The influences of I,article size on the mechanical properties of the particulate metal matrix composite;are obviously displayed in the experimental observations. However, the phenomenon can not be predicted directly u...The influences of I,article size on the mechanical properties of the particulate metal matrix composite;are obviously displayed in the experimental observations. However, the phenomenon can not be predicted directly using the conventional elastic-plastic theory. It is because that no length scale parameters are involved in the conventional theory. In the present research, using the strain gradient plasticity theory, a systematic research of the particle size effect in the particulate metal matrix composite is carried out. The roles of many composite factors, such as: the particle size, the Young's modulus of the particle, the particle aspect ratio and volume fraction, as well as the plastic strain hardening exponent of the matrix material, are studied in detail. In order to obtain a general understanding for the composite behavior, two kinds of particle shapes, ellipsoid and cylinder, are considered to check the strength dependence of the smooth or non-smooth particle surface. Finally, the prediction results will be applied to the several experiments about the ceramic particle-reinforced metal-matrix composites. The material length scale parameter is predicted.展开更多
Micromechanics-based constitutive models offer superior ability to estimate the effective mechanical properties for the composites,which greatly promote the computational efficiency in the multiscale analysis for comp...Micromechanics-based constitutive models offer superior ability to estimate the effective mechanical properties for the composites,which greatly promote the computational efficiency in the multiscale analysis for composite structures.In this work,a thermo-viscoelastic model for particle-reinforced composites is proposed to estimate their thermal-mechanical coupling behaviors in terms of a micromechanics-based homogenization method in the time domain.The matrix and particles of the composites are modeled as“thermo-rheologically complex”viscoelastic materials.The temperature-dependent effective elastic strain energy ratios of particle to composite are proposed to evaluate the contributions of the matrix and particles.The thermo-viscoelastic model for the composites is then formulated by superposing the matrix and particle’s contributions.Finite element simulations based on the representative volume element models are employed to validate the constitutive model under various thermal-mechanical coupling loads.The effects of the loading rate,viscous parameter and particle content on the effective thermal-mechanical responses of the composites are also comprehensively discussed.The experimental data from literature are also employed to verify the constitutive model.The findings show that the proposed thermo-viscoelastic model can accurately predict the thermal-mechanical coupling behaviors for the particle-reinforced composites.展开更多
A systematical simulation has been carried out on the indentation creep test on particle-reinforced composites. The deformation, failure mechanisms and life are analyzed by three reasonable models. The following five ...A systematical simulation has been carried out on the indentation creep test on particle-reinforced composites. The deformation, failure mechanisms and life are analyzed by three reasonable models. The following five factors have been considered simultaneously: creep property of the particle, creep property of the matrix, the shape of the particle, the volume fraction of the particle and the size (relative size to the particle) of the indentation indenter. For all the cases, the power law respecting to the applied stress can be used to model the steady indentation creep depth rate of the indenter, and the detail expressions have been presented. The computer simulation precision is analyzed by the two-phase model and the three-phase model. Two places of the stress concentration are found in the composites. One is ahead of the indentation indenter, where the high stress state is deduced by the edge of the indenter and will decrease rapidly near to a steady value with the creep time. The other one is at the interface, where the high stress state is deduced by the misfit of material properties between the particles and matrix. It has been found that the creep dissipation energy density other than a stress parameter can be used to be the criterion to model the debonding of the interfaces. With the criterion of the critical creep dissipation energy density, a power law to the applied stress with negative exponent can be used to model the failure life deduced by the debonding of interfaces. The influences of the shape of the particles and the matching of creep properties of particle and matrix can be discussed for the failure. With a crack model, the further growth of interface crack is analyzed, and some important experimental phenomena can be predicted. The failure mechanism which the particle will be punched into matrix has been also discussed. The critical differences between the creep properties of the particles and matrix have been calculated, after a parameter has been defined. In the view of competition of failure mechanisms, the best matching of the creep properties of the two phases and the best shape of the particles are discussed for the composite design.展开更多
