Subsurface Crystal Structural Evolution Mechanism of Single Crystal Coppers during Nano-indentation

Abstract

Abstract: 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.

Key words: nano-indentation, spherical harmonic function, subsurface damage, dislocation nucleation, crystal structure transformation

摘要： 为研究纳米压印中单晶铜亚表层晶体结构演变机理，采用分子动力学方法构建纳米压印仿真模型并模拟单晶铜纳米压印过程。采用改进的中心对称参数法分析单晶铜试件位错形核过程及缺陷演化机理，发现纳米压印时位错缺陷在压头下方形核并沿{1 1 1}滑移系向试件内部扩展形成堆垛层错，试件表面有原子台阶残留，试件亚表面损伤层存在V形位错等典型缺陷。针对位错形核区域及位错扩展区域材料晶体结构状态的识别，采用球谐函数法对模拟结果进行分析。由分析结果可知:位错形核区域材料晶体结构由FCC转变为排列更为紧密的HCP和ICO结构；位错扩展区域材料主要转变为DFCC结构。

关键词: 纳米压印, 球谐函数, 亚表层损伤, 位错形核, 晶体结构演变

CLC Number:

TP391.9

WANG Quanlong1;ZHANG Chaofeng1;WU Meiping1,2;CHEN Jiaxuan3. Subsurface Crystal Structural Evolution Mechanism of Single Crystal Coppers during Nano-indentation[J]. China Mechanical Engineering.

王全龙1;张超锋1;武美萍1,2;陈家轩3. 单晶铜纳米压印亚表层晶体结构演变机理[J]. 中国机械工程.

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