晶粒尺寸对掺氦纳米多晶铁机械性能影响的分子动力学模拟研究

采用分子动力学方法研究了晶粒尺寸对掺氦纳米多晶铁机械性能的影响.在拉伸形变过程中,纳米多晶铁将产生裂纹与晶格畸变,通过模拟XRD谱探索二者之间的联系.拉伸模拟结果显示,由于晶界氦原子的引入,峰值应力将显著减小.另外,在拉伸模拟中观察到,沿晶裂纹的产生与长大随着晶界氦原子的引入而增强.研究结果表明,晶界氦原子能够促进沿晶...

Molecular Dynamics Simulation Study of the Effect of Grain Size on the Mechanical Property of Nano-polycrystalline Iron Doped with He

Molecular dynamics(MD) simulations were performed to investigate the effects of grain size on the mechanical properties of nano-polycrystalline iron doped with helium(He). Simulated X-ray diffraction(XRD) was used to explore the relationship between the generation of cracks and the distortion of crystal structural in nano-polycrystalline iron during tensile deformation. The simulation results show that the peak stresses are obviously decreased due to the introduction of He atoms into the grain boundaries of nano-polycrystalline iron. In addition, it is observed that the generation and growth of intergranular cracks are significantly enhanced by He atoms which are distributed at grain boundary(GB) regions during tensile simulation. The results suggest that the intergranular cracks are promoted by GB He atoms, and the size and number of cracks increase with the increasing grain size of nano-polycrystalline iron. The separation of peak {200} and {211} are significantly observed in the XRD patterns during loading. The diffraction angle of subpeaks is higher in the XRD patterns of nano-polycrystalline iron with GB He than in that without He during the strain range from 6% to 10%, and the diffraction angle of subpeaks and the growth of cracks increase with the increasing grain size. It is demonstrated that the degradation of mechanical property caused by intergranular cracks has close relationship with the change of structural distortion obtained by simulated XRD patterns in nano-polycrystalline iron.