铜基异构纳米金属多层膜变形机制与加工硬化行为研究

This project is focused on the systematic investigation of the plastic deformation and the work hardening behavior in Cu-based nanostructured metallic multilayers with different crystal structures. The nanostructured crystalline/crystalline (FCC/BCC Cu/Mo and FCC/HCP Cu/Zr) and crystalline/amorphous (Cu/Cu-Zr) multilayers with equal layer thickness (h) spanning from 2 to 200 nm will be prepared on Si substrate, respectively. The traditional nanoindentation tests and microcompression methodology will be used to investigate the (strain) rate sensitivity of hardness/strength and mechanical response of all the three types of Cu-based nanostructured multilayers. With these mechanical measurements, the effects of (intrinsic and extrinsic) size, hetero-phase interface density and crystal structure as well as the external loading conditions on the mechanical properties and deformation modes of Cu-based nanostructured multilayers could be revealed, which permit the exploration of the deformation mechanisms and the physics of work hardening in metallic multilayers. Combining these experimental findings, a phenomenological dislocation-based model will be constructed to better describe the work hardening behaviors in metallic multilayers. Compared with the mechanics of monolithic constituent films, it is also expected that the experimental results would clearly elucidate the size effects and interface constraining effects with respect to the variation of layer thickness and interface density, to better understand the relationships of microstructure - dimensional constraint - performance of materials in a very fundamental way. The resuls would provide with the technological support to design nanoscale devices and materials with better reliability and higher performance.

本项目拟在刚性基体上分别制备组元层厚度(h)相等、调制周期(λ)系列变化（λ = 2h = 4 ~ 400 nm）的晶体/晶体（FCC/BCC型Cu/Mo、FCC/HCP型Cu/Zr）和晶体/非晶（Cu/Cu-Zr）Cu基异构纳米金属多层膜，采用纳米压痕法和微纳柱体压缩法测定表征Cu基纳米金属多层膜硬度/强度的(应变)速率敏感性及其力学响应，系统研究不同特征尺寸、界面密度和异型结构下纳米多层膜力学性能与变形方式随加载条件变化规律，探索Cu基金属多层膜宏观塑性的微观机制及其加工硬化行为的物理本质，尝试定量描述多层膜的硬化行为并建立相关理论模型。通过与等厚度各组元材料单质膜的力学行为对比，澄清纳米多层膜中层厚变化引起的尺寸约束和界面密度变化引起的界面约束效应，并揭示纳米金属多层膜微观组织结构-约束效应-服役性能之间的关系。为设计高可靠性与高性能纳米器件和材料提供技术支撑。

微纳尺度多层异质金属薄膜，已成为目前高性能微元器件以及互连结构的核心材料体系，其在复杂的微加工制备和随后的服役过程中的变形损伤是导致系统失效的关键因素。本项目将传统的材料科学与工程中微观组织-性能关系的二维研究空间拓展到微观组织-外观尺寸-性能关系的三维研究空间，系统研究了具有不同特征结构参数与界面结构/特性金属多层膜/微纳米柱体力学行为及其组元与尺寸效应，取得了以下三方面重要研究结果：.（1）研究了微纳尺度多晶组元材料（Cu、Ni、Zr等）薄膜力学性能的关联性与本征变形机制，探索了包含若干晶粒多晶微柱体中表面与界面及其耦合作用对于其力学特性的影响，阐明了纳米结构组元薄膜材料中孪生协调晶粒演化的微观机制，通过与纳米多层膜材料的力学特性对比发现了同质晶界/孪晶界与异相界面在塑性变形中的本质区别，揭示了金属多层膜与组元材料塑性变形特性随应变演化的微观机理，为深入理解结构材料的力学特性和变形过程提供了理论指导。. （2）研究了有/无孪晶界面的晶体/晶体Cu/X(X = Cr, Zr)与晶体/非晶Cu/Cu-Zr纳米金属多层膜/微柱体（调制比η = 1）的塑性变形特性（强度、应变速率敏感性与激活体积）与加工硬化行为及其内在/外观尺寸与界面效应，揭示了晶体/晶体与晶体/非晶金属多层膜/微柱体塑性变形的微观机制与加工硬化/软化的物理本质并阐明了二者变形行为的异同，归纳了不同界面结构的铜基多层膜塑性变形行为的一致性，提炼出晶体-非晶结构材料自韧化的微观机制与途径，构建/完善了基于尺寸与界面效应的金属多层膜显微结构-介观变形特性的相关理论模型。这一系列研究结果不仅为合理选择与调控金属多层膜组元材料微观结构、内在/外观特征尺寸提供了理论依据，也为优化多层膜材料的使役性能、提高微电子器件材料的服役寿命提供了参考，具有重要的工程应用价值。.（3）研究了的柔性基体Cu/X (X =Cr, Nb, Mo, Zr, Cu-Zr) 纳米金属多层膜拉伸性能与断裂行为及其尺寸效应，发现了纳米层状金属结构材料延性（与断裂韧性）的奇异性及延性-强度的尺度律，揭示了软相Cu层对硬相X层的异相约束效应机理，发展/建立了评价柔性基体金属多层膜的膜/基界面结合性能的新方法/新理论以及多层膜屈曲断裂行为的新判据，为其工程应用提供了实验证据和理论指导。