The magnetic properties, structure defects of electrodeposited Fe-Ni-P alloys with various compositions and the thermostability at amorphous state have been studied by DSC, positron annihilation and electronic integra...The magnetic properties, structure defects of electrodeposited Fe-Ni-P alloys with various compositions and the thermostability at amorphous state have been studied by DSC, positron annihilation and electronic integrating instrument methods. The results show that the thermostability of amorphous Fe-Ni-P alloys increases with Fe content. Emergence and recrystallization of stable phases defer as the P content of the coating increases. The minimum H-c, B-r and P-h occur at 9.4 P (wt pet) content. Maximum H-c, B-r and P-h occur at the weight ratio of Fe to Ni equaling to 1/9.展开更多
A series of Ni-Fe-Ga alloys near the prototype Heusler composition (X2YZ) were prepared through arc-melting suction-casting method. The dependences of the transformation behavior on the alloy composition and anneali...A series of Ni-Fe-Ga alloys near the prototype Heusler composition (X2YZ) were prepared through arc-melting suction-casting method. The dependences of the transformation behavior on the alloy composition and annealing treatment were studied in detail by an optical microscope, X-ray diffraction, and differential scanning calorimeters methods. The experimental results show that the martensitic transformation temperatures increase almost linearly with increasing Ni content in all the NiFeGa alloys. Annealing the Ni55.5Fe18Ga26.5 alloy at 100-500 ℃ for 3 h and at 300 ℃ for 1-10 h shifts the martensitic transformation start temperature by almost 20 ℃ to high temperature. The variations in the martensitic transformation temperatures in these alloys are discussed in terms of structural differences resulting from alloy composition and annealing treatment.展开更多
The Ni-Cr-Mo-Cu multi-element surface alloying with the electric brushplating Ni interlayer on the low carbon steel substrate has been investigated. By theelectrochemical method in 3.5 percent (mass fraction) NaCl sol...The Ni-Cr-Mo-Cu multi-element surface alloying with the electric brushplating Ni interlayer on the low carbon steel substrate has been investigated. By theelectrochemical method in 3.5 percent (mass fraction) NaCl solution, the corrosion resistance of thecomposite alloying layer and single alloying layer is determined. The experimental results showthat the corrosion resistance of the composite alloying layer is obviously better than that of thesingle alloying layer. The structure and composition of passive films formed on the two kinds ofalloyed layers after electrochemical tests in 3.5 percent NaCl solution have been studied usingX-ray photoelectron spectroscopy (XPS). It is concluded that the double glow plasma surface alloyingof low carbon steel with the electric brush plating Ni interlayer is an appropriate technique toenhance the corrosion resistance compared with the single double glow surface alloying.展开更多
The microstructure ofthe Mg/MmNi5-x (CoAlMn )x composite hydrogen storage material preparedby the method of mechanical alloyingwas characterized by X-ray diffraction, SEM and particle size distribution analysis. By me...The microstructure ofthe Mg/MmNi5-x (CoAlMn )x composite hydrogen storage material preparedby the method of mechanical alloyingwas characterized by X-ray diffraction, SEM and particle size distribution analysis. By measuring PCTcurves, the hydrogen absorption properties of the composite was evaluated.The results show that nanocrystallinecomposite structure can be obtainedunder adequate ball milling condition. The reactive activation and hydrogen absorption capacity are improved compared with the sole MmNi5-x(CoAlMn)x alloy. The effect ofmagnesium on the microstructure andhydrogen absorption properties of thecomposite were also evaluated.展开更多
The composition and structure of Ti 6Al 4V alloy plasma based ion implanted with nitrogen was investigated.The nitrogen depth distribution shows more antiballistic with distribution peak heightened with increased i...The composition and structure of Ti 6Al 4V alloy plasma based ion implanted with nitrogen was investigated.The nitrogen depth distribution shows more antiballistic with distribution peak heightened with increased implantation time(dose),and more like a parabola at the low implantation pulse voltage.When implantation pulse voltage is increased,the implantation depth increased with the nitrogen distribution peak being deepened,widened and lowered somewhat.TiN,TiN+Ti 2N,or Ti 2N second phases were formed in the implanted layer.The relative percentage of nitrogen content in the form of TiN increases when going deeper into the implanted(TiN formed) layer.The increase of implantation pulse width and/or time is favourable for the formation of TiN rather than Ti 2N.It is unfavourable for formation of any nitrides when implantation pulse voltage is decreased to 30kV or less.Tiny crystalline particles (made mainly of Ti 2N and a smaller percentage of TiO 2 phases) of regular shapes such as triangle and tetragon, etc .(about 20 nm) are found distrbuted dispersively in the near surface region of samples implanted at the high implantation pulse voltage (75kV).展开更多