TiB_2particle-reinforced 7075 Al alloy was synthesized to investigate the effect of TiB_2 particles on microstructure of semisolid 7075 Al alloy slurry. The mean grain size and shape factor of 3 wt% TiB_2/7075 composi...TiB_2particle-reinforced 7075 Al alloy was synthesized to investigate the effect of TiB_2 particles on microstructure of semisolid 7075 Al alloy slurry. The mean grain size and shape factor of 3 wt% TiB_2/7075 composite could reach 92 lm and 0.64 at 630 ℃ for 23 min,respectively, and for 6 wt% TiB_2/7075 composite, they are100 lm and 0.64 at 630 ℃ for 33 min. The microstructure evolution for TiB_2/7075 composites in semisolid state includes three-stage process. a-Al begins to nucleate and grow up into rosette grains due to a low degree of supercooling at first. Then rosette grains begin to fuse or grow up at different rates. Finally, the dissolution rate and the growth rate of α-Al reach equilibrium.展开更多
Al 2O 3 particle-reinforced material (6061 alloy ), which is one of new composites and characterized by high strength and small spe cific gravity, good wear resistance and corrosion resistance, has been widel y used i...Al 2O 3 particle-reinforced material (6061 alloy ), which is one of new composites and characterized by high strength and small spe cific gravity, good wear resistance and corrosion resistance, has been widel y used in industry. But it is difficult to machine. Because of electric conducti vity, it can be shaped and processed by electro-machining means. However, this kind of material is mixed with the electrically conductive substances and the di electrically conductive substances, its machining process shows substantially di fferent from the machining of ordinary metal materials. This paper, based on a c ontrast experiment, investigates the machining mechanism and technique by WEDM t o shape the material and gives the optimum selection for the electric paramete rs in operation. The technologic index of shaping the new material by WEDM includes the cutting r ate and the surface roughness. There are a lot of factors that affect the techno logic index of WEDM, in which the electric parameters such as the machining volt age and current as well as the pulse duration, interval and frequency, play an i mportant part. In this experiment, the study focus mainly on the effect of the e lectric parameters on machining process and an orthogonal design is employed to select the proper electric parameters. By experiment, we find how the voltage and current affect machining process and study the removal mechanism by WEDM-HS to machine Al 2O 3 particle-reinforce d material. Besides the machining current and voltage, there are still other fac tors that can affect machining process and state. In order to find out which is the most important factor and to optimize the electric parameters, the orthogona l design has been adopted to perform the experiment. By the analysis to the rela tive differences among different factor levels, the rank of significance for fou r factors is in turn the pulse duration, the voltage, the machining current and the pulse interval. At last we can draw a conclusion that 6061 alloy can be shaped by WEDM-HS, and give the suitable electric parameters to obtain good surface roughness and high machining efficiency.展开更多
Mechanical damping of composites reinforced by randomly distributed particles due to interfacial sliding is analyzed. The matrix is elastically isotropic, and the particles are assumed rigid and of identical radii. An...Mechanical damping of composites reinforced by randomly distributed particles due to interfacial sliding is analyzed. The matrix is elastically isotropic, and the particles are assumed rigid and of identical radii. An auxiliary problem is solved at first for the steady-state response of an infinite matrix containing a single inclusion to a harmonic external load. The result is then used to derive the explicit expression of the specific damping capability of the composite by using Mori-Tanaka＇s mean-field method. Numerical results are given and discussed in detail. It is concluded that the overall damping of the composite depends on several factors, including volume fraction of particles, Poisson＇s ratio of matrix and a dimensionless parameter that incorporates the combined effects of particle size, matrix stiffness, interracial viscosity and vibration frequency. The result is expected to be helpful in tailoring the damping performance of particle-reinforced composites.展开更多
This paper proposes a state-of-the-art three-dimensional Voronoi cell finite element method(3D VCFEM)aimed at investigating the mechanical properties of particle-reinforced composites(PRCs)in space under different mic...This paper proposes a state-of-the-art three-dimensional Voronoi cell finite element method(3D VCFEM)aimed at investigating the mechanical properties of particle-reinforced composites(PRCs)in space under different microstructural properties.Firstly,the modified residual energy generalized function of 3D VCFEM was proposed by applying the hybrid stress element method,and the element format of the 3D Voronoi element was constructed.On this basis,the interaction between the matrix and the inclusions was considered,and the higher-order stress function including the interaction stress term was constructed.Secondly,to solve the difficulty of integrating easily due to the complexity and irregularity of the integration region in space,Delaunay tetrahedra were introduced within the 3D Voronoi element for mesh refinement.It simplified the integration process.Finally,to verify the accuracy and efficiency of the 3D VCFEM model,comparative models of 3D VCFENM and FEM were established for analysis and discussion.The stress field and strain field were compared and analyzed for the first time.An example was also given for the presence of a large number of randomly distributed inclusion particles.The results showed that under the same accuracy,3D VCFEM had the advantages of convenient mesh delineation and high computational efficiency compared with FEM,which provided a new way of thinking to analyze the actual PCRs.展开更多
