Pre-deformation of casting billet with equivalent strain of 4.71 was performed by composite technology of forward extrusion-equal channel angular extrusion(FE-ECAE). And the microstructure evolution of pre-deformed billet in the semi-solid isothermal treatment process and recrystallization was studied. The results show that the sizes of recrystallized grains in the process are fine and uniform, which has a great influence on the subsequent microstructure evolution and the liquid phase distribution in the se...