Abstract: Two mechanisms-deformation enhanced transformation and dynamic recrystallization of ferrite are involved during deformation of undercooled austenite in a low carbon steel, leading to effective ferrite grain refinement. In comparison with isothermal transformation, deformation significantly accelerates austenite to ferrite transformation, leading to a very high nucleation rate. Deformation enhanced transformation is a nucleation dominant process. The results of EBSD and TEM indicate that ferrite dynamic recrystallization also plays an important role on grain refinement as well as deformation enhanced transformation. The misorientation of sub-grain boundaries is assumed to increase by further straining, accompanied by grain rotation, finally leading to the recrystallized small ferrite grains. Study on the effect of strain rate on microstructure homogeneity indicates that microstructure tends to be distributed in a laminar manner at lower strain rate.
Abstract: By means of the mercurial barometer and pore size analyzer, the effects of bridged particles on the pore volume distribution in nano-meter cemented carbide powder and its compact were investigated. Also the apparent density, specific surface area and green density were studied before and after sedimentation separating and high energy shear milling by BET specific surface area analyzer and SEM. The results show that there is more than one peak on pore volume distribution pattern because of the presence of bridged particles. The apparent density and green density can be greatly improved by high-energy milling.
Abstract: The characteristics of swell-shrinkage kinetic curve during sintering the compact of W-Ni-Fe 10% with primary mean grain size less than 200 nm in hydrogen atmosphere was researched by high temperature dilatometer. And the effects of the average size of tungsten particle and green density on shrinkage commence temperature, sharp shrinkage temperature and shrinkage rate were also studied. It shows that shrink age commence temperature and sharp shrinkage temperature of the compact with ultrafine grain are 970℃ and 1240 ℃ respectively. The maximum shrinkage rate is 9 μm/℃. The shrinkage ratio decreases with the increase of green density and increases with the increase of sintering temperature.
Abstract: Describes the influence of the concrete JR drop on the results of electrochemical measurements carried out on reinforcing steel corrosion in concrete and the resulted errors in judgement or evaluation of rebar corrosion. Through a new electrochemical measuring method i.e transient switch method conducted on reinforcing steel corrosion in concrete, not only the influence of JR drop but also the influence of concentration polarization in rebar surface can be effectively eliminated. Thus polarization curves can be obtained under the influence of electrochemical polarization only. Kinetics parameters of the electrochemical processes can be calculated referring to stationary methods using the data obtained.
Abstract: W-15%Cu alloys were sintered with mechanically activated powder in order to develop new preparing processes and improve properties of the alloys. The microstructures of activated powder and sintered alloys were observedand its properties such as density were measured. The results show that through mechanical activation, the surface energy and deformation energy of particles increase, and sintering processes were improved. Conglomeration microstructures in the alloys appear, W particles were sintered between each other mainly by way of solid sintering in the conglomerations, and liquid sintering between conglomeration and conglomeration. Microstructure of sintered alloys is compact and homogeneous. The relative density of the alloys is bigger than 98%. W and Cu are well-touched within the micromter scale, and some dissolving happened between the phases.
Abstract: A new technology of styrene grafting surface modification of titanium dioxide is introduced. The main technological parameters have been studied, and the optimal combination of the parameters has been obtained. The modification mechanisms were analyzed that the process of styrene grafting surface modification of titanium dioxide is essentially a combination of negative ion polymerization and free radical polymerization, there is C-O bonds create on the surface of modified titanium dioxide. Whereas the mechanical-chemical effects caused by stirring mill, the chemical effects caused by initiating agent, the external and internal heating can all promote the modification process.
Abstract: Surface tensions of slag and matte in Jinchuan nickel flash smelting process were respectively calculated by the way of Butler equation and polynomial fit. Based on Girifalco-Good equation interfacial tensions between slag and matte were calculated. The relationship between interfacial tension and slag composition、surface tension as well as temperature was discussed. Some advice for decreasing the noble metal loss in Jinchuan nickel flash smelting process slags was given.
Abstract: By a special thermomechanical control process(TMCP-RPC), relaxation for a certain time after control rolling and then direct quenching/accelerated cooling, the strain induced precipitions and defect structure in deformed austenite resulted in refinement of intermediate transformation microstructure. Following this relaxation-precipitation-control phase transformation (RPC) process,800 MPa grade plate steel with an ultra-fine mixture microstmcture of bainite and martensite was obtained. The effect of processing parameters on the microstructure and the mechanical properties was revealed.
