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Showing papers by "University of Science and Technology Beijing published in 2003"


Journal ArticleDOI
TL;DR: In this paper, the microstructure of the new nickel-based superalloy, INCONEL alloy 740, was investigated by means of thermodynamic calculation, OM, SEM, TEM and X-ray diffraction.
Abstract: By means of thermodynamic calculation, OM, SEM, TEM and X-ray diffraction, microstructural stability was investigated on the new nickel-based superalloy, INCONEL alloy 740. Some mechanical properties of the new alloy were also studied. The results indicated that the microstructure of this alloy maintained good thermal stability to at least 750 °C. The major precipitates were MC, M23C6 and γ′ during prolonged aging at temperatures below 704 °C. Small amount of η precipitates formed at grain boundaries in sample aged at 750 °C in 1000 h and large amount of intragraunlar η precipitates formed a Widmanstatten pattern in sample aged at 849 °C for 1000 h. γ′ phases grew rapidly with increasing in temperature and partially resolutioned after 849 °C aging for 1000 h. Harmful phases, such as σ phase, have not been detected in these samples. The impact toughness of alloy declined and there was a ductile/brittle transition with increasing aging temperature and time. Room temperature microhardness of alloy decreased with an increase in temperature mainly due to the growth of γ′ phases. Elevated-temperature microhardness of alloy for standard heat-treated condition was higher than room temperature microhardness. In comparison to NIMONIC alloy 263, the new alloy exhibited higher ductility and higher tensile strength.

184 citations


Journal ArticleDOI
TL;DR: In this paper, the octahedral multiple twin nucleus is confirmed to be responsible for the formation of the tetraleg ZnO nanostructure, which is likely to be a candidate as building blocks for contructing photonic crystals.

166 citations


Journal ArticleDOI
TL;DR: The photoluminescence spectra of Bicrystalline ZnO nanowires show a weak UV emission at 385 nm and a strong green emission at 495 nm as mentioned in this paper.

142 citations


Journal ArticleDOI
TL;DR: Wang et al. as mentioned in this paper focused on fracture behavior and extent in floor strata with reference to the double face mining above the confined aquifer in Yangzhuang colliery, China, including a systematic and comprehensive study which covers the in situ survey of the geological structure and hydraulic process, laboratory experiments on the mechanical and permeating properties of rocks, and in situ measurement of stress and fluid flow in the floor stratata and the pressure distribution in the mining gateways.

114 citations


Journal ArticleDOI
TL;DR: In this paper, an innovative spray-deposition technique has been applied to produce in situ TiC/Al and Al-20Si-5Fe-3Cu-1Mg composites, which can solve the problems of losses and agglomeration of the reinforcement particles when they are injected into the spray cone of molten droplets during spray forming process.

100 citations


Journal ArticleDOI
TL;DR: In this paper, a X80 pipeline steel loaded over yield is unloaded and charged with hydrogen, and the difference is defined as the hydrogen-induced stress, which can be added to the external stress to enhance the plastic deformation.
Abstract: A X80 pipeline steel loaded over yield is unloaded and charged with hydrogen. The yield strength of the charged specimen loaded in air is lower than the flow stress before unloading, and the difference is defined as the hydrogen-induced stress, which can be added to the external stress to enhance the plastic deformation. The hydrogen-induced stress, σad, increases linearly with increasing hydrogen concentration C0, i.e., σad=−14.1+3.89C0. Fracture stress at slow strain rate tests during dynamic hydrogen charging increases also linearly with increasing hydrogen concentration, i.e. σF(H)=675−6.1C0. Threshold stress of hydrogen-induced cracking (HIC) during dynamic hydrogen charging under constant stress decreases linearly with increasing the logarithm of hydrogen concentration, i.e., σHIC=669−124 ln C0.

84 citations


Journal ArticleDOI
TL;DR: In this paper, the solid solution limit of Pb1−xSrxTiO3 was determined in the composition range of 0≤x≤1.0 at room temperature (RT).

83 citations


Journal ArticleDOI
TL;DR: In this paper, the optimum process for the separation and purification of Al-13 was investigated in detail in the presence of various influencing factors, including the concentration and basicity of polyaluminum chloride (PACl, Al/SO4 ratio, Ba/SO 4] ratio and ultrasonic reaction.

