电塑性效应及其应用

评述显示电塑性效应的最早实验，电塑性研究的新近信息和电塑性技术的应用前景。利用高密度电流脉冲刺激导致的电塑性现象，是一种综合物理效应，它主要由电子对位错的有效推动作用引起，焦尔热效应、磁压缩效应、电流集肤效应、电子润滑剂效应起辅助作用。与传统拨丝工艺比较，电塑性拨丝显著降低拔制力，增大金属的塑性，改进丝的质量和性能，减免中间退火，强化生产，提高生产力，节约能源，改善生态环境，是一种有发展前途的新的拔丝工艺。

Residual elastic stress strain field and geometrically necessary dislocation density distribution around nano-indentation in TA15 titanium alloy

Nanoindentation and high resolution electron backscatter diffraction（EBSD） were combined to examine the elastic modulus and hardness of α and β phases,anisotropy in residual elastic stress strain fields and distributions of geometrically necessary dislocation（GND） density around the indentations within TA15 titanium alloy.The nano-indention tests were conducted on α and β phases,respectively.The residual stress strain fields surrounding the indentation were calculated through crosscorrelation method from recorded patterns.The GND density distribution around the indentation was calculated based on the strain gradient theories to reveal the micro-mechanism of plastic deformation.The results indicate that the elastic modulus and hardness for α p hase are 129.05 GPas and 6.44 GPa,while for β phase,their values are 109.80 GPa and 4.29 GPa,respectively.The residual Mises stress distribution around the indentation is relatively heterogeneous and significantly influenced by neighboring soft β phase.The region with low residual stress around the indentation is accompanied with markedly high a type and prismatic-GND density.

关于电塑性拔丝和其结构演变的讨论

简介了几种常用钢种电塑性拔丝的主要实验结果，综合分析钢丝电塑性变形不同层次结构的演变过程，对电塑性变形的机制问题进行了讨论。在微观结构层次上，电塑性效应基本上产生于强脉冲电流的电子对运动位错的激活作用，推动滑移变形的发展。在介观层次上，高密度的脉冲电流造成大量超弥散结构的伸长区，十分有利于向错的大量发射，实现变形的转动机制，导致大的变形甚至超塑性变形。这是电塑性变形最本质阶段。宏观层次上，强电流的脉冲刺激，主要在于减弱织构的发展，改善组织的形态，造成有利的应力应变状态。

斜切蓝宝石衬底MOCVD生长GaN薄膜的透射电镜研究

利用MOCVD技术在斜切角度为0.3°的c面蓝宝石衬底上生长了非故意掺杂GaN薄膜,并采用透射电子显微镜对材料的质量和材料内部缺陷进行了分析.研究发现斜切蓝宝石衬底上外延的GaN材料中,位错在距离衬底0.8μm附近大量湮灭,同时位错扎堆出现.基于上述现象,提出了斜切衬底上GaN材料中位错的湮灭机制,解释了斜切衬底能够提高GaN晶体质量的原因.

The growth of the screw dislocation of nacreous layer on Pteria penguin

In response to various environmental factors in offshore South China Sea,a group of microstructures of the screw dislocation are assembled in multiphase screw dislocations on the surface of the nacreous layer of Pteria penguin from the coastal waters of Hainan Island,China.The results of the transmission and scanning electronic microscope testing show that organic matter periodically secreted by epithelial histology of mantle of Pteria penguin pre-forms the original screw dislocation growth tem-plate in the form of film,along with its function to select,identify,and adhere to the amorphous calcium carbonate particles as the fine organic venations diffused in the epitaxial screw growth area.With the inducement and screw modulation of the or-ganic film and venations,the amorphous calcium carbonate particles gradually evolve into the pseudohexagonal self.aragonite microsheet with long-range order and screw dislocation structure by location-selecting tropism and screw dislocation growth.Numerous micron-scale aragonite microsheets join in the cluster's interactive movement and screw dislocation self-assembly of the organic film,stacking forward along the axis C spirally and forming the nacreous layer with screw dislocation structure.

The effect of boron on the electronic structure of dislocation in NiAl

The segregation effect of B on the [100]（010） edge dislocation core in NiA1 single crystals is investigated using the DMol method and the discrete variational method within the framework of density functional theory. The impurity segregation en- ergy and the charge distribution are calculated. The effects of B on the dislocation motion are discussed. The results show that B prefers to segregate at the Center-Al dislocation core. Moreover, B forms strong bonding states with its neighboring host atoms, which may not be beneficial to the motion of the dislocation. Therefore, it can be expected that the strength of NiAl single crystals may be increased.

Different structural origins for different sized surface pits observed on a-plane GaN film

A correlation study between the observed surface morphology using high-resolution scanning electron microscopy(HRSEM) and the observed structural imperfections using transmission electron microscopy(TEM) has been conducted for a-plane Ga N. There are three different sized asymmetric surface pits: large pit of 500 nm–2 ?m in side length, medium pit of 50 nm in side length, and small pit with side lengths of less than 5 nm, which originate from incomplete island coalescence, screw dislocation, and partial dislocation(PD), respectively. Both screw dislocation and PD can produce pits on the free surface because they have a perpendicular line tension to the surface, which must remain in balance with the surface tension. The two types of dislocation lead to distinctive pit sizes because the PD has a smaller Burgers vector component along the dislocation line than the pure screw dislocation. A pit that is produced in the island-coalescing process is much larger than those caused by dislocations because island coalescence is a kinetic process that involves large-scale mass transportation, whereas the dislocation mediates the surface in the local area. These three types of surface pits sometimes interact with one another in space. The coalescence of the island determines the surface morphology at large scales, whereas the defects affect the details.