Refinement of Primary Si Grains of Al–21%Si Alloy Using Vibration Mold

Japan The grain re fi nement of primary Si in Al ­ 21 % Si alloy was investigated using mechanical vibration during solidi fi cation. The number of primary Si grains increased and the primary Si grain size decreased with increasing amplitude and frequency of the vibration. Because the frequency and amplitude a ff ect the grain re fi nement, the primary Si size can be determined from the excitation force including those factors. The primary Si size decreases with increasing excitation force. To determine the grain re fi nement mechanism after applying vibration, the cooling rate during solidi fi cation and vibration start time were changed. Based on this study, the cooling rate did not a ff ect the grain re fi nement. The primary Si was re fi ned when vibration was applied in the beginning of casting. On the other hand, the primary Si was not re fi ned when the vibration application was continued after pouring. The results of this study suggest that the grain re fi nement is caused by the crystallization of many primary Si grains on the wall of the mold and at the upper surface of the molten metal and the continuous transport of the grains into the molten metal based on the convection of the molten metal due to the