Solid Fraction Examination at Flow Cessation and Flow Cessation Mechanism of Al-Si-Mg Alloy

Abstract

The aim of this study is to experimentally determine the solid fraction at the cessation of the flow of a molten Al-Si-Mg alloy (JIS-AC4CH) ceases. In this study, an experimental apparatus to measure the melt temperature during flow was developed and was used to perform highly accurate temperature measurements. An immersion-type optical-fiber radiation thermometer without emissivity correction was used for the temperature measurement device in this apparatus. The solid fraction was calculated from the area of primary crystals when the molten metal at any temperature was quenched. The melt temperature at flow cessation was higher than the eutectic reaction temperature, and the solid fraction in the melt front was approximately 0.2. However, the maximum solid fraction was found at a position slightly away from the melt front toward the pouring gate, and was approximately 0.3. It was inferred for this Al-Si-Mg alloy, that the flow cessation mechanism was a mixture of skin formation and mushy formation types.