Generally, friction and wear occur on the surface of the materials. It is necessary to investigate the dry sliding friction and wear behavior of surface. In this paper, 3-D topographical parameters were used to invest...Generally, friction and wear occur on the surface of the materials. It is necessary to investigate the dry sliding friction and wear behavior of surface. In this paper, 3-D topographical parameters were used to investigate the topographical characteristics of dry sliding surfaces for particle-reinforced alu-minum composites on semi-metallic friction material. The experimental results indicate that the surface topography of the particle-reinforced aluminum composites can be divided into two types, the flaking-off pit type and the groove type. The composites whose surface topography is the flaking-off pit type possess superior heat conductivity and bearing area, lower wear rate, and higher friction coefficient than the groove type. Consequently, the flaking-off pit type surface topography is much better than the groove type for particle-reinforced aluminum composites on semi-metallic friction materials in dry sliding.展开更多
An in situ autogenous particle-reinforced Ti-2.5Zr-2Al-1(Si,C)titanium alloy is prepared by vacuum induction melting.The wide range of an effective strain between 0.2 and 1.2 and the corresponding microstructure are o...An in situ autogenous particle-reinforced Ti-2.5Zr-2Al-1(Si,C)titanium alloy is prepared by vacuum induction melting.The wide range of an effective strain between 0.2 and 1.2 and the corresponding microstructure are obtained by the double-cone high-throughput compression test and finite element simulation.The deformation mechanism diagram with strains of 0.2-1.2 and strain rates of 0.7-1.5 s^(-1)at 900℃ is constructed.When the strain rate is 1.3 s^(-1),dynamic recovery occurs in the small strain range(<0.377),dynamic recrystallization(DRX)occurs in the medium strain range(0.377-1.182),and deformation instability occurs in the large strain range(>1.182),resulting in the deformation bands.High-angle annular dark field and high-resolution transmission electron microscopy are used to determine the existence of bimodal particle distribution,namely micron-scale TiC particles and nano-scale Ti5Si3 and(Zr,Si)particles.The average radius of the(Zr,Si)nanoparticles measured by small angle neutron scattering is 19.3 nm,and the volume fraction is 0.35%.DRX grains with an average size of 0.49μm are obtained at 900°C,strain rate of 1.3 s^(-1),and strain of about 0.6.Micron-scale particles stimulated DRX nucleation,while nanoscale particles hindered the growth of new grains,resulting in grain refinement.展开更多
A new,cost-effective porous polymer composite was developed by reinforcing polypropylene(PP)with cenosphere particles.This study investigates how the composite’s dielectric properties are affected by their porosity.D...A new,cost-effective porous polymer composite was developed by reinforcing polypropylene(PP)with cenosphere particles.This study investigates how the composite’s dielectric properties are affected by their porosity.Dielectric constant(ε′)measurements were taken over a range of frequencies at roomtemperature.A theoreticalmodel was developed to explain the electrical conductivity of the porous PP/cenosphere composites.The study thoroughly examined how the inclusion of cenosphere particles influenced key electrical parameters,including dielectric constant,dissipation factor(tanδ),DC(direct current)conductivity,and AC(alternating current)conductivity.The results revealed that increasing the cenosphere content caused a decrease in the dielectric constant,while the dissipation factor increased.The developed porous PP/cenosphere composite exhibits a unique balance of low dielectric constant,lightweight structure making it suitable for several practical applications.Its low dielectric constant and reduced DC conductivity make it an excellent candidate for electronic packaging,insulating layers,and high-frequency components,where minimal energy loss and signal interference are required.The lightweight nature of the cenosphere-reinforced structure also suggests potential use in aerospace and automotive industries for lightweight insulation panels or structural components.Furthermore,its cost-effectiveness and tunable porosity could enable applications in microwave substrates,radar-absorbing materials,and energy-efficient building materials where dielectric control and weight reduction are critical.Additionally,DC conductivity was found to decline with higher cenosphere concentrations.The theoretical model was in good agreement with the experimental data.展开更多
