Ab initio perspective of the ⟨110⟩ symmetrical tilt grain boundaries in bcc Fe: application of local energy and local stress
Ab initio perspective of the ⟨110⟩ symmetrical tilt grain boundaries in bcc Fe: application of local energy and local stress
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DOI：
10.1007/s10853-014-8038-1
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发表时间：
2014-06-01
影响因子：
4.5
通讯作者：
Kohyama, Masanori
中科院分区：
文献类型：
--
作者：
Bhattacharya, Somesh Kr.;Tanaka, Shingo;Kohyama, Masanori
多晶金属的力学性能与晶界的微观结构、稳定性和弹性性能密切相关。通过使用从头算局部能量，局部应力和局部杨氏模量，我们试图提供一个全面的看法，一系列的< 110 >对称倾斜GB（STGB）在体心立方铁的稳定性和结构特性。我们处理了四个代表性的STGB，Sigma 3（112），Sigma 3（111），Sigma 11（332）和Sigma 9（221）GB，旋转角度范围从109.47 A度到38.94 A度。Sigma 3（112）GB由于四元环的稳定结构单元而显示出特殊的稳定性，除了显著的键方向变化（如堆垛层错或孪晶）之外，键长变化可以忽略不计。其他GB是由5-3和体结构单元的周期性排列构成的，就像通常的重合GB一样，而Sigma 9（221）GB中的5-3单元具有小角度倾斜GB中的边缘位错阵列的特征，例如在两个边缘处交替的压应力和拉应力以及在两侧上相对宽的局部能量和局部应力的分布。在除了Sigma 3（112）GB之外的GB中，通常存在两种界面原子;具有较大原子体积的原子显示出较高的局部能量、拉伸应力和增强的磁矩，而形成压缩键的另一种原子显示出较低的局部能量、压缩应力和减小的磁矩。对于四个GB，在结构单元中平均的局部杨氏模量的范围为根据结构无序或GB能量的程度的体积杨氏模量的60%至90%。在Fe晶界的结构单元中，局域杨氏模量、局域能量、局域应力、局域磁矩和局域成键性质之间存在明显的相关性。
The mechanical properties of polycrystalline metals are strongly dependent on the microscopic structure, stability, and elastic properties of grain boundaries (GBs). By using ab initio local energy, local stress, and local Young's modulus, we attempt to provide a comprehensive view on the stability and structural properties of a series of < 110 > symmetrical tilt GBs (STGBs) in bcc Fe. We deal with four representative STGBs, the Sigma 3 (112), Sigma 3 (111), Sigma 11 (332), and Sigma 9 (221) GBs with the rotation angles ranging from 109.47A degrees to 38.94A degrees. The Sigma 3 (112) GB shows special stability due to stable structural units of four-membered rings with negligible bond-length changes except for substantial bond-direction changes, like stacking faults or twins. The other GBs are constructed by periodic arrangement of 5-3 and bulk structural units as usual coincidence GBs, while the 5-3 unit in the Sigma 9 (221) GB has an aspect of an edge-dislocation array in a small-angle tilt GB such as alternate compressive and tensile stresses at both the edges and relatively wide spread of local energy and local stress on both sides. In the GBs other than the Sigma 3 (112) GB, there exist commonly two kinds of interface atoms; atoms with larger atomic volumes reveal higher local energies, tensile stresses, and enhanced magnetic moments, while the other kind of atoms forming compressed bonds reveal lower local energies, compressed stresses, and reduced magnetic moments. For the four GBs, the local Young's modulus averaged in the structural units ranges from 60 to 90 % of the bulk Young's modulus in accordance with the degree of structural disorder or GB energies. There exists clear correlation among the local Young's modulus, local energy, local stress, local magnetic moment, and local bonding nature at the structural units in the Fe GBs.