Solidification Behavior of Semi-Solid Hypereutectic Al-Si-(X) Alloys during Electromagnetic Stirring

摘要

Microstructural changes of Al-Si-(X) alloys during semi-solid state processing have been investigated in the present study. The main objective of this research is to investigate the effect of the electromagnetic stirring on the microstructure of Al-Si-(X) alloys. Firstly by continuous electromagnetic stirring during cooling, primary Si particles in hypereutectic Al-Si alloy tend to distribute themselves to both mold wall sides. The high concentration of primary Si at the surface increases the surface hardness and abrasive resistance of the stirred Al-Si alloy. As the rotation velocity of the magnet increases, the trends become remarkable. It has been suggested that each element having different electric conductivity has different electromagnetic forces. Secondly by adding Fe element to the Al-Si alloy, particle having a larger conductivity than Si particle is formed. During continuous electromagnetic stirring of Al-Si-Fe alloys, primary Si particles and Al_9Fe_2Si_2 particles are distributed uniformly, and the particles are fractured and then become round. It occurs due to the lots of collision between the two particles - primary Si and Al_9Fe-2Si_2 partides, since each has different velocity.