Abstract: Velocity field in meniscus zone in mold is studied on the c. c. simulator. Low melting point Pb-Sn-Bi alloy and silicon oil are adopted as simulators of molten steel and slag,respectively. It is shown that the liquid metal in meniscus zone flows toward the mold wall during the positive-strip period and flows away from the mold wall during the negative-strip period. It is also found that the flow velocity at meniscus increases during the positive-strip period and decreases during the negative-strip period at higher casting speed.
Abstract: Behavior of liquid steel meniscus is studied on the c. c. simulator. Low melting point Pb-Sn-Bi alloy and silicon oil are adopted as simulators of molten steel and slag, respectively. The shape of meniscus and the fluctuation and motion of liquid metal in meniscus zone are investigated. It is shown that the superheat of molten metal and electromagnetic force have influence on the shape of meniscus, and that the fluctuation at meniscus is intensified by increasing mold oscillation amplitude and casting speed. The velocity fields of liquid metal at meniscus are measured during the positive-strip period and the negative-strip period, respectively, from which the mechanism of oscillation mark formation is verified.
Abstract: The experiments were conducted under an Ar atmosphere at normal pressure. The results show that the copper content(mass fraction) in steel melt is reduced from 0.6 % to 0.4 % and 0.5 % respectively when ammonium chloride or urea as the decopperizing agents were added to the hot melt.NH4Cl is a better decopperizing agent than HN2CONH2.
Abstract: The decopperization experiments in steel melt were conducted at 1600℃ with the compound decopperizing agents of Al2O3-ZnO-C system with various compositions and Al2O3-ZnO-Al system respectively.The principle regarding the decopperization in steel melt with these agents and the factors influencing the decopperizing effect of these agents have been discussed.
Abstract: A method of statistical calculation misorientation distrbution between the grains was proposed using the orientation distribution function based on the Euler's space.In thes model, the misorientation distribution can be calculated not only between randomly oriented but also between the deformed matrix with various texture components and corresponding recrystallized grains with different texture. Furthemore, the experimental ODFs data can be used for calculation.
Abstract: A microstructure model of tungsten heavy alloys has been developed. On the basis of the model, the micro-mechanical behavior of tungsten heavy alloys under tensile deformation has been analyzed by computer numerical simulation with finite element method (FEM).The results show that the maximum stress is in the tensile direction and the maximum Mises stress is in tungsten grains, and there is a compressive stress in them, which is perpendicular to the tensile direction. The maximum shear stress and the first plastic flow in tungsten heavy alloys take place in matrix under tensile deformation. As the tensile deformation increases, the stress concentrates onto tungsten grains.
Abstract: On the basis of analyzing the micro-mechanical behavior, the macro-mechanical properties of 90 W heavy alloy and the effects of microstructural parameters（mechanical properties of matrix phase） on them have been calculated by computer numerical simulation. The mechanical properties of the alloy have been found to depend heavily on mechanical parameters of matrix phase. As the elastic modulus of matrix phase increases, the tensile strength of the alloy increases, while its elongation decreases. The tensile strength of the alloy has a maximum at the yield strength of matrix phase 800 MPa. When the yield strength of matrix phase<800 MPa, the tensile strength of the alloy increases with its increase, however, a opposite variation occurs when the yield strength of matrix phase> 800 MPa if the mechanical parameters except tensile strength of matrix phase are constant, both the tensile strength and the elongation of the alloy increase linearly with the increase of tensile strength of matrix phase, because the ductility of matrix phase increases with its tensile strength in this case. The elongation of the alloy is very sensitive to hardening modulus of matrix phase. As the hardening modulus increases the elongation of the alloy exponentially decreases.
Abstract: An investigation on the influence of moderate amount of Ti(4%), Mh(9%) or Nb(8%)(mass fraction) on the protection of prefromed oxide scale of an Fe-25Cr alloy has been carriedout. It has been found that protective sulfidation behaviour appeared in the sulfidation of all alloys after their preoxidation in 105 Pa (O2) at 1 000℃ for various time and, afterwards, rapid weight-gain took place. A thicker scale composed of TiO and TiCr2O4 mixtureformed on the 4%Ti containing alloy, resulting a twice longer protective period than Fe-25Cr. A porous oxide scale composed of MnO and MnCr2O4 spinel developed on the 9%Mn adding alloy, which providing rather poor protection. The addition of 8%Nb had little effect on the composition of oxide scale and the subsequent sulfidation kinetics.
Abstract: The influence of the perturbation on crystal growth patterns of plane and cell at the solid/ liquid interface during unidirectional solidification has been studied. The critical condition of the transition from plane to cell of alloys and the condition of the steady state growth of cell are given. It has been demonstrated by linear steady theory of nonlinear theory for the first time that the bifurcation mechanism of the transition from plane to cell and the interface of cell of alloy at the solid/liquid interface during unidirectional solidification is subcritical bifurcation. This bifurcation mechanism is proved by BrC4 alloy.
Abstract: Two methods were used to characterized the kinetics of SHS Si3N4 during the process of Si combustion under high pressure of nitrogen. Activation energy of 75.4 KJ·mol-1 was calculated by using method which was named “wave velocity method” compar-ing to the calculated value of 54.3 kJ·mol-1 by using the other method which was named “reaction rate method”. The discrepancy between the values calculated with these two different methods account for the “after-burn nitridation” process. As the diluent of Si3N4 added increased. The maximum combustion temperature decreased and the thermal conductivity increased smoothly. While the gas transport agent was added, thepropagating velocity of combustion wave was decreased and the activation energy was increased.
