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Asymmetric ability of grain boundaries to generate dislocations under tensile or compressive loadings

机译：在拉伸或压缩载荷下晶界产生位错的不对称能力

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In order to investigate the effect of structural units on the ability of grain boundaries to generate dislocations, tensile and compressive loading tests were performed on aluminum bicrystals with (112) tilt grain boundaries using molecular-dynamics simulations. Five favored boundaries were found for (112) boundaries in an energy minimization analysis. Each structure could be identified using only its single structural unit period: A unit for 21 with θ=0°, B unit for 211 with θ=62.96°, C unit for ∑5 with θ=90°, E unit for ∑7 with θ= 120°, and D unit for 23 with θ= 180°. The favored boundaries all show an energy cusp except for the ∑7 boundary. Other boundaries could be represented by a combination of these five structural units. When ∑11 with |B| period showing a minimum energy cusp was used as a reference structure, the core of 2/11[3 1 1] or 2/11[3 1 1] dislocations calculated for the displacement sift complete lattice of ∑11 were introduced at interfaces having larger or smaller misorientation angles than ∑11, respectively. Each grain-boundary dislocation corresponds to A and C units, respectively. For example, ∑21 with θ=44.42° and 215 with θ=78.46° consists of |BBA| and |BBC| periods, respectively. When the ∑15 bicrystal was loaded in tension, lattice dislocations having the 1/2[1 1 0] core were emitted from C units and then the C units change their structure to the B units. Therefore, the ∑15 boundary can change its structure to the energetically stable ∑11 structure by emitting dislocations from C units. For ∑21, the same structural change occurred when the ∑21 bicrystal was deformed in compression. The simulation results show that there are tilt grain boundaries having the strong anisotropic strength and that the ability of grain boundaries to generate dislocations is closely related to their structural units.
机译：为了研究结构单元对晶界产生位错能力的影响，使用分子动力学模拟对具有（112）倾斜晶界的铝双晶进行了拉伸和压缩载荷测试。在能量最小化分析中发现了（112）个边界的五个有利边界。可以仅使用其单个结构单位周期来识别每个结构：θ= 0的21个单位，θ= 62.96°的211 B单位，θ= 90°的∑5的C单位，θ7的∑7的E单位。 θ= 120°，并且D单位为23，θ= 180°。除∑7边界外，所有优先边界都显示出能量尖峰。其他边界可以通过这五个结构单元的组合来表示。当∑11与| B |将显示出最小能量尖峰的周期用作参考结构，将为∑11的位移筛分完全晶格计算的2/11 [3 1 1]或2/11 [3 1 1]位错的核引入具有较大能量的界面或小于∑11的错误取向角。每个晶界位错分别对应于A和C单位。例如，θ21= 44.42°的∑21和θ= 78.46°的215由| BBA |组成。和| BBC |期间。当将∑15双晶加载时，从C单元发射出具有1/2 [1 1 0]核的晶格位错，然后C单元将其结构改变为B单元。因此，通过从C单元发射位错，∑15边界可以将其结构改变为能量稳定的∑11结构。对于∑21，当∑21双晶受压变形时，发生了相同的结构变化。模拟结果表明，存在各向异性强度强的倾斜晶界，且晶界产生位错的能力与其结构单元密切相关。

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