Ab initio calculation of traction separation laws for a grain boundary in molybdenum with segregated C impurites
Ab initio calculation of traction separation laws for a grain boundary in molybdenum with segregated C impurites
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DOI：
10.1088/0965-0393/21/7/075005
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发表时间：
2013-09
影响因子：
1.8
通讯作者：
A. M. Tahir;R. Janisch;A. Hartmaier
中科院分区：
文献类型：
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作者：
A. M. Tahir;R. Janisch;A. Hartmaier
用从头算方法测定了碳对钼中Σ5(31 10)[0 0 1]对称倾斜晶界（STGB）晶界能、分离功（WoS）和断裂强度等力学性能的影响。根据我们的从头计算结果，我们推导出了牵引-分离定律，该定律可用于采用黏结带的连续介质裂缝模拟。结果表明，随着晶界处C原子数量的增加，晶界的能量降低，表明偏析的驱动力很强。晶界单轴拉伸试验表明，分离的C原子对晶界内聚能或WoS的影响很小，而对于完整的单层C， Σ5(31 10)[0 0 1] STGB的强度提高了近30%，强度的提高伴随着晶界刚度的增加和界面多余体积的减小。将特征参数组合成与浓度相关的牵引分离规律。对不同体系标度行为的研究表明，即使对于不同的碳浓度，能量-位移曲线也可以用通用结合能关系很好地描述。这些发现为大大简化有杂质和无杂质晶界的从头算牵引分离定律的计算开辟了道路。
We have determined the influence of carbon on mechanical properties such as grain boundary energy, work of separation (WoS) and fracture strength of the Σ5(3 1 0)[0 0 1] symmetrical tilt grain boundary (STGB) in molybdenum with ab initio methods. From our ab initio results, we derived traction–separation laws that can be used in continuum simulations of fracture employing cohesive zones. Our results show that with an increasing number of C atoms at the grain boundary, the energy of the grain boundary is lowered, indicating a strong driving force for segregation. Uni-axial tensile tests of the grain boundary reveal that there is only a small effect of segregated C atoms on the cohesive energy or WoS of the grain boundary, while the strength of the Σ5(3 1 0)[0 0 1] STGB increases by almost 30% for a complete monolayer of C. This increase in strength is accompanied by an increase in grain boundary stiffness and a decrease of the interface excess volume. The characteristic parameters are combined in the concentration-dependent traction–separation laws. A study of the scaling behaviour of the different investigated systems shows that the energy–displacement curves can be well described by the universal binding energy relationship even for different C concentrations. These findings open the way for significant simplification of the calculation of ab initio traction separation laws for grain boundaries with and without impurities.