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1.
The AlMnCe/Al2O3 metal/ceramic composite with 3D micro-cellular structure is prepared by spark plasma sintering (SPS) at 520 ℃. It consists of consecutive nano-Al2O3 sintering body phase and AlMnCe alloy discrete phase. The microstructure of sample, characteristic of the micro-cellular structure and microstructure of the interface are investigated via scanning electron microscope (SEM) and transmission electron microscope (TEM) method. The results indicate that two kinds of interfaces are formed in the sample during SPS process, one is the micro-nano type metal/ceramic interface between the metal cellular body and the nano-ceramic cellular wall, the other is the nano-nano type ceramic/ceramic interface in the nano-ceramic cellular wall. The fusion transition area with a width 200-300 nm at interface of the AlMnCe alloy and nano-Al2O3 sintering body is formed. The AlMnCe alloy has a sufficient immersional wetting for the Al2O3 cellular wall. The bonding of interface between the nano-Al2O3 sintering body and the AlMnCe alloy particle is powerful, and new phase and crack is not found.  相似文献   

2.
The effects of alloying elements on the mechanical properties as well as electrical conductivity in Cu-15% (mass fraction) in-situ composites were systemalically studied and high strength and high electrical conductive Cu base in-situ composites have been developed. The best combination is the addition of 0.1% to 0.2% Zr, Ti, or Sn in Cu-15%Cr in-situ composite, thermomechanical treatment to refine the microstructure and optimizing the precipitation of second phase. The strength is controlled by high density of dislocations in the Cu matrix, the lamellar spacing of the second phase, and the fine Cr precipitates. The aging treatment to reduce solute atoms has a beneficial effect on the increase of electrical conductivity. The addition of Zr, or Ti of about 0. 15% to 0.2% promotes the precipitation of Cr particles.  相似文献   

3.
With the means of electron backscattered diffraction (EBSD), mechanical properties test and digital eddy current metal conductivity, the single crystal copper cold- welded joint was tested and analyzed, the structure change of cold- welded joint and the effect of heat treating on the structure and property of cold- welded joint were discussed. The results show that: The deformation area of the single crystal copper cold welded joint is broken, the crystalline grain at the interface of the joint is refined, and the single crystal structure is still maintained in the base metal area. The hardness of the deformation area increases greatly, the conductivity of the joint does not change much, and the tensile strength of the joint reaches about 70% of that of the base metal. At the interface of the heat treating joint, the single crystal structure of the deformation area and the base metal area are destroyed, and the grains grow up at the interface and the orientation is different. The hardness of the joint interface is much lower than that of the non-heat treating joint, the electrical conductivity of the joint is good, and the tensile strength of the joint is higher than that of the base metal.  相似文献   

4.
The thick and hard ceramic coatings were deposited on 2024 AI alloy by microarc oxidation in the electrolytic solution. Microstructure, phase composition and wear resistance of the oxide coatings were investigated by SEM, XRD and friction and wear tester. The microhardness and thickness of the oxide coatings were measured. The results show that the ceramic coating is mainly composed of α-Al2O3 and γ-Al2O3. During oxidation, the temperature in the microarc discharge channel is very high to make the local coating molten. From the surface to interior of the coating, microhardness increases gradually. The microhardness of the ceramic coating is HV 1 800, and the microarc oxidation coatings greatly improve the antiwear properties of aluminum alloys.  相似文献   

5.
The effects of boron on electrical conductivity of aluminum and the action mechanism have been investigated.The results indicate that,by combining with the trace amounts of transition elements Ti,V and Zr to form two kinds of insoluble borides,boron can significantly improve the electrical conductivity of commercial aluminum.One of the borides contains 54.42% B,13.70% Al and 23.39%(mole fraction) transition elements (including Ti,V,Zr and Fe)and is in the form of fine particles,The other one,in hexagonal shape,contains 78.59% B,14.97%Al and 2.56% (mole fraction)transition elements (including Ti,V and Fe),Neither Cr nor Mn is found in these borides,The conversion of some transition metal impurities from solid solution state to the boride precipitates form leads to a decrease in electrical resistivity,and this decrease constitutes 86.2% of that can be achieved by complete removal of transition element impurities from aluminum melts.  相似文献   

