由于较高的综合力学性能，氮化硅陶瓷球得到广泛的工程应用，但是极端工况下依然存在明显失效开裂现象。在一般氧化物烧结助剂的基础上添加少量过渡金属化合物能起到优化材料设计和进一步提高性能的作用，但是相关作用机理还未有明确探知。在添加Al2O3和Y2O3烧结助剂基础上，分别添加TiN、Fe3Si和WC等过渡金属化合物，并采用热等静压烧结方法制备了氮化硅陶瓷轴承球。采用X射线衍射检测其物相组成，采用扫描电子显微镜和透射电子显微镜研究其组织结构特点，并使用纳米压痕法对其力学性能进行了研究。结果表明，添加TiN可有效抑制烧结过程中有害物相Si2N2O的生成；添加TiN和WC有利于烧结过程Al和O向氮化硅基体中扩散，形成了Sialon相；添加Fe3Si则不具有上述作用；添加TiN可获得晶粒尺寸细小均匀的β-Si3N4组织；添加Fe3Si会生成粗大β-Si3N4晶粒相互穿插桥接且其空隙填充细小β-Si3N4晶粒的烧结组织；添加WC则生成粗细晶共存的非均匀组织。与添加Fe3Si和WC相比，添加TiN的氮化硅陶瓷球具有更高的硬度和更大的弹性模量等更好的力学性能。

Domain pattern is the carrier of electromechanical property. A novel domain pattern will open a gate for ferroelectric nanodevice. A distinctive topological domain pattern termed as hierarchical vortex (Hvo) has been found in polycrystalline ferroelectric based on the first-principles-based atomistic method. The Hvo pattern displays a unique structure, which is a flux-closing vortex encircle an anti-vortex or a vortex and anti-vortex pair (VA). Each Hvo structure could be regarded as a single vortex to forming a vortex–anti-vortex pair with anti-vortex or forming a vortex–vortex array with the vortex. The mechanism of HVo obtained in polycrystalline ferroelectric has been found that the grain boundary (GB) equals the domain wall when the first-order vortex is in the vortex. The HVo will open a new view of the domain topology pattern and its evolution.Domain pattern is the carrier of electromechanical property. A novel domain pattern will open a gate for ferroelectric nanodevice. A distinctive topological domain pattern termed as hierarchical vortex (Hvo) has been found in polycrystalline ferroelectric based on the first-principles-based atomistic method. The Hvo pattern displays a unique structure, which is a flux-closing vortex encircle an anti-vortex or a vortex and anti-vortex pair (VA). Each Hvo structure could be regarded as a single vortex to forming a vortex–anti-vortex pair with anti-vortex or forming a vortex–vortex array with the vortex. The mechanism of HVo obtained in polycrystalline ferroelectric has been found that the grain boundary (GB) equals the domain wall when the first-order vortex is in the vortex. The HVo will open a new view of the domain topology pattern and its evolution.

先进第三代中锰汽车钢具有强塑积高、成本低廉等优点，应用前景广阔，但其焊缝区的淬硬性大，影响后续加工和使用。采用光纤激光器对6 mm厚中锰汽车钢进行焊接，研究了焊接热输入对焊缝成形、组织、冲击韧性和断裂行为的影响。结果表明，当热输入为150～500 J/mm时，激光焊接属于深熔焊，焊缝成形较好；焊缝区的硬度随着热输入的增大呈减小趋势。当热输入较小时，焊缝组织为马氏体，随着热输入的增加，焊缝中有少量的贝氏体组织生成；焊缝在－40 ℃温度下的冲击韧性随着热输入的增加先增加后降低，当热输入为300 J/mm时，冲击韧性最高，断口呈韧性断裂；中锰钢焊缝组织中原奥氏体晶界、马氏体板条束界和板条块界均对裂纹的扩展起阻碍作用，裂纹扩展功与平均有效晶粒尺寸呈反比关系，与大角度晶界密度呈正比关系。

Fine finishing of tungsten alloy is required to improve the surface quality of molds and precision instruments. Nevertheless, it is difficult to obtain high-quality surfaces as a result of grain boundary steps attributed to differences in properties of two-phase microstructures. This paper presents a theoretical and experimental investigation on chemical mechanical polishing of W–Ni–Fe alloy. The mechanism of the boundary step generation is illustrated and a model of grain boundary step formation is proposed. The mechanism reveals the effects of mechanical and chemical actions in both surface roughness and material removal. The model was verified by the experiments and the results show that appropriately balancing the mechanical and chemical effects restrains the generation of boundary steps and leads to a fine surface quality with a high removal rate by citric acid-based slurry.

