为了研究冷轧工艺对IF钢显微组织的影响.本文借助电子背散射衍射技术,研究了20%到75%冷轧压下率的IF钢退火后的微观结构、晶界特征分布和晶界连通性.结果表明:随着冷轧压下率的增加,冷轧态晶粒逐渐由等轴状变为纤维状,退火态晶粒逐渐细化并变得均匀,小角晶界的出现频率呈下降趋势;随机晶界的出现频率呈明显上升趋势,且随机晶界占绝对优势;而CSL晶界在冷轧压下率40%以下时,变化较小,40%以上时,含量明显增加.大变形量轧制后的IF钢CSL晶界主要由Σ3晶界组成,而小变形量轧制后主要是Σ3和Σ13b晶界.对于75%压下率,还含有较多的Σ7,Σ9和Σ11等CSL晶界.通过增加冷轧压下率,0-CSL三叉晶界的含量减少,1-CSL三叉晶界的含量增加.因此,通过改变冷轧工艺,可以优化IF钢板的晶界特征分布及连通性.

With the aim of investigating effect of cold rolling on the microstructure of interstitial-free steel, microstructure, grain boundary character distribution and grain boundary connectivity were studied by means of electron back-scatter diffraction technology. The results showed that the fibrous grains were changed into equiaxed ones in the microstructure of the IF steel after cold rolled with reduction ranged from 20% to 75%. Furthermore, the higher the cold rolling reduction, the finer and more uniform grains of steel were observed after annealed. The amount of low-angle grain boundaries decreased, whereas the frequency of random grain boundaries increased sharply with the increasing of cold reduction from 20%to 75%. However, the proportion of CSL grain boundaries increased with increasing cold reduction, but there was a negligible fluctuation in the cold reduction of 40%. The majority of grain boundaries were random grain boundaries. CSL grain boundaries of IF steel were mainly compo

本文采用重合位置点阵理论构建了α-Fe的Σ3[110](112)对称倾转晶界模型,通过基于密度泛函理论的平面波超软赝势方法研究了稀土La元素在α-Fe中的占位倾向.结果表明,La在α-Fe晶界的杂质形成能最低,因而La原子倾向于占据晶界区;掺杂La前后的α-Fe晶界电子结构计算结果显示,La占位于α-Fe晶界会使体系中的电荷发生重新分配,将提供更多电子用于晶界区成键,使得Fe原子得到更多的电子,这将导致掺杂区原子间结合有离子化趋势,从而使La与晶界区相邻Fe原子之间的相互作用加强,也使晶界原子与晶界两侧Fe原子的键合加强,从能量角度解释了材料宏观力学性能变化的原因;计算同时发现,La加入后,也使晶界上的原子成键区态密度左移,降低了体系的总能量,使晶界结构更为稳定.

Theα-FeΣ3[110] (112) symmetrical tilt grain boundary model is established by the coincidence site lattice theory. First-principles plane wave ultrasoft pseudopotential method based on the density functional theory is used to calculate the La occupying tendency in α-Fe. The results show that La elements tend to be located at grain boundary in theα-Fe since the impurity formation energy keeps lowest. On this basis, the electronic structure of La doped in α-Fe grain boundary is also calculated. The results indicate that the charges in the system are redistributed to provide more electrons for the grain boundary bonding when the La occupiesα-Fe grain boundary. Meanwhile, Fe atoms obtain more electrons, and the La doped region combination has the ion-tendency toward strengthening the interaction between La atom and Fe atoms in the adjacent boundary region, and the Fe atom bonds in the grain boundaries and on both sides of the grain boundary also strengthen, which is the reas

电子背散射衍射技术EBSD在测定晶体取向、显微织构及统计晶界结构参数等方面具有独特的优势,可统计分析晶体中晶粒大小和晶界结构。金属宏观性能与晶界结构联系紧密。本文综述了近些年用EBSD技术研究各类金属材料(如铁基、镍基、铜基、钛基等)晶界中取得的众多新进展,如发现重结晶可以使特殊晶界比例增高,小角度晶界与材料耐火性能之间有密切联系以及特殊晶界在动态破坏和疲劳中起着重要作用等。这些结果建立了材料晶界性质和宏观性能之间的联系,为金属材料性能判定提供参考,也为材料学研究提供新依据。

Due to the unique advantage on grain boundary misorientation and micro-texture,electron back scatter diffraction was usually used to analyze the grain size and boundary in crystals statistically.The macroscopical performance of metal was closely associated with grain boundaries.Recent processes on the grain boundary of a series of metals,such as Fe-,Ni-,Cu- and Ti-based materials,by EBSD were reported in the paper.It was found that recrystallization would increase the fraction of special grain boundary,low angle grain boundary was in xtricably inked with the fire resistance and special grain bound ry played an important role in dynamic damage and fatigue et al.These results established the connection between the properties of grain boundary and the macroscopical performance,providing a reference for performance deter-mination and new evidence for ma rial science.

本文利用透射电镜‘双倾拉伸实验’技术,原位研究了Au多晶纳米线在拉伸状态下的变形行为。实验发现由纳米晶粒组成的多晶纳米线在室温下具有-48%的大塑性变形能力。这种大塑性变形能力由晶界滑移和晶界的迁移相互协调实现。在滑移的同时,通过晶界原子扩散导致的晶界迁移来协调晶界滑移,避免空洞和裂纹的产生。

In this paper, the deformation behaviors of nanocrystalline gold nanowire were in-situ observed with homemade TEM double tilt tensile device. The nanocrystalline nanowires exhibit approximate 48% of homogeneous elongation ability. The in-situ TEM observation indicates that the ultra-large plastic deformation is realized through the coordination of grain boundary sliding and grain boundary migration. During the deformation process, the grain boundary sliding provides the large plastic deformation ability, which is at the mean time accommodates by the grain boundary migration.

采用晶体相场法研究了单轴拉伸下三角相双晶变形过程及机理，并重点分析了小角对称与非对称晶界和大角对称与非对称晶界在变形过程中的演化及微观机理，变形过程中应力方向与初始晶界方向平行。结果表明，小角对称晶界由柏氏矢量夹角呈60?的两种刃型位错组成，变形过程中不同类型的位错运动方向相反，并各自与另一晶界上同一类型位错相互吸引以致部分位错发生湮没；小角非对称晶界上的位错类型单一，在应力作用下先沿水平方向攀移，后各自分解成柏氏矢量约呈120?的两位错，并通过位错运动和湮没最终形成理想单晶；大角晶界在应力的作用下先保持水平状态而后锯齿化并发射位错，伴随着位错运动和湮没，最终大角非对称晶界发生分解，而大角对称晶界则重新平直化，表明大角对称晶界比大角非对称晶界更稳定，这与实验和分子动力学模拟结果一致。

Phase field crystal method is used to investigate the deformation process and mechanism of twined structure of a trigonal phase under uniaxial tensile deformation, and the evolution and corresponding micro-mechanism of low-angle symmetric and asymmetric grain boundaries (GB) as well as high-angle symmetric and asymmetric GB during deformation process are analyzed in detail. The deformation is performed under the condition that the direction of applied stress is parallel to that of initial GB. Results show that low-angle symmetric GB is composed of two kinds of edge dislocations with the angle made by Burgers vectors being around 60?During deformation, two kinds of dislocations in low-angle symmetric GB move along two opposite directions, then meet with the same kind of dislocation emitted from another GB leading to the annihilation of partial dislocations. As to the low-angle asymmetric GB, its only one kind of dislocation first climbs and moves along the horizontal direction of the ap