The solvent debinding of water soluble binder in powder injection moulding (MIM) was investigated systematically, including the effects of solvent types, temperature and the thickness of green parts on the solvent deb...The solvent debinding of water soluble binder in powder injection moulding (MIM) was investigated systematically, including the effects of solvent types, temperature and the thickness of green parts on the solvent debinding rate. After studying the debinding of a green part with a thickness of 4.26 mm, it was found that, the debinding rate of polyethylene glycol(PEG) in water and alcohol was high initially, and then decreased; however, it would increase with temperature increasing. At room temperature, the dissolution rate of PEG in water was higher than that in alcohol, but the latter would be much faster with temperature increasing because the debinding activation energy in alcohol was 51.44 kJ·mol -1 ·K -1 , much higher than 24.23 kJ·mol -1 ·K -1 in water. With a green part thickness larger than 4.26 mm, the debinding was controlled by diffusion; but with that smaller than 2.36 mm, the debinding was controlled by both dissolution and diffusion.展开更多
The aging behavior of 2618 (Al Cu Mg Fe Ni) alloy added trace Sc and Zr was studied by Vicker’s hardness measurement at 200 and 300 ℃, and the tensile properties(yield strength, ultimate tensile strength and elongat...The aging behavior of 2618 (Al Cu Mg Fe Ni) alloy added trace Sc and Zr was studied by Vicker’s hardness measurement at 200 and 300 ℃, and the tensile properties(yield strength, ultimate tensile strength and elongation) of alloys were measured at 20, 200, 250 and 300 ℃. The microstructures were observed by using optical microscope, SEM and TEM. It was found that the addition of Sc and Zr to 2618 alloy resulted in a uniform distribution of fine coherent Al 3(Sc,Zr) precipitates which had obvious aging hardening effect and made the S’ phase precipitate more homogeneously. The strength of alloy increased at ambient and elevated temperature without a decrease of ductility because of the precipitation strengthening and thermal stability of Al 3(Sc,Zr) particles. The ductile fracture of alloy occurred by microviod nucleation, growth and coalescence, so the microvoid coalescence was the dominant fracture mechanism. Al 3(Sc,Zr) particles could inhabit the recrystallization process of alloy 2618.展开更多
A simple analytic modified embedded atom method (M EAM ) Inciuding a modified term for hcp metals has been developed from the MEAM applied to the fcc and bcc metals. The enthalpiesof formation of all binary alloy syst...A simple analytic modified embedded atom method (M EAM ) Inciuding a modified term for hcp metals has been developed from the MEAM applied to the fcc and bcc metals. The enthalpiesof formation of all binary alloy systems for eight transition hcp metals are calculated with theMEAM. The calculations are in agreement with the experimental data avallable and resultscalculated from the Miedema theory. One can conclude that our MEAM is also effective toapply to the hcp metals and their alloys.展开更多
Carbide nucleation, growth and trapping behavior in directionally solIdified MAR-M247 LC alloyand the corresponding mechanism have been investigated. Carbide forming element enrichmentcontrols the carbide nucleation a...Carbide nucleation, growth and trapping behavior in directionally solIdified MAR-M247 LC alloyand the corresponding mechanism have been investigated. Carbide forming element enrichmentcontrols the carbide nucleation and the carbide growth behavior. If the carbide forming elementenrichment and the nucleation sites are suitable, carbide nucleation can occur both above andbelow the liquidus temperature. Heterogeneous carbide nucleation is the preferred nucleationmechanism at low carbide forming element enrichment. Carbide growth occurs mainIy at inter-secondary ry dendrite arm area and lower part of the mushy zone. The carbides are subsequentlytrapped at these positions after growing to a certain size. Some carbides are only partially trappedby the solid-liquid interface and the carbide growth accelerates after being partially trapped. Acritical growth rate exists between 2×10-6 m/s and 5 ×10-6 m/s. The carbide volume fractiondecreases in the directionally solidified part at slow growth rate that is caused by the lack ofsuitable growth site and the low trapping ability of the solid-liquid展开更多