Solidification structure is a key aspect for understanding the mechanical performance of metal alloys,wherein composition and casting parameters considerably influence solidification and determine the unique microstru...Solidification structure is a key aspect for understanding the mechanical performance of metal alloys,wherein composition and casting parameters considerably influence solidification and determine the unique microstructure of the alloys.By following the principle of free energy minimization,the phase-field method eliminates the need for tracking the solid/liquid phase interface and has greatly accelerated the research and development efforts geared toward optimizing metal solidification microstructures.The recent progress in the application of phasefield simulation to investigate the effect of alloy composition and casting process parameters on the solidification structure of metals is summarized in this review.The effects of several typical elements and process parameters,including carbon,boron,silicon,cooling rate,pulling speed,scanning speed,anisotropy,and gravity,on the solidification structure are discussed.The present work also addresses the future prospects of phase-field simulation and aims to facilitate the widespread applications of phase-field approaches in the simulation of microstructures during solidification.展开更多
A ceramic layer was prepared on the surface of Al2O3f/ZL109 composites by means of micro-arc oxidation (MAO) technique. The surface morphology and phase constituent of the ceramic layer were analyzed using scanning ...A ceramic layer was prepared on the surface of Al2O3f/ZL109 composites by means of micro-arc oxidation (MAO) technique. The surface morphology and phase constituent of the ceramic layer were analyzed using scanning electron microscope and X-ray diffraction. The polarization curves of the composites before and after MAO treatment were measured and analyzed. The results showed that after Al2O3f/ZL109 composites were treated using MAO technique in silicate solution, the ceramic layer formed, and it was composed of Al, Si, and mullite phase. Al and Si came from Al alloy matrix of the composites, and the mullite phase formed in process of MAO. Al2O3 fiber in the composites affects the electric conductivity of the composites, the MAO reaction is promoted, and the cera- mic layer forming on the composite material side is slightly thicker than that on the Al alloy side. After Al2O3f/ZL109 composites were treated using MAO technique, the corro- sion resistance of the composites is significantly improved.展开更多
Ni-W alloys and their composite deposits are electroplated on the metals when an appropriate complex agent is selected on the base of the theories of electrochemistry and complex chemistry, and the principle of induce...Ni-W alloys and their composite deposits are electroplated on the metals when an appropriate complex agent is selected on the base of the theories of electrochemistry and complex chemistry, and the principle of induced codeposition. Effects of the bath composition, pH value, temperature and current density on the electrode position of Ni-W alloys and their composite deposits have been investigated, and the effect of heat treatment temperature on the hardness, structure and cohesive force of the amorphous Ni-W alloys and their composite deposits are also discussed. Results showed that the alloys containing more than 44 wt pct W content and the composite deposits containing 7.8 wt pct SiC content could be obtained by making use of the appropriate bath composition and plating conditions. Alloys and their composite deposits with over 44 wt pct W content show amorphous structure. The hardness of amorphous Ni-W alloys and their composite deposits increases obviously when heated, and can reach to 1350 HV and 1520 HV respectively for 46 wt pct W content. The cohesion on Cu, carbon steel and stainless steel is very good.展开更多
Mm0.3Ml0.7Ni3.55Co0.75Mn0.4-Al0.3 alloy has high chemical activity and favorable plateaus pressure. Mg2Ni is in favor of high hydrogen storage capacity and low weight, but it is difficult to be activated. In order to ...Mm0.3Ml0.7Ni3.55Co0.75Mn0.4-Al0.3 alloy has high chemical activity and favorable plateaus pressure. Mg2Ni is in favor of high hydrogen storage capacity and low weight, but it is difficult to be activated. In order to improve the capacity and cycle performances of hydrogen-storage alloy electrodes, Mm0.3Ml0.7Ni3.55Co0.75Mn0.4-Al0.3-x%Mg2Ni(x=0, 5, 10, 30) composite hydrogen storage alloys prepared by two-step re-melting were investigated in this work. The influences of Mg2Ni content on the cycle stabilities were analyzed by electrochemical methods. It was observed by XRD that the main phase of all the alloys is LaNi5 and the crystal lattice parameters of LaNi5 are changed with the increasing of x value, i.e, a-axis and unit cell volume decrease and c-axis decreases nonlinearly. The c-axis of alloy with x=5 is larger than the others. With the increasing of x value, capacity retentions of the composite hydrogen storage alloys rise from 66.21% while x=0 to 82.04% while x=10, but the capacity retention of the composite alloy with 30% Mg2Ni declines because of its decreasing axial ratio. More over, the composite alloy with 5% Mg2Ni shows the best cycle stability and higher discharge capacity, and it is an appropriate candidate for battery materials.展开更多
