CuΣ15晶界结构低能化转变的微观机制研究

Study on microscopic mechanism of low-energy transition of CuΣ15 grain boundary structure

采用分子动力学模拟方法对CuΣ15晶界的结构转变过程进行了系统研究,发现在单轴拉伸作用下CuΣ15[112](512)晶界会向Σ11[112](131)晶界发生低能化结构转变。位错演化和原子运动轨迹分析表明,该结构转变过程主要在两种肖克莱不全位错b_(1)=1/6[211]和b_(3)=1/6[121]的共同作用下完成。首先b_(1)位错从与Σ15晶界六边形结构单元的5和6号原子处形核并发射,此后其在{111}面上滑移导致内禀型堆垛层错的形成;b_(3)位错随后在与b_(1)同样位置形核并发射,引起{111}面上原子二次重排,从而导致堆垛层错消失。在上述位错作用下,CuΣ15晶界中原本组成六边形结构单元的5和6号原子脱离晶界区域,沿{111}面进入晶粒内而变为体相原子,剩余4个原子则重新排列形成四边形结构单元;CuΣ15晶界由此逐步完成向Σ11晶界的结构低能化转变。

The molecular dynamics simulation method was employed to symmetrically investigate the structural transformation process of CuΣ15 grain boundary(GB).It is found that the CuΣ15[112](512)GB undergoes an energy-lowering structural transformation to theΣ11[112](131)GB under uniaxial tension action.The analysis of dislocation evolution and atomic movement trajectory indicates that the structural transformation process is mainly completed under the joint action of two Shockley partial dislocations b_(1)=1/6[211]and b_(3)=1/6[121].Firstly,the b_(1) dislocation nucleates and emits from the atom 5 and atom 6 of the hexagonal structure unit of15 GB.Then,it slips on the{111}plane,leading to the formation of intrinsic stacking faults.The b_(3) dislocation then nucleates and emits at the same position with b_(1),causing a rearrangement of atoms on{111}plane and the disappearance of the stacking faults.With the above-mentioned dislocation action,the atom 5 and atom 6,which originally formed the hexagonal structural unit of the CuΣ15 GB,break away from the original GB region and enter into grain interior along the{111}plane,these two atoms thus turn into bulk atoms,while the remaining four atoms rearrange and then form the quadrilateral structural unit,in which way the energy-lowering structural transformation from CuΣ15 GB toΣ11 GB gradually completes.