A simple analytic embedded atom method for bcc Fe and fcc Al metals is used to calculate thethermodynamic properties of the disordered solid solution and ordered intermetallic alloys of Fe aluminides. The thermodynami...A simple analytic embedded atom method for bcc Fe and fcc Al metals is used to calculate thethermodynamic properties of the disordered solid solution and ordered intermetallic alloys of Fe aluminides. The thermodynamic properties, such as the dilute-limit heats of solution, formation enthalpies of disordered solid solutions and intermetallic compounds (Fe3Al in the D03 structuretype, FeAl in the B2 structure type, and Fe13Al3) are in good agreement with the experimentaldata, and with the results calculated using the first principles and Miedema theory.展开更多
To solve the so called “white rust” and ’water bridge" problems of the aluminum fins for heat exchanger of automobile air conditioner, aimed at nationalizing the art of hydrophilic coating technology, the choi...To solve the so called “white rust” and ’water bridge" problems of the aluminum fins for heat exchanger of automobile air conditioner, aimed at nationalizing the art of hydrophilic coating technology, the choice of coating forming and curing materials was investigated. By measuring the water contact angle, SEM surface scanning and ingredients analysis of the coating, optimal parameters and composition are acquired. The coating forming mechanisms of the composition was also expatiated. The coating obtained has good hydrophilic and other properties.展开更多
Aiming at the optimization of the operation condition, a general numerical method for calculating pulverized coal combustion in a full scale furnace fired tangentially at four corners is adopted. “ k ε ” turbulence...Aiming at the optimization of the operation condition, a general numerical method for calculating pulverized coal combustion in a full scale furnace fired tangentially at four corners is adopted. “ k ε ” turbulence model is used for the gas phases and a stochastic approach based on the Lagrangian technique is used for particle phases. Two competing reactions model for the coal devolatilization and PDF (the probability density function) method for the combustion of the gas phases are employed. In the numerical simulations, assuming the air distribution of second port level is of pagoda, waist drum and uniform type. The results show that pagoda type air distribution is advantageous to ignition and smooth combustion of pulverized coal, and suitable to inferior coal combustion in practice. In the present furnace, the igniting distance at 1st and 3rd corner is longer than that at 2nd and 4th corner. The results from numerical calculations are in good agreement with those of observed in practice.展开更多
The paper presents a novel material preparation technology—Solid liquid mixed casting technology. In the technology, large amounts of homogeneous alloy powder or heterogenous powder with perfect wettability are added...The paper presents a novel material preparation technology—Solid liquid mixed casting technology. In the technology, large amounts of homogeneous alloy powder or heterogenous powder with perfect wettability are added into the superheated melt. After strong agitation, the mixed melt can be cast or hot processed. Applying solid liquid mixed casting, three kinds of Al Si alloys were investigated. The results show that, when the mass of powder accession to alloy melt is about 1, the mean size of primary Si in hyper eutectic alloy can be controlled at less than 5 μm; and the mean grain size of α phase in hypo eutectic alloy is less than 10 μm. This technology has the advantage of preparing material with very fine microstructure by fairly simple casting process, and may be a new practicable and valuable metal preparation technology.展开更多
Young′s Modulus of concrete is studied on the basis of triaxial compressive experiments. The authors proposed two empirical equations to calculate its static Young′s modulus and dynamic Young′s modulus when dynamic...Young′s Modulus of concrete is studied on the basis of triaxial compressive experiments. The authors proposed two empirical equations to calculate its static Young′s modulus and dynamic Young′s modulus when dynamic Poisson ratio μ d varies nearby 0.20.P wave velocity and elastic modulus have the same varying tendency as letter N. μ,μ d decrease with the increase of loading rate and μ d has a great effect on the parameters E d and E D.展开更多
The general structure of expert system for controlling sintering process has been proposed. It includes knowledge base, inference engine, data acquisition system, learning system, knowledge base management system, exp...The general structure of expert system for controlling sintering process has been proposed. It includes knowledge base, inference engine, data acquisition system, learning system, knowledge base management system, explanation system and so on. The control functions consist of sintering chemical composition control centered on basicity and sintering process state control centered on permeability. The adaptive prediction of sintering chemical composition, the control strategy centered on basicity, the control strategy centered on permeability, the judgement of permeability and the prediction of burn through point were studied. The software of system, which includes about 1 000 expert rules, was successfully applied in off line control of sintering process in a sintering plant.展开更多
