硼向晶界扩散机理的研究

通过解变温扩散方程,导出非平衡晶界偏聚的数学表达式,建立了晶界贫硼局域尺寸与淬火加热温度、冷却速度以及非平衡晶界偏聚扩散激活能与扩散系数之间的关系,所得结果与实验结果相一致.     

硼在晶界的平衡偏聚与非平衡偏聚

在含硼20×10-6的GH128合金TLP扩散连接区中,硼在奥氏体晶界存在两类偏聚,即平衡偏聚和非平衡偏聚.晶界非平衡偏聚的一个重要特征是等温偏聚动力学曲线上出现极大值.在较低温度下等温,非平衡偏聚促进了晶界硼相的析出和平衡偏聚的建立.在连续冷却时,硼在晶界的偏聚是保温时形成的平衡偏聚和冷却时形成的非平衡偏聚的迭加.加热温度升高,其控制因素由前者转变成后者;冷却速度降低,后者增强.     

微量硼对20 MnVB 与25 MnTiB 钢淬透性的影响

本研究工作采用硼自射线照像技术,使用了 SSNTD(CAB)[固体核径迹探测器(为醋酸纤维)]检测 B 放射性同位素的重新分布.由此研究了 ppm 数量级的 B 对合金淬透性的贡献.研究时发现在高温臭氏体化过程中硼偏聚消失,含硼合金在淬火过程中产生的硼在晶界的偏聚为一非平衡热力学过程.奥氏体化后,偏聚程度随淬火温度的升高而增加,在晶界附近出现贫硼区,是晶界非平衡偏聚之突出特征.研究结果表明:微量硼对提高合金的淬透性是有利的.     

奥氏体晶界的硼偏聚对合金钢淬透性的影响

讨论了加硼合金钢在奥氏体化过程中，硼向奥氏体晶界扩散而造成的晶界硼偏聚，它阻止了新相形核，该理论能很好地解释微量硼提高合金钢淬透性的机理。     

微量硼在60Si2MnREB钢中的扩散与分布

采用平面接触型裂变径迹探测器研究了微量硼在60Si2MNREB钢中的分布，讨论了硼在60Si2MnREB晶界的非平衡偏聚机制及其对板材淬透性的影响。     

12Cr1MoV钢蒸汽管运行后金属中合金元素的晶界偏聚

研究了12Cr1MoV钢蒸汽管运行过程中金属内部的溶质合金元素的晶界偏聚现象。实验结果表明:12Cr1MoV钢蒸汽管金属在高温高压蒸汽作用下长期服役期间,晶界区的溶质合金元素百分含量逐渐增高,发生晶界“偏聚”现象。同时,在铁元素体晶粒内部形成了溶质合金元素的“贫化层”。晶界偏聚程度和铁素体晶粒内贫化层厚度均与运行时间有关。文中对获得的实验结果作了理论解释,并对晶界偏聚与蒸汽管金属老龄化的关系进行了讨论.     

硼在瞬时液相扩散连接中的作用机制

本文研究B在Ni基耐热合金瞬时液相扩散连接中的作用机制,采用经过改进的B的核反应产物粒子径迹照相方法和离子探针二次离子照相术及二次离子质谱逐点分析,探明了B在扩散连接区及其附近的分布,对分布与组织性能之间的关系进行了分析研究,发现在高温下经长时间扩散处理之后仍有相当数量的B聚集于基体金属的表层,很难向其“贫B区”长程扩散.此种偏聚是一个非平衡动力学过程,而扩散则是一个多级反应过程.对二次离子质谱逐点分析结果按菲克扩散方程计算得到在1000℃到1130℃温度区间B的扩散系为:D=0.89×10~(-7)cm~2/s～7.12×10~(-7)cm~2/s.     

