Fundamental Characterization of the Quality and Performance of Important Primary Aluminum Casting Alloys

初级Al-7% Si-Mg铸造合金如A356和357已广泛用于结构应用中，其中更高和更一致的机械性能是维持铸造部件安全标准的关键要求。Mg的添加通过沉淀硬化增加强度以提供强度和延展性的特定组合。通常作为杂质存在的铁由于铁金属间化合物的形成而对合金性能具有负面影响，特别是薄片形式的脆性β-铁A15 FeSi相，其引起与进料相关的问题，导致孔隙形成和早期断裂。π-铁Al 9 FeMg 3Si 5相的形成也是不希望的，因为它束缚Mg并降低合金强度/延展性。因此，目标是保持尽可能低的Fe水平。Al-9%Si合金比356和319合金更耐铁腐蚀。Al-9% Si-Cu-Mg合金的延展性与含有低Si水平的合金相比显示出巨大的改善，即使在存在高Cu、Mg和Fe含量的情况下。虽然其原因尚不清楚，但这是一个重要的观察结果，具有巨大的合金开发潜力。另一个感兴趣的领域是与无Be 357（Al-7% Si-Mg）合金的生产有关的领域。这些含镁量高的合金用于要求高屈服强度的铸件。然而，高Mg也导致π相的形成。虽然Be被用来消除这一阶段，但其有毒性质使得有必要寻求其他替代品。拟议的研究计划将解决这两个主要问题，通过（i）Al-9%Si合金的基本表征（359和354型合金）使用质量指数概念来优化拉伸性能，以及（ii）通过对合金显微组织和Be-100的相关机械性能的基本表征，对Al-Si-Mg合金中pi-A19 FeMg 3Si 5相的形成进行了全面的研究。免费357合金，重点是铁杂质的影响。铝工业和铸件生产商应用这些研究结果将对加拿大经济产生明显的好处。

Primary Al-7%Si-Mg foundry alloys such as A356 and 357 have been used extensively in structural applications where higher and more consistent mechanical properties are a key requirement to uphold the safety standards of the cast components. Addition of Mg increases strength via precipitation hardening to provide specific combinations of strength and ductility. Iron, usually present as an impurity, has a negative influence on the alloy properties due to the formation of iron intermetallics, notably the brittle beta-iron A15FeSi phase in the form of platelets which cause feeding-related problems, resulting in porosity formation and early fracture. The formation of the pi-iron A19FeMg3Si5 phase is also undesirable, as it ties up Mg and lowers the alloy strength/ductility. The target, therefore, is to keep the Fe level as low as possible. It has been reported recently that Al-9%Si alloys are more tolerant to iron than 356 and 319 alloys. The ductility of Al-9%Si-Cu-Mg alloys showed vast improvements compared to those containing low Si levels, even in the presence of high Cu, Mg, and Fe contents. While the reason for this is yet to be understood, this is a significant observation, with immense potential for alloy development. Another area of interest is that related to the production of Be-free 357 (Al-7%Si-Mg) alloys. These alloys, containing high Mg levels, are used in castings which require high yield strengths. However, the high Mg also leads to the formation of the pi-phase. While Be is used to eliminate this phase, its toxic nature has made it necessary to seek other alternatives. The proposed research program will address these two main concerns through (i) a fundamental characterization of Al-9%Si alloys (359 and 354 type alloys) using the quality index concept to optimize the tensile properties, and (ii) a comprehensive study of pi-A19FeMg3Si5 phase formation in Al-Si-Mg alloys through a fundamental characterization of the alloy microstructure and related mechanical properties of Be-free 357 alloys, with emphasis on the effect of iron impurities. The application of these findings by the aluminum industry and castings producers would be of distinct benefit to the Canadian economy.