The influence of micro-Ca/In alloying on the microstructural charac teristics,electrochemical behaviors and discharge properties of extruded dilute Mg-0.5Bi-0.5Sn-based(wt.%)alloys as anodes for Mg-air batteries are e...The influence of micro-Ca/In alloying on the microstructural charac teristics,electrochemical behaviors and discharge properties of extruded dilute Mg-0.5Bi-0.5Sn-based(wt.%)alloys as anodes for Mg-air batteries are evaluated.The grain size and texture intensity of the Mg-Bi-Sn-based alloys are significantly decreased after the Ca/In alloying,particularly for the In-containing alloy.Note that,in addition to nanoscale Mg_(3)Bi_(2)phase,a new microscale Mg_(2)Bi_(2)Ca phase forms in the Ca-containing alloy.The electrochemical test results demonstrate that Ca/In micro-alloying can enhance the electrochemical activity.Using In to alloy the Mg-Bi-Sn-based alloy is effective in restricting the cathodic hydrogen evolution(CHE)kinetics,leading to a low self-corrosion rate,while severe CHE occurred after Ca alloying.The micro-alloying of Ca/In to Mg-Bi-Sn-based alloy strongly deteriorates the compactness of discharge products film and mitigates the"chunk effect"(CE),hence the cell voltage,anodic efficiency as well as discharge capacity are greatly improved.The In-containing alloy exhibits outstanding discharge performance under the combined effect of the modified microstructure and discharge products,thus making it a potential anode material for primary Mg-air battery.展开更多
An efficient and safe hydrogen storage method is one of the important links for the large-scale development of hydrogen in the future. Because of its low price and simple design, Ti-based hydrogen storage alloys are c...An efficient and safe hydrogen storage method is one of the important links for the large-scale development of hydrogen in the future. Because of its low price and simple design, Ti-based hydrogen storage alloys are considered to be suitable for practical applications. In this paper, we review the latest research on Ti-based hydrogen storage alloys. Firstly, the machine learning and density functional theory are introduced to provide theoretical guidance for the optimization of Ti-based hydrogen storage alloys. Then, in order to improve the hydrogen storage performance, we briefly introduce the research of AB type and AB2 type Ti-based alloys, focusing on doping elements and adaptive after treatment. Finally, suggestions for the future research and development of Ti-based hydrogen storage alloys are proposed. .展开更多
To quantify the nonuniform micromechanical performance of welded joint,the load-displacement curves by nanoindentation test were introduced to examine different zones including base metal,coarse grained heat affected ...To quantify the nonuniform micromechanical performance of welded joint,the load-displacement curves by nanoindentation test were introduced to examine different zones including base metal,coarse grained heat affected zone,partially melted zone,weld metal near the fusion boundary and weld metal center.The results showed that the strengthening effect of weld metal was more obvious than that of heat affected zone for nickel based welded joint and especially in coarse grained heat affected zone,the hardening resulted from overheating was not apparent.Nickel based weld metal with high content of alloying elements which were often segregated at interdendritic regions or precipitated in grain interior under nonequilibrium solidification contributed to the characteristics that differ from conventional low alloy steel welded joint.展开更多
This paper aims to investigate if the dental restoration of nickel-chromium based alloy （Ni-Cr） leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had...This paper aims to investigate if the dental restoration of nickel-chromium based alloy （Ni-Cr） leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni-Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination. Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. Compared to the control group, the urinary level of Ni was significantly higher in the patient group of 〈 1 month of the restoration duration, among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain. Urinary levels of Cr were significantly higher in the three patient groups of 〈1, 1 to 〈3 and 3 to 〈6 months, especially in those with a higher metal crown exposure index. Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups. Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration. Potential short- and long-term effects of Ni-Cr alloy restoration need to be investigated.展开更多
