The 2024/3003 aluminum gradient alloys are prepared by semi continuous casting. The influences of throttle bore diameter of embedded nozzle and temperature of internal melt on composition distribution, macrostructure,...The 2024/3003 aluminum gradient alloys are prepared by semi continuous casting. The influences of throttle bore diameter of embedded nozzle and temperature of internal melt on composition distribution, macrostructure, hardness are analyzed, and the stability of gradient distribution of composition, macrostructure and hardness along the axial direction of the ingot is also studied. The results show that diffe rent composition profiles can be achieved by adjusting the processing parameters; the volume fraction of inner alloy in the ingot can be increased by enlarging the throttle bore diameter and elevating the temperature of inner melt; quasi steady solidification can be realized within 20 s during cast processing, and consistent quality ingot is obtained by controlling the casting speed and liquid height of inner melt.展开更多
The microstructure and mechanical properties of steel/Al structure material produced by additive manufacturing （AM） was investigated in this work based on the cold metal transfer welding. The results show that the m...The microstructure and mechanical properties of steel/Al structure material produced by additive manufacturing （AM） was investigated in this work based on the cold metal transfer welding. The results show that the microstructure gradually changed from the steel side to the aluminum side. The microstructure in the steel layer consisted of vermiform like ferrite and anstenite structure, while in the aluminum layer the microstructure was constituted by c^-A1 grains and typical reticulate distributive Al-Si eutectic structure. Besides, a 7 y.m thickness Ni-Al intermetallic compound layer was emerged at the interface of nickel and aluminum layer. The maximum room-temperature tensile strength of the Steel-Al structure materials was found to be 54 MPa, the rupture morphology showed a brittle fracture characteristic.展开更多
FeCrAl(f)/HA biological functionally gradient materials(FGMs) were successfully fabricated by the hot pressing technique.Scanning electron microscope(SEM),energy dispersive spectrometer(EDS) and bending strength test ...FeCrAl(f)/HA biological functionally gradient materials(FGMs) were successfully fabricated by the hot pressing technique.Scanning electron microscope(SEM),energy dispersive spectrometer(EDS) and bending strength test machine were utilized to characterize the microstructure,component,mechanical properties and the formation of the Ca-deficient apatite on the surface of these materials.The results indicate that an asymmetrical FeCrAl(f)/HA FGM,consolidating powders prepared by mixing HA with 3%–15%(volume fraction) is successfully prepared.Both of the matrix and FeCrAl fiber are integrated very tightly and bite into each other very deeply.And counter diffusion takes place to some extent in two phase interfaces.The elemental compositions of the FeCrAl(f)/HA FGM change progressively.Ca and P contents increase gradually with immersion time increasing,and thereafter approach equilibrium.The bone-like apatite layer forms on the materials surface,which possesses benign bioactivity,and the favorable biocompatibility can provide potential firm fixation between FeCrAl(f)/HA asymmetrical FGM implants and human bone.展开更多
( TiB2-TiAl)/TiAl symmetrically function gradient materials ( FGM) were prepared by spark plasma sintering ( SPS). Owing to the difference, of the thermal expansion coefficients between TiB2 and TiAl, a compressive su...( TiB2-TiAl)/TiAl symmetrically function gradient materials ( FGM) were prepared by spark plasma sintering ( SPS). Owing to the difference, of the thermal expansion coefficients between TiB2 and TiAl, a compressive surface stress was introduced to the FGM fry the thermal expansion mismatch. The hardness values of the uniform materials and the FGM were tested, respectively. For the FGM with a compressive surface stress, hardness is obviously superior to that of the uniform material. When the FGM was subjected to heat treatment, the hardness decreased due to a partial relaxation of the compressive surface stress.展开更多
Rechargeable lithium batteries with high-capacity cathodes/anodes promise high energy densities for nextgeneration electrochemical energy storage.However,the associated limitations at various scales greatly hinder the...Rechargeable lithium batteries with high-capacity cathodes/anodes promise high energy densities for nextgeneration electrochemical energy storage.However,the associated limitations at various scales greatly hinder their practical applications.Functional gradient material(FGM)design endows the electrode materials with property gradient,thus providing great opportunities to address the kinetics and stability obstacles.To date,still no review or perspective has covered recent advancements in gradient design at multiple scales for boosting lithium battery performances.To fill this void,this work provides a timely and comprehensive overview of this exciting and sustainable research field.We begin by overviewing the fundamental features of FGM and the rationales of gradient design for improved electrochemical performance.Then,we comprehensively review FGM design for rechargeable lithium batteries at various scales,including natural or artificial solid electrolyte interphase(SEI)at the nanoscale,micrometer-scale electrode particles,and macroscale electrode films.The link between gradient structure design and improved electrochemical performance is particularly highlighted.The most recent research into constructing novel functional gradients,such as valence and temperature gradients,has also been explored.Finally,we discussed the current constraints and future scope of FGM in rechargeable lithium batteries,aiming to inspire the development of novel FGM for next-generation high-performance lithium batteries.展开更多
