2011 Volume 52 Issue 5 Pages 830-833
It is known that mechanical vibrations which applied during solidification affect microstructure refinement. However, it is not completely understood which factor of vibrations is important for microstructure refinement. Factors of vibrations are frequency, acceleration, velocity and amplitude. In this study, the effect of mechanical vibrations on microstructure refinement of Al-7 mass% Si alloys was investigated systematically. The mechanical vibrations were applied to the melt in an alumina crucible from about 923 K to 863 K, and the crucible was quenched in water at 863 K. As a result, it was found that the velocity of mechanical vibrations corresponding to the vibration energy is important factor for primary crystals refinement. The mechanical vibrations with high velocity regardless of frequency can refine the primary crystals. It is considered that the mechanical vibrations promote heterogeneous nucleation just below the liquidus temperature.