界面结构对小周期金属多层膜塑性变形机理的影响

Recently, the tendency of new functional materials and devices to be miniature, integrated and laminated makes the mechanical behavior of those materials in nanoscale a key scientific issue for the development of the multilayers and devices. This project is to study the effects of the interfacial structure on the plastic deformation mechanisms of metallic multilayers with a periodicity of a few nanometers. We will prepare Cu/Ni nanoscale multilayers with coherency interfaces and Cu/Nb nanoscale multilayers with incoherency interfaces via electron beam evaporation deposition in high vacuum, adjust interfacial structure by controlling depostion process, investigate plastical deformation behavior of those nanoscale metallic multilayers by nanoindentation under different conditions and observe deformation character in the plastic deformation zones through transmission electron microscopy (TEM),scanning electron microscopy (SEM) and focused ion beam (FIB) . Through this project, we are going to discuss the role of interfacial structure on the plastic deformation behavior of metallic multilayers with a periodicity of a few nanometers, develop a fundamental understanding of the plastic deformation mechanisms in nanoscale metallic multilayers with different interfaical structure, and provide valuable insights into the development of various artificial layer structures and functional laminated materials.

近年来，新型功能材料及器件向小型化、集成化和复合化发展的趋势，使得尺寸在纳米量级的层状材料和柔性多层器件在使用过程中的服役行为成为其发展的关键科学问题。本项目研究界面结构对小周期金属多层膜塑性变形机理的影响，采用超高真空电子束蒸发镀膜工艺制备具有共格界面结构的Cu/Ni和具有非共格界面结构的Cu/Nb纳米多层膜，通过控制镀膜工艺过程调整界面结构，利用纳米压痕技术研究不同界面结构纳米多层膜在不同加载条件下的塑性变形行为，利用汇聚离子束系统、扫描电镜、投射电镜观察压痕区域的塑性变形特征，探讨界面结构在金属多层膜塑性变形行为中的作用，阐明周期在几个纳米尺度范围时，具有不同界面结构的金属多层膜的塑性变形机理，为各种不同人工结构和功能的多层膜材料的发展提供科学依据。

气相沉积金属多层膜能够在纳米尺度范围准确控制各层厚度和界面结构，非常适宜于用来研究多层膜的力学性能和塑性变形机理。本项目采用物理气相沉积法制备了Cu/Ni、Cu/Nb、Cu/Zr和Cu/Ti纳米多层膜，通过真空退火工艺调控纳米多层膜的界面结构，研究了界面结构对金属多层膜力学性能和塑性变形机理的影响，为各种不同人工结构和功能的多层膜材料的发展提供科学依据。.研究结果表明，随周期减小，Cu/Ni和Cu/Nb纳米多层膜的界面共格程度增大。Cu/Ni纳米多层膜在小周期可形成共格界面，Cu/Nb纳米多层膜在小周期可形成半共格界面。400℃真空退火后，Cu/Ni纳米多层膜的共格界面结构可转变为半共格界面结构，Cu/Nb纳米多层膜的半共格界面结构可转变为非共格界面结构。Cu/Zr和Cu/Ti纳米多层膜在小周期仍具有非共格界面结构。.界面共格程度是影响小周期Cu/Ni和Cu/Nb纳米多层膜强度的主要因素。Cu/Ni纳米多层膜的强度在周期为4nm时达到最大值2.49GPa，与界面上的共格应力相等；Cu/Nb纳米多层膜的强度在周期为5nm时达到最大值3.03GPa，接近其理论界面强度。400℃真空退火处理减小了小周期Cu/Ni和Cu/Nb纳米多层膜界面的共格程度，导致强度显著减小。.纳米多层膜的弹性模量与界面处的应力状态有关，受界面结构的影响。Cu/Ni和Cu/Nb纳米多层膜的弹性模量均超过了弹性模量平均值，并随界面共格程度增大而增大。具有非共格界面结构的Cu/Ti纳米多层膜在小周期出现弹性模量下降。400℃真空退火处理后，小周期Cu/Ni和Cu/Nb纳米多层膜界面的共格程度减小，弹性模量随之减小。.纳米多层膜的应变率敏感性受层内晶粒尺寸和界面结构两个因素的影响。Cu/Ni纳米多层膜的非共格界面密度和层内晶粒尺寸随周期减小同时减小，m值随周期减小而增大；具有层状结构的Cu/Zr纳米多层膜的非共格界面密度随周期减小而增大，m值随周期减小而减小；对Cu/Nb纳米多层膜来说，周期减小引起的非共格界面密度增大和层内晶粒尺寸减小对m值的影响相互抵消，m值随周期减小基本保持不变。