不同晶向金属纳米线拉伸力学性能分子动力学研究

MOLECULAR DYNAMICS STUDY OF THE TENSILE MECHANICAL BEHAVIOR OF METALLIC NANOWIRES WITH DIFFERENT ORIENTATION

在经典等温分子动力学框架下,采用位移控制加载方式,准静态数值模拟常温金属纳米线单向拉伸,研究了面心立方晶格(FCC)单晶金属铜纳米线的弹塑性力学性能.研究发现<100>,<110>,<111>不同晶向的纳米线拉伸呈现不同变形力学性能,具有不同的屈服性能和等效弹性刚度.<111>晶向拉伸具有最高的屈服强度,<100>晶向次之,<110>晶向屈服强度最小.特别发现<100>晶向屈服应变最大,而<110>晶向和<111>晶向的屈服应变相近,且比<100>晶向屈服应变的一半还要小.不同晶向的等效弹性模量顺序为E<111>>E<110>>E<100>.通过分析晶向不同纳米线对应不同表面情况、变形过程中位错局部结构具有不同的演化方式、位错发射相关的临界分解剪应力不同,解释了纳米线弹塑性变形的机理.

The mechanical properties and tension deformation of the single-crystalline FCC Cu nanowires are simulated with different orientation under uniaxial tension. The yield and elastic modulus in three different orientations of 〈100〉, 〈110〉 and 〈 111〉 are investigated by the quasi-static classic MD （Molecular dynamics） based on an embedded-atom method potential at room temperature. It is found that nanowires have different mechanical properties when tensioned in different orientations. The yield stress of Cu nanowire is the highest in the 〈111〉 orientation,the second in the 〈100〉 orientation and the lowest in the 〈110〉 orientation; however,the ductility of Cu nanowire is the best in the 〈100〉 orientation,but poor in the 〈111〉 and 〈110〉 orientations. The effective young＇s moduli of Cu nanowire are markedly different in different crystallographic orientations, i. e. E〈111〉 〉E〈110〉 〉E〈100〉. Detailed discussion on the stress-strain relation and underlying deformation mechanism of the nanowires is given,paying more attention to the local dislocation structure evolution and the critical resolved shear stress.