Semi-solid 5083 aluminum alloy billets were prepared by SIMA with hot extrusion at high extrusion ratio for pre-deformation. Effects of some processing parameters

such as extrusion ratio

isothermal temperature and holding time

on microstructure evolution of the semi-solid alloy billets were investigated

and influences of isothermal temperature on the segregation of dominant elements in the alloy billets were observed by SEM （scanning electron microscope） and EDS. The results indicate that microstructure evolution of the semi-solid alloy billets prepared by SIMA is closely related to the processing parameters. Desirable semi-solid 5083 alloy billets can be obtained with the extrusion ratio of 17.3 at 605℃ for 15

2

0 min. Distribution of the Mn element in the alloy is independent of the isothermal temperature

however

distribution of Al

Mg element are dependent on the temperature

where segregation is more and more serious with increasing in isothermal temperature. Low point phase segregated from the grain boundary is mainly composed of Mg element.