Abstract: The influence of copper content on the formation of cube texture in aluminum foil for high voltage anode electrolytic capacitor was investigated based on the quantitative texture analysis, and the mechanism of the influence was also discussed. It was shown, that the increase of copper content will change the segregation state of copper atoms around dislocations, and influence the deformation behaviors as well as the orientation distribution after cold rolling. The following recrystallization behaviors and the volume of corresponding cube texture will also be changed. Lower copper content and higher annealing temperature for grain growth will benefit the increase of cube texture.
Abstract: The preparation process of HDDR ternary NdFeB anisotropic powder was studied. The research results showed that the effects of desorption rate of hydrogen on the magnetic properties of HDDR ternary NdFeB anisotropy were remarkable, and slow desorption treatment was beneficial to the attainment of strong anisotropy. By the optimum HDDR treatment, the HDDR ternary NdFeB anisotropy bonded magnet with Br of 0.78 T,iHc of 640 kA·m-1 and (BH)max of 84kJ·m-3 can be obtained.
Abstract: The synthesize BBr3 by way of boron bromination was introduced. In preparation of element boron, B203 was reduced by Mg element, the preparated method is more facile to handle and has higher productivity compared with other methods. It is found that polyfluortetraethylene pipes are more resistence to corrosion of bromine and boron bromide at high temperatures. The condensation of high-temperature BBr3 gas can be carried out by use of ice-salt bath.
Abstract: The growth of {100} oriented CVD diamond film under three different chemical models (Including Harris model, F-B model and model proposed in this paper, respectively) is simulated in atomic scale by using KMC method. The results show that: (1) the growth mechanism from CH3 is suitable for the growth of {100} oriented CVD diamond film; (2) the deposition rate under model containing double-carbon radicals is lower than that under model containing one-carbon radicals for {100} oriented diamond film;(3) the acquisition of diamond film with low surface roughness under relatively high deposition rate is feasible; (4) the simulation results for Harris' model are in well agreement with those predicted by Harris and experiment results.
Abstract: The special designed SEM in-situ tensile tests have been conducted to trace the whole process of crack initiation and propagation till to fracture in Al2O3 seeded P/M Rene 95 alloy And the distriblltion of stress and strain around inclusions has been calculated by means of an elasto-plastic finite element method (FEM) model with the commercial software ANSYS. The results show that the characteristic parameters of inclusions such as the size, position etc. have different effect on the tension process; and initiation and propagation of the crack at inclusion/medix interface are mainly determined by the stress distribulion of matrix in or near this region.
Abstract: The experiment indicates that under general temperature, acid and anaerobic condition, adding rational nutrient and electron supplier, with J13 bacteria from mining water adopting consequent culture in high density, pulp leaching in advance, microbe immobilization and enhance energy transmitting, which the leaching time is 3 days. The rate of metal leaching is Co 95.2%, Ni 97.5%, Mn 95.8%, Cu 81.2%. The same experiment was carried out on land magnetic ores, the leaching time is 9 days. Thus, a new method is set up that under the enforce bacteria of two ores are coupled and reduced to leach the valuable metals from oxide manganese ore.
Abstract: Reports preparation of artificial opal by sedimention of SiO2 spheres in ethanol and it's microscopic and optical characterization.Results show that artificial opal belongs to analogue fcc structure,which is in agreement with theoretical calculations by L.V. Woodcock.
Abstract: The effects of different drying methods and procedures which are used to deal with poly(vinyl alcohol) on the swelling degree of poly (vinyl alcohol) gel have been investigated. The solubility of poly(vinyl alcohol) dried by alcohol is larger than that of poly(vinyl alcohol) dried by the air. The swelling degree of poly (vinyl alcohol) first swelled after thawing is larger than that of poly(vinyl alcohol) without first swelled after thawing.
