Diddusion bonding of titanium alloy to tin-bronze

The vacuum diffusion bonding of titanium alloy to tin-bronze has been studied and the feasibility and appropriate processing parameters have been investigated.The maximum tensile strength of the joints is 168MPa,and a firm joint is obtained.The microstructure of diffusion bonded joint has been observed by SEM.X-ray and EPMA,and the main factors affecting diffusion bonding have been analyzed.The intermetallic compounds Ti2Cu and TiCu were formed near the interface.The width and quantity of the intermetallic compound increases with the increase of the bonding time.The formation of the intermetallic compounds results in embrittlement of the joint and the poor joint properties.     

Particulars of Use of New 850 Standard Palladium Alloys for Jewelry Production

The researches of new palladium-based alloys have been conducted, and the cast and deformed bars for jewels have been obtained. The mechanism of occurrence of welding defects (pore formation) in the production of jewelry chains of silver-containing palladium alloys has been studied. The analysis of the welded joints of the chains, obtained by argon-arc welding, has been carried out, and the properties of metal have been analyzed. Conclusions have been drawn on the possibility of use of the developed palladium alloys, which do not contain silver, for the production of wired semi-products having a low propensity for pore formation in the weld seams.     

PHASE DIAGRAM OF Nd-Fe-B TERNARY SYSTEM——I.Isothermal Section at Room Temperature

The microstructures of both as-cast and homogenized Nd-Fe-B ternary alloys have beenstudied. The stable phase regions existing in Nd-Fe-B ternary system at room temperaturehave been established by the microzone composition analysis and the phase identification.Based on the obtained results, an isothermal section of Nd-Fe-B ternary system at roomtemperature was drawn.     

Expanded Industrial Experiments of Free-alkali Recovery from Sodium Tungstate Solution by the Membrane Electrolysis Process

The technology of electrolysis with ion-exchange membrane has been widely applied in industry [11. The free-alkali recovery from sodiumtungstate solution by electyolysis with ion-exchange membrane has been stUdied in our laboratory. After success in exploratory test, furtherstudies were made on the anode of the electfolysis, the structUre of the electrolytic tank and theassemblage of the electfolytic cell, and someachievements have been obtained [2--4]. Basedon these results, the expanded exp…     

Micromechanical Analysis of In-Plane Constraint Effect on Local Fracture Behavior of Cracks in the Weakest Locations of Dissimilar Metal Welded Joint

In this work, a set of GTN(Gurson–Tvergaard–Needleman) parameters of the Alloy52 M dissimilar metal welded joint(DMWJ) have been calibrated, and a micromechanical analysis of in-plane constraint effects on the local fracture behavior of two cracks, which located in the weakest regions of the DMWJ, has been investigated by the local approach based on the GTN damage model. The results show that the partition of the material and the variation of the q_2 parameter make the J-resistance curves obtained by numerical simulations close to the experimental values. The numerical J-resistance curves and crack growth paths are consistent with the experiment results, which show that the GTN damage model can incorporate the in-plane constraint effect. Furthermore, after the stress, strain and damage fields at the crack tip during the crack propagation process have been calculated, and the change of the J-resistance curves, crack growth paths and fracture mechanism with in-plane constraint have been analyzed.     

APPLICATION OF SIMILARITY PRINCIPLE TO STRATIFICATION THEORY STUDY IN GRAVITY CONCENTRATION

The stratification processes have been studied by the application of the similarity principle,and the similarity criteria has also been derived.Two possible π-equations were deduced fromthe experimental results.The approach of the π-equation to predict separating results and tocontrol the separating processes is presented with examples.     

Numerical simulation analysis of Guixi copper flash smelting furnace

A numerical simulation analysis for reactions of chalcopyrite and pyrite particles coupled with momentum,heat and mass transfer between the particle and gas in a flash smelting furnace is presented.In the simulation.the equations governing the gas flow are solved numerically by Eular method.The particle phase is introduced into the gas flow by the particle-source-in-cell technique(PSIC),Predictions including the fluid flow field,temperature field,concentration field of gas phase and the tracks of particles have been obtained by the numerical simulation.The visualized results show that the reaction of sulfide particles is almost completed in the upper zone of the shaft within 1.5m far from the central jet distributor (CJD)type concentrate burner,The simulation results are in good agreement with data obtained from a series of experiments and tests in the plant and the error is less than 2%.     

