High hopes are placed on the semi-solid process as a near net shape forming method for producing high performance products. However, the semi-solid process has such disadvantages as poor formability in low fluidity, and difficulties in making the semi-solid slurry. In the previous work, we tried to make the semi-solid slurry by applying mechanical vibrations, and successfully obtained slurry with small and spherical solid particles. In this study, we evaluated the fluidity of JIS AC4CH aluminum alloy slurry made by applying mechanical vibrations. We also improved fluidity by applying shear stress to slurry at the gate of the mold, and investigated the effects of shear rate on the fluidity of the slurry. The slurry was prepared by applying mechanical vibrations in the frequency of 50Hz and acceleration amplitude 166.6m/s2 (17G). The fluidity was evaluated by injecting slurry into a metallic mold with spiral cavity through a gate, as flow length into the cavity. The shear rate at the gate was controlled by changing the thickness of the gate from 1.0mm, 2.2mm, and 4.0mm. The fluidity of the slurry made by applying mechanical vibrations had about 25 to 40% of the fluidity of liquid aluminum. On the other hand, by applying shear stress at the gate, the fluidity was increased by approximately 30%. The α-phase particles in the specimen became fine and spherical with increasing shear rate. As just described, semi-solid slurry with high fluidity can be obtained by the addition of mechanical vibration and applying shear rate. Moreover, the mechanical vibration slurry indicated approximately the same fluidity as electromagnetic stirring slurry by applying high shear rate and high casting pressure. This method is expected to enable the production of the semi-solid forming products with complex configurations.
