EFFECT OF MECHANICAL VIBRATIONS ON MICROSTRUCTURE REFINEMENT OF Al-7 MASS Si ALLOYS

摘要

Mechanical vibration treatment is known to induce microstructurerefinement. However, it is not completely understood which factorof vibrations is important for microstructure refinement. Factorsof vibrations include frequency, acceleration, velocity andamplitude. In our study, it was found that velocity of mechanicalvibrations, namely, the energy of vibrations is important factor forprimary crystals refinement. This study aims to investigate effectsof casting conditions with the mechanical vibrations onmicrostructure refinement of Al-7mass%Si alloys. Free space areafor vibrating the melt affects the microstructure refinement.Moreover, primary crystal particles become rosette-like and finewhen the mechanical vibrations are applied to the melt from about923 K to 888 K (liquidus – 2 K). Thus, it was found that themechanical vibrations promote heterogeneous nucleation justunder the liquidus temperature.