Effect of Rare Earth Elements on Transformation Behavior and Microstructure Characteristics in X80 Pipeline Steel

The studies of the rare earth elements (RE) in low carbon steels suggest that the RE inhibits the ferrite transformation, which is the same effect as Mo alloying in pipeline steels. The purpose of this work is to discuss the relationships between the RE microalloying and the microstructure in pipeline steels. The X80 pipeline steels with different RE and Mo additions have been produced by vacuum induction furnace. The Gleeble-2000 thermal simulator, optical microscopy, and scanning electron microscopy with EBSD have been used. The continuous cooling transformation (CCT) curve was obtained and analyzed, combined with the study of microstructure. The results indicate that the microstructure of thermal simulator test metal is characteristic of quasi-polygonal ferrite and bainite, and trace RE could significantly inhibit the transformation of quasi-polygonal ferrite. The 0.0040wt% content of RE plays the same role as 0.1 wt% content of Mo alloying in pipeline steels. What’s more, the fine bainite grained structure is obtained with RE microalloying. Theoretically RE could be employed in pipeline steels as microalloying, and a partial substitution of Mo by RE is possible.     

FACTORS ON VISCOSITY STABILITY OF MOLD FLUXES

Viscosity stability indexes of mold flux at high temperature and low temperature have been introduced, and the effects of flux compositions on viscosity stability indexes have been studied. Two mold fluxes have been developed by analyzing the effects of flux viscosity stability on the process and the condition of continuous casting slab of medium carbon steel. The results show that the fluxes are suitable for the process.     

Study of Carbon Contaminated Epitaxial Silicon

The properties of the carbon contaminated silicon epitaxial layer and its surface have been studied by means of JAMP-10Auger electron microprobe and JEM-2000FX transmission scanning electron microscope.The results show that the fog defectson the surface are due to carbon contamination.The existence of SiC in the silicon epitaxial layer has been identified by the elec-tron diffraction analysis.     

Edge detection of molten pool and weld line for CO2 welding based on B-spline wavelet

Due to the disturbances of spatters, dusts and strong arc light, it is difficult to detect the molten pool edge and the weld line location in CO2 welding processes. The median filtering and self-multiplication was employed to preprocess the image of the CO2 welding in order to detect effectively the edge of molten pool and the location of weld line. The B-spline wavelet algorithm has been investigated, the influence of different scales and thresholds on the results of the edge detection have been cornered and analyzed. The experimental results show that better performance to extract the edge of the molten pool and the location of weld line can be obtained by using the B-spline wavelet transform. The proposed edge detection approach can be further applied to the control of molten depth and the seam tracking.     

EXTRACTION KINETICS OF YTTRIUM WITH PURIFIED CYANEX 923 FROM NITRATE MEDIUM

Mass transfer and extraction kinetics of yttrium with the purified Cyanex 923 in n-heptane from nitrate medium have been investigated by using a constant interfacial cell with laminar flow at 298K. The interfacial adsorption properties of purified Cyanex 923-heptane-0.20mol/L (H, Na)NO3 were studied at 298K. The experimental results show that the mass transfer is controlled by diffusion and the chemical reactions are carried out in the interfacial zone. The extraction rates of yttrium were measured at different chemical compositions by varying ionic strength, pH values and the purified Cyanex 923 concentrations. The initial extraction rate equations were obtained.     

SURFACE SEGREGATION IN Mo-La ALLOY WIRE

The surface segregation in Mo-4wt-% La alloy wire has been studied by using Auger elec-tron spectroscopy.The process of the segregation is that the La atoms diffuse from the grainboundaries to surface.The experimental results were analysed by kinetics of grain boundarydiffusion.The diffusion activation energy E_(?)=1.6 eV was obtained.     

ACOUSTIC EMISSION AND HYDROGEN EVOLUTION DURING SOLIDIFICATION OF ALUMINUM ALLOYS

Study of the solidification process of both Al-Si and Al-Cu alloys proved the presence ofacoustic emission phenomena.Two peaks of count rate have been observed.The total countsof both peaks increase with the increasing hydrogen content of the alloy.The mechanism ofproducing the acoustic emission has been discussed.At the same time,results obtained by oth-er techniques strongly support the good correlation between the acoustic emission andhydrogen releasing during solidification.The bubble nucleation between dendrite arms is themain cause of the first peak,while the fracture of the bridge connecting the interdendrites atthe later stage of solidification is the main cause of the second peak.It is probably due to thehydrogen evolution and accumulation to create high pressure in the interdendritie region.     