Abstract: Taking the Metal-Organic Vapor Phase Epitaxy (MOVPE) of GaN and (Ga1-xInx)P semiconductors as examples, the pyrolysis effect of NH3 and PH3 vapor sources on the composition spaces for growing GaN and(Ga1-xInx)P compounds has been studied. According to the situation of NH3 and PH3 pyrolysis in experimental conditions, the thermodynamic models for different pyrolysis status are built. Furthermore, the composition spaces for growing Ⅲ-Ⅴ semiconductors are calculated and predicted with the aid of the Thermocalc software. The correspondence of the theoretical analysis with the experimental data indicates that for the thermodynamic analysis of MOVPE process of GaN and (Ga1-xInx)P semiconductors, the calculation and prediction must be conducted under the conditions of the complete equilibrium or the constraint equilibrium based on the practical pyrolysis of NH3 and PH3 vapor sources. The analysis of the complete thermodynamic equilibrium is only applied to some specific temperature region or certain epitaxy process after typical pretreatment of vapor sources.
Abstract: To improve fatigue property and corrosion resistance of powder metallurgy (P/W) ferrous parts, a new technique was conducted, in which after compacting a dense surface layer first formed on the green compacts through chemical treatment and then sintering. Green compacts of iron powders were chemically treated by means of electroless nickel-phosphorus (EN) plating before sintering. Samples with the density ranged from 6.2~7.0 g·cm-3) were used in the experiments. After plating and sintering at temperature of 1 170℃, the morphology of the dense EN coating on various densified samples was examined with a scanning electronic microscope, and energy dispersive spectroscopy was used to analyze the nickel and phosphorus contents of the coating. The result shows that nickel content decreased in a gradient pattern. The diffusion distance of Ni can attain 220 llm, while some phosphorus existed in the form of Fe2P particles and segregated within ferrous substrate and spherated the porosity of the coating.
Abstract: The influence of Relaxation-Precipitation-Controlling Transformation(RPC) technique on the microstructure of low carbon steels was studied by thermal simulation. The results indicated that the ultra-fine bainite/martensite composite microstructure was obtained. With the strain increasing the refinement was promoted. As the final rolling temperature increases the refinement was hindered. When the precipitation speed during relaxing is comparable to the dislocation evolution rate, the best processing is obtained.
Abstract: A new physicochemistry method for producing fine-grade rubber power is introduced. The main factors influencing the effective time in producing fine-grade rubber power are also discussed. The experimental results show that the grade of rubber powder produced with physicochemistry method is much finer than that with conventional method. Prolonged grinding time, increased ratio of rubber-power /agent and decreased filling volume can lead to fine-grade rubber powder. The results also show that the mechanical properties of rubber powder by physicochemistry method are superior to that by conventional one, the tensile strength for 60-80 mesh grade rubber powder is the lowest, and for 140-200 mesh grade being the highest.
Abstract: Based on the behavior of pressure and flow velocity during semisolid A1Si7Mg slurry filling processes, a three dimensional model of slurry flow coupled with apparent viscosity is established. Relating to boundary condition and cavity air pressure, simulation on semisolid aluminum alloy casting has been investigated with the help of the SOLA-VOF algorithm. It is shown that flow velocity of semisolid slurry have mark effects on the flow patterns. Lower flow velocity result in mold filling steadily and prevent gas porosity. Under certain flow velocity, using process in which mold filling along the radial lead to lower filling resistance when compared with the axial, none of these castings have defects. Finally, simulation results is in agreement with the experimental results.
Abstract: The precipitation behavior of α-Cr phase during long-term exposure at high temperatures was analyzed using the microstructural analysis approaches in INCONEL718 and INCONEL625 alloys. The structure analysis and thermodynamic calculation results show that, with increasing the exposure time, α-Cr phase precipitates and grows usually clinging to δ phase in IN718 alloy, for IN625 alloy, α-Cr phase precipitates and grows usually clinging to M6C carbide and δ phase. This precipitation behavior possibly is due to the solubility of Cr in δ and M6C phase dramatically decreasing with decreasing the temperature.
Abstract: Ta/NiO/NiFe/Ta multilayers were prepared by magnetron sputtering. The composition and chemical states at the interface region of NiO/NiFe were studied using the angle-resolved X-ray photoelectron spectroscopy (XPS). The results show that there are two thermodynamically favorable reactions at NiO/NiFe interface: NiO+Fe = Ni+FeO and 3NiO+2Fe =3 Ni+Fe2O3 The thickness of the chemical reaction as estimated by angle-resolved XPS was about 1-1.5 nm. These interface reaction products are magnetic defects, and- the exchange coupling field Hex and the coercivity Hc of NiO/NiFe are affected by these defects.
