1994 年 44 巻 9 号 p. 504-509
A semi-solid slurry of a hypereutectic Al-Si alloy containing fine primary silicon crystals is producible by "slurry-melt mixing (SMM)" process. In the SMM process, a melt of a phosphorus-added hypereutectic Al-Si alloy (second-alloy melt) is mixed with a semi-solid slurry of a hypoeutectic Al-Si alloy (first-alloy slurry) which has been solidified with stirring in a furnace-cooled vessel. In this study, the change in apparent viscosity of the stirred slurry, whose silicon content changed from 8 to 20mass% by mixing of molten Al-32mass%Si alloy, was measured continuously during the SMM process. Immediately after the mixing of the second-alloy melt, the apparent viscosity decreases drastically from 7 to about 0 Pa•s. This abrupt change is attributed to the following facts: (1) The primary alpha-phase which has been crystallized in the first alloy remelts rapidly in the mixed alloy. (2) The fraction of the primary silicon in the mixed alloy is lower than that of the primary alpha-phase in the first alloy, though there is a strong driving force of crystallization of the primary silicon in the mixed alloy in comparison with the conventionally solidified Al-20mass%Si alloy. (3) The apparent viscosity of the hypereutectic alloy is similar in order of magnitude to that of the hypoeutectic alloy of the same fraction solid.