The structure of Mo-15.16 Si, Mo-30 Si and Mo-36.3 Si (wt pct) elemental powder mixture during mechanical alloying was studied using electron microscopy and X-ray diffraction. It had been found that, in all the system...The structure of Mo-15.16 Si, Mo-30 Si and Mo-36.3 Si (wt pct) elemental powder mixture during mechanical alloying was studied using electron microscopy and X-ray diffraction. It had been found that, in all the systems under study, silicon disappeared initially during mechanical alloying (MA). In the Mo-Si systems all products were in form of amorphous state after long time milling, but there were different intermediate products. MoSi2 and Mo5Si3 intermetallic compounds in the MO-30Si and Mo-36.3Si (wt pct) were directly synthesized from elements through inter-diffussion process. The high density of defects and interface of nano-crystal lines induced by ball milling would promote the reaction process. Only in the Mo-15.16Si (wt pct) system was Mo(Si) Supersaturated solid solution formed as an intermediate product. Schematic free-energy diagram of Mo-Si system based on the thermodynamics was used to analyze the difference among the intermediate state展开更多
The influence of phase components of tungsten oxide on homogeneity of ultrafine tungsten powder by conventional hydrogen reduction techniques was studied. Results show that phase components of tungsten oxide play a cr...The influence of phase components of tungsten oxide on homogeneity of ultrafine tungsten powder by conventional hydrogen reduction techniques was studied. Results show that phase components of tungsten oxide play a crucial role on homogeneity of metal tungsten powder; ultrafine and homogeneous tungsten powder can be produced from oxides which consist of only one phase. Due to the different reduction rates (or different reduction paths) of oxide which comprises different phases, the multi phase components tungsten oxide leads to a fine but in homogeneous metal tungsten powder.展开更多
By the one atom theory the electronic structure of bcc V has been determined to be [Ar](3d n) 1.799 8 (3d c) 2.657 8 (4S c) 0.171 1 (4s f) 0.371 3 . According to this electronic structure of bcc V, its potential curve...By the one atom theory the electronic structure of bcc V has been determined to be [Ar](3d n) 1.799 8 (3d c) 2.657 8 (4S c) 0.171 1 (4s f) 0.371 3 . According to this electronic structure of bcc V, its potential curve, cohesive energy, lattice parameter, elasticity and linear thermal expansion coefficient were calculated. The electronic structures of the primary state crystals of fcc V, hcp V and the primary state liquid—V have also been studied.展开更多
The relation between damage and modal parameters of skeleton has been discussed and analysed. Some significant results for detecting damage have been obtained by using experimental data of ω di and ζ i . Then, the m...The relation between damage and modal parameters of skeleton has been discussed and analysed. Some significant results for detecting damage have been obtained by using experimental data of ω di and ζ i . Then, the modal experiments of four type of skeleton have been performed, the modal bifurcation phenomenon is discovered. It follows that this method for studying skeleton damage is a very promising method through theoretical and experimental analysis.展开更多
文摘The solvent debinding of water soluble binder in powder injection moulding (MIM) was investigated systematically, including the effects of solvent types, temperature and the thickness of green parts on the solvent debinding rate. After studying the debinding of a green part with a thickness of 4.26 mm, it was found that, the debinding rate of polyethylene glycol(PEG) in water and alcohol was high initially, and then decreased; however, it would increase with temperature increasing. At room temperature, the dissolution rate of PEG in water was higher than that in alcohol, but the latter would be much faster with temperature increasing because the debinding activation energy in alcohol was 51.44 kJ·mol -1 ·K -1 , much higher than 24.23 kJ·mol -1 ·K -1 in water. With a green part thickness larger than 4.26 mm, the debinding was controlled by diffusion; but with that smaller than 2.36 mm, the debinding was controlled by both dissolution and diffusion.
