单晶铜纳米压痕的取向效应和尺寸效应研究

Study on Orientation Effect and Size Effect of Single Crystal Copper Nanometer Indentation

采用离散位错动力学法(DDD)以及晶体塑性有限元法(CPFEM)对单晶(001)、(011)和(111)晶面进行纳米压痕模拟研究。分别分析了载荷-位移曲线、弹性模量、纳米硬度以及弹性回复率与晶粒取向和压入深度的关系。DDD和CPFEM的模拟结果均表明:压痕硬度均随压入深度的减小而增大,呈现明显的尺寸效应。不同的是DDD的模拟结果显示:不同压入晶面的硬度关系为(111)晶面>(001)晶面>(011)晶面,呈现明显的取向效应。而CPFEM的模拟结果显示:不同压入晶面的硬度大致相同。此外,DDD模拟相对于CPFEM模拟结果,得到3个压痕面的压痕响应差异较大。两种方法模拟结果的差异主要是因为模拟尺度的不同,DDD模拟的尺度较小,其硬度响应与位错结构紧密相关。而CPFEM相对唯象,其模拟的尺度较大,微结构敏感特性不明显。

Discrete dislocation dynamics(DDD)and crystal plasticity finite element method(CPFEM)were used to simulate the nanoindentation of three crystal planes which were(001)crystal plane,(011)crystal plane and(111)crystal plane of single crystal copper.The relationship between load-displacement curve,elastic modulus,nano-hardness,elastic recovery rate and indentation depth was analyzed respectively,and the relationship between these quantities and grain orientation was also analyzed respectively.The simulation results of DDD and CPFEM both show that the indentation hardness increases with the decrease of indentation depth,showing an obvious size effect.The results of DDD and CPFEM are disparate.The simulation results of DDD indicate that the hardness relationship of different indented crystal planes is(111)crystal plane>(001)crystal plane>(011)crystal plane,displaying an obvious orientation effect.The CPFEM simulation results demonstrate that the hardness of different indented crystal plane is almost identical.In addition,in the results of DDD simulation,the indentation response of the three indentation planes is quite different,which is different from CPFEM simulation.The reason for this phenomenon is that the simulation scales of the two methods are disparate.The DDD simulation has a small scale and its hardness response is closely related to the dislocation structure,while CPFEM is relatively phenomenological,with a large simulation scale and insignificant microstructure sensitivity.