Fracture and Stability of Metallic Nanotwinned Structures

技术摘要：过去几年的研究提供了令人信服的证据，证明与纳米晶和细晶金属相比，纳米孪晶金属具有非凡的性能。其中一些增强的性能包括超高屈服强度、高延展性、良好的导电性和高应变率敏感性。这些特性使得纳米孪晶金属在结构应用方面具有极大的吸引力。该项目的目的是通过有重点的实验和计算模拟工作，对纳米孪晶金属的稳定性和断裂机制提供定量的见解。这些关键问题如果得不到解决，将限制这些纳米结构金属和合金的实际应用，这主要是由于对最佳性能的实现和稳定性的担忧。为此，该项目的具体目标是调查孪晶界面在纳米孪晶金属的脆性和延性响应中的作用，并研究孪晶界面的中介过程，如孪晶-孪晶相互作用和孪晶界面处的裂纹/缺陷形核，以便预测实现纳米孪晶金属最佳性能的临界孪晶片层厚度。非技术摘要：拟议的研究有望对纳米结构金属科学和技术的几个重要领域产生影响，为控制其行为的变形机制提供有价值的见解。特别是，它将提供对纳米晶和纳米孪晶金属的最佳结构性能的定量了解，涉及诸如强度、延展性、稳定性和断裂机制等关键问题。这一统一的实验、建模和制造工作的最终目标是开发批量合成纳米孪晶金属的工艺路线，以实现其作为下一代结构材料的潜力。拟议的研究还将有助于通过教育和外联努力丰富社区。参与该项目的研究生和本科生将在纳米力学和计算材料科学的多学科领域奠定坚实的基础。此外，通过该项目取得的科学进展将被纳入研究人员在其机构制定的课程。

TECHNICAL SUMMARY: Research over the past few years has provided compelling evidence for the extraordinary properties of nanotwinned metals as compared to their nanocrystalline and fine-grained counterparts. Some of these enhanced properties include ultra-high yield strength, high ductility, good electrical conductivity, and high strain rate sensitivity. Such characteristics make nanotwinned metals highly attractive materials for structural applications. The aim of this project is to provide quantitative insight into the stability and fracture mechanisms in nanotwinned metals by way of a focused experimental and computational modeling effort. These critical issues, if unaddressed, would limit the practical application of these nanostructured metals and alloys, largely due to concerns over the achievement and stability of optimal properties. To this end, the specific objectives of the project are to investigate the role of twin boundaries in the brittle versus ductile response of nanotwinned metals and to study twin boundary-mediated processes such as twin-twin interactions and crack/defect nucleation at twin boundaries, in order to predict the critical twin lamella thickness for optimal performance of nanotwinned metals.NON-TECHNICAL SUMMARY: The proposed research is expected to have an impact on several important areas of nanostructured metal science and technology by way of providing valuable insight into the deformation mechanisms governing their behavior. In particular, it will provide a quantitative understanding into the optimal structural performance of nanocrystalline and nanotwinned metals, with regards to critical issues such as strength, ductility, stability, and fracture mechanisms. The ultimate goal of this unified experimental, modeling and manufacturing effort is the development of processing routes for bulk synthesis of nanotwinned metals, which would realize their potential as next generation structural materials. The proposed research would also contribute to the enrichment of the community through education and outreach efforts. Graduate and undergraduate students working on the project, would develop a strong foundation in the multidisciplinary areas of nanomechanics and computational materials science. In addition, the scientific advances made through this project would be integrated into the coursework developed by the investigators at their institutions.