Semi-solid Eutectic Al-si Alloy Of The Electromagnetic Stirring Process And Performance Study

Hypereutectic Al-Si alloy with the quality of low density, good heat stability and high wear-resistance, is an ideal wear-resistant and heat-resistant material. Its wear-resistance and physical property increase with the increase of silicon content. However, the ductility and mechanical property of the alloy will be deteriorated for the increase of silicon content so that the use of high silicon content Al-Si alloy is restricted. Semi-solid metal forming technology is a new metal forming technology and it is a forming technology with enormous developmental potentiality. Using self-made electromagnetic stirring device of the laboratory, two groups of experiments, isothermal electromagnetic stirring and continuously cooling electromagnetic stirring were carried out to investigate microstructure of semi-solid hyper-eutectic Al-Si alloy influenced by these parameters i.e. isothermal temperature, stirring time, cooling rate and stirred power.The experiments results show that primary silicon crystal fragmentation occurs in the course of stirring and the size of primary silicon phase tends to constant after 20-30 minutes and homogenized distribution.In the condition of isothermal electromagnetic stirring, the solid phase proportion of 580℃ is more than that of 600℃, and high solid phase proportion is propitious to collision and friction of primary silicon phase, so the size of primary silicon is small. But low temperature has negative effect that the primary silicon will reunite easily if the stirring time is too long. In the condition of continuously cooling electromagnetic stirring, primary silicon will reunite and grow if the stirring time is more than 30 minutes. The size of the primary silicon will be smaller for the increase of cooling rates. So the cooling rates is higher, the primary silicon is smaller in the condition that other parameters are same. If the cooling rate is too high, the stirring time will shut down, so the cooling rate can not be too high. In the condition that other parameters are same, the cut force of the electromagnetic stirring and collision probability of primary silicon will rise by the increase of stirring power, so the size of primary silicon is smaller than lower stirring power. For hypereutectic Al-Si alloy, the mechanical property of semi-solid metal(SSM) sample is higher than that of metal mold sample because primary silicon turns to be smaller and α -phase evolves toward sphericity.