PROBLEM TO BE SOLVED: To reduce defective castings such as shrinkage cavity compared with a case where a completely molten alloy is used by providing a semi-solidified alloy free from deformation of a preliminarily formed body having a specified solid phase ratio, and achieving the pressurized impregnation of the semi-solidified alloy at the specified pressurized impregnation speed.
SOLUTION: The solid phase ratio of a semi-solidified alloy is 10-70%, and the pressurized impregnation speed of the semi-solidified alloy is 1-30 cm/s. Preferably, a preliminarily formed body is arranged in a part of or a whole part of a space of a casting die, and the semi-solidified alloy is pressurization-cast in the space of the casting die. A prefoam is installed in the whole part of or a part of the inside of the cavity, the semi-solidified alloy is impregnated in the prefoam by the pressurization- casting process to obtain a composite material in which a whole of or a part of parts for a machine are reinforced. The filter effect of the prefoam realizes a structure in which the solid phase in the semi-solidified alloy is deposited in the vicinity of the interface between the prefoam and the alloy, and since the solute concentration of the solid phase is lower than the initial concentration of the semi-solidified alloy, and the solid phase is excellent in ductility, it functions as a stress-mitigation layer for the thermal stress, etc.