66 citations


Journal ArticleDOI
TL;DR: In this paper, the interaction between superstructures and grain boundary in graphite has been investigated by STM and it has been found that the misorientation angle between two domains is 4.0 ± 0.2°, resulting in overlapping with the substrate lattice in the non-superstructure domain.

66 citations


Journal ArticleDOI
TL;DR: In this article, the influence of growth conditions such as the molar ratio of starting materials, temperature, pressure, the position of Li3N in the crucible on the growth of GaN single crystals was studied.

64 citations


Journal ArticleDOI
TL;DR: In this article, the primary crystallization of amorphous Zr70Cu20Ni10 alloy has been investigated by employing the differential scanning calorimetry (DSC) and transmission electron microscopy (TEM).

Journal ArticleDOI
TL;DR: In this paper, the process of polymer grafting modification activated by mechano-chemical effects, the changes of mechanical and fluid properties of high impact polystyrene (HIPS) plastics with modified calcium carbonate fillers, the interactions between the modifying reagents and the surface of the filler particles and the action of the mechanochemical effect in polymer graftging modification were investigated.

Journal ArticleDOI
TL;DR: In this paper, the synthesis, microstructures and properties of γ-aluminum oxynitride (AlON) were analyzed and the Gibbs energy of AlON with different compositions and temperatures were evaluated.
Abstract: This paper deals with the synthesis, microstructures and properties of γ-aluminum oxynitride (AlON). The thermodynamic properties of AlON were analyzed and the Gibbs energy of AlON with different compositions and temperatures were evaluated. Based on thermodynamic studies, AlON has been synthesized. The microstructures, mechanical properties and oxidation resistance of the synthetic AlON have been examined and discussed.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the oxidation behavior of ternary compound Ti 3 SiC 2 in the temperature range of 1000-1500°C for up to 20 hours exposure.
Abstract: The oxidation behavior of ternary compound Ti 3 SiC 2 is investigated in the temperature range of 1000–1500 °C for up to 20 h exposure. The scales formed on the Ti 3 SiC 2 matrix were duplex, consisting of an outer layer and an inner layer over the temperature ranges. The outer layer was pure TiO 2 (rutile), and the inner layer consisted of SiO 2 and TiO 2 . At the temperature 1300 °C and below, the oxidation kinetics of Ti 3 SiC 2 followed the parabolic law. When the temperature rose to 1400 °C, the oxidation behavior followed the parabolic-linear law. The activation energy was calculated to be 325 kJ mol −1 over the temperature range of 1000–1400 °C. A number of pores existing in the boundary of the outer layer and the inner layer provide the cannel for oxygen diffusion. The effect of pores and impurities on oxidation behavior was analyzed, and the morphology of oxidation products was observed through scanning electron microscope.

Journal ArticleDOI
TL;DR: In this article, an anisotropic Nd/sub 15.0/Fe/sub 72.7/Co/sub 3.8/Al/sub 1.0 magnet was produced by the spark plasma sintering technique.
Abstract: We have produced an anisotropic Nd/sub 15.5/Dy/sub 1.0/Fe/sub 72.7/Co/sub 3.0/B/sub 6.8/Al/sub 1.0/ magnet by the spark plasma sintering (SPS) technique and compared it with a magnet of the same composition processed by the conventional sintering method. We investigated magnetic properties, microstructure, and constituents by a B-H loop-line instrument, a scanning electron microscope, and an energy-dispersive X-ray detector, and studied the effects of processing conditions on the magnetic properties, dimensional precision, and density. We also examined the magnet's electrochemical properties in electrolytes and its corrosion behavior in oxidizing environments. We found that the microstructure of the SPS NdFeB magnet is different from that of the conventional one. In the SPS-processed magnet, the grain size is fine and uniform while the distribution of the Nd-rich phase is heterogeneous. The SPS NdFeB magnet has a maximum energy product of 240 kJ/m/sup 3/ and a coercive force of 1260 kA/m. The density of the magnet reaches 7.58 g/cm/sup 3/, and its dimensional precision is about 20 /spl mu/m. The electrochemical properties and the corrosion resistance of the SPS NdFeB magnet are better than those of the conventional one. The SPS process is a promising method for the production of NdFeB magnets with ideal overall performance.