Because of the low temperature gradient and growth rate, the microstructure of the conventional single crystal superalloy made by HRS processing is coarse dendrite with well developed sidebranches and has serious segr...Because of the low temperature gradient and growth rate, the microstructure of the conventional single crystal superalloy made by HRS processing is coarse dendrite with well developed sidebranches and has serious segregation. With the help of the high tem展开更多
Low cycle fatigue tests on nickel base superalloy GH536 were performed at 600, 700 and 800℃. The strain-life and cyclic stress-strain relationship were given at various temperatures. The change in fatigue life behavi...Low cycle fatigue tests on nickel base superalloy GH536 were performed at 600, 700 and 800℃. The strain-life and cyclic stress-strain relationship were given at various temperatures. The change in fatigue life behavior and fatigue parameters with tem- perature increasing was discussed. At low and intermediate total strain amplitudes, the fatigue life was found to decrease with increasing temperature.展开更多
Cu-Ni-Al alloys at different concentrations were obtained using a high frequency induction melting unit, keeping a balance in the nominal compositions. Light alloys are important to be used in industrial applications....Cu-Ni-Al alloys at different concentrations were obtained using a high frequency induction melting unit, keeping a balance in the nominal compositions. Light alloys are important to be used in industrial applications. Aluminum additions result in a positive hardness increment of the ternary alloys in comparison with the binary Cu-Ni alloys. Generalized wear mechanisms of the alloys with low aluminum content are basically type abrasive, while samples with 5 and 10 at.% Al present an oxidative-adhesive wear mechanism. Wear results have indicated that aluminum addition affects positively the wear resistance, mainly in samples with high aluminum content product of the creation during the test of different oxides corresponding to the elements present in the alloys.展开更多
An electroless plating nickel treatment was processed to improve the active behaviors and discharge capacities of Zr based AB 2 alloys. The effects of the nickel coating on the surface appearance, the structure of the...An electroless plating nickel treatment was processed to improve the active behaviors and discharge capacities of Zr based AB 2 alloys. The effects of the nickel coating on the surface appearance, the structure of the alloy powders and the electrode characteristics were investigated. It is found that the Ni rich layer formed through electroless plating nickel treatment plays an important role on the initial activation property and the discharge capacity of Zr based alloy. The optimal content of electroless plating nickel is about 15%, and the discharge capacity of the electrode can be increased to 400?mA·h·g -1 after 6 cycles. Although coated nickel is beneficial for quick activation and discharge capacity, excessive electroless plating nickel can result in a decreased discharge capacity.展开更多
Rare earth-Mg-Ni-based alloys with superlattice structures are new generation negative electrode materials for the nickel metal hydride batteries.Among them,the novel AB_(4)-type superlattice structure alloy is suppos...Rare earth-Mg-Ni-based alloys with superlattice structures are new generation negative electrode materials for the nickel metal hydride batteries.Among them,the novel AB_(4)-type superlattice structure alloy is supposed to have superior cycling stability and rate capability.Yet its preparation is hindered by the crucial requirement of temperature and the special composition which is close to the other superlattice structure.Here,we prepare rare earth-Mg-Ni-based alloy and study the phase transformation of alloys to make clear the formation of AB_(4)-type phase.It is found Pr_(5)Co_(19)-type phase is converted from Ce_(5)Co_(19)-type phase and shows good stability at higher temperature compared to the Ce_(5)Co_(19)-type phase in the range of 930-970℃.Afterwards,with further 5℃increasing,AB_(4)-type superlattice structure forms at a temperature of 975℃by consuming Pr_(5)Co_(19)-type phase.In contrast with A_(5)B_(19)-type alloy,AB_(4)-type alloy has superior rate capability owing to the dominant advantages of charge transfer and hydrogen diffusion.Besides,AB_(4)-type alloy shows long lifespan whose capacity retention rates are 89.2%at the 100;cycle and 82.8%at the 200;cycle,respectively.AB_(4)-type alloy delivers 1.53 wt.%hydrogen storage capacity at room temperature and exhibits higher plateau pressure than Pr_(5)Co_(19)-type alloy.The work provides novel AB_(4)-type alloy with preferable electrochemical performance as negative electrode material to inspire the development of nickel metal hydride batteries.展开更多
