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。

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.