Fundamentals of grain coalescence and applications to aluminum alloy industrial solidification processes

晶粒聚结基础及其在铝合金工业凝固过程中的应用

• 批准号: RGPIN-2016-03656
• 负责人: Phillion, Andre
• 金额: $ 2.04万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=708405
• 关键词: Fundamentals; grain; coalescence; applications; aluminum

Near-net-shape casting provides the most cost-effective way to manufacture light metal alloy components of complex shape. However, casting defects such as hot tearing reduce product quality and process efficiency. Hot tearing is characterized as a spontaneous failure of semi-solid metallic alloys due to the rupture of liquid films between grains, and occurs near the end of solidification where deformation becomes localized to the grain boundaries. The occurrence of hot tearing is intimately linked with the semi-solid's gradual evolution from isolated grains surrounded by liquid to a coherent and percolated solid network, a process known as grain coalescence. If grain coalescence is retarded and therefore finishes at lower temperatures, hot tearing susceptibility is significantly increased. The objective of this Discovery Grant research program is to develop new knowledge of the process of grain coalescence, followed by application of the new knowledge to improve the quality of high-strength Al-Cu casting alloys that are used in the automotive and aerospace sectors. Over the next 5 years, my research team will utilize experimentation and simulation to quantify the influence of alloy content and processing parameters on the dynamic evolution of grain coalescence, and the impact of this process on semi-solid constitutive behaviour and hot tearing. Through this research, 7 HQP will be trained in developing processing/structure/defect phenomenological models, and in applying these relationships within mathematical models of aluminum alloy casting processes. Research Approach: As a first step, a numerical model will be developed to predict grain coalescence. Concurrently, model materials with known microstructure will be created and then used as part of in-situ (restrained casting tests) and ex-situ (semi-solid tensile tests) characterization of the coalescence transition. Then, the experimental and numerical results will be used to propose a constitutive law of semi-solid mechanical behaviour based on the dynamic evolution of coalescence. Finally, the new tools will be applied to a finite element simulation of the sand casting process used to produce components made from B206 (an industrial Al-Cu casting alloy) for a tidal turbine application to demonstrate the improved ability to predict hot tearing in an industrial process. Industrial Impact: Hot tearing is a major defect that lowers the productivity of aluminum alloy casting and wrought products. In many cases (e.g. high reliability complex shape castings), products cannot even be manufactured because of the high occurrence of this defect. The results of this research are anticipated to lead to a greatly improved understanding of coalescence and hence hot tearing, and will provide a predictive tool for use by industry in macro-scale process simulations of Al-Cu castings.

近净形铸造为制造形状复杂的轻金属合金部件提供了最经济有效的方法。然而，热撕裂等铸造缺陷降低了产品质量和工艺效率。热撕裂的特征是半固态金属合金由于晶粒之间的液体膜破裂而自发失效，并发生在凝固结束时变形局部化到晶界的地方。热撕裂的发生与半固体从被液体包围的孤立颗粒逐渐演变成一个连贯和渗透的固体网络密切相关，这一过程被称为颗粒聚结。如果晶粒聚结延迟，因此在较低温度下完成，则热撕裂敏感性显着增加。