Cold Metal Transfer (CMT) welding technique is a new welding technique introduced by Fronius company. CMT welding of nickel-based alloy with stainless steel was carried out using CuSi3 filler wire in this paper. Effec...Cold Metal Transfer (CMT) welding technique is a new welding technique introduced by Fronius company. CMT welding of nickel-based alloy with stainless steel was carried out using CuSi3 filler wire in this paper. Effects of welding parameters, including welding current, welding speed, etc, on weld surface appearance were tested. Microstructure and mechanical properties of CMT weld were studied. The results show that the thickness of interface reaction layer of the nickel-based alloy is 14.3 μm, which is only 4.33% of base material. The weld is made up of two phases, α-copper and iron-based solid solution. Rupture occurs initially at the welded seam near the edge of stainless steel in shear test. The maximum shear strength of the CuSi3 welded joint is 184.9 MPa.展开更多
Ni398 and Ni818 base alloy coatings were deposited on 1045 steel by electrospark deposition technique (ESD). Forming properties, thickness, microhardness and wear resistance of the coatings were investigated. The chem...Ni398 and Ni818 base alloy coatings were deposited on 1045 steel by electrospark deposition technique (ESD). Forming properties, thickness, microhardness and wear resistance of the coatings were investigated. The chemical composition and crosssection morphology were analyzed through energy dispersive spectrum (EDS) and metalloscope. The results show that the technological parameter window of Ni398 is larger than that of Ni818 electrode. However, other properties of the Ni818 coating, such as thickness and microhardness, were better than those of the Ni398 coating. Especially the wornout volume of Ni818 coating is only 1/6 of that for 1045 steel and 1/3 for Ni398 coating. Chemical composition analysis indicated that the addition of Mo promoted grain refinement of nickel alloy. Metallographic analysis shows that the molten droplets of Ni398 coatings have an average structure thickness of 20-40 μm while the microstructure of Ni818 coatings is flat with width of 5-20 μm.展开更多
The microstructural features and high temperature tensile properties of M963 superalloy at as cast, as solutioned and as aged conditions were investigated in detail. The results show that the solution treatment at 1?2...The microstructural features and high temperature tensile properties of M963 superalloy at as cast, as solutioned and as aged conditions were investigated in detail. The results show that the solution treatment at 1?220?℃ for 4?h, AC causes an increase in high temperature yield strength but a drastic drop in high temperature ductility due to the precipitation of both the secondary carbide M 6C along grain boundaries and at the interdendritic regions and very fine γ ′ particles in the dendrite cores. Aging treatment following the solution treatment can improve the high temperature tensile properties of M963 superalloy due to the coarsing of the γ′ precipitate. One stage aging at 850?℃ for 16?h following the solution treatment causes an increase in both strength and ductility of alloy M963, and two stage aging of 1?089?℃ / 2?h, AC plus 850?℃ / 16?h, AC following the solution treatment further increases the ductility of alloy M963 but slightly decreases its strength.展开更多
Orthogonal experiment is employed to study a new kind of multiplex flux for nickel-base superalloy. This activated TIG welding flux is composed of NaF, MgF2 and CaF2, and their proportion is 5:4:1. Compared with conve...Orthogonal experiment is employed to study a new kind of multiplex flux for nickel-base superalloy. This activated TIG welding flux is composed of NaF, MgF2 and CaF2, and their proportion is 5:4:1. Compared with conventional TIG welding, the penetration increases 164% by the action of the flux. Tensile test result indicates that the fracture strength of the mixed flux A-TIG weld bead is higher than base metal, and it increases along with the decrement of the welding current. The average extensibility of the weldment is beyond 100%, which means perfect ductility. Metallographs elucidate that there exist lots of deep and evenly distributed dimples on the fracture section of weld bead while on that of base metal there only exists a few shallow dimples and massive tearing ridge.展开更多