Journal ArticleDOI
TL;DR: In this paper, an in situ displacement reaction of Si and TiC powders has been used to synthesize a composite with high flexural strength and fracture toughness, which has been shown to have better oxidation resistance than monolithic Ti3SiC2 at high temperatures.

Journal ArticleDOI
TL;DR: An on-line system that consists of continuous-flow liquid membrane extraction, C18 precolumn, and liquid chromatography with UV detection was applied to trace analysis of sulfonylurea herbicides in water with detection limits of 10-50 ng l(-1) when enriching a 120-ml sample.

Proceedings ArticleDOI
01 Jan 2003
TL;DR: In this article, low cycle isothermal mechanical fatigue testing of both bulk solders and solder joints of eutectic Sn-37wt%Pb and Sn-40wt%Ag05wt%Cu was carried out in a systematic manner at room temperature over a wide range of strain ranges (1-10%).
Abstract: Low cycle isothermal mechanical fatigue testing of both bulk solders and solder joints of eutectic Sn-37wt%Pb and Sn-35wt%Ag and Sn-40wt%Ag-05wt%Cu were carried out in a systematic manner at room temperature over a wide range of strain ranges (1%-10%) The eutectic Sn-37wt%Pb was used as a reference Both for bulk solders and solder joints, the low cycle fatigue behavior of the solder alloys tested was found to be strongly dependent on strain rate Regarding solder joints, both lead free solders also depicted somewhat better fatigue properties, compared to Sn-37Pb The experimental results from both experimental methods (bulk solder specimens and solder joints) were compared Concluding from an environmental point of view, and from the present bulk and solder joint isothermal mechanical fatigue experiments, both Sn-35wt%Ag and Sn-40wt%Ag05wt%Cu lead-free solders are advisable replacements to Sn-37wt%Pb

Journal ArticleDOI
TL;DR: In this paper, a powder MBE method based on the plastic flow forming of pastes was used to fabricate metal-ceramic composite pipes, and it was shown that sound extrudates can be obtained no matter what mixing ratios of zirconia and stainless steel powders are used.

Journal ArticleDOI
TL;DR: In this article, a new idea to fabricate aluminum matrix composites strengthened by combined in-situ particle strengthening and in-Situ alloying has been proposed, and the reaction mechanism of the Al2O3 particulate obtained by this method was studied.
Abstract: A new idea to fabricate aluminum matrix composites strengthened by combined in-situ particle strengthening and in-situ alloying has been proposed. Following the concept of in-situ alloying and in-situ particle strengthening, aluminum matrix composites reinforced by Cu and α-Al2O3 particulate (material I) and the same matrix reinforced by Cu, Si alloying elements and α-Al2O3 particulate (material II) have been obtained. SEM observation, EDS and XRD analysis show that the alloy elements Cu and Si exist in the two materials, respectively. In-situ Al2O3 particulates are generally spherical and their mean size is less than 0.5 μm. TEM observation shows that the in-situ α-Al2O3 particulates have a good cohesion with the matrix. The reaction mechanism of the Al2O3 particulate obtained by this method was studied. Thermodynamic considerations are given to the in-situ reactions and the distribution characteristic of in-situ the α-Al2O3 particulate in the process of solidification is also discussed.

Journal ArticleDOI
TL;DR: In this paper, the stability of RT13-xMx and its derivative structure was studied by using the interatomic pair potential obtained with the lattice inversion method, and all the site positions of the compounds with either the cubic or tetragonal structure were really congruent with the experimental one.
Abstract: By using the interatomic pair potential obtained with the lattice inversion method, the stability of RT13-xMx (R = La, Ce, Pr and Nd; T = Co and Fe; M = Si, Al, Cr, V and Ti) of the NaZn13 type and its derivative structure are studied. The structural transition of LaT13-xSix (T = Co and Fe) between the cubic one with the space group Fm3c and the tetragonal one with 14/mcm is imitated from the viewpoint of energy. As for the function of the third elements, Al and Si are beneficial to the phase stability of RT13-xMx, whereas Cr, Ti and V are unfavourable to the stability. In the calculation, the range of x, with which RT13-xMx could crystallize in the cubic or tetragonal structures, agrees with the experiments very well. The calculated crystallographic parameters coincide with the experimental observation. In the cubic structure, Si and Al prefer the 96i site, and in the tetragonal structure Si first occupy the 16l(2) site, then the 16k site. In addition, all the site positions of the compounds with either the cubic or tetragonal structure are really congruent with the experimental one.