6.
This paper gives a brief introduction to the four research methods for the study on thermal conductivity of cast irons,including experimental measurement,statistical analysis,effective medium theory and numerical simulation.Recent studies on the thermal conductivity of various cast irons are reviewed through the influence of alloying elements,structural constituents,and temperature.The addition of alloying elements is the main reason that restricts the thermal conductivity of cast irons,especially spheroidal graphite cast iron.The connectivity of graphite has a significant effect on the thermal conductivity of flake and compacted graphite cast irons,semiquantitative and quantitative analysis of this factor is a key and difficult point in the study of thermal conductivity of cast irons.The thermal conductivities of different types of cast irons show varying degrees of dependence on temperature.This phenomenon is the combination of graphite and matrix,rather than just depending on graphite morphology.The study of the relationship between individual phase and temperature is the focus of future research.These summaries and discussions may provide reference and guidance for the future research and development of high thermal conductivity cast irons.  相似文献   

7.
Ag-28Cu-8Sn(wt%) alloy is a widely used brittle silver-based brazing filler metal.The wire of brazing filler metal was prepared by continuous casting process and dieless drawing technology.The phase structure was measured by X-ray diffraction(XRD),and the microstructure of wetting interface,cast states,processing states and fracture morphologies were characterized by the optical microscopy(OM) and scanning electron microscopy(SEM),respectively.The electrical conductivity,hardness,tensile strength and elongation rate were tested as well.Furthermore,the solid-liquid phase temperature was measured by a differential scanning calorimeter(DSC),and the wettability of brazing filler metal was tested by spreading method.The outcomes obtained show that the as-cast microstructure is a typical three-zone structure,including region of surface fine grain,zone of columnar grain and region of center equiaxed crystal.Ag-28Cu-8Sn alloy is mainly composed of Ag-rich a-phase,Cu-rich pphase and intermediate compounds.Grain refinement appears in the cross section,as for grains of the longitudinal section,the shape is changed from ribbon to fiber to form a silk texture.The strength and hardness improve with the increase in the true strain,while the conductivity and elongation are reduced.Furthermore,the solid-phase temperature is 605.9℃,and the liquid-phase temperature is 725.1℃.The spreading area of Ag-28Cu-8Sn brazing filler metal is 174 mm~2,and the metallurgical bonding occurs between Ag-28Cu-8Sn brazing filler metal and Cu matrix.In addition,compared with cold drawing process,there are not any microcracks at the fracture morphology for the alloy fabricated by dieless drawing.The dieless drawing process overcomes some processing defects of traditional cold drawing,and the processing performance of Ag-28Cu-8Sn alloy is improved.  相似文献   

8.
Nanocrystalline rare earth mixed oxides SmFe1-xCoxO3-δ were prepared by sol-gel method at 1073K for 2h calcination and characterized by X-ray diffraction(XRD) and scanning electron microscope(SEM).The results show that SmFe1-xCoxO3-δhas the structure of perovskite type.The conductivity of the materials increases with the temperature rising and the maximum conductivity at 1073 K is 2.6 S/cm with the best mole ratio of Fe^3 to Co^3 being 1:4.This kind of oxide is a conductive ceramic material by means of conduction of electron and oxygen anion.  相似文献   

9.
A ceramic layer was prepared on the surface of Al2O3f /ZL109 composites by means of micro-arc oxidation (MAO) technique. The surface morphology and phase constituent of the ceramic layer were analyzed using scanning electron microscope and X-ray diffraction. The polarization curves of the composites before and after MAO treatment were measured and analyzed. The results showed that after Al2O3f /ZL109 composites were treated using MAO technique in silicate solution, the ceramic layer formed, and it was composed of Al, Si, and mullite phase. Al and Si came from Al alloy matrix of the composites, and the mullite phase formed in process of MAO. Al2O3 fiber in the composites affects the electric conductivity of the composites, the MAO reaction is promoted, and the ceramic layer forming on the composite material side is slightly thicker than that on the Al alloy side. After Al2O3f /ZL109 composites were treated using MAO technique, the corro- sion resistance of the composites is significantly improved.  相似文献   