Ni–Al powder and Ni–Al composite coatings were fabricated by twin-wire arc spraying(TWAS). The microstructures of Ni-5wt%Al powder and Ni-20wt%Al powder were characterized by scanning electronic microscopy(SEM) ...Ni–Al powder and Ni–Al composite coatings were fabricated by twin-wire arc spraying(TWAS). The microstructures of Ni-5wt%Al powder and Ni-20wt%Al powder were characterized by scanning electronic microscopy(SEM) and energy dispersive spectroscopy(EDS). The results showed that the obtained particle size ranged from 5 to 50 μm. The morphology of the Ni–Al powder showed that molten particles were composed of Ni solid solution, NiAl, Ni_3Al, Al_2O_3, and NiO. The Ni–Al phase and a small amount of Al_2O_3 particles changed the composition of the coating. The microstructures of the twin-wire-arc-sprayed Ni–Al composite coatings were characterized by SEM, EDS, X-ray diffraction(XRD), and transmission electron microscopy(TEM). The results showed that the main phase of the Ni-5wt%Al coating consisted of Ni solid solution and Ni Al in addition to a small amount of Al_2O_3. The main phase of the Ni-20wt%Al coating mainly consisted of Ni solid solution, Ni Al, and Ni_3Al in addition to a small amount of Al and Al_2O_3, and Ni Al and Ni_3Al intermetallic compounds effectively further improved the final wear property of the coatings. TEM analysis indicated that fine spherical NiAl_3 precipitates and a Ni–Al–O amorphous phase formed in the matrix of the Ni solid solution in the original state.展开更多
The program of the Division of Materials Sciences for.intermetallic materials will be surveyed. This program is carried out at Department of Energy National Laboratories and at U.S. universities. Areas of research inc...The program of the Division of Materials Sciences for.intermetallic materials will be surveyed. This program is carried out at Department of Energy National Laboratories and at U.S. universities. Areas of research include theory and material simulation, microalloying, high resolution studies of structure and composition, mechanical properties, point defects and dislocation mechanics, phase transformations, and processing. Finally, general considerations will be discussed for the future program.展开更多
Thermal contact resistance plays a very important role in heat transfer efficiency and thermomechanical coupling response between two materials,and a common method to reduce the thermal contact resistance is to fill a...Thermal contact resistance plays a very important role in heat transfer efficiency and thermomechanical coupling response between two materials,and a common method to reduce the thermal contact resistance is to fill a soft interface material between these two materials.A testing system of high temperature thermal contact resistance based on INSTRON 8874 is established in the present paper,which can achieve 600 C at the interface.Based on this system,the thermal contact resistance between superalloy GH600 material and three-dimensional braid C/C composite material is experimentally investigated,under different interface pressures,interface roughnesses and temperatures,respectively.At the same time,the mechanism of reducing the thermal contact resistance with carbon fiber sheet as interface material is experimentally investigated.Results show that the present testing system is feasible in the experimental research of high temperature thermal contact resistance.展开更多
This study was conducted to understand the relationship between various critical temperatures and the stability of the secondary phases inside the heat-affected-zone(HAZ)of welded Grade 91(Gr.91)steel parts.Type IV cr...This study was conducted to understand the relationship between various critical temperatures and the stability of the secondary phases inside the heat-affected-zone(HAZ)of welded Grade 91(Gr.91)steel parts.Type IV cracking has been observed in the HAZ,and it is widely accepted that the stabilities of the secondary phases in Gr.91 steel are critical to the creep resistance,which is related to the crack failure of this steel.In this work,the stabilities of the secondary phases,including those of the M23C6,MX,and Z phases,were simulated by computational thermodynamics.Equilibrium cooling and Scheil simulations were carried out in order to understand the phase stability in welded Gr.91 steel.The effect of four critical temperatures—that is,Acl(the threshold temperature at which austenite begins to form),Ac3(the threshold temperature at which ferrite is fully transformed into austenite),and the M23C6 and Z phase threshold temperatures—on the thickness of the HAZ and phase stability in the HAZ is discussed.Overall,the simulations presented in this paper explain the mechanisms that can affect the creep resistance of Gr.91 steel,and can offer a possible solution to the problem of how to increase creep resistance at elevated temperatures by optimizing the steel composition,welding,and heat treatment process parameters.The simulation results from this work provide guidance for future alloy development to improve creep resistance in order to prevent type IV cracking.展开更多
A new type of lightweight AlNiLa medium entropy amorphous alloy composite ribbons(labled as MEAAC ribbons)were prepared by vacuum arc melting technology and high-speed single roller meltspinning method.The microstruct...A new type of lightweight AlNiLa medium entropy amorphous alloy composite ribbons(labled as MEAAC ribbons)were prepared by vacuum arc melting technology and high-speed single roller meltspinning method.The microstructure and thermal stability of MEAAC ribbons were examined using X-ray diffraction,differential scanning calorimeter,and scanning electron microscope.Meanwhile,the hardness and surface roughness of these ribbons were measured by Vickers microhardness tester and atomic force microscope.The potentiodynamic polarization curves and electrochemical impedance spectroscopy(EIS)were applied to investigate the corrosion behavior of these MEAAC ribbons in simulated seawater(3.5wt%NaCl corrosive solution)at room temperature.The results demonstrate that AlNiLa MEAAC ribbons in the as-received state are mainly composed of amorphous phase and intermetallic compounds.The hardness values of all melt-spun ribbons are above 310 HV_(0.1).With the increase of Al content,the linear polarization resistances of four various AlNiLa MEAAC ribbons are negligibly different numerically.It is also found that Al_(45)Ni_(27.5)La_(27.5) MEAAC ribbons have the most positive corrosion potential and the smallest corrosion current density at the same time;hence it may be a kind of potential material for metal surface protection in harsh ocean environment.展开更多
