超硬纳米多层膜微结构与力学性能及其优化

Tougher and tougher requirements are brought forward for tool and mould materials due to the rapid development of the manufacturing and processing industries, such as super-hardness, high heat-resistance, excellent anti-wear capability, high strength and toughness, and long life. Super-hard nano-multilayer coatings, as a kind of promising materials that may satisfy the above requirements, have been receiving increasing attention. In this project, the fundamental mechanical properties and the failure patterns of super-hard nano-multilayer coatings with typical material combinations, as well as the effects of modulation parameters and the environmental and loading conditions, are to be studied with a multi-scale approach, including the first principle calculation, molecular dynamics analysis, nano-structural characterization, and in-situ testing of the mechanical properties. The effects of the principal influencing factors on the mechanical properties of super-hard nano-multilayer coatings and their action mechanisms, the mechanisms of hardening, and the effects of different patterns of defects and doped elements, are to be investigated. The characterization of the deeper-level microstructures, and the quantitative relationships between the microstructure based on multi-scale analyses and the macroscopic mechanical properties, are to be established. The trans-scale approach spanning atomic and continuum analyses and the methods for the testing of mechanical properties of a coating and multi-layer-coatings are to be developed, to provide the preperation of nano-multilayer coatings, the evaluation and prediction of their mechanical properties with mechanics support. The macroscopic constitutive modeling and the corresponding analytical approach, taking into account the effects of atomic structures and nano-scale properties, are to be developed for practical engineering applications.

制造和加工业的迅猛发展对刀具和模具材料提出了超硬、耐磨、耐热、强韧、寿命等要求。超硬纳米多层膜以满足上述要求的优良力学性能和可设计性使其作为最富前景的刀具涂层材料受到极大关注。拟针对超硬纳米多层膜材料，采用基于第一性原理计算、分子动力学分析、纳观组织结构解析及原位纳米力学性能测试相结合的方法研究不同调制参数和服役条件下典型材料组合类型纳米涂层及多层膜的基本力学特性及失效形式，明确主要影响因素及其作用机理；揭示超硬纳米多层膜的硬化机制、不同类型缺陷和机能元素掺杂等对多层膜特性及失效机理的影响，建立深层次微结构的表征和基于多层次认识的材料微结构与其宏观性能间的定量关联。发展原子—连续介质跨尺度分析的分析方法和涂层及多层膜力学特性的新测试方法；为多层膜材料的制备、力学性能的评价和预测等提供力学支撑。建立计及原子结构和纳观特性的超硬纳米多层膜材料宏观特性分析方法和本构模型，为其实际应用提供依据。

现代制造和加工业对刀具、工具和模具表面的强度、硬度、耐磨性和寿命等提出了日益严苛的要求，超硬纳米多层膜(HNMLC)以具有满足上述要求的优良力学性能和可设计性使其作为最富前景的涂层材料备受关注。本项目围绕HNMLC的致硬机理开展研究，取得了重要的研究进展。. 在界面特性方面，制备了若干超硬纳米多层膜，分析了界面共格特征；获得了硬度与调制参数间的关系；发现了金刚石/立方氮化硼组合的新的界面匹配模式和界面特性,拓展了其可能的应用前景。采用第一性原理计算分析了HNMLC界面的原子构型、电子态、化学键和电荷分布，明确了模版效应及其作用范围。. 在塑性变形机理方面,将能预言滑移系开动次序的广义层错能作为确定势函数及其参数的必要约束,构建并优化了典型硬质陶瓷的势函数。发展了基于MD模拟的硬质陶瓷力学特性的分析方法；揭示了不同硬质陶瓷在压痕过程中的微结构变化和缺陷运动，明确了B1、B3和B4结构硬质陶瓷塑性变形的主要机制主要有位错滑移和不全滑移，孪生和相变。. 在孪晶HNMLC的致硬机理方面，分析了微结构与孪晶界面的相互作用导致的强弱化及影响因素，揭示了孪晶界对提升硬质陶瓷力学性能的作用及相关的强弱化机理，得到了多层膜硬度随孪晶厚度间的变化规律；明确了该变化规律与金属孪晶多层膜的差异及原因。对同为B3结构的金刚石和硅纳米孪晶的剪切特性与微结构的分析表明，glide-set面的不全滑移引起的退孪可解释孪晶金刚石强度与延性的极大提高，而孪晶硅以shuffle-set面上的全滑移为主导不能引起退孪。对纳米孪晶金刚石/立方氮化硼孪晶受剪特性的研究亦显示了其超高的强度和延性。. 在纳米多晶硬质陶瓷的晶粒尺寸效应、不同类型缺陷和掺杂对多层膜特性及失效机理的影响，计及不同强弱化机理的强硬化描述，非弹性变形及损伤的微-宏观模型的构建及微宏观关联等方面的研究也取得了良好的进展。结果可为高性能多层膜涂层的设计、优化和性能裁剪等提供力学支撑，为其实际应用提供依据。