Keywords: 
• 纯铜 /
• 非共格 Σ3 晶界 /
• 分子动力学模拟

Abstract: It has been reported that incoherent Σ3 boundaries play an important role in the evolution of grain boundary characteristic distri-bution in the low to medium stacking fault energy in face-centered cubic metals. In order to ascertain the characteristics of incoherentΣ3 boundaries with varied (h1k1l1)/(h2k2l2) interface matching, the structural stability of [0 1 ˉ1] tilt incoherent Σ3 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 ˉ1] tilt incoherent Σ3 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)/(ˉ1 1 1) twin boundary plane, the smaller the grain boundary matching value and thus the more unstable the incoherent Σ3 boundary. With the smallest Φ angle, (2 5 5)/(ˉ2 1 1) is stable and almost no structural change is observed during annealing processes. With increasing Φangle, the incoherent Σ3 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.