10.
The effects of two different heat-treatment atmospheres,nitrogen atmosphere and reducing nitrogen atmosphere with carbon,on the properties of Y2O3-doped aluminum nitride (AlN) ceramics were investigated.The AlN powder as a raw material was synthesized by self-propagating high-temperature synthesis (SHS) and compacts were fabricated by employing powder injection molding technique.The polymer-wax binder consisted of 60 wt.% paraffin wax (PW),35 wt.% polypropylene (PP),and 5 wt.% stearic acid (SA).After the removal of binder,specimens were sintered at 1850℃ in nitrogen atmosphere under atmospheric pressure.To improve the thermal conductivity,sintered samples were reheated.The result reveals that the heat-treatment atmosphere has significant effect on the properties and secondary phase of AlN ceramics.The thermal conductivity and density of AlN ceramics reheated in nitrogen gas are 180 W·m-1 K-1 and 3.28 g,cm-3 and the secondary phase is yttrium aluminate.For the sample reheated in reducing nitrogen atmosphere with carbon,the thermal conductivity and density are 173 W.m-1.K-1 and 3.23 g·cm-3,respectively,and the secondary phase is YN.  相似文献   

11.
Formation of the structure welded joints is investigated by fractal analysis and the quantitative criteria of the structural homogeneity of the metal of welded joints are determined.  相似文献   

12.
连铸机连杆在机组试车阶段即发生断裂,完全未达到工作时限。为分析其断裂原因,采用扫描电子显微镜、能谱仪、光学显微镜等检测设备,通过断裂部位的断口分析、非金属夹杂物分析、显微组织分析等可知,连铸机连杆断裂的主要原因是奥氏体晶粒粗化及存在魏氏组织。  相似文献   

13.
应用ANSYS有限元分析软件,建立了货车轮对滚动轴承压装过程的状态接触模型,并进行压装过程求解分析,得出压装力-位移(Fp-x)的分段拟合方程和高次拟舍方程和压装力--位移曲线。本文所得结论为货车轮对滚动轴承压装质量的判断提供了理论依据。  相似文献   

14.
在型腔模设计中 ,推杆直径大小的确定一般是根据经验或依据类比法确定 ,这样确定的推杆往往与生产实际有一定的差距 ,通过对推杆的受力状况进行分析 ,从理论计算角度对推杆直径进行确定。  相似文献   

15.
This paper presents the computation results for the passage of a current through electrodes of various shapes. In particular, cylindrically shaped contacts and rectangular current-carrying buses are considered. The effect of the electrode boundaries and the location of the contact spots on the value of the contact resistance was estimated. It was shown when the contact resistance can admittedly differ from the values found using the available analytical formulas.  相似文献   

16.
Results of investigations into the effect of conditions of adaptive pulsed-arc welding on the mechanical properties and distribution of residual stresses in welded joints in plates of 09G2S low-alloy steel are presented. Pulsed-arc welding increases the impact toughness of the weld metal at subzero temperatures in comparison with the stationary conditions, and compressive residual welding stresses were detected.  相似文献   

17.
龚伟权 《模具工业》2001,(11):30-31
从板料拉伸变形可能产生的缺陷入手 ,将传统的用2副模具拉伸的工件用1副模具成形 ,在模具结构上进行了改进 ,以保证设计目标的实现。在试模中准确地分析产生缺陷的原因 ,并予以消除  相似文献   

18.
学院制是当今国内外大学通行的大学内部管理形式.从理论上讲,学术地位应是学院地位的核心,行政权力只是为学院的学术地位服务的.但在现实中,学院的学术地位低、行政权力虚,且地位既不确定也不稳定,还不同程度地存在着责、权、利分离的现象.影响学院现实地位的原因很复杂,既有大学的办学理念和发展定位,也有学院的设置依据、重点职能及其完成情况,还有学院规模、特色、财力状况、人际关系、开放性、下设专业的现状和发展前景等.这样的地位现状对大学使命和职能的完成也会造成不良的影响.通过分析,本文还对大学学院的未来地位做了方向性的预测.  相似文献   

19.
电机端盖成形工艺及模具设计   总被引:6,自引:3,他引:3  
介绍了电机端盖冲压成形工艺及其模具设计 ,对中心带局部变形结构的拉伸件提供了工艺分析与模具设计的范例  相似文献   

20.
影响板料胀形性能的参数的研究   总被引:1,自引:0,他引:1  
本文利用有限元数值模拟方法对影响板料胀形性能的参数进行了研究,并得出了各参数对板料胀形性能影响程度的规律。  相似文献   

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