Journal ArticleDOI
TL;DR: In this paper, a model to describe the precipitation kinetics of AlN under thermomechanical process conditions of CSP, which predicted volume fraction evolution and the precipitate size of strain induced precipitation on the basis of classical nucleation theory.
Abstract: Morphology and precipitation kinetics of AlN were investigated both experimentally and using a predictive model in hot strip of low carbon steel produced by compact strip production (CSP), a process for the production of hot strip from a continuously cast thin slab using direct charging. By an electrolytic dissolution technique and TEM analysis, the shapes of AlN were cube or plate, the precipitates were uniform and very fine, with average size less than 8 nm. The paper presents a model to describe the precipitation kinetics of AlN under thermomechanical process conditions of CSP, which predicted volume fraction evolution and the precipitate size of strain induced precipitation on the basis of classical nucleation theory. For the process conditions of this paper, about 3 s time was sufficient for appreciable strain induced precipitation occurred immediately and entirely on dislocations after the sixth finishing rolling pass, and the computing radius of precipitate was 2 nm, which was in good agreement with experimental data. The differences of AlN precipitation between CSP and conventional process are also discussed.

Journal ArticleDOI
TL;DR: In this paper, the formation and growth of shear bands and microcracks in bulk metallic glasses of Zr 57 Cu 15.4 Ni 12.6 Al 10 Nb 5 and Zr 41.2 Cu 12.5 Ni 10 Ti 13.8 Be 22.5 have been investigated through in situ tensile tests in scanning electron microscope using a single-edge notched specimen.
Abstract: Formation and growth of shear bands and microcracks in bulk metallic glasses of Zr 57 Cu 15.4 Ni 12.6 Al 10 Nb 5 and Zr 41.2 Cu 12.5 Ni 10 Ti 13.8 Be 22.5 have been investigated through in situ tensile tests in scanning electron microscope using a single-edge notched specimen. Atom force microscope was used to study the three-dimension pattern of fine shear bands. The results show that besides shear stress, normal stress plays also an important role in forming and growing of shear bands, which appear first during loading. Mode II shear microcrack will initiate and propagate first in the shear planes along shear bands. The mode II cracks will open and become a shallow I+II complex crack because there is a component of normal stress. As soon as the complex crack (or cracks) becomes a mode I crack penetrating the thickness through propagating from the surface (or surfaces) toward the centre, the specimen will fracture immediately.

Journal ArticleDOI
TL;DR: In this paper, a spray-deposited hypereutectic Al-Si alloy was synthesized by the spray atomization and deposition technique, and the microstructure and mechanical properties of the spray alloy were studied using optical microscopy, scanning electron microscopy and X-ray diffraction, and tensile tests.

Journal ArticleDOI
TL;DR: In this paper, the roles of hydrogen and martensites in hydrogen embrittlement in slow strain rate tensile tests and hydrogen-induced delayed cracking (HIC) in sustained load tests for type 304L stainless steel were quantitatively studied.
Abstract: The roles of atomic hydrogen and hydrogen-induced martensites in hydrogen embrittlement in slow strain rate tensile tests and hydrogen-induced delayed cracking (HIC) in sustained load tests for type 304L stainless steel were quantitatively studied. The results indicated that hydrogen-induced martensites formed when hydrogen concentration C 0 exceeded 30 wppm, and increased with increasing C 0 . The relative plasticity loss caused by the martensites increased linearly with increasing volume fraction of matensite. The plasticity loss caused by atomic hydrogen I δ (H) increased with increasing C 0 and reached a saturation value I δ (H) max =40% when C 0 >100 wppm. I δ (H) decreased linearly with increasing logarithm of strain rate e , i.e., I δ (H), %=−21.9−4.3 ln e . HIC at sustained load was due to atomic hydrogen, and the threshold stress intensity for HIC decreased linearly with increasing ln C 0 , i.e., K IH =91.7−10.1 ln C 0 . The fracture surface of HIC was dimpled if K I was high or/and C 0 low; otherwise it was quasi-cleavage. The boundary line between ductile and brittle fractography was K I −54+25 exp(− C 0 /153)=0.

