振動鋳型装置を用いたAl-21%Si 合金の初晶Si の微細化

抄録

  Refinement of primary Si grains of Al-21%Si alloy was investigated by applying mechanical vibration during solidification. The more the frequency or half amplitude was increased, the more the size of primary Si grains decreased and the number of primary Si grains increased. Because each frequency and half amplitude affected grain refinement, it is thought that the primary Si grain size can be summarized by the excitation force equation which takes both parameters into account, and evaluated based on its relation with excitation force, where the primary Si grain size decreases with increasing excitation force. In order to clarify the mechanism of grain refinement by applying vibration, the cooling rate during solidification and the starting time of vibration were changed. The cooling rate did not affect the grain refinement in the range of this study. The primary Si grain became refined when vibration was applied during casting. On the other hand, it did not become refined when vibration was applied to the mold after casting. These results suggest that grain refinement is promoted by many primary Si grains crystallizing at the wall of the mold and upper surface of molten metal, and moving continuously into the molten metal by the convection of the molten metal due to the vibration.