轴向拉伸下氮化钛纳米杆变形机制及力学性能的分子动力学研究

本文使用分子动力学软件包lammps并采用第二近邻改进型嵌入原子法(2NN MEAM)模拟了单晶氮化钛纳米杆的轴向拉伸破坏过程，分析了分别沿100]、111]晶向的不同截面尺寸、不同拉伸应变率、不同温度下的氮化钛纳米杆的力学性能，详细描述了氮化钛纳米杆拉伸变形过程。研究发现, 拉伸晶向、截面尺寸、拉伸应变率及温度均会对TiN纳米杆的拉伸变形过程及屈服强度、弹性模量等力学性能产生不同程度的影响。 沿100]晶向的拉伸，截面尺寸越大，屈服强度越低；而沿111]晶向，截面尺寸越大，屈服强度越大。应变率越大，屈服强度及屈服应变越大，但对于弹性模量几乎无影响。温度越高，材料的屈服强度、屈服应变及弹性模量越小，断裂应变越大。不同拉伸条件下的氮化钛纳米杆的拉伸过程均包括弹性变形、塑性变形与断裂阶段。100]晶向的弹性模量都要高于111]晶向。

The Study on the Deformation Mechanisms and Mechanical Properties of TiN Nanorod under the Axial Tensile Process Based on Molecular Dynamic

The software package lammps based on molecular dynamic with Modified Embedded-Atom Method(2NN MEAM) is used to simulate the tensile fracture behavior of single crystal TiN nanorod. The mechanical property of TiN with different cross sections is analyzed under different strain rates and different temperatures along 100]、111] directions. The tensile process is described in detail. The study has found that the tensile direction, cross section size, tension strain rate and temperature all have different effects on the tensile process, yield stress, elastic modulus of TiN nanorod. The larger the cross section, the lower the yield stress along 100] direction tension, however, the larger the cross section, the larger the yield stress along 111] direction tension. The yield stress and yield strain increase with strain rate, but strain rate has little effect on the yield modulus. When the temperature of simulation system rises, the yield stress, yield strain and yield modulus of TiN material tend to be smaller, but the fracture strain will be larger. Under different tension condition, the tensile process of TiN nanorod all contains elastic deformation, plastic deformation and fracture stage. The elastic modulus along 100] direction is always lager than that along 111] direction.