Alumina fiber-reinforced zinc alloy composites were manufactured by squeeze casting, and the eutectic transformation in the zinc alloy composites was studied. The results indicate that there is a fine and close interf...Alumina fiber-reinforced zinc alloy composites were manufactured by squeeze casting, and the eutectic transformation in the zinc alloy composites was studied. The results indicate that there is a fine and close interface between the fiber and the matrix, and the alloy elements can improve the combination between the fibers and the matrix in the composites. The fibers can serve as the sites of heterogeneous nucleation of the eutectic in the zinc alloy during the solidification of the composites, and the silicon on the interface between the fibers and the matrix plays a leading role during the coupled growth of the eutectic so that the eutectic transformation of the composites consists of Al-Si eutectic transformation and Zn-AI eutectic transformation.展开更多
The purpose of this paper is to review the current state of development of new composite materials for advanced aircraft engines. The advantages and disadvantages of Ti-base.NiAl-base, and MoSi_2-base composites as re...The purpose of this paper is to review the current state of development of new composite materials for advanced aircraft engines. The advantages and disadvantages of Ti-base.NiAl-base, and MoSi_2-base composites as replacements for today's Ni-base superalloys are discussed from the standpoint of key technical issues. current status, and future directions. Results describing progress in both improved understanding of the mechanisms of deformation and fracture, and improved material performance will be covered.展开更多
The superplasticity of an Al203p/6061Al composite, fabricated by powder metallurgy techniques, has been investigated. Instead of any special thermomechanical processing or hot rolling, simple hot extrusion has been em...The superplasticity of an Al203p/6061Al composite, fabricated by powder metallurgy techniques, has been investigated. Instead of any special thermomechanical processing or hot rolling, simple hot extrusion has been employed to obtain a fine grained structure before superplastic testing. Superplastic tensile tests were performed at strain rates ranging from 10-2 to 10-4 s-1 and at temperatures from 833 to 893 K. A maximum elongation of 200% was achieved at a temperature of 853 K and an initial strain rate of 1.67×103 s-1. The highest value obtained for the strain rate sensitivity index (in) was 0.32. Differential scanning calorimeter was used to ascertain the possibility of any partial melting in the vicinity of optimum superplastic temperature. These results suggested that no liquid phase existed where maximum elongation was achieved and deformation took place entirely in the solid state.展开更多
Fly Ash Cenospheres(FACs)are obtained from the coal power plants in the form of hollow spherical particles by burning the coal.FAC was started to use in early 1980-1985 as lightweight filler material in producing comp...Fly Ash Cenospheres(FACs)are obtained from the coal power plants in the form of hollow spherical particles by burning the coal.FAC was started to use in early 1980-1985 as lightweight filler material in producing composites of cementitious and at present many researchers are focusing on use of FAC as filler in polymer and metals.In this paper,the systematic review on research activities and application of FAC in manufacturing light weight products are done.The influence of FAC on the physical and mechanical properties of incorporated polymer and alloy-based composites were summarized.Prospects of future for its use were also suggested and summarized in this paper.展开更多
An Fe–44Ni nanocrystalline(NC) alloy thin film was prepared through electrodeposition. The relation between the microstructure and corrosion behavior of the NC film was investigated using electrochemical methods an...An Fe–44Ni nanocrystalline(NC) alloy thin film was prepared through electrodeposition. The relation between the microstructure and corrosion behavior of the NC film was investigated using electrochemical methods and chemical analysis approaches. The results show that the NC film is composed of a face-centered cubic phase(γ-(Fe,Ni)) and a body-centered cubic phase(α-(Fe,Ni)) when it is annealed at temperatures less than 400℃. The corrosion resistance increases with the increase in grain size, and the corresponding corrosion process is controlled by oxygen reduction. The NC films annealed at 500℃ and 600℃ do not exhibit the same pattern, although their grain sizes are considerably large. This result is attributed to the existence of an anodic phase, Fe0.947Ni0.054, in these films. Under this condition, the related corrosion process is synthetically controlled by anodic dissolution and depolarization.展开更多
文摘The magnetic properties, structure defects of electrodeposited Fe-Ni-P alloys with various compositions and the thermostability at amorphous state have been studied by DSC, positron annihilation and electronic integrating instrument methods. The results show that the thermostability of amorphous Fe-Ni-P alloys increases with Fe content. Emergence and recrystallization of stable phases defer as the P content of the coating increases. The minimum H-c, B-r and P-h occur at 9.4 P (wt pet) content. Maximum H-c, B-r and P-h occur at the weight ratio of Fe to Ni equaling to 1/9.
