Subsurface defect evolution and crystal-structure transformation of single-crystal copper in nanoscale combined machining

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.

KEYWORDS:

• Nanoscale combined machining
• subsurface defects evolution
• zoned phenomenon
• stacking fault tetrahedral
• growth oscillation phenomenon

Acknowledgments

This study was funded by a grant from the China Scholarship Council (No. 201808625035), the National Natural Science Foundation of China (No. 51865027); the Abroad Exchange Fund for Young backbone teachers of Lanzhou University of Technology; and the Hongliu First-class Disciplines Development Program of Lanzhou University of Technology.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability

For legal or ethical reasons, it is currently not possible to share the raw / processed data needed to replicate these findings.

Additional information

Funding

This work was supported by China Scholarship Council: [Grant Number No. 201808625035]; Lanzhou University of Technology; National Natural Science Foundation of China: [Grant Number No. 51865027].