各向异性纳米晶铜的超光滑加工表面形成机理的仿真与实验研究

Nanocrystalline Cu is a novel nanostructured material. The ultra-smooth machned surface of nanocrystalline Cu is of important significance for the fabrication of functional nanostructures by using the probe-based mechanical nanoscratching technique. Since the deformation mechanisms, mechanical response and material removal of individual single crystalline grains are varied with their grain crystallographic orientations, the nanoscratching of nanocrystalline Cu which typically involves multiple grains exhibits strong local anisotropic characteristic, giving the same magnitude of probe radius with grain size. Consequently, it’s difficult to achieve the global uniformity of the machined surface quality of nanocrystalline Cu. In this project, we perform molecular dynamics simulations to investigate the anisotropic nanoscratching mechanisms of nanocrystalline Cu, in conjunction with experimental validations: 1) Developing advanced post-processing algorithm to quantitatively distinguish different deformation mechanisms of nanocrystalline Cu; 2) Investigating the anositropic nanoscratching mechanisms of nanocrystalline Cu and the influence on its initial properties by means of molecular dynamics simulations, and subsequently establishing the prediction models of the friction coefficient and the materials pile up of nanocrystalline Cu under nanoscratching; 3) Performing mechanical nanoscratching experiments of nanocrystalline Cu to validate the prediction model obtained from molecular dynamics simulations. The research work presented in this project will establish prediction models of the friction coefficient and the materials pile up of nanocrystalline Cu that can be used to refine the machinability of the material and the machined surface quality, which is thus of significant theoretical importance and practical value for guiding the achievement of ultra-smooth surface of nanocrystalline Cu by using the probe-based mechanical nanoscratching technique.

纳米晶铜是一种新型纳米结构材料，获得其超光滑加工表面对于使用微探针纳米机械刻划加工技术制造功能表面纳米结构具有重要意义。由于针尖半径与晶粒尺寸在相同量级，而不同晶体取向的晶粒其变形机理、机械响应与材料去除方式均不同，致使纳米晶铜在刻划加工中呈现局部各向异性的特性，难以获得整体均匀的加工表面质量。本项目采用分子动力学仿真方法研究纳米晶铜的超光滑加工表面形成机理并开展实验验证：（1）开发定量辨别纳米晶铜的不同微观变形机理的分子动力学仿真数据后处理算法；（2）使用分子动力学仿真方法研究纳米晶铜的各向异性纳米加工变形机理及其对原材料特性的影响，建立纳米晶铜的摩擦系数和材料堆积的预测模型；（3）开展纳米晶铜的纳米机械刻划加工实验并验证预测模型。本项目将获得用于调控纳米晶铜加工性能和加工表面质量的预测模型，对于指导使用微探针纳米机械刻划加工技术获得纳米晶铜的超光滑加工表面具有重要的理论意义与实用价值。

纳米晶铜是一种新型的纳米结构材料，研究其金刚石微探针纳米机械刻划加工机理对于制造功能表面纳米结构具有重要意义。由于针尖半径与晶粒尺寸在相同数量级，而具有不同晶体取向的单晶晶粒其变形机理、机械响应与材料去除方式均不同，致使纳米晶铜在纳米机械刻划加工中呈现出各向异性的特性，难以获得均匀的加工表面质量。本项目采用分子动力学仿真方法研究纳米晶铜的各向异性纳米机械刻划加工机制并开展实验验证：（1）分别从自由表面、位错运动、孪晶变形和晶界变形四个方面研究来定量辨别纳米晶铜的不同微观变形机理，为深入研究纳米晶铜的加工变形机理提供了可靠的技术支撑；（2）获得了晶体铜的刻划加工机理：单晶铜的加工变形主要由位错形核及滑移来主导，双晶铜的加工变形由位错-晶界相互作用及位错机理共同作用，多晶铜的加工变形由位错机理、位错-晶界相互作用、晶界机理及孪晶变形共同作用，不同变形模式存在激烈的竞争，导致晶体铜加工变形呈现出强烈的各向异性加工特性，为晶体铜的纳米加工机理提供了新内涵；（3）获得了刻划深度、刻划次数、刀具几何参数、晶界结构和晶粒尺寸等工艺参数对晶体铜刻划过程的影响规律，并据此初步建立了综合考虑本征参数和非本征参数的加工预测模型，为优化晶铜铜纳米机械加工工艺提供了理论依据；（4）开展了纳米晶铜的纳米机械刻划加工的实验，研究了刻划次数、微探针方向、晶体取向等工艺参数对纳米刻划加工的影响，实验结果与仿真结果吻合较好，证明了当前开展分子动力学仿真的有效性和高精度，为使用分子动力学仿真研究纳米加工过程提供了重要的证据。本项目的研究将获得用于调控加工表面质量的摩擦系数和材料堆积的预测模型，对于指导纳米晶铜的金刚石微探针纳米机械刻划加工具有重要的理论意义与实用价值。