基金Funded by the Foundation for Department of Science and Technology of Jiangxi Province (No.ZDG03800)the Foundation for Department of Education of Jiangxi Province(No.GJJ11579)
文摘A series of Ni-Fe-Ga alloys near the prototype Heusler composition (X2YZ) were prepared through arc-melting suction-casting method. The dependences of the transformation behavior on the alloy composition and annealing treatment were studied in detail by an optical microscope, X-ray diffraction, and differential scanning calorimeters methods. The experimental results show that the martensitic transformation temperatures increase almost linearly with increasing Ni content in all the NiFeGa alloys. Annealing the Ni55.5Fe18Ga26.5 alloy at 100-500 ℃ for 3 h and at 300 ℃ for 1-10 h shifts the martensitic transformation start temperature by almost 20 ℃ to high temperature. The variations in the martensitic transformation temperatures in these alloys are discussed in terms of structural differences resulting from alloy composition and annealing treatment.
文摘The Ni-Cr-Mo-Cu multi-element surface alloying with the electric brushplating Ni interlayer on the low carbon steel substrate has been investigated. By theelectrochemical method in 3.5 percent (mass fraction) NaCl solution, the corrosion resistance of thecomposite alloying layer and single alloying layer is determined. The experimental results showthat the corrosion resistance of the composite alloying layer is obviously better than that of thesingle alloying layer. The structure and composition of passive films formed on the two kinds ofalloyed layers after electrochemical tests in 3.5 percent NaCl solution have been studied usingX-ray photoelectron spectroscopy (XPS). It is concluded that the double glow plasma surface alloyingof low carbon steel with the electric brush plating Ni interlayer is an appropriate technique toenhance the corrosion resistance compared with the single double glow surface alloying.
文摘The microstructure ofthe Mg/MmNi5-x (CoAlMn )x composite hydrogen storage material preparedby the method of mechanical alloyingwas characterized by X-ray diffraction, SEM and particle size distribution analysis. By measuring PCTcurves, the hydrogen absorption properties of the composite was evaluated.The results show that nanocrystallinecomposite structure can be obtainedunder adequate ball milling condition. The reactive activation and hydrogen absorption capacity are improved compared with the sole MmNi5-x(CoAlMn)x alloy. The effect ofmagnesium on the microstructure andhydrogen absorption properties of thecomposite were also evaluated.
文摘The composition and structure of Ti 6Al 4V alloy plasma based ion implanted with nitrogen was investigated.The nitrogen depth distribution shows more antiballistic with distribution peak heightened with increased implantation time(dose),and more like a parabola at the low implantation pulse voltage.When implantation pulse voltage is increased,the implantation depth increased with the nitrogen distribution peak being deepened,widened and lowered somewhat.TiN,TiN+Ti 2N,or Ti 2N second phases were formed in the implanted layer.The relative percentage of nitrogen content in the form of TiN increases when going deeper into the implanted(TiN formed) layer.The increase of implantation pulse width and/or time is favourable for the formation of TiN rather than Ti 2N.It is unfavourable for formation of any nitrides when implantation pulse voltage is decreased to 30kV or less.Tiny crystalline particles (made mainly of Ti 2N and a smaller percentage of TiO 2 phases) of regular shapes such as triangle and tetragon, etc .(about 20 nm) are found distrbuted dispersively in the near surface region of samples implanted at the high implantation pulse voltage (75kV).