TEM STUDY OF BONDING LAYERS IN DISSIMILAR ALLOY EXPLOSIVE BONDING JOINTS

The bonding layers in dissimilar alloy explosive bonding joints,γ/α stainless steels,copper/carbon steel and brass/γ-stainless steel have been studied by means of TEM tech-nique.The results show that the bonding is obtained by diffusion and local melting at the con-tact surface.The structure of bonding layer not only responds to the compositions of the bond-ing alloys,but also the difference between their thermal conductivities,melting points andrecrystallization temperatures,Because of the small molten region and fast cooling rate,thestructure of molten region could be amorphous or microcrystals,and both stable andmetastable phases exsist.     

Two-stage precipitation process of iron and arsenic from acid leaching solutions

A leaching process for base metals recovery often generates considerable amounts of impurities such as iron and arsenic into the solution. It is a challenge to separate the non-valuable metals into manageable and stable waste products for final disposal, without loosing the valuable constituents. Boliden Mineral AB has patented a two-stage precipitation process that gives a very clean iron-arsenic precipitate by a minimum of coprecipitation of base metals. The obtained product shows to have good sedimentation and filtration properties, which makes it easy to recover the iron-arsenic depleted solution by filtration and washing of the precipitate. Continuos bench scale tests have been done, showing the excellent results achieved by the two-stage precipitation process.     

Inelastic constitutive equation of plasma-sprayed ceramic thermal barrier coatings

Ceramic thermal barrier coatings (TBCs) are a very important technology for protecting the hot parts of gas turbines (GTs) from a high-temperature environment. The coating stress generated in the operation of GTs brings cracking and peeling damage to the TBCs. Thus, it is necessary to evaluate precisely such coating stress in a TBC system. We have obtained a stress-strain curve for a freestanding ceramic coat specimen peeled from a TBC coated substrate by conducting the bending test. The test results have revealed that the ceramic coating deforms nonlinearly with the applied loading. In this study, an inelastic constitutive equation for the ceramic thermal barrier coatings deposited by APS is developed. The obtained results are as follows: (1) the micromechanics-based constitutive equation was formulated with micro crack density formed at splat boundary, and (2) it was shown that the numerical results for a nonlinearly deformed beam simulated by the developed constitutive equation agreed with the experimental results obtained by cantilever bending tests.     

Study on accuracy of casting flow simulation

In the field of casting flow simulation, the application of body-fitted coordinate (BFC) has not been widely used due to the difficulty and low efficiency of grid generation, despite the availability of good quality analysis results. Cartesian coordinates, on the other hand, have been used predominantly in casting process simulations because of their relatively easy and fast grid generation. However, Cartesian grid systems cannot obtain accurate results because they cannot express the geometries properly. In this study, Cut Cell method was applied to solve this problem. The three-dimensional incompressible viscous governing equation was analyzed using a function defined for the volume and area of the casting in the cutting cell . Using the Cut Cell method, accurate flow analysis results were also obtained in the Cartesian grid systems. The tests of simple shape and the applications of actual casting product have been tried with Cut Cell method.     

STRUCTURE, MECHANICAL PROPERTIES AND THERMAL STABILITY OF DIAMOND-LIKE CARBON FILMS PREPARED BY ARC ION PLATING

Diamond-like Carbon (DLC) films have been prepared on Si(lO0) substrates by arc ion plating in conjunction with pulse bias voltage under He atmosphere. The deposited films have been characterized by scanning electron microscopy and atomic force microscopy. The results show that the surface of the film is smooth and dense without any cracks, and the surface roughness is low. The bonding characteristic of the films has been studied by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. It shows the sp^3 bond content of the film deposited at -200V is 26. 7%. The hardness and elastic modulus of the film determined by nanoindentation technique are 30.8 and 250.1GPa, respectively. The tribological characteristic of the films reveals that they have low friction coefficient and good wear-resistance. After deposition, the films have been annealed in the range of 350-700℃ for 1h in vacuum to investigate the thermal stability. Raman spectra indicate that the ID/IG ratio and G peak position have few detectable changes below 500℃. Further increasing the annealing temperature, the hydrogen can be released, the structure rearranges, and the phase transition of sp^3 configured carbon to sp^2 configured carbon appears.     

Study on Relationship between InGaAsP/InP LPE Wafer Morphology,Interface Property and Device Characteristics

Five kinds of InGaAsP/InP heterostructure materials grown with LPE have been measured by means of Auger electronanalysis,X-ray double-crystal diffraction,selective etching and surface morphology analysis.The relation between crystalmismatch and interface property of such materials has been studied and the results could be understood in terms of the growth ki-netics at the heterojunction interface.The comparison of the characteristics of the electronic and optoelectronic devices fabricatedwith the wafers under different interface properties has been carried out.And it also has been demonstrated that the wafer surfacemorphology changes with the compositional gradation by certain relation.