A Y2O3 dispersion strengthened nickel-based superalloy sheet(0.15 mm thick) was prepared by electron beam physical vapor deposition(EB-PVD) technology.Different heat treatments were used to improve the mechanical prop...A Y2O3 dispersion strengthened nickel-based superalloy sheet(0.15 mm thick) was prepared by electron beam physical vapor deposition(EB-PVD) technology.Different heat treatments were used to improve the mechanical properties of the alloy sheet.Differential thermal analysis(DTA) was used to examine the thermal stability of the as-deposited sheet.Element contents,phase composition and microstructure investigations on as-deposited and heat treated specimens were performed by X-ray fluorescence spectrometer(XRF),X-ray diffraction(XRD) and scanning electron microscopy(SEM).Tensile tests were conducted at room temperature on specimens as-deposited and heat treated.The results show that the as-deposited sheet is composed of equiaxed grains on the substrate side and columnar grains on the evaporation side.The as-deposited sheet shows poor ductility due to micropores between columnar grains.The strength and ductility can be improved effectively by annealing at 800°C for 3 h.For samples treated at 1100°C,the strength drops down due to the precipitates of Y3Al5O12(YAG).展开更多
The morphological evolution of the γ' phase in nickel-based superalloy жc6y during various solution heat treatments was investigated. The significant changes of the γ' precipitates were observed in the solu...The morphological evolution of the γ' phase in nickel-based superalloy жc6y during various solution heat treatments was investigated. The significant changes of the γ' precipitates were observed in the solution-treated samples. The coarsening and dissolution of γ' phase simulta-neously occurred at intermediate temperatures. In some areas, the primary precipitates became blunt and the adjacent ones were intercon-nected with each other via a diffuse neck, indicating a coarsening process of the primary γ' population. The coarsening was dominated by the precipitate agglomeration mechanism (PAM) rather than by the well-known Ostwald ripening mechanism. In other areas, the partial dissolu-tion of the γ' precipitates began to occur, spreading gradually from dendrite cores to interdendritic regions. In addition, a flower-like γ' struc-ture was developed during the subsolvus solution treatments. The observable long filaments composed of erraticly shaped precipitates were caused by the heterogeneous nucleation of the cooling precipitates during water quenching.展开更多
The hot compression testing of hot isostatically pressed(HIPed) spray formed(SF) nickel-base superalloy was carried out by thermal mechanical simulator in the temperature range of 1 050-1 140 ℃ at strain rates of 0.0...The hot compression testing of hot isostatically pressed(HIPed) spray formed(SF) nickel-base superalloy was carried out by thermal mechanical simulator in the temperature range of 1 050-1 140 ℃ at strain rates of 0.01-10 s-1 and engineering strain of 50%. A processing map was developed on the basis of these data by using the principles of dynamic materials modeling. The microstructural evolution of deformed samples was also examined on the basis of optical and electron microscopic observations. The map exhibits two domains: the instability domain at the temperatures of 1 050 ℃ -1 110 ℃ and strain rate of 0.01 s-1, the stability domain at the temperatures of 1 110 ℃- 1 140 ℃ and strain rates of 1 s-1-10 s-1, with a peak efficiency of about 40%. The dynamic recrystallization(DRX) is observed in the stability domain and the deformed specimens are no cracking or instabilities. However, there is no DRX in the instability domain and the alloy exhibits flow instability with cracks due to poor workability. The optimum hot working condition was determined in the stability domain.展开更多
A series of directional solidification experiments have been performed to study the effect of cooling rate on the precipitation behavior of MC carbide in nickel-based superalloy under the temperature gradient of 500 K...A series of directional solidification experiments have been performed to study the effect of cooling rate on the precipitation behavior of MC carbide in nickel-based superalloy under the temperature gradient of 500 K·s-1.Results reveal that the morphology of MC carbide changes from coarse block to fine strip,then to Chinese-script,and their sizes reduce gradually with the increasing of cooling rate from 2.53 K·s-1 to 36.4 K·s-1.At low cooling rates,most of these carbides are found to be located at the grain boundary and interdendritic regions,while the coupled growth of some carbides and γ matrix in the center of γ grains is occurred at high cooling rate.The main elements forming MC carbide are Ta,W,and Hf.展开更多