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3702401)the National Natural Science Foundation of China(Nos.51901013,52122408,52071023)+3 种基金financial support from the Fundamental Research Funds for the Central Universities,China(University of Science and Technology Beijing(USTB),Nos.FRF-TP-2021-04C1,06500135)financial support from the Qilu Young Talent Program of Shandong University,Zhejiang Lab Open Research Project,China(No.K2022PE0AB05)the Shandong Provincial Natural Science Foundation,China(No.ZR2023MA058)the Guangdong Basic and Applied Basic Research Foundation,China(No.2023A1515011819)。
文摘Solidification structure is a key aspect for understanding the mechanical performance of metal alloys,wherein composition and casting parameters considerably influence solidification and determine the unique microstructure of the alloys.By following the principle of free energy minimization,the phase-field method eliminates the need for tracking the solid/liquid phase interface and has greatly accelerated the research and development efforts geared toward optimizing metal solidification microstructures.The recent progress in the application of phasefield simulation to investigate the effect of alloy composition and casting process parameters on the solidification structure of metals is summarized in this review.The effects of several typical elements and process parameters,including carbon,boron,silicon,cooling rate,pulling speed,scanning speed,anisotropy,and gravity,on the solidification structure are discussed.The present work also addresses the future prospects of phase-field simulation and aims to facilitate the widespread applications of phase-field approaches in the simulation of microstructures during solidification.
基金financially supported by the National University Student Innovation Program (No. 101011202)
文摘A ceramic layer was prepared on the surface of Al2O3f/ZL109 composites by means of micro-arc oxidation (MAO) technique. The surface morphology and phase constituent of the ceramic layer were analyzed using scanning electron microscope and X-ray diffraction. The polarization curves of the composites before and after MAO treatment were measured and analyzed. The results showed that after Al2O3f/ZL109 composites were treated using MAO technique in silicate solution, the ceramic layer formed, and it was composed of Al, Si, and mullite phase. Al and Si came from Al alloy matrix of the composites, and the mullite phase formed in process of MAO. Al2O3 fiber in the composites affects the electric conductivity of the composites, the MAO reaction is promoted, and the cera- mic layer forming on the composite material side is slightly thicker than that on the Al alloy side. After Al2O3f/ZL109 composites were treated using MAO technique, the corro- sion resistance of the composites is significantly improved.
文摘Ni-W alloys and their composite deposits are electroplated on the metals when an appropriate complex agent is selected on the base of the theories of electrochemistry and complex chemistry, and the principle of induced codeposition. Effects of the bath composition, pH value, temperature and current density on the electrode position of Ni-W alloys and their composite deposits have been investigated, and the effect of heat treatment temperature on the hardness, structure and cohesive force of the amorphous Ni-W alloys and their composite deposits are also discussed. Results showed that the alloys containing more than 44 wt pct W content and the composite deposits containing 7.8 wt pct SiC content could be obtained by making use of the appropriate bath composition and plating conditions. Alloys and their composite deposits with over 44 wt pct W content show amorphous structure. The hardness of amorphous Ni-W alloys and their composite deposits increases obviously when heated, and can reach to 1350 HV and 1520 HV respectively for 46 wt pct W content. The cohesion on Cu, carbon steel and stainless steel is very good.
基金supported by the National Natural Science Foundation of China (No.51004010)the Research Fund for the Doctoral Program of Higher Education of China (No.20090006120022)
基金Project Supported bythe Talents Development Foundation of Inner Mongolia Autonomous Region (200608)
文摘Mm0.3Ml0.7Ni3.55Co0.75Mn0.4-Al0.3 alloy has high chemical activity and favorable plateaus pressure. Mg2Ni is in favor of high hydrogen storage capacity and low weight, but it is difficult to be activated. In order to improve the capacity and cycle performances of hydrogen-storage alloy electrodes, Mm0.3Ml0.7Ni3.55Co0.75Mn0.4-Al0.3-x%Mg2Ni(x=0, 5, 10, 30) composite hydrogen storage alloys prepared by two-step re-melting were investigated in this work. The influences of Mg2Ni content on the cycle stabilities were analyzed by electrochemical methods. It was observed by XRD that the main phase of all the alloys is LaNi5 and the crystal lattice parameters of LaNi5 are changed with the increasing of x value, i.e, a-axis and unit cell volume decrease and c-axis decreases nonlinearly. The c-axis of alloy with x=5 is larger than the others. With the increasing of x value, capacity retentions of the composite hydrogen storage alloys rise from 66.21% while x=0 to 82.04% while x=10, but the capacity retention of the composite alloy with 30% Mg2Ni declines because of its decreasing axial ratio. More over, the composite alloy with 5% Mg2Ni shows the best cycle stability and higher discharge capacity, and it is an appropriate candidate for battery materials.