Functionally gradient samples are prepared by getting metal Ni or Cu bonded with Ni-matrix composites reinforced by TiB2 particles by field activated diffusion bonding process. The intermetallic compound of Ni3Al has ...Functionally gradient samples are prepared by getting metal Ni or Cu bonded with Ni-matrix composites reinforced by TiB2 particles by field activated diffusion bonding process. The intermetallic compound of Ni3Al has been applied as a mediate layer in order to reduce residual stress. The microstracture, phase composition of the interfaces between the metal and Ni3Al are determined and the mechanical properties of the gradient materials are characterized. Elemental concentration profiles across the interfaces between layers showed significant diffusion dissolution and formation of firm bonds. Measured micro-hardness values of the sample increased monotonically from the metal substrate to the surface layer of composites. The values for the surface composite layer ranged from about 2 000 HK to 3 300 HK. The results of this investigation demonstrate the feasibility of field activated diffusion bonding process for rapid preparation of FGMs.展开更多
The method of lines(MOL) for solving the problems of functionally gradient materials(FGMs) was studied. Navier’s equations for FGMs were derived, and were semi-discretized into a system of ordinary differential (equa...The method of lines(MOL) for solving the problems of functionally gradient materials(FGMs) was studied. Navier’s equations for FGMs were derived, and were semi-discretized into a system of ordinary differential (equations(ODEs)) defined on discrete lines with the finite difference. By solving the system of ODEs, the solutions to the problem can be obtained. An example of three-point bending was given to demonstrate the application of MOL for a crack problem in the FGM. The computational results show that the more accurate results can be obtained with less computational time and resources. The obvious difficulties of numerical method for crack problems in FGMs, such as the effect of material nonhomogeneity and the existence of high gradient stress and strain near a crack tip, can be overcome without additional consideration if this method is adopted.展开更多
Because of the large coefficient of thermal expansion (CTE) (23 ppm K^(–1)), aluminum faces challenges in meeting the demands of high dimensional stability in precision instruments, microelectronics, and aerospace. F...Because of the large coefficient of thermal expansion (CTE) (23 ppm K^(–1)), aluminum faces challenges in meeting the demands of high dimensional stability in precision instruments, microelectronics, and aerospace. Filling negative thermal expansion (NTE) particles into aluminum can create composites with either zero or low CTEs. However, the resulting composites usually have poor thermal conductivity due to their monolithic configuration, i.e., the NTE particles are filled randomly. Thus, heat sinks should be equipped to assist their usage (e.g., in thermal management). This in turn causes strong thermal stress in the packaging system owing to the high contrast in the CTEs between those monolithic composites and heat sinks typically made of copper or aluminum. Here, we propose a gradient configuration for low-CTE aluminum composite, inspired by the bamboo structure. The gradient distribution of NTE particles (Zn_(0.5)Sn_(0.3)Mn_(0.2)NMn_(3), ZSM) was obtained by laying up several layers of ZSM/Al with the ZSM fraction ranging from 0 to 28 vol.%. In the gradient composite, the CTE near room temperature varies from 3.4 pm K^(–1) on one side to 21 ppm K^(–1) on the other side. Such a gradient CTE distribution would facilitate the low-thermal-stress designs and thus help stabilize the dimension of a precision system. Furthermore, this composite has a high thermal conductivity of 130 W m^(–1) K^(–1) and strong toughness when the flexural loading is applied on the 28 vol.% ZSM/Al side. Our research provides a novel approach to designing metallic matrix composites with unprecedented performance.展开更多
Based on the analyses of the severity of cutting process as well as the failure mechanisms of ceramic tools, a model for designing functionally gradient ceramic tool materials with symmetrical distribution is presente...Based on the analyses of the severity of cutting process as well as the failure mechanisms of ceramic tools, a model for designing functionally gradient ceramic tool materials with symmetrical distribution is presented, by which a Al 2O 3/(W,Ti)C ceramic tool material FG 2 was developed. Multi objective optimization method was employed in designing the compositional distribution of this ceramic tool material. The results of both continuous and intermittent cutting tests are indicative of the much better cutting behavior of the functionally gradient ceramic tool FG 2 than that of the common ceramic tool SG 4.展开更多
Thispaper proposed a new methodof producing Ceramic/ Metalfunctionally gradient mate rialby electroless platingtechnique. The experimentof producing SiC/ Ni PFGM wascar ried out with self made electroless plating ...Thispaper proposed a new methodof producing Ceramic/ Metalfunctionally gradient mate rialby electroless platingtechnique. The experimentof producing SiC/ Ni PFGM wascar ried out with self made electroless plating facilities. The results show that the thickness of FGMcoating andthegradientdistribution ofcompositioncanbecontrolled byoptimizingelec trolessplating technology and changing the parameters such as plating time, the additionspeed and concentration of SiCparticles. Analysisdemonstratesthatthereisastrongrelation ship amongthe SiCcontent,the microstructureandthe mechanicalproperty ofthe FGM.展开更多
Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in th...Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in this paper, according to which an Al 2O 3-TiC functionally gradient ceramic tool material FG-1 was synthesized by powder-laminating and uniaxially hot-pressing technique. The thermal shock resistance of the Al 2O 3-TiC functionally gradient ceramics FG-1 was evaluated by water quenching and subsequent three-point bending tests of flexural strength diminution. Comparisons were made with results from parallel experiments conducted using a homogeneous Al 2O 3-TiC ceramics. Functionally gradient ceramics exhibited higher retained strength under all thermal shock temperature differences compared to homogeneous ceramics, indicating the higher thermal shock resistance. The experimental results were supported by the calculation of transient thermal stress field. The cutting performance of the Al 2O 3-TiC functionally gradient ceramic tool FG-1 was also investigated in rough turning the cylindrical surface of exhaust valve of diesel engine in comparison with that of a common Al 2O 3-TiC ceramic tool LT55. The results indicated that the tool life of FG-1 increased by 50 percent over that of LT55. Tool life of LT55 was mainly controlled by thermal shock cracking which was accompanied by mechanical shock. While tool life of FG-1 was mainly controlled by mechanical fatigue crack extension rather than thermal shock cracking, revealing the less thermal shock susceptibility of functionally gradient ceramics than that of common ceramics.展开更多