In the present study,the passive film formed on the G3 nickel-base alloy tubing under corrosive conditions including H_2S,CO_2,and Cl^- at 130℃and 205℃is studied with X-ray photoelectron spectroscopy(XPS).The result...In the present study,the passive film formed on the G3 nickel-base alloy tubing under corrosive conditions including H_2S,CO_2,and Cl^- at 130℃and 205℃is studied with X-ray photoelectron spectroscopy(XPS).The results reveal that the passive film formed at 205℃consists of Cr,Ni,Fe,S and O elements and is over 470 nm in thickness. The passive film can be divided into three layers,the outer-layer is composed of NiS,and Cr_2S_3,the intermediate-layer of Cr(OH)_3,Ni(OH)_2,NiS_2,Cr_2S_3 and a small quantity of NiO and Cr_2O_3,and the inner-layer of NiO,Cr_2O_3,and alloy elements.Due to the invasion of S^(2-) into the passive film and the decrease of the content of chromium oxide in the film,the corrosion resistance of the G3 alloy in the sour environment at 205℃is weakened.展开更多
A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room tempera...A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room temperature,and the principle of the method was provided.Experiments and FE simulations were carried out to analyze the deformation characteristics for the part with larger variable diameter ratio(35%).The results show that visco-elasto-plastic pressure-carrying medium can meet the requirements of the room-temperature deformation condition for nickel based super-alloy sheet.The inner and outer pressure forming with the visco-elasto-plastic pressure-carrying medium can meet the requirements of dimensional accuracy for the thin-walled part with variable diameter sections.The thinning of wall-thickness is less than 4%.This method provides a new approach for near-net shape forming of nickel based super-alloy thin-walled parts with variable diameter sections.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.:51901153)Shanxi Scholarship Council of China(Grant No.:2019032)+1 种基金Natural Science Foundation of Shanxi(Grant No.:202103021224049)the Science and Technology Major Project of Shanxi Province(Grant No.:20191102008,20191102007)。
文摘The influence of micro-Ca/In alloying on the microstructural charac teristics,electrochemical behaviors and discharge properties of extruded dilute Mg-0.5Bi-0.5Sn-based(wt.%)alloys as anodes for Mg-air batteries are evaluated.The grain size and texture intensity of the Mg-Bi-Sn-based alloys are significantly decreased after the Ca/In alloying,particularly for the In-containing alloy.Note that,in addition to nanoscale Mg_(3)Bi_(2)phase,a new microscale Mg_(2)Bi_(2)Ca phase forms in the Ca-containing alloy.The electrochemical test results demonstrate that Ca/In micro-alloying can enhance the electrochemical activity.Using In to alloy the Mg-Bi-Sn-based alloy is effective in restricting the cathodic hydrogen evolution(CHE)kinetics,leading to a low self-corrosion rate,while severe CHE occurred after Ca alloying.The micro-alloying of Ca/In to Mg-Bi-Sn-based alloy strongly deteriorates the compactness of discharge products film and mitigates the"chunk effect"(CE),hence the cell voltage,anodic efficiency as well as discharge capacity are greatly improved.The In-containing alloy exhibits outstanding discharge performance under the combined effect of the modified microstructure and discharge products,thus making it a potential anode material for primary Mg-air battery.
文摘An efficient and safe hydrogen storage method is one of the important links for the large-scale development of hydrogen in the future. Because of its low price and simple design, Ti-based hydrogen storage alloys are considered to be suitable for practical applications. In this paper, we review the latest research on Ti-based hydrogen storage alloys. Firstly, the machine learning and density functional theory are introduced to provide theoretical guidance for the optimization of Ti-based hydrogen storage alloys. Then, in order to improve the hydrogen storage performance, we briefly introduce the research of AB type and AB2 type Ti-based alloys, focusing on doping elements and adaptive after treatment. Finally, suggestions for the future research and development of Ti-based hydrogen storage alloys are proposed. .
基金supported by the Primary Research&Developement Plan of Jiangsu Province(BE2017168)
文摘To quantify the nonuniform micromechanical performance of welded joint,the load-displacement curves by nanoindentation test were introduced to examine different zones including base metal,coarse grained heat affected zone,partially melted zone,weld metal near the fusion boundary and weld metal center.The results showed that the strengthening effect of weld metal was more obvious than that of heat affected zone for nickel based welded joint and especially in coarse grained heat affected zone,the hardening resulted from overheating was not apparent.Nickel based weld metal with high content of alloying elements which were often segregated at interdendritic regions or precipitated in grain interior under nonequilibrium solidification contributed to the characteristics that differ from conventional low alloy steel welded joint.
