电磁搅拌制备半固态大过共晶铝硅合金的研究

【作者】 王凯；

【导师】 樊刚；

【作者基本信息】 昆明理工大学 ， 材料学， 2004， 硕士

【摘要】 本文针对目前Al-Si合金相关应用和理论研究多集中于亚共晶和共晶合金的现实，在前人的基础成果和研究方法的基础上，对大过共晶Al-Si合金电磁搅拌进行了系统分析，深入研究了搅拌功率、等温时间、冷却速度等影响半固态加工效果的因素对大过共晶铝硅合金中初生硅和共晶硅的大小、形状和分布的影响，揭示了大过共晶铝硅合金的成分、组织、性能之间的内在关系，为研制新型的大过共晶铝硅合金提供理论依据和工业应用方向。 研究结果表明：剧烈的搅拌使得初生相在长大过程中，不断发生着枝晶臂的弯曲融合、熔断和机械断裂，从而使晶体以等轴生长及合并生长的方式向球形形态发展长大。较高的搅拌强度可以有效地减小初晶硅的尺寸，并使之边角钝化和均匀化。同时，随着电磁搅拌强度的增加，初生相球化且初生硅相尺寸减小。过高的冷却速率不利于初生相球化，但高强的电磁搅拌有利于球化和均化初生晶粒。对于Al-25％Si％材料，经过复合处理试棒比同种成分的金属型试棒的室温σ_b提高20～30％；延伸率δ提高2.8～4.5％，在相同的磨损条件下半固态铸造试样磨耗比金属型试样降低21％。 本文的特色之处在于通过电磁搅拌对高含Si量的大过共晶铝硅合金进行了全面系统的研究。在国内属于开创性研究，研究成果将应用于结构材料、高耐磨材料等生产领域，对材料工业、汽车和摩托车从业的发展具有重大的经济意义和推动作用。更多还原

【Abstract】 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.更多还原