纳米压痕诱导单晶铜弹塑性变形分析与破坏机理研究

Analysis of Elastic-Plastic Deformation Behaviors and Failure Mechanisms for Single Crystal Copper Induced by Nanoindentation

目的从微观角度实现对微机电系统中微器件局部接触区域弹塑性演化过程和原子迁移演变规律的探寻。方法运用经典分子动力学法,基于EAM和Morse混合势函数,对硬质金刚石探头与软质金属铜基底展开纳米压痕接触特性研究。结果纳米压痕中位错环构型生成与演变有规可循,位错环在受载荷影响时,有着4个演变阶段,即位错环萌芽期→生长期→繁衍期→维持期。当载荷达到一定程度时,压痕中铜基质内密排六方结构的HCP容易与附近类似结构发生关联耦合效应,产生刃型位错和形成螺旋式位错结构,随后以脱落方式构成棱柱形位错结构,并向基底底部发射。另外,整个纳米压痕中,铜基质亚表面损伤最为严重,探头与基底接触区域两侧的位错环迁移处应力较集中。结论纳米接触中铜基质内位错环出现与演变过程,是衡量局部接触塑性变形强弱程度的重要依据和非接触区域损伤程度的内在表现。此次研究结果对细观尺度接触变形行为有着深层次认识,也对纳尺度设计出优异摩擦学性能的微结构有着重要借鉴作用。

The paper aims to investigate the elastic-plastic deformation behaviour and the evolution of atomic migration in the local contact region of micro devices in micro electro-mechanical system(MEMS)from microscopic perspective.Therefore,it was studied that the deformations between sphere diamond probe and soft metal copper based on the mixed potential function of EAM and Morse by using the classical molecular dynamics method.It was found that the evolution of dislocation ring under loading process showed an interesting micro phenomenon that there were four stages on the evolution of dislocation ring was observed obviously,namely formal stage→growth stage→reproduction stage→maintenance stage.Furthermore,the arranged hexagonal structures were easily to take place the strong coupling effect around it,which resulting the configuration structure of edge dislocation and spiral dislocation were formed and emitted to the bottom of the base finally as loading exceed a certain point.In addition,the subsurface damage of copper bases became more serious than other places under nanoindentation process,followed by the migration and evolution of dislocation loops on both sides of the contact area between the probe and the substrate.The occurrence and evolution process of dislocation ring in copper bases has significance response features to measure the strength of plastic deformation on local contact region,and also is a good way to represent the intrinsic manifestation of subsurface damage on nano-contact area.This research results will have deeply insight on micro-scale contact deformation behaviors and plays an important role in designing micro-structures with excellent tribological properties.