Molecular dynamics simulation on mechanisms of plastic anisotropy in nanotwinned polycrystalline copper with{111}texture during tensile deformation

含有{111}织构的纳米孪晶多晶铜在拉伸变形过程中塑性各向异性机制的分子动力学模拟

Based on molecular dynamics(MD)simulation,the mechanisms of plastic anisotropy in nanotwinned polycrystalline copper with{111}texture during tensile deformation were systematically studied from the aspects of Schmid factor of the dominant slip system and the dislocation mechanism.The results show that the Schmid factor of dominated slip system is altered by changing the inclining angle of the twin boundaries(TBs),while the yield stress or flow stress does not strictly follow the Schmid law.There exist hard and soft orientations involving different dislocation mechanisms during the tensile deformation.The strengthening mechanism of hard orientation lies in the fact that there exist interactions between the dislocations and the TBs during plastic deformation,which leads to the dislocation blocking and reactions.The softening mechanism of soft orientation lies in the fact that there is no interaction between the dislocations and the TBs because only the slip systems parallel to the TBs are activated and the dislocations slip on the planes parallel to the TBs.It is concluded that the plastic anisotropy in the nanotwinned polycrystalline copper with{111}texture is aroused by the combination effect of the Schmid factor of dominated slip system and the dislocation mechanism.

基于分子动力学模拟,从主导滑移系的斯密特因子和位错机制两个方面系统研究含有{111}织构的纳米孪晶多晶铜在拉伸变形过程中的塑性各向异性机制。结果表明:主导滑移系的斯密特因子随着孪晶界倾角的改变而变化,但屈服应力或流动应力并不严格遵守斯密特定律。在拉伸变形过程中存在涉及不同位错机制的硬取向和软取向。硬取向的硬化机制在于塑性变形过程中存在位错与孪晶界之间的相互作用,从而导致位错塞积和位错反应。软取向的软化机制在于没有位错与孪晶界之间的相互作用,这是由于只有平行于孪晶界的滑移系被激活,使得位错在平行于孪晶界的晶面上运动。因此,可以推断,含有{111}织构的纳米孪晶多晶铜的塑性各向异性是由主导滑移系的斯密特因子与位错机制共同作用的结果。