Abstract: The effect of catalysts and additive containing Li on reduction of Fe2O3 by carbon monoxide has been studied by experimental methods. It is found that both of the catalysts and the additive have catalytic effect, moreover, the catalyst containing Li is more affective. X-ray diffraction showed that the main phases in catalyst containing Li are α-Fe and FeO, therefore, it is considered that α-Fe and FeO can also promote the reduction of Fe2O3 by carbon monoxide
Abstract: The effect of NaCJ on the corrosion behavior of API P105 steel in the CO2-saturated solution was studied by electrochemical impedance spectrum(EIS) and polarization measurement. The results showed the increase of NaCl concentration decreased the the corrosion rate of the steel, which could be attribulted the decrease of hydroxide ion concentration and the dissolution of CO2, and the adsorption of Cl- obeyed the Temkin isotherm.
Abstract: The tetrapod-like ZnO whiskers were synthesized by oxidation of the Zn powders. High purity and perfect crystalline T-ZnO whiskers with different sizes were obtained by controlling gas supersaturation in the reaction container. The length of legs of the whiskers is approximately 5-30 jim and the geometrical edge size of centering nucleus is approximately 1-2 μm. Especially, the whiskers had long tail about 100nm. The whiskers grew via Vapor-Solid mechanism. Gas supersaturation in the reaction container is the key to prepare high-quality T-ZnO whiskers.
Abstract: The nanocomposite permanent alloys which is composed of Pr2(Fe,Co)14B and α-(Fe,Co) and Pr2(Fe,Co)17 were made by single-roller rapid quenching. The X-ray diffraction method, room-temperature magnetic measurement and thermal magnetic analysis were used to analyze the microstructure and magnetic properties of Pr7.5Dy1Fe86-xCoxNb1B4.5(x=10,15) alloys. Magnetic properties of the ribbons annealing at different temperature and for various time were extensively studied. Permanent magnetic properties still keep a high level in the ribbons that were annealed at 700℃ for six hours. This result implies that thermal stability of the alloys may be enhanced by adding Co and Nb at the same time.
Abstract: On the basis of theory of steel strengthening, the influence of microstructures on properties in low carbon steel is analyzed. Combined with the condition of production, the relationships between micro-structures and properties in low carbon steel are studied. The formulas which describe these relationships are derives from experiments and regression analysis.
Abstract: The nucleation of ultra-fine ferrite inside austenite was followed during deformation-enhanced transformation in a Q235 low carbon steel. EBSD technique was applied to reveal the orientation features of ferrite formed at different places. Results indicate that there are two typical nucleation sites inside austenite, namely, deformation bands and deformation inhomogeneities near austenite grain boundaries. Increasing austenite grain size and decreasing deformation temperature favor to the ferrite formation at deformation bands. In the suitable deformation temperatures of A3-Ar3 for ultra-fine ferrite, the deformation near A, leads to a uniform distribution of ferrite as well as second phases. The band-like ferrite and second phases caused by the nucleation at deformation bands gives rise to not only the anisotropy in microstructure but also in ferrite orientation.
Abstract: The bio-desulphurization experiments on slag were carried out. The results show that pulp density, Fe3+ concentration and pH are effect on Thiobacillus ferrooxidans(T.f.) consistency free in the solution and desulphurization rate. The bio-desulphurization from slag is due to the combination of the direct bacterial action on the mineral surface with the indirect leaching by the ferric ion produced by the bacteria into the solution. Desulphurization rate and oxidative activity of the T.f. are influenced by the growth of T.f adhered to the mineral, mineral density, Fe3+ concentration and pH consistency. The addition of ferric ion can interfere in the bacteria oxidative activity and result in inhibiting effect on the desulphurization, some sediment on the surface of the mineral are formed to reduce desulphurization rate.
Abstract: Over one thousand samples which was acquired from original excavation sites provided abundant speciments for the microstructure study of ancient Chinese copper arntefacts. The results show that the materials of ancient Chinese copper include pure copper, arsenic copper,lead bronze, lead-tin bronze, brass, lead brass, silver copper, arsenic paktong and nickel paktong, etc. The microstructure of ancient Chinese copper artefacts illustrate the casting structure of different composition, working structure including hot working and cold working and unusual cases, which differ from those of the modem copper alloys.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
