Development and characterization of lightweight alloys for next-generation automotive engines

目前汽车应用中铝合金开发的动力主要是由于政府立法要求汽车制造商显著提高新车的燃料效率。铝合金比铁合金轻约65%，因此在许多汽车应用中具有巨大的潜力。工业轻量化的另一个重点是开发先进的、低排量的、高功率密度的发动机。这种趋势经常要求动力系统部件的操作温度和压力增加，因此由于例如强度不足，使得许多目前使用的合金不适合于它们各自的应用。这两种趋势都导致了对高性能合金的需求，以及开发和测试新合金系统的需求。 基于Al-Si、Al-Cu以及Al-Ce系统的许多铝合金正在被开发，目的在于改进耐磨性、强度、可铸造性和降低成本。然而，这些合金的机械性能在很大程度上取决于所得的微观结构，这可能取决于微合金化添加和工艺变量。微观结构特征的变化导致不同合金的比较适用性测试结果的模糊性。 在这个发现计划中，我们将采取创新的方法来开发具有针对特定应用的机械性能的高性能合金。由于这些性能取决于合金成分和微观结构中存在的金属间相，为了研究相演变的动力学，该项目将包括使用FactSage软件进行凝固和冷却的热力学计算，实验热分析（DSC）和原位中子衍射（ND），用于相演变的真实的时间监测。FactSage和DSC分析可能无法提供足够的信息，由于纯理论平衡或Scheil近似的计算中的凝固模式的已知限制，而在DSC中检测到的热转化可能涉及到几个阶段的同时演变。这些缺点可以通过应用原位ND结合Rietveld分析来解决。 这种新的方法将允许研究微合金化添加剂可能对微观结构演变的具体影响，允许真实的时间监测单个固相的演变，这是只有ND分析才能获得的能力。本研究中使用的样品将进一步使用“更传统的”光学和SEM显微镜和XRD进行分析。 这项研究将为HQP提供制造和材料科学领域的实践和基础知识，并为最具挑战性的应用（如下一代发动机的气缸体和发动机缸盖）的先进轻质合金开发提供坚实的基础。

The current impetus in aluminum alloy development for automotive applications has been mainly due to government legislation requiring automotive manufactures to significantly improve fuel efficiency of new vehicles. Aluminum alloys are ~65% lighter than ferrous alloys, and therefore have a great potential to be used in many automotive applications. Another focus of lightweighting in the industry is to develop advanced, low-displacement, high power density engines. This trend frequently demands increased operating temperatures and pressures for powertrain components, therefore making many currently used alloys unfit for their respective applications due to, for example, insufficient strength. Both trends lead to demand for higher-performing alloys and the need to develop and test new alloying systems. Many aluminum alloys are being developed based on Al-Si, Al-Cu, as well as Al-Ce systems, aiming improved wear resistance, strength, castability, and lower cost. Mechanical properties of these alloys, however, largely depend on resulting microstructure, which may depend on micro-alloying additions and process variables. Variations in microstructure characteristics lead to ambiguity of results of comparative fitness-for-service testing of different alloys. In this Discovery program, we will undertake an innovative approach to the development of higher performing alloys with mechanical properties tailored to a specific application. As these properties are dependent upon alloy composition and intermetallic phases present in the microstructure, to study kinetics of phase evolution this project will include thermodynamic calculations of the solidification and cooling using the FactSage software, experimental thermal analysis (DSC), and in-situ neutron diffraction (ND) for real time monitoring of phase evolution. FactSage and DSC analysis may not provide sufficient information due to the known limits of either pure-theoretical equilibrium or Scheil approximation of the solidification mode in calculations, while the heat transformations detected in DSC may relate to simultaneous evolution of several phases. Such shortcomings can be addressed with application of in-situ ND coupled with Rietveld analysis. This novel approach will allow for studying specific effect that microalloying additions may have on microstructure evolution, allowing real time monitoring of evolution of individual solid phases, a capability only available with ND analysis. The samples used in this study will further be analyzed using “more traditional” optical and SEM microscopy and XRD. This research will provide HQPs hands-on and fundamental knowledge in the fields of manufacturing and materials science, and provide a solid foundation for advanced lightweight alloys development for the most challenging applications, such as cylinder blocks and engine heads for the next generation engines.