Chen Weihua, Zhang Shengbin, Bian Zhiao, Zheng Min, Chen Jiao, Zhu Zongxiao
School of Mechanical and Electrical Engineering, Lanzhou University of Technology, Lanzhou, 730050, China.
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, PR China.
J Mol Model. 2024 Dec 21;31(1):26. doi: 10.1007/s00894-024-06255-x.
This study employs molecular dynamics simulations to investigate the nanoscale tribological behavior of a single transverse grain boundary in a nickel-based polycrystalline alloy. A series of simulations were conducted using a repetitive rotational friction method to explore the mechanisms by which different grain boundary positions influence variations in wear depth, friction force, friction coefficient, dislocation, stress, and internal damage during repeated friction processes. The results reveal that the grain boundary structure enhances the strength of the nanoscale nickel-based polycrystalline alloy. When the friction surface is far from the transverse grain boundary, the grain boundary's obstructive effect is weaker, leading to larger ranges of atomic displacement and migration of internal defects. This results in smaller fluctuations in friction force and coefficient, along with the formation of numerous densely packed downward defect bundles. At the grain boundary, two grains undergo relative slip along the grain boundary interface, while atoms below the grain boundary remain largely unaffected. When the grain boundary is closer to the friction surface, more wear debris atoms accumulate in front of and on the sides of the friction grinding ball, increasing the friction force during the process. If the friction grinding ball breaches the grain boundary layer, its supporting and strengthening effects are diminished, leading to a significantly greater wear depth compared to when the grain boundary remains intact.
In this paper, nanoscale modeling was performed in the large-scale atomic/molecular parallel simulator simulation environment (LAMMPS). Three potential functions, namely EAM potential, Morse potential, and Tersoff potential, are used to simulate the interaction between atoms during the processing. The model was visualized and analyzed in three dimensions by Open Visualization Tool (OVITO).
本研究采用分子动力学模拟方法，研究镍基多晶合金中单个横向晶界的纳米级摩擦学行为。使用重复旋转摩擦方法进行了一系列模拟，以探索不同晶界位置在重复摩擦过程中影响磨损深度、摩擦力、摩擦系数、位错、应力和内部损伤变化的机制。结果表明，晶界结构增强了纳米级镍基多晶合金的强度。当摩擦表面远离横向晶界时，晶界的阻碍作用较弱，导致原子位移范围较大和内部缺陷迁移。这导致摩擦力和摩擦系数的波动较小，同时形成大量密集堆积的向下缺陷束。在晶界处，两个晶粒沿晶界界面发生相对滑动，而晶界下方的原子基本不受影响。当晶界更靠近摩擦表面时，更多的磨损碎片原子在摩擦磨球前方和侧面堆积，增加了过程中的摩擦力。如果摩擦磨球突破晶界层，其支撑和强化作用减弱，导致磨损深度比晶界保持完整时显著更大。
本文在大规模原子/分子并行模拟器模拟环境（LAMMPS）中进行纳米级建模。使用三种势函数，即EAM势函数、莫尔斯势函数和Tersoff势函数，来模拟加工过程中原子之间的相互作用。通过开放可视化工具（OVITO）对模型进行三维可视化和分析。