基金financially supported by the International Cooperation Project Foundation in Science and Technology of China(No.2008DFR50070)
文摘Ni–Al powder and Ni–Al composite coatings were fabricated by twin-wire arc spraying(TWAS). The microstructures of Ni-5wt%Al powder and Ni-20wt%Al powder were characterized by scanning electronic microscopy(SEM) and energy dispersive spectroscopy(EDS). The results showed that the obtained particle size ranged from 5 to 50 μm. The morphology of the Ni–Al powder showed that molten particles were composed of Ni solid solution, NiAl, Ni_3Al, Al_2O_3, and NiO. The Ni–Al phase and a small amount of Al_2O_3 particles changed the composition of the coating. The microstructures of the twin-wire-arc-sprayed Ni–Al composite coatings were characterized by SEM, EDS, X-ray diffraction(XRD), and transmission electron microscopy(TEM). The results showed that the main phase of the Ni-5wt%Al coating consisted of Ni solid solution and Ni Al in addition to a small amount of Al_2O_3. The main phase of the Ni-20wt%Al coating mainly consisted of Ni solid solution, Ni Al, and Ni_3Al in addition to a small amount of Al and Al_2O_3, and Ni Al and Ni_3Al intermetallic compounds effectively further improved the final wear property of the coatings. TEM analysis indicated that fine spherical NiAl_3 precipitates and a Ni–Al–O amorphous phase formed in the matrix of the Ni solid solution in the original state.
文摘The program of the Division of Materials Sciences for.intermetallic materials will be surveyed. This program is carried out at Department of Energy National Laboratories and at U.S. universities. Areas of research include theory and material simulation, microalloying, high resolution studies of structure and composition, mechanical properties, point defects and dislocation mechanics, phase transformations, and processing. Finally, general considerations will be discussed for the future program.
基金supported by the Fundamental Research Funds for the Central Universities (FRF-BR-10-007A and FRF-AS-09-001A)the National Natural Science Foundation of China (10872104)
文摘Thermal contact resistance plays a very important role in heat transfer efficiency and thermomechanical coupling response between two materials,and a common method to reduce the thermal contact resistance is to fill a soft interface material between these two materials.A testing system of high temperature thermal contact resistance based on INSTRON 8874 is established in the present paper,which can achieve 600 C at the interface.Based on this system,the thermal contact resistance between superalloy GH600 material and three-dimensional braid C/C composite material is experimentally investigated,under different interface pressures,interface roughnesses and temperatures,respectively.At the same time,the mechanism of reducing the thermal contact resistance with carbon fiber sheet as interface material is experimentally investigated.Results show that the present testing system is feasible in the experimental research of high temperature thermal contact resistance.
基金This material is based upon work supported by the US Department of Energy(DOE)(DE-FE0027800).The authors would like to thank the DOE National Energy Technology Laboratory program managers,Dr.Karol Schrems and Dr.Jessica Mullen,and Dr.Wei Zhang from Ohio State University,for their support and guidance.
文摘This study was conducted to understand the relationship between various critical temperatures and the stability of the secondary phases inside the heat-affected-zone(HAZ)of welded Grade 91(Gr.91)steel parts.Type IV cracking has been observed in the HAZ,and it is widely accepted that the stabilities of the secondary phases in Gr.91 steel are critical to the creep resistance,which is related to the crack failure of this steel.In this work,the stabilities of the secondary phases,including those of the M23C6,MX,and Z phases,were simulated by computational thermodynamics.Equilibrium cooling and Scheil simulations were carried out in order to understand the phase stability in welded Gr.91 steel.The effect of four critical temperatures—that is,Acl(the threshold temperature at which austenite begins to form),Ac3(the threshold temperature at which ferrite is fully transformed into austenite),and the M23C6 and Z phase threshold temperatures—on the thickness of the HAZ and phase stability in the HAZ is discussed.Overall,the simulations presented in this paper explain the mechanisms that can affect the creep resistance of Gr.91 steel,and can offer a possible solution to the problem of how to increase creep resistance at elevated temperatures by optimizing the steel composition,welding,and heat treatment process parameters.The simulation results from this work provide guidance for future alloy development to improve creep resistance in order to prevent type IV cracking.
