Primary particle movement and change of property of cast iron by centrifugal effect in semi-solid processing

The particle distribution in semi-solid slurry under centrifugal field was simulated and the main factors such as fraction of solid, rotation speed, and holding time effecting the particle distributions are discussed. The simulation results showed that primary particles rich zone is produced in radially outer area and these results are in good agreement with the experiment. The centrifugal effect produces the primary particles distribution along the radial direction. Denser particles are concentrated in outside than inner side. For high fraction of solid samples, 'wall' appear in the middle of samples because of high viscosity region making particle difficult to move. Longer holding time gives denser primary particles concentrated more in outside than inner side. Higher rotation speed gives increased gradient of hardness in the radial direction. It is due to that number of primary austenite at inner side at higher rotation speed is less than that at lower rotation one. At higher rotation speed, ledeburite forms more at inner side of specimen than at the other one. It is also shown that semi-solid processing at lower fraction of solid gives higher hardness because smaller number of primary austenite, namely more ledeburite forms in microstructure. The present study gives useful information on producing material with locally changing property by semi-solid processing. (C) 2003 Elsevier Ltd. All rights reserved.