文摘The aging behavior of 2618 (Al Cu Mg Fe Ni) alloy added trace Sc and Zr was studied by Vicker’s hardness measurement at 200 and 300 ℃, and the tensile properties(yield strength, ultimate tensile strength and elongation) of alloys were measured at 20, 200, 250 and 300 ℃. The microstructures were observed by using optical microscope, SEM and TEM. It was found that the addition of Sc and Zr to 2618 alloy resulted in a uniform distribution of fine coherent Al 3(Sc,Zr) precipitates which had obvious aging hardening effect and made the S’ phase precipitate more homogeneously. The strength of alloy increased at ambient and elevated temperature without a decrease of ductility because of the precipitation strengthening and thermal stability of Al 3(Sc,Zr) particles. The ductile fracture of alloy occurred by microviod nucleation, growth and coalescence, so the microvoid coalescence was the dominant fracture mechanism. Al 3(Sc,Zr) particles could inhabit the recrystallization process of alloy 2618.
文摘A simple analytic modified embedded atom method (M EAM ) Inciuding a modified term for hcp metals has been developed from the MEAM applied to the fcc and bcc metals. The enthalpiesof formation of all binary alloy systems for eight transition hcp metals are calculated with theMEAM. The calculations are in agreement with the experimental data avallable and resultscalculated from the Miedema theory. One can conclude that our MEAM is also effective toapply to the hcp metals and their alloys.
文摘Carbide nucleation, growth and trapping behavior in directionally solIdified MAR-M247 LC alloyand the corresponding mechanism have been investigated. Carbide forming element enrichmentcontrols the carbide nucleation and the carbide growth behavior. If the carbide forming elementenrichment and the nucleation sites are suitable, carbide nucleation can occur both above andbelow the liquidus temperature. Heterogeneous carbide nucleation is the preferred nucleationmechanism at low carbide forming element enrichment. Carbide growth occurs mainIy at inter-secondary ry dendrite arm area and lower part of the mushy zone. The carbides are subsequentlytrapped at these positions after growing to a certain size. Some carbides are only partially trappedby the solid-liquid interface and the carbide growth accelerates after being partially trapped. Acritical growth rate exists between 2×10-6 m/s and 5 ×10-6 m/s. The carbide volume fractiondecreases in the directionally solidified part at slow growth rate that is caused by the lack ofsuitable growth site and the low trapping ability of the solid-liquid
文摘A simple analytic embedded atom method for bcc Fe and fcc Al metals is used to calculate thethermodynamic properties of the disordered solid solution and ordered intermetallic alloys of Fe aluminides. The thermodynamic properties, such as the dilute-limit heats of solution, formation enthalpies of disordered solid solutions and intermetallic compounds (Fe3Al in the D03 structuretype, FeAl in the B2 structure type, and Fe13Al3) are in good agreement with the experimentaldata, and with the results calculated using the first principles and Miedema theory.
文摘To solve the so called “white rust” and ’water bridge" problems of the aluminum fins for heat exchanger of automobile air conditioner, aimed at nationalizing the art of hydrophilic coating technology, the choice of coating forming and curing materials was investigated. By measuring the water contact angle, SEM surface scanning and ingredients analysis of the coating, optimal parameters and composition are acquired. The coating forming mechanisms of the composition was also expatiated. The coating obtained has good hydrophilic and other properties.
文摘Aiming at the optimization of the operation condition, a general numerical method for calculating pulverized coal combustion in a full scale furnace fired tangentially at four corners is adopted. “ k ε ” turbulence model is used for the gas phases and a stochastic approach based on the Lagrangian technique is used for particle phases. Two competing reactions model for the coal devolatilization and PDF (the probability density function) method for the combustion of the gas phases are employed. In the numerical simulations, assuming the air distribution of second port level is of pagoda, waist drum and uniform type. The results show that pagoda type air distribution is advantageous to ignition and smooth combustion of pulverized coal, and suitable to inferior coal combustion in practice. In the present furnace, the igniting distance at 1st and 3rd corner is longer than that at 2nd and 4th corner. The results from numerical calculations are in good agreement with those of observed in practice.
