Improvement of SiC_p Reinforced Cast AluminiumComposites by the ROC Method

ＩｍｐｒｏｖｅｍｅｎｔｏｆＳｉＣ＿ｐＲｅｉｎｆｏｒｃｅｄＣａｓｔＡｌｕｍｉｎｉｕｍＣｏｍｐｏｓｉｔｅｓｂｙｔｈｅＲＯＣＭｅｔｈｏｄＺｈｅｎｇＱｉｆｅｉ，ＸｉｅＳｈｕｉｓｈｅｎｇ，ＹｕａｎＧｕａｎｓｅｎ，ＳｈｉＬｉｋａｉ（郑弃非）（谢水生）（袁冠森）（...     

脉冲磁场下铝合金定向凝固磁场分布数值模拟

采用ANSYS 8.0有限元分析软件对铝合金脉冲磁场定向凝固磁场分布作了数值模拟,得到了凝固过程中的磁场分布状态.结果表明:在试样中心附近磁感应强度较强,而在端部较弱.模拟结果和实验测得结果相符合.通过数值模拟,不仅可以初步了解凝固过程中的磁场分布状态,而且有助于进一步研究凝固组织细化的原因.     

The Internal Oxidation of Ternary Alloys II: The Coupled Internal Oxidation of the Two Most-Reactive Components Under Intermediate Oxidant Pressures

The kinetics of the coupled internal oxidation of the two most-reactive components in the scaling of ternary alloys under oxidant pressures below the stability of the oxide of the most noble component are examined using a number of simplifying conditions which allow to develop an approximate analytical treatment. The precipitation of the two oxides may occur either at a single front or at two different fronts of internal oxidation. The former case corresponds to a unique solution for all the parameters involved in the process. On the contrary, the existence of two fronts of internal oxidation yields a finite range of possible solutions for the oxidation kinetics as well as for all the other relevant parameters. Even though the present treatment does not allow to predict which solution will be adopted by a real system, it is possible to set limits to the values of the parameters yielding physically-acceptable solutions. After considering a general case, the treatment is applied to a real system already examined experimentally.     

The Internal Oxidation of Ternary Alloys I: The Single Oxidation of the Most-Reactive Component Under Low Oxidant Pressures

The internal oxidation of the most-reactive component C of ternary A–B–C alloys by a single oxidant is examined assuming a gas-phase oxidant pressure below the stability of the oxides of the other two components. The precipitation of the most-stable oxide leaves behind a matrix composed of a binary alloy of the two less-reactive components, whose composition affects the solubility and diffusivity of the oxidant within the region of internal oxidation, with an effect on the reaction kinetics. Approximate relations between these properties are proposed and used to predict the kinetics of internal oxidation of C under the assumption of parabolic rate law. The results obtained for the ternary alloys are compared with the behavior of binary A–C and B–C alloys with the same C content. A new important factor in establishing the difference between the internal oxidation in ternary A–B–C alloys and in binary A–C and B–C alloys under a fixed gas-phase oxygen pressure and C content is the ratio between the concentrations of A and B in the bulk ternary alloy.     

放电等离子烧结Fe3B／（Pr,Tb）2Fe14B块体纳米晶双相复合永磁体的性能

采用放电等离子烧结技术将非晶Pr4.2Tb0.3Fe78B17.5薄带制备成块状纳米晶复合磁体。研究了烧结条件对磁体密度、微观结构和磁性能的影响。结果表明，烧结温度的升高可使磁体得到高致密度，但同时由于其晶粒长大，结果导致磁性能的恶化。在最佳烧结条件下得到磁体的磁性能为Br=1．02T，JHc=220kA／m。磁体具有较好的微观结构，平均晶粒尺寸为20nm。     

Spline-based automatic path generation of welding robot

This paper presents a flexible method for the representation of welded seam based on spline interpolation. In this method, the tool path of welding robot can be generated automatically from a 3D CAD model. This technique has been implemented and demonstrated in the FANUC Arc Welding Robot Workstation. According to the method, a software system is developed using VBA of SolidWorks 2006. It offers an interface between SolidWorks and ROBOGUIDE, the off-line programming software of FANUC robot. It combines the strong modeling function of the former and the simulating function of the latter. It also has the capability of with on-line robot. The result data have shown its high accuracy and strong reliability in experiments. This method will improve the intelligence and the flexibility of the welding robot workstation.     

