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Effect of H impurity on misfit dislocation in Ni-based single-crystal superalloy: molecular dynamic simulations 下载免费PDF全文
The effect of H impurity on the misfit dislocation in Ni-based single-crystal superalloy is investigated using the molecular dynamic simulation.It includes the site preferences of H impurity in single crystals Ni and Ni 3 Al,the interaction between H impurity and the misfit dislocation and the effect of H impurity on the moving misfit dislocation.The calculated energies and simulation results show that the misfit dislocation attracts H impurity which is located at the γ/γˊinterface and Ni3 Al and H impurity on the glide plane can obstruct the glide of misfit dislocation,which is beneficial to improving the mechanical properties of Ni based superalloys. 相似文献
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Lattice stability and the effect of Co and Re on the ideal strength of Ni:First-principles study of uniaxial tensile deformation 下载免费PDF全文
Using first-principles density functional calculations, lattice stability of γ-Ni under [001], [110], and [111] uniaxial tensions and the effect of alloying elements Co and Re on the uniaxial tensile behavior of γ-Ni were studied in this paper.With elastic constants and phonon spectra calculations, we examined the mechanical stability and phonon stability of Ni during the uniaxial tensions along the three characteristic directions. The results show that the mechanical stability and phonon stability of a lattice occurs before the maximum stress–strain point under the [001] and [111] tension, respectively.The effects of Co and Re on the ideal tensile strength of γ-Ni show a significant directivity: Co and Re have little effect on the stresses in [001] and [111] directions, but increases the ideal strength of the system in the weakest uniaxial tensile direction. Moreover, the strengthening effect of Re is significantly better than that of Co. By further analyzing electronic structure, it is found that the effect of alloying elements on the uniaxial tensile behavior of γ-Ni comes from their interactions with host atoms. 相似文献
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通过对材料点、线、面等几类不同缺陷的电子结构和声子激发研究的回顾,特别是对它们的声子激发及其局域振动模式分析,给出了材料缺陷导致的材料局域振动模式的微观图像;分析了多原子分子所具有的高频局域振动态以及采用超声或激光方法激发获得长寿命局域振动的基本原理;提出了一种能够利用耦合共振原理进行材料缺陷局域原子结构非接触调整的方法 相似文献
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The phonon spectrum and the related thermodynamic properties of
microcracks in bcc-Fe are studied with the recursion method by using
the Finnis--Sinclair
(F--S) N-body potential. The initial configuration of the microcracks is established
from an anisotropic linear elastic solution and relaxed to an
equilibrium by molecular dynamics method. It is shown that the local
vibrational density of states of the atoms near a crack tip is
considerably different from the bulk phonon spectrum, which is
closely associated with the local stress field around the crack tip;
meanwhile, the local vibrational energies of atoms near the crack
tip are higher than those of atoms in a perfect crystal. These
results imply that the crack tip zone is in a complex stress state
and closely related to the structure evolution of cracks. It is also
found that the phonon excitation is a kind of local effect induced
by microcracks. In addition, the microcrack system has a higher
vibrational entropy, which reflects the character of phonon spectrum
related to the stress field induced by cracks. 相似文献
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在镍基单晶超合金中,由于单晶Ni的晶格常数比单晶Ni3Al的稍小,在Ni/Ni3Al晶界面 上必然要出现错配.采用分子动力学模拟了镍基单晶超合金的Ni/Ni3Al晶界的结 构,考虑 了两个不同的初始模型,并进行了分子动力学弛豫.弛豫的结果均表明:由于晶格的差异形 成的错配能不是通过长程晶格错配的方式来释放,而是通过在局部区域形成位错的方式释放 的.由于Ni3Al相周围Ni相环境的不同,形成的位错也有所不同.
关键词:
镍基单晶超合金
晶界
分子动力学模拟 相似文献
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The mosaic structure in a Ni-based single-crystal superalloy is simulated by
molecular dynamics using a potential employed in a modified analytic embedded atom
method. From the calculated results we find that a closed three-dimensional misfit
dislocation network, with index of $\langle 011\rangle${\{}100{\}} and the side
length of the mesh 89.6\,{\AA}, is formed around a cuboidal $\gamma '$ precipitate.
Comparing the simulation results of the different mosaic models, we find that the
side length of the mesh only depends on the lattice parameters of the $\gamma $ and
$\gamma '$ phases as well as the $\gamma $/$\gamma '$ interface direction, but is
independent of the size and number of the cuboidal $\gamma '$ precipitate. The
density of dislocations is inversely proportional to the size of the cuboidal
$\gamma '$ precipitate, i.e.~the amount of the dislocation is proportional to the
total area of the $\gamma $/$\gamma '$ interface, which may be used to explain the
relation between the amount of the fine $\gamma '$ particles and the creep rupture
life of the superalloy. In addition, the closed three-dimensional networks assembled
with the misfit dislocations can play a significant role in improving the mechanical
properties of superalloys. 相似文献
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Using first-principles calculations in combination with Wagner–Schottky and kinetic Monte Carlo methods, the diffusion behaviors of solutes via various vacancy-mediated diffusion mechanisms in L1_2 γ-Ni_3Al were investigated. The formation energies of the point defects and the migration energies for solutes were calculated. Adding alloying elements can decrease the defect-formation energies of Ni_(Al), increase the defect-formation energies of Al_(Ni), and have little effect on the formation energy of V_(Ni). The migration energies of solutes are related with the site preference and the diffusion mechanism. The diffusion coefficients of Ni, Al, and solutes were calculated, and the concentration of antisite defects plays a crucial role in the elemental diffusion. 相似文献