse dendrite Sn and Sn segregation can be observed.The phase constituent is composed of primary α-Al phase

sub-primary α-Al phase and eutectic Sn phase.The size of spheroidized primary α-Al phase is about 50 μm in equivalent diameters.The fine eutectic Sn phase is continuously uniformly distributed along the grain boundary

forming a network structure.However

the network structure in the alloy can be converted into fine Sn dispersoids after heat treatment at 623 K for 1 hour.