Di对Mg-10Al合金显微组织与力学性能的影响

研究了Di加入量为1％～3％（质量分数，下同）[Nd—Pr混合稀土金属，w（Nd）：w（Pr）=3：1]的Mg-10Al合金的显微组织和力学性能。通过显微组织分析发现Di加入Mg-10Al合金后，析出了块状的Al2（Nd，Pr）相及杆状的Al11（Nd，Pr）3相，合金组织得到细化。Di的加入使铸态的Mg-10Al合金的力学性能提高，在Di的加入量为2％时，块状的Al2（Nd，Pr）相占主导地位，合金的抗拉强度和伸长率都达到峰值。在Di的加入量达到3％时，杆状的Al11（Nd，Pr），相增加，抗拉强度、尤其是伸长率有所降低。     

Corrosion of Three Commercial Steels Under ZnCl2 –KCl Deposits in a Reducing Atmosphere Containing HCl and H2S at 400–500°C

The corrosion of three commercial steels in a reducing atmosphere containing HCl plus H₂S in the presence of ZnCl₂–KCl deposits has been investigated at 400–500°C and compared with the corrosion of the same materials in a similar gas mixture free from H₂S. The presence of H₂S in the gas accelerated the corrosion of the three commercial steels beneath ZnCl₂–KCl deposits. All materials suffered from severe corrosion with partial detachment and spalling of the external scales. Degradation of the steels resulted from the penetration of chlorine-containing species through the scale formed initially down to the metal matrix, because chorine-rich species were detected close to the alloy/scale interface. Although the corrosion resistance generally increased with increasing Cr content, even the high-Cr stainless steel SS304 is still unable to provide good corrosion resistance against the ZnCl₂–KCl deposits in the presence of H₂S due to the bad adherence of the scales to the alloy. The mechanisms of attack are discussed on the basis of thermodynamic considerations and of the active-oxidation model.     

The corrosion of Co-Nb alloys in reducing/oxidizing-sulfidizing gases at 600–800°C

The corrosion of the two pure metals and of two alloys containing 15 and 30 wt% Nb has been studied at 600–800°C in H₂-H₂S-CO₂ gas mixtures providing 10⁻⁸ atm S₂ at all temperatures and 10⁻²⁴ atm O₂ at 600°C and 10⁻²⁰ atm O₂ at 700 and 800°C. The corrosion kinetics were rather complex, being sometimes parabolic and in other cases nearly linear. Under a constant temperature the addition of niobium generally reduced the corrosion rate, except at 700°C when pure cobalt corroded more slowly than the two alloys. The corrosion rates for the same material decreased with an increase in temperature under the same sulfur pressure. Except at 800°C under 10⁻⁸ atm S₂, which is below the dissociation pressure of cobalt sulfide, the scales presented an outer layer of pure cobalt sulfide and an inner layer of complex composition containing a mixture of double sulfide, niobium oxide and in some cases of unreacted metallic cobalt particles. The addition of niobium was generally beneficial, the effect increasing with its concentration in the alloy, but the corrosion rates of the alloys were still much higher than that of pure niobium, mainly as a result of the lack of formation of a protective layer of niobium sulfide. The corrosion behavior is examined with special reference to the consequences of the low solubility of niobium in cobalt and to the relation between the microstructure of the alloys and the scales.     

对Al-Cu合金中α-Al及Al2Cu生长行为的探讨

研究了Al-Cu合金中α-Al和Al2Cu的生长行为,分析了初生α-Al及初生Al2Cu作为共晶核心形核的能力.结果发现,在过共晶组织中,初生相Al2Cu形貌大部分有明显的拐角,观察其平面有的呈矩形,呈现小面生长特性.而α-Al与Al2Cu共晶生长时,Al2Cu择优生长特征削弱,与α-Al耦合生长呈现非小面-非小面生长,表明Al2Cu在不同的生长阶段表现出的生长行为不同.在亚共晶组织中,初生相α-Al周围形成离异共晶的Al2Cu,而过共晶组织中初生相Al2Cu周围没有离异共晶的α-Al,表明初生相Al2Cu作为共晶层片核心的能力比初生相α-Al作为共晶层片核心的能力强.