2020 年 61 巻 2 号 p. 355-360
The grain refinement of primary Si in Al–21% Si alloy was investigated using mechanical vibration during solidification. 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 affect the grain refinement, 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 refinement mechanism after applying vibration, the cooling rate during solidification and vibration start time were changed. Based on this study, the cooling rate did not affect the grain refinement. The primary Si was refined when vibration was applied in the beginning of casting. On the other hand, the primary Si was not refined when the vibration application was continued after pouring. The results of this study suggest that the grain refinement 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 vibration.
This Paper was Originally Published in Japanese in J. JFS 91 (2019) 258–263.