氟化钙(CaF2)晶体具有紫外透过率高(＞99%@193 nm)、抗激光损伤阈值高等特点, 在高功率紫外激光器、深紫外光刻机等领域具有广泛的应用。应力双折射是氟化钙晶体在实际应用中的关键性能指标, 会导致通过晶体的光束发生形变, 严重影响成像质量。采用坩埚下降法制备了尺寸为210 mm的氟化钙晶体, 系统研究了CaF2晶体的位错和小角度晶界以及结晶质量对晶体应力双折射的影响, 实验结果表明, 位错密度的增高、小角度晶界的聚集、结晶质量的变差, 会引起局部残余应力的集中, 加剧应力双折射现象。

Anisotropy is one central influencing factor on achievable ultimate machined surface integrity of metallic materials. Specifically, grain boundary has a strong impact on the deformation behaviour of polycrystalline materials and correlated material removal at the microscale. In the present work, we perform molecular dynamics simulations and experiments to elucidate the underlying grain boundaryassociated mechanisms and their correlations with machining results of a bi-crystal Cu under nanocutting using a Berkovich tool. Specifically, crystallographic orientations of simulated bi-crystal Cu with a misorientation angle of 44.1° are derived from electron backscatter diffraction characterization of utilized polycrystalline copper specimen. Simulation results reveal that blocking of dislocation motion at grain boundaries, absorption of dislocations by grain boundaries and dislocation nucleation from grain boundaries are operating deformation modes in nanocutting of the bi-crystal Cu. Furthermore, heterogeneous grain boundary-associated mechanisms in neighbouring grains lead to strong anisotropic machining behaviour in the vicinity of the grain boundary. Simulated machined surface morphology and machining force evolution in the vicinity of grain boundary qualitatively agree well with experimental results. It is also found that the geometry of Berkovich tool has a strong impact on grain boundary-associated mechanisms and resultant ploughing-induced surface pile-up phenomenon.

为了深入理解纳米Al-Ni合金低温下的电子输运过程, 使用自主研发的电磁感应加热-自悬浮定向流法制备出Al, Ni和Al-Ni纳米合金粉末, 并采用真空热压设备将纳米粉末压制成纳米晶块体, 利用自主搭建的低温热电测量系统研究了Al-Ni纳米合金的电阻率随温度(8~300 K)的变化规律。研究结果表明: Al-Ni纳米合金由于形成有序晶相而仍然与Al, Ni纳米晶一样, 电阻率随温度的降低而降低。纳米Ni3Al-Ni和NiAl-Ni在居里温度点附近出现了电阻率随温度变化的极大值点, 因为单质Ni的影响, Ni3Al-Ni的居里温度比粗晶Ni3Al提高了20 K。由于磁子-电子散射作用和声子-电子散射作用, 纳米Ni3Al-Ni, NiAl-Ni和Ni的电阻率在低温下(8~40 K)与温度呈T2和T4关系。

激光熔覆制备了一种高硬度铁基涂层，涂层平均硬度约为775 HV，未发现裂纹缺陷。对涂层显微组织进行表征，结果显示，涂层为均匀、细小的树枝晶组织形态，初生枝晶内为马氏体相，枝晶间为残余奥氏体相，残余奥氏体基体上弥散分布着颗粒状碳化物。枝晶间有Mo、Cr、W、Nb等元素偏聚，但涂层中的C元素分布均匀。枝晶间残余奥氏体存在大量层错，并在层错密集区有马氏体相析出。

碲锌镉晶体中存在着各种晶体缺陷, 其中小角晶界是制约碲锌镉晶体质量的主要晶体缺陷之一。X射线衍射形貌术是一种非破坏性地全面研究小角晶界缺陷的有效方法。采用反射式 X射线衍射形貌术对碲锌镉衬底的小角晶界缺陷进行了研究, 讨论了小角晶界类型、样品扫描方向以及入射线发散度等对小角晶界缺陷的 X射线衍射形貌的影响。为全面获得小角晶界缺陷的衍射形貌, 应尽量选择宽的入射线狭缝, 对于对称倾侧晶界和扭转晶界, 应分别平行和垂直于小角晶界方向扫描。