Strength at the nanoscale: fundamental mechanisms of plasticity in nano-structured materials

金属合金在工程上的应用在很大程度上是因为它们的高强度。最近，材料科学家发现，这种强度被所谓的纳米结构材料进一步增强。这些通常是与传统金属相同的合金，但具有细化到纳米尺度的特殊微观结构特征。然而，人们发现，纳米结构材料中控制强度和延展性的主要机制与传统材料不同。尽管这种新物理还没有被很好地理解，但它发生在现代原子模拟和纳米实验都能达到的长度尺度上。它是一种独特的制度，可以在模拟和实验之间建立直接联系。人们认为，强度在几乎每一种应用中都是至关重要的。使材料变得更坚固意味着我们可以使结构更轻、更节能、更安全或更快。这些应用范围从体育用品到节能型汽车到飞机。甚至在微电子等非结构应用中也是如此。改进的强度可以提高电路的健壮性，或者允许进一步减小芯片尺寸。他说，拟议的工作将利用先进的计算机建模技术，最近的进展使“虚拟材料实验室”成为可能。有了这些工具，可以进行详细的“虚拟实验”来测试材料，从而实现在真实实验中通常不可能实现的控制和详细程度。我们还可以研究可能并不实际存在的模型材料。但提供关于真实材料中重要特征或机制的假设的直接测试。他说，这种建模的目标是解开强度和延展性机制的细节，特别是确定传统材料和纳米结构材料在行为上的关键差异。最终，这项研究将有助于指导具有更高机械性能的材料的设计。

Metallic alloys are useful for engineering applications largely due to their high strength.  Recently, materials scientists have discovered that this strength is further enhanced by so-called "nano-structured materials".  These are often the same alloys as conventional metals, but with special microstructural features refined to the nanometer-scale.  One finds, however, that the primary mechanisms governing strength and ductility are different in nano-structured materials than in conventional ones.  This new physics is not well understood, but occurs on length scales accessible to both modern atomistic simulation and nano-experiments.  It is a unique regime where a direct link between simulation and experimentation is possible.       Strength is of fundamental importance in almost every application.  Making a material stronger means we can make structures lighter, more energy efficient, safer, or faster.  Applications range from sporting goods to fuel-efficient cars to aircraft.  Even in non-structural applications like micro-electronics, improved strength can improve the robustness of the circuitry or permit further reductions in chip sizes.     The proposed work will make use of advanced computer modeling techniques, where recent progress makes possible a "virtual materials laboratory".  With these tools, detailed "virtual experiments" can be performed to test materials, permitting a level of control and detail that is often impossible to achieve in a real experiment.  We can also study model materials that may not actually exist, but provide a direct test of hypotheses regarding important features or mechanisms in real materials.       The goal of this modeling is to unravel the details of the mechanisms of strength and ductility, and specifically to determine the key differences in behaviour between conventional materials and nano-structured materials.  Ultimately, the research will help guide the design of materials with improved mechanical properties.