基金supported by Open Fund of State Key Laboratory of Oral Diseases,Sichun University
文摘This paper aims to investigate if the dental restoration of nickel-chromium based alloy （Ni-Cr） leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni-Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination. Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. Compared to the control group, the urinary level of Ni was significantly higher in the patient group of 〈 1 month of the restoration duration, among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain. Urinary levels of Cr were significantly higher in the three patient groups of 〈1, 1 to 〈3 and 3 to 〈6 months, especially in those with a higher metal crown exposure index. Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups. Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration. Potential short- and long-term effects of Ni-Cr alloy restoration need to be investigated.
文摘Because of the low temperature gradient and growth rate, the microstructure of the conventional single crystal superalloy made by HRS processing is coarse dendrite with well developed sidebranches and has serious segregation. With the help of the high tem
文摘Low cycle fatigue tests on nickel base superalloy GH536 were performed at 600, 700 and 800℃. The strain-life and cyclic stress-strain relationship were given at various temperatures. The change in fatigue life behavior and fatigue parameters with tem- perature increasing was discussed. At low and intermediate total strain amplitudes, the fatigue life was found to decrease with increasing temperature.
文摘Cu-Ni-Al alloys at different concentrations were obtained using a high frequency induction melting unit, keeping a balance in the nominal compositions. Light alloys are important to be used in industrial applications. Aluminum additions result in a positive hardness increment of the ternary alloys in comparison with the binary Cu-Ni alloys. Generalized wear mechanisms of the alloys with low aluminum content are basically type abrasive, while samples with 5 and 10 at.% Al present an oxidative-adhesive wear mechanism. Wear results have indicated that aluminum addition affects positively the wear resistance, mainly in samples with high aluminum content product of the creation during the test of different oxides corresponding to the elements present in the alloys.
文摘An electroless plating nickel treatment was processed to improve the active behaviors and discharge capacities of Zr based AB 2 alloys. The effects of the nickel coating on the surface appearance, the structure of the alloy powders and the electrode characteristics were investigated. It is found that the Ni rich layer formed through electroless plating nickel treatment plays an important role on the initial activation property and the discharge capacity of Zr based alloy. The optimal content of electroless plating nickel is about 15%, and the discharge capacity of the electrode can be increased to 400?mA·h·g -1 after 6 cycles. Although coated nickel is beneficial for quick activation and discharge capacity, excessive electroless plating nickel can result in a decreased discharge capacity.
基金financially supported by the Natural Science Foundation of Hebei Province(Nos.E2019203414,E2020203081 and E2019203161)the National Natural Science Foundation of China(Nos.51701175 and 51971197)+1 种基金the Innovation Fund for the Graduate Students of Hebei Province(No.CXZZBS2020062)the Doctoral Fund of Yanshan University(No.BL19031)
文摘Rare earth-Mg-Ni-based alloys with superlattice structures are new generation negative electrode materials for the nickel metal hydride batteries.Among them,the novel AB_(4)-type superlattice structure alloy is supposed to have superior cycling stability and rate capability.Yet its preparation is hindered by the crucial requirement of temperature and the special composition which is close to the other superlattice structure.Here,we prepare rare earth-Mg-Ni-based alloy and study the phase transformation of alloys to make clear the formation of AB_(4)-type phase.It is found Pr_(5)Co_(19)-type phase is converted from Ce_(5)Co_(19)-type phase and shows good stability at higher temperature compared to the Ce_(5)Co_(19)-type phase in the range of 930-970℃.Afterwards,with further 5℃increasing,AB_(4)-type superlattice structure forms at a temperature of 975℃by consuming Pr_(5)Co_(19)-type phase.In contrast with A_(5)B_(19)-type alloy,AB_(4)-type alloy has superior rate capability owing to the dominant advantages of charge transfer and hydrogen diffusion.Besides,AB_(4)-type alloy shows long lifespan whose capacity retention rates are 89.2%at the 100;cycle and 82.8%at the 200;cycle,respectively.AB_(4)-type alloy delivers 1.53 wt.%hydrogen storage capacity at room temperature and exhibits higher plateau pressure than Pr_(5)Co_(19)-type alloy.The work provides novel AB_(4)-type alloy with preferable electrochemical performance as negative electrode material to inspire the development of nickel metal hydride batteries.
