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

摘要

Mechanical vibration treatment is known to induce microstructurernrefinement. However, it is not completely understood which factorrnof vibrations is important for microstructure refinement. Factorsrnof vibrations include frequency, acceleration, velocity andrnamplitude. In our study, it was found that velocity of mechanicalrnvibrations, namely, the energy of vibrations is important factor forrnprimary crystals refinement. This study aims to investigate effectsrnof casting conditions with the mechanical vibrations onrnmicrostructure refinement of Al-7mass%Si alloys. Free space arearnfor vibrating the melt affects the microstructure refinement.rnMoreover, primary crystal particles become rosette-like and finernwhen the mechanical vibrations are applied to the melt from aboutrn923 K to 888 K (liquidus – 2 K). Thus, it was found that thernmechanical vibrations promote heterogeneous nucleation justrnunder the liquidus temperature.