【作者】 程钢；

【导师】 樊刚；

【作者基本信息】 昆明理工大学 ， 材料学， 2002， 硕士

【摘要】 本课题采用自行设计制造的机械搅拌装置，利用半固态金届加工技术能破碎细化初生相的优点，对过共晶Al-Si合金进行半固态加工及变质细化复合处理，以获得具有球形初生相微粒的半固态Al-Si合金坯料。 本课题围绕着变质细化、搅拌强度、冷却速率等影响半固态加工效果的工艺参数进行实验。结果发现，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；但当冷却速率太大时，由于搅拌时间缩短，则不利于球形初生相颗粒的生成。在半固态加工中同时加磷P进行变质细化有利于获得细化的初晶硅，并能减少半固态加工的时间，提高加工效率；但机械搅拌与稀土RE变质在对共晶硅的细化作用上产生了相互制约的作用，对共晶硅形貌的改善达不到单纯进行RE变质或搅拌的效果，因此在半固态铸造中采用RE进行变质是不必要的。 半固态铸造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8～15％。更多还原

【Abstract】 Semi-solid metal process has advantage of breaking primary phase. In this article, a mechanical stirring apparatus is designed to produce semi-solid hypereutectic Al-Si alloy billet with tiny primary phase by semi-solid process and modification.Around modification and the main mechanical stirring technology parameters of agitation strength, stirring rate and cooling rate, series of trials are designed to discover the relation between technology parameters and semi-solid microstructure.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 primary crystals evolve toward more spherical.As the increasing of mechanical 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 mechanical stirring strength is necessary to spheroidize and homogenize the primary crystals.There has advantage to obtain short and thick primary silicon and improve process efficiency with P modification in semi-solid metal process. But the modification power of RE is relieved by mechanical stirring, so it is not necessary to add RE as a modifier in semi-solid metal process.The tensile strength of semi-solid metal(SSM) sample is higher 20-30% than that of metal mold sample. Elongance 8 of SSM sample is higher 2.8-4.5% than that of metal mold sample. At the same condition of abrasive wear and tear, SSM sample wear and tear is reduced 8-15% than that of metal mold sample.更多还原