向错强度与阻尼系数对纳米晶材料小角度晶界湮没的影响

Influence of Disclination Strength and Damping Coefficient on Decay of Low Angle Grain Boundaries in Nanocrystalline Materials

关键词:  位错滑移  剪切应力  晶界湮没  向错

Key words:  dislocation slip  shear stress  grain boundary annihilation  disclination

摘要:

[目的]研究一维纳米晶材料演化过程中的小角度晶界湮没过程,探究向错强度与阻尼系数对位错湮没的影响。[方法]建立位错运动方程,计算模拟小角度晶界的晶格位错在外应力作用下发生的变化。[结果]随着切应力增加,晶界由过阻尼运动变为无穷远的单向运动,向错强度越大晶界越难以湮没,并且晶界位错由同时湮没转变为两端先湮没,中心后湮没;阻尼系数越大,湮没临界切应力越大,但到达一定值时,阻尼系数不再影响临界值。[结论]晶界湮没存在临界切应力,向错强度主要影响临界切应力,阻尼系数主要影响位错初始速度和运动停止时间。

Abstract:

[Objective] The evolution process of the annihilation of small angle grain boundaries in an one-dimensional crystal material was researched, and the effects of disclination strength and damping coefficient on the annihilation of dislocations were explored.[Methods] The movement equations of dislocations were established, and the dislocation motions in low angle grain boundaries were calculated and simulated under external shear stress.[Results] With shear stress progressing, the movement of grain boundary turns to directional motion in which dislocations can go to infinity.The bigger the value of disclination strength is, the more difficult the grain boundary annihilation is.Furthermore, grain boundary annihilation changes from simultaneously running away to central dislocation releasing after escaping of dislocations in both ends.The bigger the damping coefficient is, the bigger the critical shear stress of annihilation.But when it reaches a certain point, damping coefficient doesn't have an impact on critical stress anymore.[Conclusion] There is a critical value for grain boundary annihilation.Disclination strength mainly affects critical value, while damping coefficient plays an indispensable role in original velocity and motion ceasing time of dislocation.