文摘Cold Metal Transfer (CMT) welding technique is a new welding technique introduced by Fronius company. CMT welding of nickel-based alloy with stainless steel was carried out using CuSi3 filler wire in this paper. Effects of welding parameters, including welding current, welding speed, etc, on weld surface appearance were tested. Microstructure and mechanical properties of CMT weld were studied. The results show that the thickness of interface reaction layer of the nickel-based alloy is 14.3 μm, which is only 4.33% of base material. The weld is made up of two phases, α-copper and iron-based solid solution. Rupture occurs initially at the welded seam near the edge of stainless steel in shear test. The maximum shear strength of the CuSi3 welded joint is 184.9 MPa.
基金supported by the National Natural Science Foundation of China(No.50801066)
文摘Ni398 and Ni818 base alloy coatings were deposited on 1045 steel by electrospark deposition technique (ESD). Forming properties, thickness, microhardness and wear resistance of the coatings were investigated. The chemical composition and crosssection morphology were analyzed through energy dispersive spectrum (EDS) and metalloscope. The results show that the technological parameter window of Ni398 is larger than that of Ni818 electrode. However, other properties of the Ni818 coating, such as thickness and microhardness, were better than those of the Ni398 coating. Especially the wornout volume of Ni818 coating is only 1/6 of that for 1045 steel and 1/3 for Ni398 coating. Chemical composition analysis indicated that the addition of Mo promoted grain refinement of nickel alloy. Metallographic analysis shows that the molten droplets of Ni398 coatings have an average structure thickness of 20-40 μm while the microstructure of Ni818 coatings is flat with width of 5-20 μm.
文摘The microstructural features and high temperature tensile properties of M963 superalloy at as cast, as solutioned and as aged conditions were investigated in detail. The results show that the solution treatment at 1?220?℃ for 4?h, AC causes an increase in high temperature yield strength but a drastic drop in high temperature ductility due to the precipitation of both the secondary carbide M 6C along grain boundaries and at the interdendritic regions and very fine γ ′ particles in the dendrite cores. Aging treatment following the solution treatment can improve the high temperature tensile properties of M963 superalloy due to the coarsing of the γ′ precipitate. One stage aging at 850?℃ for 16?h following the solution treatment causes an increase in both strength and ductility of alloy M963, and two stage aging of 1?089?℃ / 2?h, AC plus 850?℃ / 16?h, AC following the solution treatment further increases the ductility of alloy M963 but slightly decreases its strength.
文摘Orthogonal experiment is employed to study a new kind of multiplex flux for nickel-base superalloy. This activated TIG welding flux is composed of NaF, MgF2 and CaF2, and their proportion is 5:4:1. Compared with conventional TIG welding, the penetration increases 164% by the action of the flux. Tensile test result indicates that the fracture strength of the mixed flux A-TIG weld bead is higher than base metal, and it increases along with the decrement of the welding current. The average extensibility of the weldment is beyond 100%, which means perfect ductility. Metallographs elucidate that there exist lots of deep and evenly distributed dimples on the fracture section of weld bead while on that of base metal there only exists a few shallow dimples and massive tearing ridge.
文摘A Y2O3 dispersion strengthened nickel-based superalloy sheet(0.15 mm thick) was prepared by electron beam physical vapor deposition(EB-PVD) technology.Different heat treatments were used to improve the mechanical properties of the alloy sheet.Differential thermal analysis(DTA) was used to examine the thermal stability of the as-deposited sheet.Element contents,phase composition and microstructure investigations on as-deposited and heat treated specimens were performed by X-ray fluorescence spectrometer(XRF),X-ray diffraction(XRD) and scanning electron microscopy(SEM).Tensile tests were conducted at room temperature on specimens as-deposited and heat treated.The results show that the as-deposited sheet is composed of equiaxed grains on the substrate side and columnar grains on the evaporation side.The as-deposited sheet shows poor ductility due to micropores between columnar grains.The strength and ductility can be improved effectively by annealing at 800°C for 3 h.For samples treated at 1100°C,the strength drops down due to the precipitates of Y3Al5O12(YAG).