基金by the National Key R&D Program of China(No.2018YFC1902400)the National Natural Science Foundation of China(No.51975582)the Natural Science Foundation of Beijing,China(No.2212055)。
文摘A new type of lightweight AlNiLa medium entropy amorphous alloy composite ribbons(labled as MEAAC ribbons)were prepared by vacuum arc melting technology and high-speed single roller meltspinning method.The microstructure and thermal stability of MEAAC ribbons were examined using X-ray diffraction,differential scanning calorimeter,and scanning electron microscope.Meanwhile,the hardness and surface roughness of these ribbons were measured by Vickers microhardness tester and atomic force microscope.The potentiodynamic polarization curves and electrochemical impedance spectroscopy(EIS)were applied to investigate the corrosion behavior of these MEAAC ribbons in simulated seawater(3.5wt%NaCl corrosive solution)at room temperature.The results demonstrate that AlNiLa MEAAC ribbons in the as-received state are mainly composed of amorphous phase and intermetallic compounds.The hardness values of all melt-spun ribbons are above 310 HV_(0.1).With the increase of Al content,the linear polarization resistances of four various AlNiLa MEAAC ribbons are negligibly different numerically.It is also found that Al_(45)Ni_(27.5)La_(27.5) MEAAC ribbons have the most positive corrosion potential and the smallest corrosion current density at the same time;hence it may be a kind of potential material for metal surface protection in harsh ocean environment.
文摘Alumina fiber-reinforced zinc alloy composites were manufactured by squeeze casting, and the eutectic transformation in the zinc alloy composites was studied. The results indicate that there is a fine and close interface between the fiber and the matrix, and the alloy elements can improve the combination between the fibers and the matrix in the composites. The fibers can serve as the sites of heterogeneous nucleation of the eutectic in the zinc alloy during the solidification of the composites, and the silicon on the interface between the fibers and the matrix plays a leading role during the coupled growth of the eutectic so that the eutectic transformation of the composites consists of Al-Si eutectic transformation and Zn-AI eutectic transformation.
文摘The purpose of this paper is to review the current state of development of new composite materials for advanced aircraft engines. The advantages and disadvantages of Ti-base.NiAl-base, and MoSi_2-base composites as replacements for today's Ni-base superalloys are discussed from the standpoint of key technical issues. current status, and future directions. Results describing progress in both improved understanding of the mechanisms of deformation and fracture, and improved material performance will be covered.
基金This work was supported by the National Natural Science Foundation of China,under grant No.59781004.
文摘The superplasticity of an Al203p/6061Al composite, fabricated by powder metallurgy techniques, has been investigated. Instead of any special thermomechanical processing or hot rolling, simple hot extrusion has been employed to obtain a fine grained structure before superplastic testing. Superplastic tensile tests were performed at strain rates ranging from 10-2 to 10-4 s-1 and at temperatures from 833 to 893 K. A maximum elongation of 200% was achieved at a temperature of 853 K and an initial strain rate of 1.67×103 s-1. The highest value obtained for the strain rate sensitivity index (in) was 0.32. Differential scanning calorimeter was used to ascertain the possibility of any partial melting in the vicinity of optimum superplastic temperature. These results suggested that no liquid phase existed where maximum elongation was achieved and deformation took place entirely in the solid state.
文摘Fly Ash Cenospheres(FACs)are obtained from the coal power plants in the form of hollow spherical particles by burning the coal.FAC was started to use in early 1980-1985 as lightweight filler material in producing composites of cementitious and at present many researchers are focusing on use of FAC as filler in polymer and metals.In this paper,the systematic review on research activities and application of FAC in manufacturing light weight products are done.The influence of FAC on the physical and mechanical properties of incorporated polymer and alloy-based composites were summarized.Prospects of future for its use were also suggested and summarized in this paper.
基金financially supported by the Major State Basic Research Development Program of China (No. 2014CB643300)the National Natural Science Foundation of China (No. U1560104)the National Environmental Corrosion Platform (NECP)
文摘An Fe–44Ni nanocrystalline(NC) alloy thin film was prepared through electrodeposition. The relation between the microstructure and corrosion behavior of the NC film was investigated using electrochemical methods and chemical analysis approaches. The results show that the NC film is composed of a face-centered cubic phase(γ-(Fe,Ni)) and a body-centered cubic phase(α-(Fe,Ni)) when it is annealed at temperatures less than 400℃. The corrosion resistance increases with the increase in grain size, and the corresponding corrosion process is controlled by oxygen reduction. The NC films annealed at 500℃ and 600℃ do not exhibit the same pattern, although their grain sizes are considerably large. This result is attributed to the existence of an anodic phase, Fe0.947Ni0.054, in these films. Under this condition, the related corrosion process is synthetically controlled by anodic dissolution and depolarization.