Abstract: β-Si3N4 fibers were fabricated through combustion synthesis （CS） process.Droplets composed of Si and Al at the tip of fibers were found. It is concluded that the growth of β-Si3N4 fibers is controled mainly by VLS mechanism. Hexagonal colummna single crystal β-Si3N4 with smooth surface and without any default was also found in the conbustion process of silicon powder. VC process is the controled mechanism for the growth of colummna single crystal β-Si3N4.
Abstract: In this paper MoSi2/SiC Composites have been densified using secondary hot-press technique, and the relative density of hot-pressed composites reaches up to 92%. The typical microstructure of hot-pressed composites examined by means of SEM and XRD is characterized by SiC particles uniformly distributed in MoSi2 matrix.
Abstract: Effects of Cr and Mo on machanical properties and micro-structure of Fe3Al based alloys were investigated from the point of the strain-induced microstructural changes in Fe3Al-based alloys during room temperature deformation and high temperature creep. It is found that both Cr and Mo soluted into the matrix of Fe3Al-based alloys. TheAddition of Cr can accelerate strain-induced disordering resulting in an effect of solution softening. The addition of Mo is beneficial to creep-induced rreordering and to increase the recrys tallization temperature, resulting in solution sirengthening.
Abstract: A heat-treatmentprocedure has been applied to InSb films prepared by thermal evaporation and magnetron sputtering, the films have been recrystallised from the melt in the vaccum with Ar protection.From the X-ray diffraction and SEM structure studies, it is found that the InSb films are mixtures of InSb, In, Sb before heat treatmentand are mainly single phase of InSb after recrystallization. The InSb grains grow with faceted interface and regular morphology. Theelectron mobility of InSb films (at room temperature) have been increased greatly after heat-treatment with 1.31×104 cm2 /(V·s) to 4.4×104 cm2 /(V·s) (thermal evaporation) and 2.15×103 cm2/(V·s) to 2.04×104 cm2/(V·s) (magnetron sputtering) respectively.
Abstract: The extrustioncharacteristics of composite powders of stainless steel and zirconiahave been researched experimentally, and the upper extruded composition of the composite powders being discussed. Hydroxy-propyl methyl-cellulose (HPMC) and water was used as the binder for the extrusion. The results show that the extrudable upper compositionincreases with increasing the stainless steel powder content in composite powder, and that the reasonable content of HPMC in the binder being 10%.
Abstract: The possibility of fabricatingthe WC particles reinforced M2 high speed-steel composites by spray forming was investigated.Microstructures of composites were studied with opticalmicroscope and scanning electron microscope(SEW. In addition,hardness of composites was meassured. The composite with good prooperties was obtained by spray formingprocess.
Abstract: The behavior of WC particles of WC particle-reinforced M2 high speed steel composites（MMCs） made by spray formming with emphasis on the change of prtculate composition during the course of deposition was investigated. The dissolving-precipitating phenomenon of WC particles contacted with high-temperature liquid high speed steel was studied.The results showed that particulate composition of WC particles changed fundamentally during preparationof MMCs. In comparison with compositon of WC grain of traditional hard alloys and steel bending hard alloys, a dissolving-precipitationg mechanism interpreting the particulate changing characteristicewas proposed.
Abstract: Utilizing EAM potential,Al single crystal with molecular dynamicssimulation method was studied. Under mode Ⅰ and Ⅱ loading, the influence of temperature and loading rate on dislocation emission and the criticalstress intensity factor was analyzed.The simulatedresults show that the critical stress intensity factor for dislocation emission decreases exponentiallyas the temperature increases. Loading rate will influence the critical stress intensity factor to some degree. The critical stress intensity factor will increase as loading rate increases.
Abstract: A study on microstructures and mechanical propertiesin FeMCrAl alloys was accomplished. The results showed that, when the ratio of equivalent concentrations of M and Cr, [M]/[Cr], was higher than 0.9, the alloys formed γ-phase matrix. The alloys with [M]/[Cr] ratios of 0.6~0.8 and 0.6 formed α+γ double phases and α-phase matrixes respectively. After treating at different temperature, the phase precipitation or phase dissolution was occured. Alloys were obtained different mechanical properties.
Abstract: A method called voltage following and comparing is introduced, which eliminaies the effect of temperature on semiconductor pulse sensors.Compared with the method of voltage comparing directly which was used traditionally, it only follwos the tredency of original sine wave which is triggered by MR elements and has no relation with temperature;then shape it to square wave; thus eliminates the effect of temperature efficiently and elevates the encoder's working stability. In addition, the choices of circuitparameters and the application have been analysed.
Abstract: A method is presented for defining ranges of normal stress values, based on the construction of the membership function from the fuzzy set theory. This method was applied to a stress analysis in the railwaytraffic system of Slovenia.
Abstract: Worledge Model which describs operators’ cognitive process based on the decision-making during the accident sequences have been introduced. And using Ma’s transitiongraphis used to calculate the human error probability. The mode can be valided through thening with simulator of Nuclear Power Plant （NPP） and the meaningfulguide for study of operators reliability.
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
