仿生多级砖-墙结构金属涂层制备及多尺度强韧机理研究

Aim to the functional demand of resistance to wear and to contact induced damage for the load-bearing mechanical components, the bi-layer coating with anti-wear outer-layer and inner-layer of high strength and toughness is designed from the inspiration of the microstructure of the load-bearing biomaterials. In the present proposal, the following points will be investigated: In terms of the technology of flexible metallic cloth, the process of fabricating the inner layer with hierarchically staggered “brick- and-mortar” microstructure and the outer layer with uniform distribution of hard phase will be established. Based on the testing of macro\micro wear, the relationship between the wear resistance and particle size and content of the hard phase will be discussed, and the micro-mechanism of the wear will be analyzed by means of nanoscratch testing. On the basis of the macro strength and toughness from the micro three point bending and compact tension specimens, finite element analysis and the crack propagation in the two hierarchically staggered structure, the study of the multiscale strengthening and toughening mechanisms would be analyzed. In order to optimize the microstructure of the coating, the effect of the microstructure parameters (e.g. size, hierarchy and stagger) of the inner layer on the combination of strength and toughness is investigated, and the Ashby diagram of strength and toughness will be plotted. The findings of this project are believed to provide a novel way for the fabrication of the coating on the load-bearing mechanical component, in order to increase the service lifetime of the coating.

针对承载机械构件的耐磨、抗接触损伤的功能要求，仿制承载生物材料的微结构特征，构建表层耐磨、内层强\韧性优异的双层涂层，本研究主要包括以下内容： 利用“柔性金属布”的涂层制备技术搭建硬质相骨架，研究形成多级错列“砖-墙”微结构分布的内层涂层、硬质相均匀分布的外层涂层的制备工艺。通过宏、微观摩擦磨损测试，建立外层硬质相粒径尺寸和含量与宏观耐磨性的关联，并结合纳米划痕实验分析微观机理。基于微三点弯和紧凑拉伸试样表征内层涂层的宏观强度和韧性；利用纳米压痕测试微观力学性能并建立该有限元模型，分析内部应力应变分布；结合原位扫描电镜观察裂纹在多级错列涂层微结构中的扩展规律，分析涂层强韧化机理。利用“强度-韧性双坐标Ashby图”，研究不同微结构参数（尺寸、层级、错列等）对内层涂层的强度和韧性综合性能的影响，优化涂层微结构参数。本项目可望为承载机械构件表面涂层的构建提供新的思路，提升涂层的服役寿命。

本项目开展以仿生金属涂层制备及性能优化为目标，在仿生梯度涂层及强化层的制备工艺、涂层及强化层的宏微观力学性能探究、以及微纳米力学性能测试方法等方面取得了一些有影响的研究成果，基于柔性布成型技术制备了梯度合金涂层，试验和模拟结合证明了梯度晶有利于氧原子扩散的事实，澄清了梯度晶区别于均匀粗晶的扩散机制；分析了仿生梯度涂层的耐磨性得到提升的规律，建立模型量化讨论了疲劳致梯度强化层晶粒生长和残余应力释放关系，建立微纳结构微纳疲劳测试方法，澄清了细晶粒有助于提升疲劳裂纹萌生寿命的内在规律。获基金资助发表论文12篇，部分成果支持了2017年上海市科技进步一等奖，项目负责人还获得2018年Journal of Manufacturing Processes杰出审稿贡献奖。受聘担任中国机械工程学会材料分会青年工作委员会副秘书长、美国TMS学会纳米力学材料行为委员会和材料力学行为委员会委员（Committee member）、中国机械工程学会摩擦学分会第十三届青工委委员。