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

A356和357等原生Al-7%Si-Mg铸造合金已广泛用于结构应用，其中更高和更一致的机械性能是维护铸造部件安全标准的关键要求。Mg的加入通过沉淀硬化来提高强度，从而提供强度和延展性的特定组合。铁通常作为杂质存在，由于铁金属间化合物的形成对合金性能有负面影响，特别是以片状形式形成的脆性β -铁A15FeSi相，导致与喂入有关的问题，导致孔隙形成和早期断裂。pii -iron A19FeMg3Si5相的形成也是不可取的，因为它与Mg结合，降低了合金的强度/延展性。因此，目标是使铁含量尽可能低。最近有报道称Al-9%Si合金比356和319合金更耐铁。Al-9%Si-Cu-Mg合金的延展性比含有低Si含量的合金有很大的提高，即使存在高Cu， Mg和Fe含量。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。另一个令人感兴趣的领域是与无be 357 （Al-7%Si-Mg）合金的生产有关。这些合金含镁量高，用于要求高屈服强度的铸件。然而，高Mg也会导致pi相的形成。虽然Be被用来消除这一阶段，但它的毒性使得有必要寻找其他替代品。提出的研究计划将通过(i)使用质量指数概念对Al-9%Si合金（359和354型合金）进行基本表征以优化拉伸性能，以及（ii）通过对无be 357合金的合金显微组织和相关力学性能进行基本表征，重点研究铁杂质的影响，对Al-Si-Mg合金中的pi-A19FeMg3Si5相形成进行全面研究。铝工业和铸件生产商应用这些发现将对加拿大经济有明显的好处。

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.