扭转力下金属塑性行为的分子动力学研究

发布时间：2018-05-25 08:05

本文选题：金属 + 晶界　；参考：《郑州大学》2016年硕士论文

【摘要】：本文运用分子动力学模拟方法,以面心立方(FCC)金属块体(Al和Ni)为对象,研究了在扭转作用下其扭转晶界的演化现象,以及双金属界面(Al和Ni)的演化现象。以纳米尺度的体心立方(BCC)金属(Fe)为对象,研究了纯金属纳米线(Fe)在扭转下的塑性变形机制,以及有扭转晶界存在时纳米线的塑性变形机制。主要的研究内容和结论如下:(1)、在扭转力的作用下,我们分别研究了单金属铝和镍在100,110和111取向上的扭转晶界在顺时针扭转和逆时针扭转下的演化行为。因晶粒的取向不同,它们的晶界结构呈现出不同的结构。在100方向上,扭转晶界的初始位错结构呈现出矩形的位错网,它是由两组相互垂直的位错线构成的。在111方向上,扭转晶界的初始位错结构呈现出三角形的位错网,它是由三组位错线组成的。在110方向上,不同的金属表现出不同的位错结构,铝的位错结构是近似的矩形位错网,镍的位错结构则是曲折的位错线组成的位错网。在逆时针扭转时,上述位错网都收缩,使得位错密度增加;在顺时针扭转时,上述位错网都扩大,使得位错密度减小。从中可以看出扭转晶界在两个方向上的演化结果是不对称的。我们同样研究了铝镍双金属界面在扭转作用下的塑性变化行为,结果表明铝镍双金属界面的位错总是在界面内传播,并没有向晶粒内部传播的趋势。而单金属扭转晶界的位错不仅可以在晶界面内传播,它还可以向晶粒内部传播。对比两种情况可以发现,在扭转作用下双金属界面对晶界中位错的传播有一定的抑制作用。(2)、我们分别研究了在100,110和111取向上无缺陷铁纳米线和有扭转晶界存在铁纳米线在扭转力的作用下的塑性变形行为。对于无缺陷纳米线,在100方向上,位错在纳米线表面生成并向纳米线内部传播,逐渐形成了镜像的“C”型位错线;随着扭转的继续,位错线彼此相互作用最终形成了三维的位错网。在110方向上,在纳米线的表面逐渐形成位错滑动面,随着纳米线的扭转,位错滑动面最终相遇并形成了更大的滑动面,它们把纳米线截成了两部分。在111方向上,纳米线不仅形成了镜像的“C”型位错线,还形成了位错面。对于有扭转晶界存在的纳米线,在100方向上,初始的位错结构呈现出矩形的位错网,它是由两组相互垂直的位错线组成的。在110方向上,初始的位错结构是由四条位错线组成的“X”型结。在111方向上,初始的位错结构是由三组平行的位错线组成的位错网。研究结果表明无缺陷纳米线的塑性行为与纳米线的取向有关,有扭转晶界纳米线的塑性行为主要发生在晶界处,并且表现出与FCC金属晶界相似的演化行为。
[Abstract]:In this paper, the evolution of grain boundary and the evolution of Al and Ni at the bimetallic interface have been studied by means of molecular dynamics simulation. The plastic deformation mechanism of pure metal nanowires (Fe) under torsion and the plastic deformation mechanism of nanowires in the presence of torsional grain boundaries were studied. The main contents and conclusions are as follows: 1. Under the effect of torsional force, we have studied the evolution behavior of the grain boundaries of aluminum and nickel at 100110 and 111 orientations respectively under clockwise and counterclockwise torsion. Because of the different orientation of the grains, their grain boundary structures show different structures. In the 100 direction, the initial dislocation structure of the torsional grain boundary presents a rectangular dislocation network, which is composed of two sets of perpendicular dislocation lines. In the 111 direction, the initial dislocation structure of the torsional grain boundary presents a triangular dislocation network, which is composed of three sets of dislocation lines. In the 110 direction, different metals exhibit different dislocation structures. The dislocation structure of aluminum is an approximate rectangular dislocation network, while the dislocation structure of nickel is a dislocation network composed of zigzag dislocation lines. In counterclockwise torsion, the above dislocation net shrinks, which makes the dislocation density increase, and when clockwise torsion, the above dislocation network is enlarged, which makes the dislocation density decrease. It can be seen that the evolution of the torsional grain boundary is asymmetric in both directions. The plastic behavior of Al-Ni bimetallic interface under torsion is also studied. The results show that the dislocation of Al-Ni bimetallic interface always propagates within the interface and does not propagate to the grain interior. The dislocation of single metal torsional grain boundary can propagate not only within the crystal interface, but also into the grain. By comparing the two cases, we can see that The bimetallic interface has a certain inhibitory effect on the propagation of dislocation in grain boundaries under torsional action. We have studied the defects of iron nanowires on 100110 and 111 orientations and the existence of iron nanowires in torsional grain boundaries under the effect of torsional force, respectively. The plastic deformation behavior of. For non-defective nanowires, dislocations form on the surface of nanowires and propagate to nanowires in the 100 direction, gradually forming mirrored "C" type dislocation lines; as torsion continues, The dislocation lines interact with each other and finally form a three-dimensional dislocation network. In the direction of 110, the dislocation slip surface is gradually formed on the surface of nanowires. With the torsion of nanowires, the dislocation slip surfaces finally meet and form larger sliding surfaces, which cut the nanowires into two parts. In the 111 direction, the nanowires not only form the mirror "C" type dislocation line, but also form the dislocation plane. For nanowires with torsional grain boundaries, the initial dislocation structure presents a rectangular dislocation network in the 100 direction, which is composed of two sets of perpendicular dislocation lines. In the 110 direction, the initial dislocation structure is a "X" type junction consisting of four dislocation lines. In the 111 direction, the initial dislocation structure is composed of three sets of parallel dislocation lines. The results show that the plastic behavior of non-defect nanowires is related to the orientation of nanowires. The plastic behavior of nanowires with torsional grain boundaries mainly occurs at grain boundaries and shows the evolution behavior similar to that of FCC metal grain boundaries.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB383.1;O344

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