Journal ArticleDOI
TL;DR: In this article, a low-Co hydrogen storage alloy with outstanding properties was obtained with a content of Co as low as 2.7 wt. The microstructures of the alloy were investigated by XRD and TEM in order to understand and explain these special properties.

Journal ArticleDOI
TL;DR: An evolution model based on cellular automata for the investment behavior in the stock market is formulated in this article, where the simulation results and analyses of various states of stock market show that investors' imitation degree and the macro factors are the key determinants to the stability of the market.
Abstract: The modeling theory and method using cellular automata are applied to the study on the complexity in the stock market. An evolution model based on cellular automaton for the investment behavior in the stock market is formulated. The simulation results and analyses of various states of the stock market show that investors’ imitation degree and the macro factors are the key determinants to the stability of the stock market. We observed that more diversity in the investment views of agents and lower imitation among investors are in favor of the normal development of the stock market.

Journal ArticleDOI
TL;DR: In this article, double glow plasma surface alloying of low carbon steel with electric brush plating Ni interlayer was used to enhance the corrosion resistance of a single alloying layer without electric brush-plating interlayer.
Abstract: The present study concerns double glow plasma alloying of low carbon steel with predeposited Ni (by electric brush plating) to enhance corrosion resistance of a single alloying layer without electric brush plating interlayer. The composition and microstructure of the alloying layer were analyzed using scanning electron microscopy and X-ray diffraction. The results indicated that the composite layer consists of single γ phase, but the single alloying layer without predeposited Ni interlayer (by brush plating) consisted of a γ matrix and several precipitates (M 6 C and μ phase). Owing to thermal effects during the double glow plasma alloying process, Ni could diffuse toward the substrate, which taken as a barrier layer for carbon was effective to decrease the content of carbon in the composite alloying layer and at the same time formation of interface diffusion between the brush plating layer and the substrate could improve the adhesion strength. Corrosion resistance of the composite alloying layer was investigated by an electrochemical method in 3.5% NaCl and 5% HCl solution, and 20-h immersion tests in 20% H 2 SO 4 and 20% HCl solution. The experimental results showed that the corrosion resistance of composite layer was better than that of the single alloying layer. Thus, it was concluded that double glow plasma surface alloying of low carbon steel with electric brush plating Ni interlayer was an appropriate technique to enhance the corrosion resistance as compared with single double glow surface alloying.

Journal ArticleDOI
TL;DR: In this paper, a consistent T-x phase diagram for the Si-N binary system is obtained by means of the CALPHAD (CALculation of PHAse Diagrams) method.
Abstract: Motivated by the thermodynamic assessment of the Ga–N and In–N binaries, the thermodynamic parameters of the Si–N system are optimized in a similar way. The intermetallic compound Si 3 N 4 is treated as stoichiometric and the terminal solution phase diamond_Si as the pure diamond_Si. The liquid solution phase is assumed to be a substitutional solution with Redlich–Kister formula for the expression of its excess Gibbs energy. The fugacity of nitrogen is considered when describing the behavior of the gas phase, especially with high pressure. The complete T – x phase diagram for the Si–N binary system is given. In this optimization a consistent thermodynamic data set for the Si–N system is obtained by means of CALPHAD (CALculation of PHAse Diagrams) method. The calculation results agree well with experiments.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the film-induced tensile stress and susceptibility to stress corrosion cracking (SCC) in the methanol solution at various potentials at stable open-circuit potential and under anodic polarization.
Abstract: The flow stress of a specimen of α-Ti before unloading is different with the yield stress of the same specimen after unloading and forming a passive film through immersing in a methanol solution at various constant potentials. The difference is the passive film-induced stress. The film-induced stress and susceptibility to stress corrosion cracking (SCC) in the methanol solution at various potentials were measured. At the stable open-circuit potential and under anodic polarization, both film-induced tensile stress σ p and susceptibility to SCC had a maximum value. The film-induced stress and SCC susceptibility, however, decreased steeply with a decrease in potential under cathodic polarization. When the potential V ≤−280 mV SCE , the film-induced stress became compressive; correspondingly, susceptibility to SCC was zero. Therefore, the variation of film-induced stress with potential was consistent with that of susceptibility to SCC. A large film-induced tensile stress is the necessary condition for SCC of α-Ti in the methanol solution. The symbol and amount of the film-induced stress were related to the compositions of the passive film, which have been analyzed using the X-ray photoelectron spectrum (XPS).