孪晶对α铁力学性能影响的模拟研究

发布时间：2018-04-23 13:16

本文选题：分子动力学模拟 + 纳米孪晶铁　；参考：《西安石油大学》2017年硕士论文

【摘要】：本文选取纳米孪晶BCC金属铁,通过分子动力学模拟的方法,研究了纳米孪晶铁在拉伸载荷下的变形行为,考察了在拉伸载荷下不同孪晶厚度、温度、孪晶界不同旋转角度对材料力学性能的影响,以及孪晶界对裂纹扩展的影响。利用可视化软件(OVITO)分析纳米孪晶铁的微观变形机制。主要包含以下内容:(1)研究了不同孪晶厚度的纳米孪晶铁在不同温度时受到拉伸载荷的力学行为。结果发现,随着孪晶厚度的增大,纳米孪晶铁的杨氏模量和屈服强度也随之增大,遵循反常的Hall-Petch关系,其变形机制以孪晶界处产生的变形孪晶为主导。单晶铁的塑性变形同样以孪晶变形为主;温度对纳米孪晶铁的变形机制没有影响,温度越高,其屈服强度和杨氏模量越小。(2)研究了孪晶界不同旋转角度和温度对纳米孪晶铁力学行为的影响。研究结果表明:将孪晶界旋转一定角度后,由于其施密特因子增大,孪晶界处更容易滑移,峰值应力相应降低,此时纳米孪晶铁的变形则以孪晶界的迁移和去孪晶为主;温度对其变形机制并无明显影响。(3)研究了裂纹垂直和平行于孪晶界时模型在拉伸载荷下的力学行为,结果表明:孪晶界的加入会使材料的峰值应力下降,降低材料的力学性能,其变形机制以裂纹尖端发射位错和裂纹的扩展为主。当孪晶界垂直于裂纹时,孪晶界对裂纹的扩展有阻碍作用。
[Abstract]:In this paper, the deformation behavior of nano twin iron under tensile load is studied by molecular dynamics simulation, and the influence of different twin thickness, temperature and twinning angle on the mechanical properties of the material under tensile load, and the influence of twin boundary on the mechanical properties of the material under tensile load, and the effect of the twin boundary on the crack propagation are investigated. The visualization of the effect of the twin grain boundary on the crack propagation is investigated. The effect of the twin boundary on the crack propagation is investigated. The effect of the twin boundary on the crack propagation is investigated. The microcosmic deformation mechanism of the nano twin iron is analyzed by software (OVITO). The main contents are as follows: (1) the mechanical behavior of the tensile load of the nanocrystalline iron with different twin thickness at different temperatures is studied. The results show that the young's modulus and yield strength of the nanocrystalline iron increase with the increase of the twin thickness, and follow the anomalous H. The deformation mechanism of all-Petch is dominated by the deformation twins produced at the twin boundary. The plastic deformation of the single crystal iron is mainly twin deformation, and the temperature has no effect on the deformation mechanism of the nanocrystalline iron. The higher the temperature, the smaller the yield strength and the young's modulus. (2) the twin grain boundaries with different rotation angles and temperatures are studied on the twin iron twin iron. The results show that when the twin boundary is rotated at a certain angle, the twin boundary is more prone to slip and the peak stress decreases as its Schmidt factor increases. At this time, the deformation of the nanocrystalline iron is dominated by the twin boundary migration and the twinning, and the temperature has no obvious influence on the deformation mechanism. (3) the crack vertical is studied. The mechanical behavior of the model under the tensile load at the time of twin boundaries shows that the addition of twin boundaries will decrease the peak stress of the material and reduce the mechanical properties of the material. The deformation mechanism is mainly caused by the emit dislocation and the crack propagation at the crack tip. When the twin boundary is perpendicular to the crack, the twin boundary has a hindrance to the crack growth.

【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;O614.811

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