Electromagnetic Stirring The Preparation Of Semi-solid Hypereutectic Al-si Alloy

The current theory and application of Al-Si alloy mainly focus on the research of eutectic and hypereutectic, therefore we systematically analyzed the preparation of hypereutectic Al-Si alloy withelectromagnetic stirring based on the methods and results of predecessors.A electromagnetic stirring apparatus is designed to produce hypereutectic Al-20%~30%Si alloy billet with tiny primary phase by semi-solid process. Around the main electromagnetic stirring technology parameters of agitation strength, stirring rate and cooling rate, series of trials are designed to find the influence of technology parameters on the size, shape and distribution of primary Si and eutectic Si, and discover the correlation between technology parameters and semi-solid microstructure providing evidences for theory and showing the direction for industry development.The experiments results show that, during solidification, the early growth of the primary crystals of Al-Si alloy slurry continues dendritially. With further vigorous agitation, the dendrite arms gradually bend and merge. Meanwhile, the dendrite arms are melted and/or ruptured into numerous small crystals at the root of arms. As the continuous growth, the primarycrystals evolve toward more spherical. As the increasing of electromagnetic stirring strength, primary phase is spherer and the size of primary silicon decreases. The experiments show that too high cooling rate disadvantages the formation of spherical primary crystals, while higher electromagnetic stirring strength is necessary to spheroidize and homogenize the primary crystals. For Al-25%Si alloy, the tensile strength of semi-solid metal(SSM) sample is higher 20~30% than that of metal mold sample. Elongance 8 ofSSM sample is higher 2.8~4.5% than that of metal mold sample. At the samecondition of attrition wear and tear, SSM sample wear and tear is reduced 21% than that of metal mold sample.The characteristic of this essay is that we systematically analyzed the preparation of hypereutectic Al-Si alloy with electromagnetic stirring. The results will be applied to fields as structure material with high abrasive wear and tear, which will boost the economics and its development.