(中南大學(xué) 輕質(zhì)高強結(jié)構(gòu)材料國家級重點實驗室，長沙 410083)
摘 要: 本文通過分析對稱傾斜晶界的結(jié)構(gòu)特點，建立了一套基于倒易空間陣點的對稱傾斜晶界構(gòu)建方法，并通過基于嵌入原子勢分子動力學(xué)模擬研究了體心立方鎢不同旋轉(zhuǎn)軸和傾斜角的對稱傾斜晶界結(jié)構(gòu)、界面能和分離功。結(jié)果表明：在傾斜角或其對應(yīng)的余角較小的情況下(＜20°)，隨著傾斜角的增大，晶界能增加，說明小角度晶界具有較低的晶界能；而傾斜角較大時，晶界能出現(xiàn)了局域極小值，對應(yīng)著特殊的大角度對稱傾斜晶界，通過界面原子結(jié)構(gòu)確定了其重位點陣參數(shù)；不同旋轉(zhuǎn)軸下的對稱傾斜晶界的晶界能都不相同，如以[110]和[111]為旋轉(zhuǎn)軸時，體心立方Σ3(112)孿晶界具有最低的晶界能。分離功的結(jié)果表明，以[100]為旋轉(zhuǎn)軸的特殊大角度對稱傾斜晶界易于斷裂，而以[110]和[111]旋轉(zhuǎn)軸的孿晶界Σ3(112)及偏離其一定角度的大角度晶界具有高的分離功，在鎢及鎢合金的界面結(jié)合和斷裂強度上起主要作用。
關(guān)鍵字: 分子動力學(xué)模擬；對稱傾斜晶界；鎢；晶界能；表面能；分離功
（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