Functionally gradient/graded materials （FGMs）, an emerging new class of materials, are the outcome of the recent innovative concepts in materials technology. FGMs are in their early stages of evolution and expected ...Functionally gradient/graded materials （FGMs）, an emerging new class of materials, are the outcome of the recent innovative concepts in materials technology. FGMs are in their early stages of evolution and expected to have a strong impact on the design and development of new components and structures with better performance. FGMs exhibit gradual transitions in the microstructure and/or the composition in a specific direction, the presence of which leads to variation in the functional performance within a part. The presence of gradual transitions in material composition in FGMs can reduce or eliminate the deleterious stress concentrations and result in a wide gradation of physical and/or chemical properties within the material. Functionally graded metal-ceramic composites are also getting the attention of the researchers. Among the fabrication routes for FGMs such as chemical vapour deposition, physical vapour deposition, the sol-gel technique, plasma spraying, molten metal infiltration, self propagating high temperature synthesis, spray forming, centrifugal casting, etc., the ones based on solidification route are preferred for FGMs because of their economics and capability to make large size products. The present paper discusses and compares various solidification processing tech- niques available for the fabrication of functionally gradient metals and metal-ceramic composites and lists their properties and possible applications. The other processing methods are briefly described.展开更多
Functionally gradient materials(FGMs)have attracted tremendous attention due to their unique properties and structures.However,it is still a great challenge to prepare scalable FGMs by a universal,cost-effective,and h...Functionally gradient materials(FGMs)have attracted tremendous attention due to their unique properties and structures.However,it is still a great challenge to prepare scalable FGMs by a universal,cost-effective,and highly efficient method.Here,a strategy of combining in situ concentration regulation and spraying is developed to fabricate continuously gradient composite films(GCFs),where the component gradient variation can be well controlled.This strategy is universal and versatile,which is beneficial to inducing different components into GCFs with gradient distributions and further constructing them with diverse configurations on various substrates.The gradient design endows the composite films with excellent mechanical strength and gradient electron transport pathways,which ensures that GCFs directly serve as the electrodes in electrochemical devices.As a proof of concept,free-standing GCFs based on V2O5 nanomaterials are used as cathodes of aqueous zinc-ion batteries.The resultant devices deliver superior electrochemical performances in comparison with the counterparts of homogeneous case.Therefore,this universal strategy provides a promising route in the scalable production of FGMs and further extends their applications in various fields.展开更多
gradient aluminum alloy was prepared by semi-continuous casting using double-stream-pouring technique. The microstructures of the as-cast, pressed and heat-treated alloys were analyzed by scanning electron microscope ...gradient aluminum alloy was prepared by semi-continuous casting using double-stream-pouring technique. The microstructures of the as-cast, pressed and heat-treated alloys were analyzed by scanning electron microscope and transmission electron microscope. And the mechanical properties of the alloy in pressed and heat-treated states were studied. The results show that the ingots with diameter of 65 mm and external thickness （about） 5.5 mm are obtained when the temperatures of the melt in the internal and external ladles are 1 023 and 1 003 K, respectively, and the nozzle diameter is 2.0 mm. The microstructures of the as-cast alloy consist of α（Al）+（θ（CuAl2））+S（Al2CuMg） in the internal region and （α（Al）+MnAl6） in the external region. The phases found in the internal and external layers coexist in the transition zone. The transition layer is maintained after plastic deformation and heat treatment of the alloy. The tensile strength, yield strength and elongation of the alloy are 300 MPa, 132 MPa and 16.0%, respectively, after T6 treatment. The tensile and yield strength are increased by 150.0% and （94.1%,） respectively, compared with that of 3003 aluminum alloy. The maximum hardness in the internal region of 2024/3003 gradient aluminum alloy can be increased from HRF 55 in the pressed state to HRF 70 in the heat-treated state.展开更多
Because of the different conductivities between the primary phase (low electric conduc tivity) and the metal melt, electromagnetic force scarcely acts on the primary phase. Thus, an electromagnetic repulsive force ap...Because of the different conductivities between the primary phase (low electric conduc tivity) and the metal melt, electromagnetic force scarcely acts on the primary phase. Thus, an electromagnetic repulsive force applied by the metal melt exerts on the pri mary phase when the movement of the melt in the direction of electromagnetic force is limited. As a result, the repulsive force exerts on the primary phase to push them to move in the direction opposite to that of the electromagnetic force when the metal melt with primary phase solidifies under an electromagnetic force field. Based on this, a new method for production of in situ surface composite and gradient material by electromagnetic force is proposed. An in situ primary Si reinforced surface composite of Al-15wt%Si alloy and gradient material of Al-l9wt%Si alloy were produced by this method. The microhardness of the primary Si is HV1320. The reinforced phase size is in the range from 40μm to 100μm. The wear resistance of Al-Si alloy gradient material can be more greatly increased than that of their matrix material.展开更多
