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利用分子动力学方法研究了单晶铜中纳米空洞的成核与早期生长过程.研究结果表明:高应变率拉伸作用下,在缺陷原子或空位密集区首先启动(111)-[211],(111)-[211],(111)-[211],(111)-[211]4个滑移系的位错.空洞在特定滑移系层错交叠,即(111)-[211]和(111)-[211]滑移系的层错交叠以及(111)-[211]和(111)-[211]滑移系的层错交叠形成的空穴串处成核.这些空穴串分别沿[011]和[011]方向,与加载方向垂直.相对于其他的滑移系交叠,这种滑移系交叠形成的空穴串的截面积最大.此后,空洞通过发射位错长大,形状类似长条形;伴随其他类型位错的生长,空洞逐渐演化为柱形-椭球形-类球形.对于含双空洞的单晶铜体系,受已存空洞周围应力分布的影响,多个滑移体系同时启动,空洞在3个滑移系的层错交汇点的空穴处成核,其形状受交汇处位错线运动方向的影响,类似扁三角形,并在位错的滑移和攀移作用下逐渐演化为类球形.我们根据畸变场计算了3个层错面交叠处的空穴体积,发现108个不同交叠构型中,只有4种构型的交叠引起的空穴体积最大,空洞成核容易,其他情况不能使空洞成核.
The nucleation and early growth of nano-voids in single-crystal copper were studied by molecular dynamics method. The results show that (111) - [211] are initiated first in defect atoms or vacant sites under high strain rate tensioning, (111) - [211], (111) - [211], and the faults of four slip systems in the special slip system are overlapped, that is, (111) - [211 (111) - [211] slip system and hole trains formed by the stacking faults of (111) - [211] and (111) - [211] slip systems. These holes are perpendicular to the loading direction in [011] and [011] direction, respectively, and the cross-sectional area of the hole string formed by the overlapping of the slipping lines is the largest with respect to the other slip lines. With the growth of emission dislocations, the shape of the holes is similar to the shape of a bar. With the growth of other types of dislocations, the voids gradually evolve into columnar-ellipsoid-like spheres. For single crystal copper systems with double voids, Distribution, multiple slip systems are activated at the same time. The holes nucleate at the holes at the intersection of the three slip systems. The shape of the holes is affected by the movement direction of the dislocation lines in the interface, similar to the flat triangle, Dislocation slip and climb for And gradually evolve into a spherical shape.We calculated the volume of holes in the overlap of three layers according to the distortion field.It is found that only the overlap of the four kinds of the 108 different overlapped structures caused the largest hole volume , Hollow nucleation easy, in other cases can not make hollow nucleation.