Preparation Of A1-25% Si Alloy Semi - Solid Slurry By Rotor - Induced Nucleation

In this study, a new technology of preparing semi-solid slurry called Rotating Induced Nucleation (RIN) was promoted based on the technology of inclined plate cooling. The equipment of RIN was designed and assembled. A vertical centrifuge, which matches the RIN was also assembled. Hypereutectic Al-25%Si semi-solid slurry was fabricated by Rotating Induced Nucleation (RIN). Cylindrical casting was prepared by the vertical centrifuge with the hypereutectic Al-25%Si semi-solid slurry, which was treated by RIN. And the hypereutectic Al-25%Si was also treated by addicted P or composite technology (P+RIN). Finally, the change of the temperature of the melt on the surface of rotating rod was measured by the TP700multi-channel temperature logger.The results showed that:the RIN has greatly effect that induces nucleation on the solidification of hypereutectic Al-25%Si melt, which not only refined primary Si, but also fractured eutectic Si. But it maybe changes with different process parameters. With the increase of rotating speed, the effect of inducing nucleation of RIN is not always enhanced, but firstly enhanced and than declined. With the improvement of pouring temperature, the effect of inducing nucleation of RIN would decline evidently. When the pouring temperature is785℃(near liquidus775℃), and the rotating speed is500-600r/min, the melt of hypereutectic Al-25%Si spread on the rotating rod fully and formed a thin alloy film, so as to say that the effect of inducing nucleation of RIN reaches the best. The average size of primary Si of semi-solid slurry reduced from the casting’s200-300μm to27±5μm, the shape factor reached0.8, the number of primary Si in per unit area was60piece/mm2, and the primary Si distributed evenly.Compared to the P modification, the RIN can refine primary Si and eutectic Si better than P modification significantly. The average sizes of primary Si only half of P modification (about50μm). The number of primary Si in per unit area by RIN is1.5times than P modification (40piece/mm2). Compared to the composite modification (P+RIN), the number of primary Si in per unit area by RIN just half of it. However, the average size of primary Si in both of them is closed. Compared with the cylindrical casting by conventional centrifugal, the micro structure of cylindrical casting that formed in semi-solid slurry prepared by RIN improved obviously. But there are some cold shuts on the surface of the cylindrical casting due to the decrease of the melt fluidity. And the distribution uniformity of the internal organization needs to be improved.