Investigation of the propagation of the wave in SAW sensors is a basis for the research and design of the sensors. With the advance of the sensor, both the effect of environment on the surface ply and the geometry of ...Investigation of the propagation of the wave in SAW sensors is a basis for the research and design of the sensors. With the advance of the sensor, both the effect of environment on the surface ply and the geometry of waveguide are complicated. To consider the complication, a model with gradient surface ply and multilayer waveguide of SH wave propagation in sensor is proposed. The equation of wave velocity is derived by a transfer matrix method. Through the equation, the function of wave velocity increment via the change of parameters in the surface ply is obtained. The effect of the inhomogeneity on the function is also studied. Finally, some influencing factors of the behavior of the sensor are discussed.展开更多
This paper presents an exact solution of the crack tip field in functionally gradient material with exponential variation of elastic constants. The dimensionless Poisson＇s ratios v0 of the engineering materials （iro...This paper presents an exact solution of the crack tip field in functionally gradient material with exponential variation of elastic constants. The dimensionless Poisson＇s ratios v0 of the engineering materials （iron, glass …… ） are far less than one; therefore, neglecting them, one can simplify the basic equation and the exact solution is easy to obtain. Although the exact solution for the case v0 ≠ 0 is also obtained, it is very complicated and the main result is the same with the case v0 = 0 （it will be dealt with in Appendix VII）. It has been found that the exponential term exp（ax ＋ by） in the constitutive equations becomes exp（ ax /2 ＋ by/2- kr /2 ） in the exact solution.展开更多
The thermal stability and mechanical properties of a gradient-nanograined structure(GNS)CoCrNi medium entropy alloy(MEA)processed by ultrasonic surface rolling were studied by using isothermal/isochronal annealing tes...The thermal stability and mechanical properties of a gradient-nanograined structure(GNS)CoCrNi medium entropy alloy(MEA)processed by ultrasonic surface rolling were studied by using isothermal/isochronal annealing tests combined with quasi-in-situ electron backscatter diffraction(EBSD)characterization and Vickers micro-hardness(HV)measurements.A layer by layer high-throughput investigation method was used to quantitatively study the grain growth kinetics and grain boundary evolution with different initial grain sizes,which could effectively save specimen and time costs.The grain nucleation and growth,as well as shrink and disappearance process throughΣ3 coincidence site lattice boundary migration with slightly lattice rotation during annealing were directly revealed.The layer by layer grain growth kinetics and calculated activation energy indicate that the thermal stability of nanograined top surface layer is relatively higher than that of nano-twined subsurface layer for the gradient CoCrNi MEA processed by ultrasonic surface rolling.Further analysis show that the grain boundary relaxation and dynamic recrystallization of the topmost nano-grains led to the decrease of grain boundary energy,thus improving their thermal stability.The present work provided theoretical basis for the application of CoCrNi MEA at high temperatures.Moreover,the high-throughput method on the investigation of grain stability by using gradient structure can be easily extended to other materials and it is of great significance for understanding the microstructural evolution of gradient materials.展开更多
A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes＇ law. Acrylonitrile- butadiene-styren...A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes＇ law. Acrylonitrile- butadiene-styrene/Cu （ABS/Cu） gradient polymeric composites were prepared successfully using this technique. The gradient structures, electrically conductive performance and mechanical properties of the ABS/Cu composites were investigated. Optical microscope observation shows that the gradient distribution of Cu particles in ABS matrix was formed along their thickness-direction. The electrically conductive testing results indicate that the order of magnitude of surface resistivity was kept in 10^15 Ω at ABS rich side, while that declined to 10^5 Ω at Cu particles rich side, and the percolation threshold was in the range of 2.82 vo1%- 4.74 vol% Cu content at Cu particles rich side. Mechanical test shows that the tensile strength reduced insignificantly as the content of Cu increases owing to the gradient distribution.展开更多
After applying torsion to cylindrical 304 stainless steel samples,a gradient structure along the radial direction was obtained.It was found that the volume fraction of a0-martensite increased gradually from the center...After applying torsion to cylindrical 304 stainless steel samples,a gradient structure along the radial direction was obtained.It was found that the volume fraction of a0-martensite increased gradually from the center to the surface of samples.The possibility of deformation-induced martensitic transformation was analyzed theoretically,whose conclusions were consistent with the experimental results.It was found that torsional deformation could produce abundant deformation twin and deformation-induced martensite,which could affect the tensile property of steel distinctly.The existence of deformation and martensite during torsion could increase the strength but deteriorate the ductility dramatically during the tensile test,which should be attributed to the weakening of work hardening ability.As a result of severe deformation,both strain-induced and stress-induced martensite have been observed.Also,two types of martensitic transformation mechanisms during torsional deformation were discussed.展开更多
文摘The 2024/3003 aluminum gradient alloys are prepared by semi continuous casting. The influences of throttle bore diameter of embedded nozzle and temperature of internal melt on composition distribution, macrostructure, hardness are analyzed, and the stability of gradient distribution of composition, macrostructure and hardness along the axial direction of the ingot is also studied. The results show that diffe rent composition profiles can be achieved by adjusting the processing parameters; the volume fraction of inner alloy in the ingot can be increased by enlarging the throttle bore diameter and elevating the temperature of inner melt; quasi steady solidification can be realized within 20 s during cast processing, and consistent quality ingot is obtained by controlling the casting speed and liquid height of inner melt.
