镍基合金源其在高温下展现出高强度、热稳定性、耐腐蚀性，使其成为航空涡轮叶片制造的首选型材。成形零件表面质量对工件服役性能至关重要，而具有纳米级表面形貌是提高表面质量的有效途径。镍基合金属于典型难加工材料，外力作用下，工件内部形成损伤区域，表现为间隙原子的点缺陷、位错的线缺陷、层错的面缺陷。实验研究工件塑性损伤，很难动态追踪结构的演化过程。分子动力学作为一种研究材料特性的重要方法，已被广泛用于研究切削加工中工件微观结构的变化。因此本文采用分子动力学模拟及其对照实验，深入研究材料去除机理、塑性变形机制以及亚表层损伤机理，以期为镍基合金加工表面质量提升和减少亚表层缺陷提供理论指导。

建立了单晶镍基合金纳米斜切模型。计算弹性常数和力学常数选取合适的势能函数，采取斜切方式探索材料的去除机制。分析了切屑和加工表面原子位移矢量，揭示了切屑的成形机制。追踪各层原子在加工过程的瞬时位置，统计每层原子的位移，得出了滞流层位置和未切削厚度。

建立了不同切削速度、切深、刀具半径的单晶镍基合金纳米切削模型。数值拟合揭示了侧流原子数与进给距离之间存在二次多项式关系。利用盒子中心邻域平均移动法获取了不同切深对应的温度和静水应力梯度云图，发现切深增加，温度云图的峰值增大，而峰值压缩静水应力却先增大后略有减小。理论计算了位错发射前后能量差与发射角的关系，揭示了最有可能的位错发射角度。研究了切削过程中工件缺陷演化瞬态图，揭示了工件缺损伤的成形机制，发现刀具半径增加促进更多FCC原子发生相态转变。

研究了不同晶体取向纳米切削单晶镍基合金表面形貌差异，并与单晶镍同等模型进行对比。分析不同晶体取向加工时的滑移机制，统计大位移原子数，表明{001}<100>晶向、 {011}<100>晶向、{111}<110>晶向镍基合金模型大位移原子数量大于单晶镍，而{221}<110>晶向、{310}<001>晶向却小于单晶镍。建立了对称倾侧晶界镍基合金纳米加工模型，依据局部熵值计算，揭示出Σ5{201}<112>模型原子排列有序性最好，而Σ3{112}<110>结构相对最不稳定。利用原子间距和空间角度分布，提出了计算表面原子畸变程度的方法，发现畸变程度最大的是Σ5{201}<112>，畸变程度最小的是Σ3{112}<110>。通过分析不同晶界对位错缺陷的阻隔效应，揭示了Σ9{221}<110>模型中晶界对缺陷跨越晶粒的阻隔效应最强，Σ3{112}<110>模型最弱。

研究了不同前角、刃半径、后角对多晶镍基合金纳米切削表面质量和亚表层损伤的影响，发现随着刀具前角由负转正，拉伸残余应力增加。刃半径增大，整体残余应力减小。后角增大，拉伸残余应力先增大后减小。晶界处存在位错网络，限制了位错的扩展以及晶粒内部的缺陷损伤。前角由负变为正，位错密度和相变原子总数减少。刃半径增加，位错密度也增加，相变原子总数先增加后减少。后角增大，位错密度呈现波动特征，相变原子数减少。

建立了同时含有γ和γ′相的双相多晶镍基合金纳米切削模型，依据表层滑移路径和大位移原子数分析，揭示了异相晶界对滑移的阻隔效应较强。计算晶粒迁移后表面原子畸变程度，显示γ′相原子的畸变程度要大于γ相。原子势能以及切削力延时的分析说明刀具切削晶界时导致晶界偏转和弯曲。分析位错和缺陷，发现γ相比γ′相更易发生位错激活和位错滑移。

进行了镍基合金纳米切削实验，发现了材料侧流现象。通过计算镍基合金的热物性常数与已有实验结果对照，并且针对镍基合金微纳米切削实验过程中特有现象对分子动力学模拟结果进行了验证。

Nickel-based alloys exhibit high strength, thermal stability, and corrosion resistance at high temperatures, making them the preferred profile for manufacturing aviation turbine blades. The surface quality of the formed parts is crucial to their service performance, and having a nanoscale surface morphology is an effective way to improve surface quality. Nickel-based alloys are typically difficult to machine materials. Under external forces, damage areas are formed inside the workpiece, manifested as point defects of interstitial atoms, line defects of dislocations, and surface defects of stacking faults. It is challenging to dynamically track the evolution process of the structure during experimental research on plastic damage of workpieces. Molecular dynamics, as an important method for studying material properties, has been widely used to study the changes in the microstructure of workpieces during machining. Therefore, this dissertation adopts molecular dynamics simulation technology and comparative experiments to deeply study the removal mechanism, plastic deformation mechanism, and subsurface damage mechanism during material removal process, in order to provide theoretical guidance for improving surface quality and reducing subsurface defects in efficient machining of nickel-based alloys. The main research work of this dissertation includes:

         The establishment of single crystal nickel-based alloy nano oblique cutting model has been made. To calculate the elastic constant and mechanical constant, select an appropriate potential energy function, and investigate the material removal mechanism through oblique cutting. The forming mechanism of chips was revealed by analyzing the displacement vectors of chips and machined surface atoms. In addition, the instantaneous positions of atoms in each layer during the machining process are dynamically tracked, and combined with the displacement statistics of each layer atom, the position of the stagnant layer and the uncut thickness are obtained. 

By employing various cutting speeds, depths, and tool radius, the nano-cutting model for single crystal nickel-based alloys was developed. Numerical fitting reveals a quadratic polynomial 

relationship between the number of lateral flow atoms and the feed distance. The box center neighborhood average moving method was used to obtain corresponding temperature and hydrostatic stress gradient cloud maps for different cutting depths. It was found that as the cutting depth increased, the peak value of the temperature cloud map increased, while the peak compressive hydrostatic stress first increased and then slightly decreased. The relationship between the energy difference before and after dislocation emission and the emission angle was determined through theoretical calculations, which revealed the most likely emission angle for dislocation. The transient evolution diagram of defects was studied during the cutting process, which revealed the forming mechanism of defect damage in the workpiece. It was found that increasing the tool radius would promote more FCC atoms to undergo phase transition.

The surface morphology differences were analyzed between nano-cutting single-crystal nickel-based alloys with differing crystal orientations and compared them to the same model made of single-crystal nickel. The slip mechanism was analyzed during processing with different crystal planes and orientations, and counted the number of large displacement atoms. The results showed that the nickel-based alloy model had a larger number of large displacement atoms in the {001}<100>, {011}<100>, and {111}<110>crystal orientations than single crystal nickel, while the {221}<110>and {310}<001>crystal orientations were smaller than single crystal nickel. The nickel based alloy nano-cutting model with symmetrical tilted grain boundaries was established, and based on the calculation of local entropy values, it was revealed that Σ5{201}<112> model has the best ordered atomic arrangement, while Σ3{112}<110> structure is relatively unstable. By utilizing the distance between atoms and the angular distribution in space, it is proposed to calculate the degree of distortion of surface atoms. It is found that the one with the highest degree of distortion is Σ5{201}<112>, the one with the smallest degree of distortion is Σ3{112}<110>. By analyzing the barrier effect of different grain boundaries on dislocation defects, it is revealed that the barrier effect of Σ9{221}<110> grain boundary on defect crossing grains is the strongest, Σ3{112}<110>is the weakest. 

The effects of different rake angles, edge radius, and flank angles on the surface quality and subsurface damage of nano-cutting polycrystalline nickel-based alloy was studied. It was found that as the tool rake angle changes from negative to positive, the tensile residual stress increases. With the edge radius increasing, the overall residual stress decreases. As the flank angle increases, the tensile residual stress first increases and then decreases. There is a dislocation network at the grain boundaries, which limits the extension of dislocations and the damage caused by defects inside the grains. The rake angle changes from negative to positive, and the dislocation density and total number of phase transition atoms decrease. With the increase of edge radius, the dislocation density also increases, and the total number of phase transition atoms first increases and then decreases. As the flank angle increases, the dislocation density exhibits fluctuating characteristics, and the number of phase transition atoms decreases.

The nano-cutting model simultaneously containing γ and γ′ was established for dual-phase polycrystalline nickel-based alloys. Based on the analysis of surface slip path and large displacement atomic number, it was revealed that the barrier effect of heterogeneous grain boundaries on slip is strong. The degree of distortion of surface atoms after grain migration was calculated, showing that after migration the degree of distortion of γ′ phase atoms should be greater than γ. According to the analysis of atomic potential energy and cutting force delay, cutting tools lead to grain boundary deflection and bending. The study of dislocations and defects shows that  γ compare γ′ more prone to dislocation activation and dislocation slip.

Through nickel-based alloy nano-cutting experiments, the atomic side flow phenomenon was discovered. By comparing the thermal property constants of nickel based alloys with existing experimental results, and validating the molecular dynamics simulation results against the unique phenomena in the micro nano cutting experiment of nickel-based alloys.