单晶铜纳米压印亚表层晶体结构演变机理

To investigate the subsurface crystal structure evolution mechanism of single crystal coppers in nano-indentation, molecular dynamics method was used to construct the simulation model of nano-indentation and realize the simulation of nano-indentation processes.The improved center symmetry method was used to analyze the dislocation nucleation processes and defect evolution mechanism of single crystal copper specimens.It is found that the dislocation defect nuclear is under the indenter, extend along the {1 1 1} slipping system to the internal of specimens, and the stacking faults are formed.The atomic steps are remained on the surfaces of specimens, and typical defects exist in subsurface damage layers of the specimens, such as V-shaped dislocation.Aiming at recognizing crystal structural status of the dislocation nucleation areas and dislocation extension areas of the specimens, the spherical harmonic function method was used to analyze the simulation results.The analysis results show that the material crystal structure is arranged from FCC(face-centered cubic) to HCP(hexagonal close-packed) and ICO(icosahedron) structure which are more closely in dislocation nucleation areas, and the crystal structure is arranged from FCC to DFCC(deformed face-centered cubic) structure in dislocation extension areas.