纯铜[0 1 1]倾侧型非共格∑3晶界结构稳定性分子动力学模拟研究

有研究表明, 非共格∑₃晶界的行为在中低层错能面心立方金属晶界 特征分布演化中发挥着重要作用. 为了掌握不同界面匹配的非共格∑₃晶界的特性, 本文利用分子动力学(MD)模拟方法首先研究了纯铜的[0 1 1]倾侧型 非共格∑₃晶界在700–1100 K温度范围内和常压下的结构稳定性. MD模拟采用原子间相互作用长程经验多体势, 步长为5×10^-15 s. 模拟结果表明: 所研究的五个非共格∑₃晶界, 其结构稳定性存在很大差异, 其一般规律是, 与(1 1 1)/(1 1 1)共格孪晶界之间的夹角(Φ角)越小, 晶界匹配值越大, 则非共格∑₃晶界越稳定; 反之亦然. Φ角最小的 (2 5 5)/(2 1 1)非共格∑₃晶界较稳定, 在退火过程中几乎不发生变化. 随着Φ角的增大, 非共格∑₃晶界不再稳定, 这类晶界会通过Miller指数较高一侧晶体每三层原子面合并为一层原子面 (或Miller指数较低一侧晶体每一层原子面分解为三层原子面)的机理 转变为亚稳的“台阶”状晶界, 台阶面部分地处于精确的能量极低 的{111}/{111}共格孪晶界上; 当提高温度退火时, 这种“台阶”状晶界最终会全部转变成稳定平直的{111}/{111}共格孪晶界.关键词：纯铜∑₃晶界')" href="#">非共格∑₃晶界分子动力学模拟

Molecular dynamics simulation on the struatural stability of [0 1 1] tilt incoherent ∑3 gain boundaries in pure copper

It has been reported that incoherent ∑₃ boundaries play an important role in the evolution of grain boundary characteristic distribution in the low to medium stacking fault energy in face-centered cubic metals. In order to ascertain the characteristics of incoherent ∑₃ boundaries with varied (h₁k₁l₁)/(h₂k₂l₂) interface matching, the structural stability of [0 1 1] tilt incoherent ∑₃ grain boundaries in pure copper, at temperatures ranging from 700 to 1100 K and under the normal pressure, was studied by molecular dynamics (MD) simulations. Long-range empirical potential (LREP) was used in the simulation in which the time-step was chosen to be 5× 10^-15 s (5 fs). Simulation results show that the structural stabilities of [0 1 1] tilt incoherent ∑₃ grain boundaries are different from one another. The general trend is that the larger the angle (Φ) by which the grain boundary plane deviates from the ideal (1 1 1)/(1 1 1) twin boundary plane, the smaller the grain boundary matching value and thus the more unstable the incoherent ∑₃ boundary. With the smallest Φ angle, (2 5 5)/(2 1 1) is stable and almost no structural change is observed during annealing processes. With increasing Φ angle, the incoherent ∑₃ boundaries will not be stable any longer. They are usually changed into the meta-stable step-like boundaries during annealing by the mechanisms in which every three atomic layers in the high Miller-index side will merge into one atomic layer, or each atomic layer in the low Miller-index side decomposes into three atomic layers. Some of the steps of these boundaries are located at the exact {111}/{111} planes. As the annealing temperature increases, such step-like boundaries will change completely into straight and stable {111}/{111} coherent twin boundaries.
Keywords：pure copper∑₃ grain boundary')" href="#">incoherent ∑₃ grain boundarymolecular dynamics simulation