Hydrogen-based Pore Formation in Aluminum Alloy Castings

从汽车行业增加气孔使用的角度来看，控制近净形状铝合金铸件中的气孔形成是至关重要的，因为气孔的存在会严重破坏承受循环载荷的部件的性能。与气孔相关的缺陷导致的生产率降低以及过度设计许多部件的需要也增加了成本，进一步侵蚀了铸铝产品的商业采用率。 铝合金铸件显微疏松的形成机制是复杂的，这是因为它依赖于凝固过程中发生的许多现象的相互作用，包括氢溶度的降低、体积收缩、气孔形核位置的存在和凝固组织的发展。有一个持续的基础研究的需要，以了解这些不同的现象及其对孔隙形成的贡献。下面描述的拟议研究计划将集中于其中的两个现象：1)锶基改性对凝固微结构的影响；2)表面氧化膜夹带在成核气孔中的作用。这两个学科领域继续着申请者在过去21年中对理解和预测铸造过程中缺陷形成的主要研究兴趣。 由此产生的知识和在工业环境中应用这些知识的工具将对初级金属生产商和近净形状铝产品的制造商都有重大好处。这项工作的主要成果，如果成功地应用于商业，将降低铸造成本，近净形状的铝产品，这是由于减少了与气孔形成相关的产品产量损失。第二个结果将是能够在需要良好疲劳性能的应用中扩大铸造、近净形状铝产品的使用，从而增加加拿大铸造业的市场机会。

The control of pore formation in near-net-shape aluminum alloy castings is critical from the standpoint of increasing their use in the automotive sector as the presence of pores can act to seriously undermine the performance of components subject to cyclic loading. Reduced productivity associated with pore-related defects and the need to over-design many components also adds cost, further eroding increased commercial adoption of cast aluminum products. The mechanism of microporosity formation in aluminum alloy castings is complex, owing to its dependence on the interaction of a number of phenomena occurring during solidification including the decrease in hydrogen solubility, volumetric shrinkage, the presence of suitable sites for pore nucleation and the development of the solidification microstructure. There is an on-going need for fundamental research to understand these various phenomena and their contribution to pore formation. The proposed research program described below will focus on two of these phenomena: 1) the role of the solidification microstructure as influenced by strontium-based modification; and 2) the role of surface oxide film entrainment in nucleating pores. Both subject areas continued the applicants overarching research interest for the past 21 years in understand and predicting defect formation in casting processes. The resulting knowledge and the tools to apply this knowledge in an industrial setting will be of significant benefit to both the primary metal producers and manufactures of near-net-shape aluminum products. The primary outcome of this work, if successfully applied commercially, will be a reduction in the cost-to-cast, near-net-shape, aluminum products stemming from a reduction in product yield loss associated with pore formation. A secondary outcome will be the ability to expand the use of cast, near-net-shape aluminum products in applications that demand good fatigue performance thus increasing market opportunities for the Canadian foundry industry.