Microstructure characteristics and apparent viscosity of hypereutectic Al-24/100 Si alloy melt during semi-solid state stirring

摘要

The microstructural evolution and apparent viscosity of hypereutectic Al-24/100Si alloy during semi-solid state shearing were studied with a Searte type viscometer. When the alloy melt was continuously stirred from 720 deg. C to eutectic temperature, the primary Si crystals were gradually changed from elongated platelets to near-spherical shapes. It was found that some nondendriticα-phase formed when the melt was stirred below 585 deg. C. The experiment showed that the semi-solid stirring had strong effect on inhibiting the anisotropic growth of Si crystals during solidification. The apparent viscosity of the alloy melt increased slowly with the decreasing of temperature before the formation of nondendriticα-phase, which caused the dramatic increase of apparent viscosity.