In-situ particle reinforced aluminum composite coatings were fabricated on 7075 aluminum alloy by ultrasonic-assisted laser alloying.The coatings consisted of Fe_(4) Al_(13),TiB_(2),TiC,Cr_(7) C_(3),Cr_(2) B,andα-Al....In-situ particle reinforced aluminum composite coatings were fabricated on 7075 aluminum alloy by ultrasonic-assisted laser alloying.The coatings consisted of Fe_(4) Al_(13),TiB_(2),TiC,Cr_(7) C_(3),Cr_(2) B,andα-Al.TiB_(2) and TiC were well bonded to theα-Al interface,with interfacial mismatch rates of 5.8%and 6.8%,re-spectively.Ultrasonic vibration did not alter the phase structure but promoted the synthesis of more in-situ reinforcements and slightly increased surface roughness.Higher ultrasonic power led to increased coating depth and dilution rates due to intensive convection.Compared with the distinct enrichment observed without vibration,ultrasonic assistance resulted in more uniform elemental distributions.The cavitation and acoustic flow effects refined the intermetallic compounds and in-situ reinforcements,im-proving their distribution.An ultrasonic power exceeding 3,000 W further broke needle-like intermetallic compounds into finer particles.The ultrasonic-assisted coatings presented higher and more uniform mi-crohardness values and superior wear resistance.The primary wear mechanism for all the coatings was abrasive wear,whereas the coatings without ultrasonic vibration exhibited more severe wear.展开更多
Improving interfacial bonding and alloying design are effective strategies for enhancing mechanical properties of particle-reinforced steel matrix composites(SMCs).This study prepared SMCs with uniformly distributed T...Improving interfacial bonding and alloying design are effective strategies for enhancing mechanical properties of particle-reinforced steel matrix composites(SMCs).This study prepared SMCs with uniformly distributed TiC_(P)in matrix using master alloying method.The TiC(002)/Fe(011)interface model was established based on the orientation relationship of(011)_(Fe)//(002)_(TiC),and[100]_(Fe)//[100]_(TiC).The effects of single and co-doping of alloying elements(Mn,Cr,Mo,Ni,Cu and Si)on the interface bonding behavior of TiC/Fe in composites were investigated in conjunction with first principles.The results demonstrate that the interface between TiC and matrix is continuous and stable.Compared to the undoped TiC/Fe interface,single-doping Mn,Cr,and Mo can improve the stability of TiC/Fe interface and enhance tensile strength.Conversely,single-doping with Ni,Cu,and Si reduced the interface stability and marginally reduces tensile strength.Relative to the undoped and singly Ni-doped TiC/Fe interfaces,the co-doping Ni-Mo boosts binding energy and separation work at the TiC/Fe interface,which is conducive to the interface bonding between TiC_(P)and matrix,and thus improves the mechanical properties of composites.Thus,in the alloying design of TiC particle reinforced low-alloy SMCs,incorporating Mn,Cr,Mo,and Ni into matrix can enhance the overall mechanical properties of composites.展开更多
Hot compression tests of the extruded 7075Al/15%SiC (volume fraction) particle reinforced composite prepared by spray deposition were performed on Gleeble?1500 system in the temperature range of 300?450 °C and st...Hot compression tests of the extruded 7075Al/15%SiC (volume fraction) particle reinforced composite prepared by spray deposition were performed on Gleeble?1500 system in the temperature range of 300?450 °C and strain rate range of 0.001?1 s?1. The results indicate that the true stress?true strain curve almost exhibits rapid flow softening phenomenon without an obvious work hardening, and the stress decreases with increasing temperature and decreasing strain rate. Moreover, the stress levels are higher at temperature below 400 °C but lower at 450 °C compared with the spray deposited 7075Al alloy. Superplastic deformation characteristics are found at temperature of 450 °C and strain rate range of 0.001?0.1 s?1 with corresponding strain rate sensitivity of 0.72. The optimum parameters of hot working are determined to be temperature of 430?450 °C and strain rate of 0.001?0.05 s?1 based on processing map and optical microstructural observation.展开更多
In this work, an in situ synthesized TiC-reinforced metal matrix composite （MMC） coating of approximately 350-400μm thickness was fabricated on a gray cast iron （GCI） substrate by plasma transferred arc （PTA） s...In this work, an in situ synthesized TiC-reinforced metal matrix composite （MMC） coating of approximately 350-400μm thickness was fabricated on a gray cast iron （GCI） substrate by plasma transferred arc （PTA） surface alloying of Ti-Fe alloy powder. Microhard- ness tests showed that the surface hardness increased approximately four-fold after the alloying treatment. The microstructure of the MMC coating was mainly composed of residual austenite, acicular martensite, and eutectic ledeburite. Scanning electron microscopy （SEM） and X-ray diffraction analyzes revealed that the in situ TiC particles, which were formed by direct reaction of Ti with carbon originally contained in the GCI, was uniformly distributed at the boundary of residual anstenite in the alloying zone. Pin-on-disc high-temperature wear tests were performed on samples both with and without the MMC coating at room temperature and at elevated temperatures （473 K and 623 K）, and the wear behavior and mechanism were investigated. The results showed that, after the PTA alloying treatment, the wear resistance of the sam- ples improved significantly. On the basis of our analysis of the composite coatings by optical microscopy, SEM with energy-dispersive X-ray spectroscopy, and microhardness measurements, we attributed this improvement of wear resistance to the transformation of the microstruc- ture and to the presence of TiC particles.展开更多
