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

目前汽车用铝合金发展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油效率。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。业内轻量化的另一个重点是开发先进的、低排量、高功率密度的发动机。这一趋势经常要求动力总成部件的工作温度和压力更高，因此使许多目前使用的合金不适合其各自的应用，例如，由于强度不足。这两种趋势都导致了对更高性能合金的需求，以及开发和测试新的合金化系统的需要。*许多铝合金都是基于Al-Si、Al-Cu和Al-Ce系统开发的，目的是改善耐磨性、强度、铸造性能和降低成本。然而，这些合金的力学性能在很大程度上取决于所产生的显微组织，这可能取决于微合金化的添加和工艺变量。微结构特征的差异导致不同合金的比较适用性测试结果不明确。*在本发现计划中，我们将采取创新的方法来开发具有特定应用定制的机械性能的更高性能的合金。由于这些性能取决于合金成分和显微组织中存在的金属间化合物相，为了研究相演变动力学，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)和用于实时监测相演变的原位中子衍射(ND)。FactSage和DSC分析可能不能提供足够的信息，这是由于计算中的纯理论平衡或Scheil近似的已知限制，而DSC中检测到的热转变可能与几个相的同时演化有关。这些缺点可以通过应用原位钕结合Rietveld分析来解决。这一新的方法将允许研究微合金化添加对组织演变的特定影响，允许实时监测单个固相的演变，这一能力仅适用于ND分析。本研究中使用的样品将进一步使用“更传统”的光学显微镜、扫描电子显微镜和X射线衍射仪进行分析。*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，并为先进轻质合金的开发提供坚实的基础，用于最具挑战性的应用，如下一代发动机的气缸体和发动机盖。

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.