基金supported by the National Natural Science Foundation of China(Grant No.51475104,51435004)the National Basic Research Program of China(2013CB035500)
文摘The microstructure and mechanical properties of steel/Al structure material produced by additive manufacturing （AM） was investigated in this work based on the cold metal transfer welding. The results show that the microstructure gradually changed from the steel side to the aluminum side. The microstructure in the steel layer consisted of vermiform like ferrite and anstenite structure, while in the aluminum layer the microstructure was constituted by c^-A1 grains and typical reticulate distributive Al-Si eutectic structure. Besides, a 7 y.m thickness Ni-Al intermetallic compound layer was emerged at the interface of nickel and aluminum layer. The maximum room-temperature tensile strength of the Steel-Al structure materials was found to be 54 MPa, the rupture morphology showed a brittle fracture characteristic.
基金Project(51274247)supported by the National Natural Science Foundation of ChinaProject(2012BAE06B00)supported by the National High Technology Research and Development Program to China+1 种基金Project(2011QNZT046)supported by the Fundamental Research Funds of Central South Universities of ChinaProject supported by Hunan Postdoctoral Scientific Program,China
文摘FeCrAl(f)/HA biological functionally gradient materials(FGMs) were successfully fabricated by the hot pressing technique.Scanning electron microscope(SEM),energy dispersive spectrometer(EDS) and bending strength test machine were utilized to characterize the microstructure,component,mechanical properties and the formation of the Ca-deficient apatite on the surface of these materials.The results indicate that an asymmetrical FeCrAl(f)/HA FGM,consolidating powders prepared by mixing HA with 3%–15%(volume fraction) is successfully prepared.Both of the matrix and FeCrAl fiber are integrated very tightly and bite into each other very deeply.And counter diffusion takes place to some extent in two phase interfaces.The elemental compositions of the FeCrAl(f)/HA FGM change progressively.Ca and P contents increase gradually with immersion time increasing,and thereafter approach equilibrium.The bone-like apatite layer forms on the materials surface,which possesses benign bioactivity,and the favorable biocompatibility can provide potential firm fixation between FeCrAl(f)/HA asymmetrical FGM implants and human bone.
基金Funded by the Natural Science Foundation of China (No. 50172037)
文摘( TiB2-TiAl)/TiAl symmetrically function gradient materials ( FGM) were prepared by spark plasma sintering ( SPS). Owing to the difference, of the thermal expansion coefficients between TiB2 and TiAl, a compressive surface stress was introduced to the FGM fry the thermal expansion mismatch. The hardness values of the uniform materials and the FGM were tested, respectively. For the FGM with a compressive surface stress, hardness is obviously superior to that of the uniform material. When the FGM was subjected to heat treatment, the hardness decreased due to a partial relaxation of the compressive surface stress.
基金financial support from the National Natural Science Foundation of China(Nos.52261160384 and 52072208)the Project of Department of Education of Guangdong Province(No.2022ZDZX3018)+2 种基金the Natural Science Foundation of Guangdong(No.2023A1515010020)the Innovation and Technology Fund(No.ITS-325-22FP)the Shenzhen Science and Technology Program(No.KJZD20230923114107014)。
文摘Rechargeable lithium batteries with high-capacity cathodes/anodes promise high energy densities for nextgeneration electrochemical energy storage.However,the associated limitations at various scales greatly hinder their practical applications.Functional gradient material(FGM)design endows the electrode materials with property gradient,thus providing great opportunities to address the kinetics and stability obstacles.To date,still no review or perspective has covered recent advancements in gradient design at multiple scales for boosting lithium battery performances.To fill this void,this work provides a timely and comprehensive overview of this exciting and sustainable research field.We begin by overviewing the fundamental features of FGM and the rationales of gradient design for improved electrochemical performance.Then,we comprehensively review FGM design for rechargeable lithium batteries at various scales,including natural or artificial solid electrolyte interphase(SEI)at the nanoscale,micrometer-scale electrode particles,and macroscale electrode films.The link between gradient structure design and improved electrochemical performance is particularly highlighted.The most recent research into constructing novel functional gradients,such as valence and temperature gradients,has also been explored.Finally,we discussed the current constraints and future scope of FGM in rechargeable lithium batteries,aiming to inspire the development of novel FGM for next-generation high-performance lithium batteries.
