Effect of lateral contraction and magnetism on the energy release upon fracture in metals: First-principles computational tensile tests
Effect of lateral contraction and magnetism on the energy release upon fracture in metals: First-principles computational tensile tests
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DOI：
10.1103/physrevb.79.144114
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发表时间：
2009-04
影响因子：
3.7
通讯作者：
Z. Tian;J. Yan;W. Xiao;W. Geng
中科院分区：
文献类型：
--
作者：
Z. Tian;J. Yan;W. Xiao;W. Geng
在许多情况下，在材料断裂时存在能量释放。以镍5210晶界为例，利用密度泛函理论计算拉伸实验，研究了横向收缩效应、泊松效应对拉伸的影响以及磁性对断裂点能量释放的影响。计算结果表明，对于纯晶界和硫偏聚晶界，泊松效应都能显著降低晶界系统的总能量。而对于3111晶界，由于Ni111面的紧密堆积，计算单元的横向优化仅具有较小的影响。令人惊讶的是，磁性被发现，以减少大部分的能量释放断裂时的晶界，这样的弱磁性金属。因此，材料的计算极限抗拉强度将显著降低。分离的硫原子降低了应变过程中亚稳态和基态构型之间的能垒。在断点附近，界面原子的自旋极化显著增强，这引入了系统的额外能量降低。
On many occasions, there is an energy release upon fracture of materials. Taking the 5 210 grain boundary in nickel as an example, we have studied the effect of lateral contraction the Poisson effect upon stretching and the effect of magnetism on the energy release at the break point, using density-functional theory computational tensile tests. For both clean and sulfur segregated grain boundaries, our calculations show that the Poisson effect can reduce the total energy of the grain-boundary system remarkably. For 3 111 grain boundary, however, lateral optimization of the computation cell has only a minor effect because of the close packing of the Ni 111 plane. Surprisingly, magnetism is found to reduce much of the energy release upon fracture for grain boundaries for such a weak magnetic metal. As a result, the calculated ultimate tensile strength of the material will be significantly diminished. Segregated sulfur atoms reduce the energy barrier between metastable and ground-state configurations in straining procedure. Near the break point, spin polarization of the interfacial atoms is significantly enhanced which introduces an extra energy lowering of the system.