S queeze casting can be supposed as a combination of casting and forging [1, 2]. In this process, high pressure is applied to the melt during solidification to obtain fine grains. The essence of mold-filling and feeding is rheological solidification of the alloy melt under pressure. Microstructure evolution is inevitable in this process, which affects the mold-filling and feeding in turn. Therefore, research on microstructure evolution during the rheological process under applied pressure is extremely meaningful. A great deal of scientific research has been done on the mechanism of microstructure evolution [3-10]. The basic methods of refining microstructure are: controlling nucleation, inhibiting dendrites growth, and prompting the initial solidification nucleation [3]. Based on these ideas, various techniques, such as mechanical stirring [4] , electromagnetic stirring [5] , strain induced melt activation [6] , casting using a cooling slope [7-9]