基金Acknowledgment The authors wish to thank the financial support for this research from the National Natural Science Foundation of China （Grant No. 50975190） and the Army Office of Research （ZAM）.
文摘Functionally gradient samples are prepared by getting metal Ni or Cu bonded with Ni-matrix composites reinforced by TiB2 particles by field activated diffusion bonding process. The intermetallic compound of Ni3Al has been applied as a mediate layer in order to reduce residual stress. The microstracture, phase composition of the interfaces between the metal and Ni3Al are determined and the mechanical properties of the gradient materials are characterized. Elemental concentration profiles across the interfaces between layers showed significant diffusion dissolution and formation of firm bonds. Measured micro-hardness values of the sample increased monotonically from the metal substrate to the surface layer of composites. The values for the surface composite layer ranged from about 2 000 HK to 3 300 HK. The results of this investigation demonstrate the feasibility of field activated diffusion bonding process for rapid preparation of FGMs.
基金Projects(90305023 59731020) supported by the National Natural Science Foundation of China
文摘The method of lines(MOL) for solving the problems of functionally gradient materials(FGMs) was studied. Navier’s equations for FGMs were derived, and were semi-discretized into a system of ordinary differential (equations(ODEs)) defined on discrete lines with the finite difference. By solving the system of ODEs, the solutions to the problem can be obtained. An example of three-point bending was given to demonstrate the application of MOL for a crack problem in the FGM. The computational results show that the more accurate results can be obtained with less computational time and resources. The obvious difficulties of numerical method for crack problems in FGMs, such as the effect of material nonhomogeneity and the existence of high gradient stress and strain near a crack tip, can be overcome without additional consideration if this method is adopted.
基金supported by the National Natural Foundation of China(No.52171146)the HFIPS Director's Fund(No.BJPY2023A08)the Natural Science Foundation of Anhui Province(No.2108085ME145).
文摘Because of the large coefficient of thermal expansion (CTE) (23 ppm K^(–1)), aluminum faces challenges in meeting the demands of high dimensional stability in precision instruments, microelectronics, and aerospace. Filling negative thermal expansion (NTE) particles into aluminum can create composites with either zero or low CTEs. However, the resulting composites usually have poor thermal conductivity due to their monolithic configuration, i.e., the NTE particles are filled randomly. Thus, heat sinks should be equipped to assist their usage (e.g., in thermal management). This in turn causes strong thermal stress in the packaging system owing to the high contrast in the CTEs between those monolithic composites and heat sinks typically made of copper or aluminum. Here, we propose a gradient configuration for low-CTE aluminum composite, inspired by the bamboo structure. The gradient distribution of NTE particles (Zn_(0.5)Sn_(0.3)Mn_(0.2)NMn_(3), ZSM) was obtained by laying up several layers of ZSM/Al with the ZSM fraction ranging from 0 to 28 vol.%. In the gradient composite, the CTE near room temperature varies from 3.4 pm K^(–1) on one side to 21 ppm K^(–1) on the other side. Such a gradient CTE distribution would facilitate the low-thermal-stress designs and thus help stabilize the dimension of a precision system. Furthermore, this composite has a high thermal conductivity of 130 W m^(–1) K^(–1) and strong toughness when the flexural loading is applied on the 28 vol.% ZSM/Al side. Our research provides a novel approach to designing metallic matrix composites with unprecedented performance.
文摘Based on the analyses of the severity of cutting process as well as the failure mechanisms of ceramic tools, a model for designing functionally gradient ceramic tool materials with symmetrical distribution is presented, by which a Al 2O 3/(W,Ti)C ceramic tool material FG 2 was developed. Multi objective optimization method was employed in designing the compositional distribution of this ceramic tool material. The results of both continuous and intermittent cutting tests are indicative of the much better cutting behavior of the functionally gradient ceramic tool FG 2 than that of the common ceramic tool SG 4.
文摘Thispaper proposed a new methodof producing Ceramic/ Metalfunctionally gradient mate rialby electroless platingtechnique. The experimentof producing SiC/ Ni PFGM wascar ried out with self made electroless plating facilities. The results show that the thickness of FGMcoating andthegradientdistribution ofcompositioncanbecontrolled byoptimizingelec trolessplating technology and changing the parameters such as plating time, the additionspeed and concentration of SiCparticles. Analysisdemonstratesthatthereisastrongrelation ship amongthe SiCcontent,the microstructureandthe mechanicalproperty ofthe FGM.
