(中南大学 轻质高强结构材料国家级重点实验室，长沙 410083)
摘 要: 本文通过分析对称倾斜晶界的结构特点，建立了一套基于倒易空间阵点的对称倾斜晶界构建方法，并通过基于嵌入原子势分子动力学模拟研究了体心立方钨不同旋转轴和倾斜角的对称倾斜晶界结构、界面能和分离功。结果表明：在倾斜角或其对应的余角较小的情况下(＜20°)，随着倾斜角的增大，晶界能增加，说明小角度晶界具有较低的晶界能；而倾斜角较大时，晶界能出现了局域极小值，对应着特殊的大角度对称倾斜晶界，通过界面原子结构确定了其重位点阵参数；不同旋转轴下的对称倾斜晶界的晶界能都不相同，如以[110]和[111]为旋转轴时，体心立方Σ3(112)孪晶界具有最低的晶界能。分离功的结果表明，以[100]为旋转轴的特殊大角度对称倾斜晶界易于断裂，而以[110]和[111]旋转轴的孪晶界Σ3(112)及偏离其一定角度的大角度晶界具有高的分离功，在钨及钨合金的界面结合和断裂强度上起主要作用。
关键字: 分子动力学模拟；对称倾斜晶界；钨；晶界能；表面能；分离功
（National Key Laboratory of Science and Technology for High-Strength Structural Materials, Central South University, Changsha 410083, China）
Abstract:This work presented a simple method for constructing symmetric tilt grain boundary over the entire misorientation angles and different rotation axis based on the symmetric relationship between reciprocal and direct lattice. The constructed symmetric tilt grain boundaries were investigated using molecular dynamics with embedded atom method (EAM) potential. The results show that when the misorientation angle is small (usually ＜20°), the grain boundary energy increases as a function of misorientation angle. This indicates the low angle grain boundary is energetically favorable. However, at higher misorientation angle there exists few local minima on the grain boundary energy, which corresponds to the stable symmetric tilt grain boundaries. The parameters for coincident site lattice (CSL) are determined for those stable symmetric tilt grain boundaries. The grain boundary energy also depends on the rotation axis, the grain boundary along [110] and [111] rotation axes has lower energy for those high angle grain boundaries, especially the Σ3(112) twin boundary. The work of separation indicates the high angle grain boundaries along [100] rotation axis is prone to crack; while the twin boundary Σ3(112) and neighbor high angle grain boundaries along [110] and [111] rotation axes have high work of separation, thus play a key role in the bonding strength and fracture toughness of tungsten and its alloys.
Key words: molecular dynamics; symmetric tilt grain boundary; tungsten; grain boundary energy; surface energy; work of separation
