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

从汽车到集成电路，工程师们寻找不同的材料，以最大限度地利用它们的独特性能。因此，结构合金的生产很少采用同样的优化策略，这可能看起来很奇怪。尽管许多材料的性能对化学有很强的依赖性，但合金通常是通过将性能与平均化学相关联来设计的。认识到这是一个机会，我们的团队处于一项运动的前沿，该运动的目标是开发新兴的加工技术，并借助先进的表征和模拟工具将原子放置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，通过利用加强原子的自然倾向来迁移到材料中的弱点。除了在物业设计方面有可能获得新的自由之外，在资源可用性日益重要的情况下，这种针对特定地点的化学策略提供了对昂贵和/或难以获得合金化元素的更有效的利用。 为了实现这种特定部位的化学和性质控制，人们可以利用化学物种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，应用最近发明的偏析工程的这种方法，自愈钢，提高了低成本太阳能电池的转换效率和光子金属纳米结构。 通过这条路线发展未来技术的一个瓶颈是我们对连续介质模型的依赖，这些模型对合金界面固有的原子化结构视而不见。这种预测复杂性的缺乏减缓了开发速度，并有可能错过当前模型校准之外的新解决方案。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，但没有一个模型很适合于合金偏析，在这种偏析中，多组分化学必须解决原子长度尺度和扩散时间尺度。 这项建议寻求通过部署一个新的模型来填补这一空白，该模型最近由我们的团队首创，专门为预测合金界面和缺陷的偏析而设计。将该模型与实验程序相结合，我们将绘制合金元素在界面上的偏析强化势图，并揭示控制界面相变和形态不稳定性的基本过程。最终目标是部署这一战略，利用作为本提案的一部分开发的基本指导界面结构-性能关系，使具有表面驱动功能的下一代高强度、轻质结构合金发生革命性变化。

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.