Al-7%Si-0.4%Mg alloy castings with systematically controlled microstructure were produced by means of several casting methods including the semi-liquid die-cast and HIP treatment. The semi-liquid die-cast alloy (SS) with the refined effective grain structure showed improved ductility compared to the sand and permanent mold cast alloys with ordinary dendrite structure. The tear toughness was investigated by Kahn-type tear tests. The SS also showed larger tear toughness than that of the permanent mold castings. Fatigue crack growth behavior was examined using CT specimens at R=0.1. Presence of refined effective grains in the SS brought about no significant change in the growth rate for the long fatigue crack compared to the castings with ordinary dendrite structure. Short fatigue crack behavior was also examined under the axial loading condition using rectangular smooth bar specimens. In the ordinary dendrite structure, grain boundaries acted as effective obstruction to the growing fatigue crack. Dendrite cell boundaries also hindered the crack advance as relatively weak barriers. On the other hand, the effective grain boundaries of the SS were moderate obstructions to the crack growth.