Mo的添加对(PrNd)FeCoAlB磁体性能和热稳定性的影响

本文研究了Mo的添加对(PrNd)-Fe-Co-Al-B磁体的磁性能、热稳定性和相结构的影响。在适宜的制作工艺条件下,适量Mo的添加可增加磁体的矫顽力,降低磁体的开路磁通不可逆损失。相结构分析表明:在(PrNd)-Fe-Co-Al-B-Mo磁体中,小量的Mo存在于主相和富稀土R相中,而在富硼相中有大量Mo的偏聚。可能是Mo偏聚在富硼相,改善了富硼相的作用,从而提高了磁体的矫顽力,降低了不可逆损失。     

凝聚系统中硼元素的扩散机制(Ⅰ)——硼在金属中的扩散

讨论硼在γFe B系统以及GH12 8合金TLP扩散连接区中的扩散机制 ,计算了它们的扩散系数与激活能 .理论计算和已有的实验结果符合很好     

硅中注入硼的扩散

硼是半导体材料中最主要的杂质，而精确控制杂质浓度剖面是半导体工艺的关键问题之一．对硼在硅中的扩散从理论与实验的结合方面进行了系统的讨论．     

Interface Defect Chemistry and Effective Conductivity in Polycrystalline Cerium Oxide

Polycrystalline cerium oxide exhibits increasing electronic and decreasing ionic conductivity upon reduction of the grain size. In the present study, the origin of this effect was examined. Temperature-programmed reduction (TPR) and oxygen titration measurements on nanocrystalline cerium oxide revealed a large excess oxygen deficiency associated with the surface. Using a two-phase model for the combined system of the bulk phase in equilibrium with a surface layer, this enhanced oxygen deficiency could be explained by a reduced binding energy of surface oxygen ions in agreement with results from atomistic computer simulations. The model also revealed that this segregation of oxygen vacancies is the origin of an intrinsic space charge potential. Translating this effect to polycrystalline cerium oxide and taking into account the segregation of dopants and the accumulation/depletion of charge carriers, it was possible to model the grain size dependence of electrical conductivity and thermopower of polycrystalline cerium oxide. A straightforward 1-dimensional numerical model and a change from Boltzmann to Fermi-Dirac statistics allowed to calculate the conductivity of heavily doped polycrystalline cerium oxide for grain sizes in the range of 5–10,000 nm and acceptor concentrations up to 20%. Using this approximation, the effect of grain size on mixed ionic/electronic conductivity and the electrolytic domain boundary was investigated.     

A new method for solving non‐linear carrier diffusion equation in axial direction of broad‐area lasers

The solution of non‐linear carrier diffusion equation associated with the axial direction of broad‐area laser has been achieved by a hybrid asymptotic‐numerical method that combines WKB approximation and the variation of constants method. The non‐linearity has been taken into account by using an iterative scheme: carrier lifetime has been linearized and calculated as a function of carrier density known from the previous iteration. Non‐uniform photon density has been taken into account. As the new method is based on analytical solutions, it is very fast and not vulnerable to large gradients of carrier concentration usually occurring in the vicinity of laser facets. Therefore, it can be useful in complicated self‐consistent thermal models of broad‐area lasers. The obtained results are compared with two simplified cases: solution of linear diffusion equation with constant coefficients and calculations neglecting the diffusion. Copyright © 2010 John Wiley & Sons, Ltd.     

Mn-Mo-B-RE系铸态钢中的硼分布

研究了Mn Mo B RE系低合金铸钢中硼的偏析和均匀化、正火、调质热处理过程中硼分布的变化 ,以及稀土元素加入和钢中Mo等元素对硼分布的影响 .硼在铸钢中有明显的偏析现象 ,经正常的均匀化处理后 ,铸钢中硼分布的均匀性受Mo的偏析强烈影响 .在特定的条件下 ,会产生沿奥氏体一定结晶学平面的硼相析出 ,会沿晶界形成粗大连续网状的硼相 ,导致脆断 .结果表明稀土元素可以抑制硼的偏析 ,从而起到保护硼的作用 .     

PRELIMINARY CONSIDERATIONS ABOUT THE ADOPTION OF UNCONVENTIONAL MAGNETIC MATERIALS AND STRUCTURES FOR INDUCTION MOTORS

ABSTRACT

The activity carried out and presented in this paper deals with the opportunity of utilizing high quality magnetic materials, such as amorphous, microcristalline or cubic texture materials for the magnetic structure of medium size induction motors.