文摘The paper presents a novel material preparation technology—Solid liquid mixed casting technology. In the technology, large amounts of homogeneous alloy powder or heterogenous powder with perfect wettability are added into the superheated melt. After strong agitation, the mixed melt can be cast or hot processed. Applying solid liquid mixed casting, three kinds of Al Si alloys were investigated. The results show that, when the mass of powder accession to alloy melt is about 1, the mean size of primary Si in hyper eutectic alloy can be controlled at less than 5 μm; and the mean grain size of α phase in hypo eutectic alloy is less than 10 μm. This technology has the advantage of preparing material with very fine microstructure by fairly simple casting process, and may be a new practicable and valuable metal preparation technology.
文摘Young′s Modulus of concrete is studied on the basis of triaxial compressive experiments. The authors proposed two empirical equations to calculate its static Young′s modulus and dynamic Young′s modulus when dynamic Poisson ratio μ d varies nearby 0.20.P wave velocity and elastic modulus have the same varying tendency as letter N. μ,μ d decrease with the increase of loading rate and μ d has a great effect on the parameters E d and E D.
文摘The general structure of expert system for controlling sintering process has been proposed. It includes knowledge base, inference engine, data acquisition system, learning system, knowledge base management system, explanation system and so on. The control functions consist of sintering chemical composition control centered on basicity and sintering process state control centered on permeability. The adaptive prediction of sintering chemical composition, the control strategy centered on basicity, the control strategy centered on permeability, the judgement of permeability and the prediction of burn through point were studied. The software of system, which includes about 1 000 expert rules, was successfully applied in off line control of sintering process in a sintering plant.
文摘The structure of Mo-15.16 Si, Mo-30 Si and Mo-36.3 Si (wt pct) elemental powder mixture during mechanical alloying was studied using electron microscopy and X-ray diffraction. It had been found that, in all the systems under study, silicon disappeared initially during mechanical alloying (MA). In the Mo-Si systems all products were in form of amorphous state after long time milling, but there were different intermediate products. MoSi2 and Mo5Si3 intermetallic compounds in the MO-30Si and Mo-36.3Si (wt pct) were directly synthesized from elements through inter-diffussion process. The high density of defects and interface of nano-crystal lines induced by ball milling would promote the reaction process. Only in the Mo-15.16Si (wt pct) system was Mo(Si) Supersaturated solid solution formed as an intermediate product. Schematic free-energy diagram of Mo-Si system based on the thermodynamics was used to analyze the difference among the intermediate state
文摘The influence of phase components of tungsten oxide on homogeneity of ultrafine tungsten powder by conventional hydrogen reduction techniques was studied. Results show that phase components of tungsten oxide play a crucial role on homogeneity of metal tungsten powder; ultrafine and homogeneous tungsten powder can be produced from oxides which consist of only one phase. Due to the different reduction rates (or different reduction paths) of oxide which comprises different phases, the multi phase components tungsten oxide leads to a fine but in homogeneous metal tungsten powder.
文摘By the one atom theory the electronic structure of bcc V has been determined to be [Ar](3d n) 1.799 8 (3d c) 2.657 8 (4S c) 0.171 1 (4s f) 0.371 3 . According to this electronic structure of bcc V, its potential curve, cohesive energy, lattice parameter, elasticity and linear thermal expansion coefficient were calculated. The electronic structures of the primary state crystals of fcc V, hcp V and the primary state liquid—V have also been studied.
文摘The relation between damage and modal parameters of skeleton has been discussed and analysed. Some significant results for detecting damage have been obtained by using experimental data of ω di and ζ i . Then, the modal experiments of four type of skeleton have been performed, the modal bifurcation phenomenon is discovered. It follows that this method for studying skeleton damage is a very promising method through theoretical and experimental analysis.