文摘Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in this paper, according to which an Al 2O 3-TiC functionally gradient ceramic tool material FG-1 was synthesized by powder-laminating and uniaxially hot-pressing technique. The thermal shock resistance of the Al 2O 3-TiC functionally gradient ceramics FG-1 was evaluated by water quenching and subsequent three-point bending tests of flexural strength diminution. Comparisons were made with results from parallel experiments conducted using a homogeneous Al 2O 3-TiC ceramics. Functionally gradient ceramics exhibited higher retained strength under all thermal shock temperature differences compared to homogeneous ceramics, indicating the higher thermal shock resistance. The experimental results were supported by the calculation of transient thermal stress field. The cutting performance of the Al 2O 3-TiC functionally gradient ceramic tool FG-1 was also investigated in rough turning the cylindrical surface of exhaust valve of diesel engine in comparison with that of a common Al 2O 3-TiC ceramic tool LT55. The results indicated that the tool life of FG-1 increased by 50 percent over that of LT55. Tool life of LT55 was mainly controlled by thermal shock cracking which was accompanied by mechanical shock. While tool life of FG-1 was mainly controlled by mechanical fatigue crack extension rather than thermal shock cracking, revealing the less thermal shock susceptibility of functionally gradient ceramics than that of common ceramics.
文摘Functionally gradient/graded materials （FGMs）, an emerging new class of materials, are the outcome of the recent innovative concepts in materials technology. FGMs are in their early stages of evolution and expected to have a strong impact on the design and development of new components and structures with better performance. FGMs exhibit gradual transitions in the microstructure and/or the composition in a specific direction, the presence of which leads to variation in the functional performance within a part. The presence of gradual transitions in material composition in FGMs can reduce or eliminate the deleterious stress concentrations and result in a wide gradation of physical and/or chemical properties within the material. Functionally graded metal-ceramic composites are also getting the attention of the researchers. Among the fabrication routes for FGMs such as chemical vapour deposition, physical vapour deposition, the sol-gel technique, plasma spraying, molten metal infiltration, self propagating high temperature synthesis, spray forming, centrifugal casting, etc., the ones based on solidification route are preferred for FGMs because of their economics and capability to make large size products. The present paper discusses and compares various solidification processing tech- niques available for the fabrication of functionally gradient metals and metal-ceramic composites and lists their properties and possible applications. The other processing methods are briefly described.
基金Ministry of Science and Technology of China,Grant/Award Number:2019YFA0705600National Natural Science Foundation of China,Grant/Award Numbers:21875121,51822205,51972231+2 种基金Ministry of Education of China,Grant/Award Number:B12015Natural Science Foundation of Tianjin City,Grant/Award Numbers:18JCJQJC46300,19JCZDJC31900Frontiers Science Center for New Organic Matter of Nankai University,Grant/Award Number:63181206。
文摘Functionally gradient materials(FGMs)have attracted tremendous attention due to their unique properties and structures.However,it is still a great challenge to prepare scalable FGMs by a universal,cost-effective,and highly efficient method.Here,a strategy of combining in situ concentration regulation and spraying is developed to fabricate continuously gradient composite films(GCFs),where the component gradient variation can be well controlled.This strategy is universal and versatile,which is beneficial to inducing different components into GCFs with gradient distributions and further constructing them with diverse configurations on various substrates.The gradient design endows the composite films with excellent mechanical strength and gradient electron transport pathways,which ensures that GCFs directly serve as the electrodes in electrochemical devices.As a proof of concept,free-standing GCFs based on V2O5 nanomaterials are used as cathodes of aqueous zinc-ion batteries.The resultant devices deliver superior electrochemical performances in comparison with the counterparts of homogeneous case.Therefore,this universal strategy provides a promising route in the scalable production of FGMs and further extends their applications in various fields.
文摘gradient aluminum alloy was prepared by semi-continuous casting using double-stream-pouring technique. The microstructures of the as-cast, pressed and heat-treated alloys were analyzed by scanning electron microscope and transmission electron microscope. And the mechanical properties of the alloy in pressed and heat-treated states were studied. The results show that the ingots with diameter of 65 mm and external thickness （about） 5.5 mm are obtained when the temperatures of the melt in the internal and external ladles are 1 023 and 1 003 K, respectively, and the nozzle diameter is 2.0 mm. The microstructures of the as-cast alloy consist of α（Al）+（θ（CuAl2））+S（Al2CuMg） in the internal region and （α（Al）+MnAl6） in the external region. The phases found in the internal and external layers coexist in the transition zone. The transition layer is maintained after plastic deformation and heat treatment of the alloy. The tensile strength, yield strength and elongation of the alloy are 300 MPa, 132 MPa and 16.0%, respectively, after T6 treatment. The tensile and yield strength are increased by 150.0% and （94.1%,） respectively, compared with that of 3003 aluminum alloy. The maximum hardness in the internal region of 2024/3003 gradient aluminum alloy can be increased from HRF 55 in the pressed state to HRF 70 in the heat-treated state.
基金supported by the National Natural Science Foundation of China(Grant No.50001008)the China Postdoctoral Science Foundation.
文摘Because of the different conductivities between the primary phase (low electric conduc tivity) and the metal melt, electromagnetic force scarcely acts on the primary phase. Thus, an electromagnetic repulsive force applied by the metal melt exerts on the pri mary phase when the movement of the melt in the direction of electromagnetic force is limited. As a result, the repulsive force exerts on the primary phase to push them to move in the direction opposite to that of the electromagnetic force when the metal melt with primary phase solidifies under an electromagnetic force field. Based on this, a new method for production of in situ surface composite and gradient material by electromagnetic force is proposed. An in situ primary Si reinforced surface composite of Al-15wt%Si alloy and gradient material of Al-l9wt%Si alloy were produced by this method. The microhardness of the primary Si is HV1320. The reinforced phase size is in the range from 40μm to 100μm. The wear resistance of Al-Si alloy gradient material can be more greatly increased than that of their matrix material.
