Putting Atoms Where they are Needed: Segregation for Property Control in Structural Alloys

从汽车到集成电路，工程师们找到不同的材料，以最好地利用它们的独特性能。结构合金的生产很少采用同样的优化策略，这似乎有些奇怪。尽管许多材料的性质与化学有很强的依赖性，但合金通常是通过将性质与平均化学相关联来设计的。认识到这是一个机会，我们的团队处于一个运动的前沿，其目标是在先进的表征和模拟工具的帮助下开发新兴的加工技术，将原子放在工程合金中需要的地方。这为新产品开发提供了突破，例如，利用强化原子迁移到材料薄弱点的自然趋势。除了在性能设计方面具有新的自由潜力之外，这种化学特定地点策略在资源可用性日益重要的情况下，可以更有效地利用昂贵和/或难以获得的合金元素。***为了实现这种特定位置的化学和性质控制，可以利用化学物质在金属中分离到界面（内部或外部）的自然倾向。在过去的5年里，应用这种方法，最近发明的“隔离工程”，自愈钢，低成本太阳能电池和光子金属纳米结构的转换效率得到了提高。***通过这条路线发展未来技术的瓶颈是我们对连续体模型的依赖，这些模型对合金界面固有的原子结构视而不见。这种预测复杂性的缺乏减缓了开发，并有可能在当前模型校准之外错过现有的新解决方案。虽然目前的原子模型对完美晶体的结构-性质关系很有价值，但没有一个很适合合金偏析，因为原子长度尺度和扩散时间尺度必须解决多组分化学。***本提案旨在通过部署我们小组最近首创的新模型来填补空白，该模型专门用于预测合金界面和缺陷的偏析。将该模型与实验程序相结合，我们将绘制界面上合金元素的偏析强化潜力，并揭示控制界面相变和形态不稳定性的基本过程。最终目标是利用本提案中开发的基本导向界面结构-性能关系，将这一策略应用于具有表面驱动功能的下一代高强度、轻质结构合金。

*** From cars to integrated circuits, engineers locate different materials to best exploit their unique properties. It may seem odd then, that the production of structural alloys rarely employs this same optimized strategy. Despite the strong chemistry dependence of many material properties, alloys are typically designed by correlating properties to average chemistry. Recognizing this as an opportunity, our group is at the leading edge of a movement whose aim is to develop emerging processing techniques aided by advanced characterization and simulation tools to put atoms where they are needed' in engineering alloys. This is providing breakthroughs in new product development by, for example, using the natural tendency of strengthening atoms to migrate to weak' points in a material. Beyond the potential for new freedom in property design, such a chemically site-specific strategy offers a more efficient use of expensive and/or difficult to source alloying elements at a time where resource availability is an increasingly important consideration.*** To achieve such site-specific chemistry and property control one can harness the natural tendency of chemical species to segregate to interfaces (internal or external) in metals. Applying this approach, recently coined segregation engineering', self-healing steels, improved conversion efficiency for low cost solar cells and photonic metallic nanostructures have been developed in the past 5 years. *** A bottleneck for the development of future technologies via this route is our reliance on continuum models that are blind to the inherently atomistic structure of alloy interfaces. This lack of predictive sophistication slows development and risks missing novel solutions existing outside of current model calibrations. While current atomistic models are valuable for structure-property relationships in perfect crystals, none are well suited for alloy segregation where atomistic length-scales and diffusional timescales must be resolved for multicomponent chemistries. *** This proposal seeks to fill the gap by deploying a new model, recently pioneered by our group, particularly designed for the prediction of segregation to alloy interfaces and defects. Integrating this model with an experimental program, we will map the segregation strengthening potential of alloying elements at interfaces and unravel the fundamental processes that control interfacial phase transitions and morphological instabilities. The ultimate goal is to deploy this strategy to revolutionize next generation high strength, lightweight structural alloys with surface driven functionality using the fundamentally guided interface structure-property relationships developed as part of this proposal.