ABSTRACT In the paper, molecular dynamics simulation is applied to study the evolution and distribution of subsurface defects during nanoscale machining process of single-crystal copper. The chip-removal mechanism and the machined-surface-generative mechanism are examined through analysis of the dislocation evolution and atomic migration of the workpieces. The findings show that under different stresses and temperatures, the difference of the binding energy leads to a zoned phenomenon in the chip. Owing to elastic deformation, some of the dislocations could be recovered and form surface steps; moreover, the work hardening of the workpiece can be achieved on account of generation of twin boundaries, Lomer-Cottrell dislocations, and stacking fault tetrahedra (SFT) by plastic deformation. A process of evolution of an immobile dislocation group containing stair-rod dislocations into SFT is discovered, which is different from the traditional Silcox-Hirsch mechanism. Furthermore, a growth oscillation phenomenon, which corresponding stacking fault planes growth and retraction during the formation of the stable SFT, is discussed.

中文翻译：

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单晶铜纳米复合加工亚表面缺陷演化及晶体结构转变

摘要 本文应用分子动力学模拟研究了单晶铜纳米加工过程中亚表面缺陷的演变和分布。通过分析工件的位错演化和原子迁移，研究了切屑去除机制和加工表面生成机制。研究结果表明，在不同的应力和温度下，结合能的差异导致芯片中出现分区现象。由于弹性变形，一些位错可以恢复并形成表面台阶；此外，由于塑性变形产生孪晶界、Lomer-Cottrell 位错和堆垛层错四面体 (SFT)，可以实现工件的加工硬化。发现了一个包含楼梯杆位错的固定位错群向SFT的演化过程，这与传统的Silcox-Hirsch机制不同。此外，还讨论了在稳定 SFT 形成过程中相应的堆垛层错面生长和收缩的生长振荡现象。