基金This study was supported by the National Natural Science Foundation of China (No. 59635140)the Doctoral Education Foundation of the Ministry of Education of ChinaAeronautics Foundation of China.
文摘Investigation of the propagation of the wave in SAW sensors is a basis for the research and design of the sensors. With the advance of the sensor, both the effect of environment on the surface ply and the geometry of waveguide are complicated. To consider the complication, a model with gradient surface ply and multilayer waveguide of SH wave propagation in sensor is proposed. The equation of wave velocity is derived by a transfer matrix method. Through the equation, the function of wave velocity increment via the change of parameters in the surface ply is obtained. The effect of the inhomogeneity on the function is also studied. Finally, some influencing factors of the behavior of the sensor are discussed.
文摘This paper presents an exact solution of the crack tip field in functionally gradient material with exponential variation of elastic constants. The dimensionless Poisson＇s ratios v0 of the engineering materials （iron, glass …… ） are far less than one; therefore, neglecting them, one can simplify the basic equation and the exact solution is easy to obtain. Although the exact solution for the case v0 ≠ 0 is also obtained, it is very complicated and the main result is the same with the case v0 = 0 （it will be dealt with in Appendix VII）. It has been found that the exponential term exp（ax ＋ by） in the constitutive equations becomes exp（ ax /2 ＋ by/2- kr /2 ） in the exact solution.
基金financial supports from the National Natural Science Foundation of China(Nos.51725503,52105144 and 52005185)Shanghai Super Postdoctoral Incentive Plan(No.2020134)Postdoctoral Fellowship for Research in Japan(FY2020 P20350)by the Japan Society for the Promotion of Science(JSPS)。
文摘The thermal stability and mechanical properties of a gradient-nanograined structure(GNS)CoCrNi medium entropy alloy(MEA)processed by ultrasonic surface rolling were studied by using isothermal/isochronal annealing tests combined with quasi-in-situ electron backscatter diffraction(EBSD)characterization and Vickers micro-hardness(HV)measurements.A layer by layer high-throughput investigation method was used to quantitatively study the grain growth kinetics and grain boundary evolution with different initial grain sizes,which could effectively save specimen and time costs.The grain nucleation and growth,as well as shrink and disappearance process throughΣ3 coincidence site lattice boundary migration with slightly lattice rotation during annealing were directly revealed.The layer by layer grain growth kinetics and calculated activation energy indicate that the thermal stability of nanograined top surface layer is relatively higher than that of nano-twined subsurface layer for the gradient CoCrNi MEA processed by ultrasonic surface rolling.Further analysis show that the grain boundary relaxation and dynamic recrystallization of the topmost nano-grains led to the decrease of grain boundary energy,thus improving their thermal stability.The present work provided theoretical basis for the application of CoCrNi MEA at high temperatures.Moreover,the high-throughput method on the investigation of grain stability by using gradient structure can be easily extended to other materials and it is of great significance for understanding the microstructural evolution of gradient materials.
基金Funded by the National Natural Science Foundation of China(No.21274007)the Beijing Natural Science Foundation+1 种基金the Key Scientific Project of Beijing Municipal Education Commission(No.KZ201110011014)the Science and Technology Innovation Platform of Beijing Municipal Education Commission(No.PXM2012-014213-000025)
文摘A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes＇ law. Acrylonitrile- butadiene-styrene/Cu （ABS/Cu） gradient polymeric composites were prepared successfully using this technique. The gradient structures, electrically conductive performance and mechanical properties of the ABS/Cu composites were investigated. Optical microscope observation shows that the gradient distribution of Cu particles in ABS matrix was formed along their thickness-direction. The electrically conductive testing results indicate that the order of magnitude of surface resistivity was kept in 10^15 Ω at ABS rich side, while that declined to 10^5 Ω at Cu particles rich side, and the percolation threshold was in the range of 2.82 vo1%- 4.74 vol% Cu content at Cu particles rich side. Mechanical test shows that the tensile strength reduced insignificantly as the content of Cu increases owing to the gradient distribution.
基金sponsored by the National Natural Science Foundation of’China(51472249)Youth Innovation Promotion Association of CAS(2017233)Fundamental Research Funds for the Central Universities(N2024005-4).
文摘After applying torsion to cylindrical 304 stainless steel samples,a gradient structure along the radial direction was obtained.It was found that the volume fraction of a0-martensite increased gradually from the center to the surface of samples.The possibility of deformation-induced martensitic transformation was analyzed theoretically,whose conclusions were consistent with the experimental results.It was found that torsional deformation could produce abundant deformation twin and deformation-induced martensite,which could affect the tensile property of steel distinctly.The existence of deformation and martensite during torsion could increase the strength but deteriorate the ductility dramatically during the tensile test,which should be attributed to the weakening of work hardening ability.As a result of severe deformation,both strain-induced and stress-induced martensite have been observed.Also,two types of martensitic transformation mechanisms during torsional deformation were discussed.