基金supported by the Aviation Industry Corporation of China (No. 201110026-01)
文摘The morphological evolution of the γ' phase in nickel-based superalloy жc6y during various solution heat treatments was investigated. The significant changes of the γ' precipitates were observed in the solution-treated samples. The coarsening and dissolution of γ' phase simulta-neously occurred at intermediate temperatures. In some areas, the primary precipitates became blunt and the adjacent ones were intercon-nected with each other via a diffuse neck, indicating a coarsening process of the primary γ' population. The coarsening was dominated by the precipitate agglomeration mechanism (PAM) rather than by the well-known Ostwald ripening mechanism. In other areas, the partial dissolu-tion of the γ' precipitates began to occur, spreading gradually from dendrite cores to interdendritic regions. In addition, a flower-like γ' struc-ture was developed during the subsolvus solution treatments. The observable long filaments composed of erraticly shaped precipitates were caused by the heterogeneous nucleation of the cooling precipitates during water quenching.
文摘The hot compression testing of hot isostatically pressed(HIPed) spray formed(SF) nickel-base superalloy was carried out by thermal mechanical simulator in the temperature range of 1 050-1 140 ℃ at strain rates of 0.01-10 s-1 and engineering strain of 50%. A processing map was developed on the basis of these data by using the principles of dynamic materials modeling. The microstructural evolution of deformed samples was also examined on the basis of optical and electron microscopic observations. The map exhibits two domains: the instability domain at the temperatures of 1 050 ℃ -1 110 ℃ and strain rate of 0.01 s-1, the stability domain at the temperatures of 1 110 ℃- 1 140 ℃ and strain rates of 1 s-1-10 s-1, with a peak efficiency of about 40%. The dynamic recrystallization(DRX) is observed in the stability domain and the deformed specimens are no cracking or instabilities. However, there is no DRX in the instability domain and the alloy exhibits flow instability with cracks due to poor workability. The optimum hot working condition was determined in the stability domain.
基金financially supported by the Scientific Research Foundation for Ph.D.,Northwest A & F University (No.Z109021103)the Special Fund for Basic Scientific Research of Central Colleges,Northwest A & F University No.Z109021114)the fund of the State Key Laboratory of Solidification Processing in NWPU (SKLSP201220)
文摘A series of directional solidification experiments have been performed to study the effect of cooling rate on the precipitation behavior of MC carbide in nickel-based superalloy under the temperature gradient of 500 K·s-1.Results reveal that the morphology of MC carbide changes from coarse block to fine strip,then to Chinese-script,and their sizes reduce gradually with the increasing of cooling rate from 2.53 K·s-1 to 36.4 K·s-1.At low cooling rates,most of these carbides are found to be located at the grain boundary and interdendritic regions,while the coupled growth of some carbides and γ matrix in the center of γ grains is occurred at high cooling rate.The main elements forming MC carbide are Ta,W,and Hf.
文摘In the present study,the passive film formed on the G3 nickel-base alloy tubing under corrosive conditions including H_2S,CO_2,and Cl^- at 130℃and 205℃is studied with X-ray photoelectron spectroscopy(XPS).The results reveal that the passive film formed at 205℃consists of Cr,Ni,Fe,S and O elements and is over 470 nm in thickness. The passive film can be divided into three layers,the outer-layer is composed of NiS,and Cr_2S_3,the intermediate-layer of Cr(OH)_3,Ni(OH)_2,NiS_2,Cr_2S_3 and a small quantity of NiO and Cr_2O_3,and the inner-layer of NiO,Cr_2O_3,and alloy elements.Due to the invasion of S^(2-) into the passive film and the decrease of the content of chromium oxide in the film,the corrosion resistance of the G3 alloy in the sour environment at 205℃is weakened.
文摘A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room temperature,and the principle of the method was provided.Experiments and FE simulations were carried out to analyze the deformation characteristics for the part with larger variable diameter ratio(35%).The results show that visco-elasto-plastic pressure-carrying medium can meet the requirements of the room-temperature deformation condition for nickel based super-alloy sheet.The inner and outer pressure forming with the visco-elasto-plastic pressure-carrying medium can meet the requirements of dimensional accuracy for the thin-walled part with variable diameter sections.The thinning of wall-thickness is less than 4%.This method provides a new approach for near-net shape forming of nickel based super-alloy thin-walled parts with variable diameter sections.