In order to evaluate the benefits introduced by these materials for reducing the iron losses in a.c. motors, digital preliminary computations have been carried out considering the characteristic of such materials (Induction versus specific losses) and the obtained results for each solution have been compared.

At the present, however, the; above mentioned materials are costly, not easy to handle and to assemble and therefore a practical solution with grain oriented steel in a crossed structure obtained alternating sheets with orthogonal grain orientation, in order to simulate the cubic texture material (i-oriented material) has been proposed.

To verify the obtained theoretical results with the digital computations, a prototype of 20 Hp, 380 V, three phases induction motor with this non conventional magnetic structure has been designed and built. The tests on the prototype to evaluate the iron losses are in good agreement with the digital simulation results.     

渗Dy处理对烧结NdFeB磁体结构与磁性能的影响

在工业生产线上制备35H、40H烧结钕铁硼磁体,应用DyF_3粉末作为镝源,进行渗镝处理试验。应用比较高的渗镝处理温度、比较长的渗镝处理时间有利于提高渗镝处理磁体的内禀矫顽力;在一定的渗镝处理温度和时间条件下,随着磁体厚度减小,渗镝处理磁体的内禀矫顽力明显提高。在1218 K保持2 h而进行渗镝处理,3.0 mm厚度40H磁体的内禀矫顽力上升幅度达到406.7 kA/m,其剩磁下降0.0187 T;而3.0 mm厚度35H磁体的内禀矫顽力上升363.8 kA/m,其剩磁下降幅度为0.0198 T。SEM与EDAX分析结果表明,Dy元素扩散进入富稀土晶界相中,并存在于主相晶粒表面区域,从而使渗镝处理磁体内禀矫顽力大幅度上升,同时其剩磁仅略微下降。     

A METHOD FOR PREDICTING TIME-CURRENT CHARACTERISTICS OF FUSELINKS

ABSTRACT

In this study a model for the calculation of prearcing time-current in fuselinks is presented. This model is based on the solution of the electric potential, current density and heat diffusion equations using the approximation of the partial derivatives by central finite differences. In this model the variation of the different parameters with temperature is taken into account in the equations. Because of the non linearity of the equations, the solution is obtained by means of a Gauss-Seidel iterative method or relaxation process. The model has been applied to the study of a real fuselink, and a perfect coincidence has been obtained between the theoretical results of the model and the experimental values. The consideration of the variability of the parameters with temperature is fundamental for the above mentioned coincidence. The model has been also used to study the behaviour of different metals as fuse elements. For the studied metals, we can conclude that to obtain different characteristic curves it is necessary to use different geometric forms, since for the same geometry there is a thickness for each material which allows to obtain the same characteristic curve. The model can also be applied to the study of geometric influence on fuselinks.     

某火电厂磨煤机高速轴断裂失效分析及预防措施

贵州某电厂磨煤机的高速轴在运行过程中发生断裂,通过金相组织分析、化学成分分析及硬度试验等方法,断裂失效的主要原因：非金属夹杂物含量较多,锻造比不够,带状组织及成分偏析导致开裂。     

非均匀沙起动研究

非均匀沙运动规律与均匀沙明显不同。本文从非均匀沙起动的特点出发，阐述了其运动机理，采用滚动起动模式。通过对附加质量力的概念及表达式和相对暴露度参数的引入，推出了非均匀沙起动公式。并用实测资料进行了验证，同其它学者们的公式相比较为合理。同时得到了均匀沙的起动公式，其系数涵盖了其它均匀沙公式。说明本文公式较好的反映了非均匀沙的起动特性。     

Oxygen Diffusion in Single- and Poly-Crystalline Zinc Oxides

¹⁸O diffusion coefficients were measured in zinc oxide ceramics using a secondary ion mass spectrometer. The results are interpreted as indicating extrinsic behavior. The values of the lattice diffusion coefficients with higher valence dopants compared with zinc ions are greater than lower valence dopant such as lithium ions. Using the data at deeper depth, the grain boundary diffusivity of oxide ions was also evaluated. Although the lattice diffusion coefficients varied by two orders of magnitude, the products of grain boundary width and grain boundary diffusion coefficient were less sensitive to the type of dopants.