The results of a theoretical study on the influence of strength of interphase boundaries in metal-ceramic composite on macroscopical characteristics of composite response such as strength, deformation capacity, fractu...The results of a theoretical study on the influence of strength of interphase boundaries in metal-ceramic composite on macroscopical characteristics of composite response such as strength, deformation capacity, fracture energy and fracture pattern are presented. The study was conducted by means of computer-aided simulation by means of movable cellular automaton method taking account of a developed ＂mesoscopical＂ structural model of particle-reinforced composite. The strength of interphase boundaries is found to be a key structural factor determining not only the strength properties of metal-ceramic composite, but also the pattern and rate of fracture. The principles for achievement of the high-strength values of particle/binder interfaces in the metal-ceramic composition due to the formation of the wide transition zones （areas of variable chemical composition） at the interphase boundaries are discussed. Simulation results confirm that such transition zones provide a change in fracture mechanism and make the achievement of a high-strength and a high deformation capacity of metal-ceramic composite possible.展开更多
Interactions between Zn-Al alloy and Al2O 3p/6061Al composite with the aid of ultrasonic vibration in air were investigated. For the composite without degassed treatment, the molten Zn-Al alloy cannot spread along the...Interactions between Zn-Al alloy and Al2O 3p/6061Al composite with the aid of ultrasonic vibration in air were investigated. For the composite without degassed treatment, the molten Zn-Al alloy cannot spread along the surface of the composite when the ultrasonic vibration amplitude is lower than 10μm. Instead, it undermines the substrate oxide layer and propagates along the substrate metal-substrate oxide interface, and penetrates into the composite at the same time. The penetration of the Zn-Al alloy into the composite makes the microstructure of the penetration zone unconsolidated. As the ultrasonic vibration amplitude increases, the spreading area of the molten Zn-Al alloy increases and the mass transfer at the interaction interface between the Zn-Al alloy and the composite intensifies. The porosity at the interaction interface results from the gas escaping from the base material by which the undermining phenomenon and the penetration of elements Zn, Cu into the composite is favoured. When the composite is degassed, the undermining zone and the penetration zone become significantly limited and the penetration zone remains consolidated. Only limited base metal melts during interaction, which is accompanied with fewer reinforcements and primary α-Al dendrites in the solidified Zn-Al alloy.展开更多
Micromechanical theory is applied to study the nonlinear elastic and viscoelastic constitutive relations of polymeric matrix filled with high rigidity solid particles. It is shown that Eshelby's method can be exte...Micromechanical theory is applied to study the nonlinear elastic and viscoelastic constitutive relations of polymeric matrix filled with high rigidity solid particles. It is shown that Eshelby's method can be extended to the case of nonlinear matrix and Eshelby's tensor still exists provided that Poisson's ratio of the nonlinear matrix assumes constant value in deforming process and the rigidity of elastic filling particles is much higher than that of the matrix. A new method for averaging process is proposed to overcome the difficulty that occured in applying the ordinary equivalent inclusion method or the seff-consistant method to nonlinear matrices. A rather simple constitutive equation is obtained finally and the strengthening effect of solid particles to composites is investigated.展开更多
A new method was applied to produce an Al-0.5wt%Ti-0.3wt%Zr/5vol%B_4C composite via stir casting with the aim of characterizing the microstructure of the resulting composite. For the production of the composite, large...A new method was applied to produce an Al-0.5wt%Ti-0.3wt%Zr/5vol%B_4C composite via stir casting with the aim of characterizing the microstructure of the resulting composite. For the production of the composite, large B4 C particles（larger than 75 μm） with no pre-heating were added to the stirred melt. Reflected-light microscopy, X-ray diffraction, scanning electron microscopy, field-emission scanning electron microscopy, laser particle size analysis, and image analysis using the Clemex software were performed on the cast samples for microstructural analysis and phase detection. The results revealed that as a consequence of thermal shock, B_4 C particle breakage occurred in the melt. The mechanism proposed for this phenomenon is that the exerted thermal shock in combination with the low thermal shock resistance of B_4 C and large size of the added B_4 C particles were the three key parameters responsible for B_4 C particle breakage. This breakage introduced small particles with sizes less than 10 μm and with no contamination on their surfaces into the melt. The mean particle distance measured via image analysis was approximately 60 μm. The coefficient of variation index, which was used as a measure of particle distribution homogeneity, showed some variations, indicating a relatively homogeneous distribution.展开更多
The interface of ceramic particles and metal matrixes extremely impacts the mechanical properties of particle-reinforced metal matrix composites,especially at elevated temperatures.We provide a strategy for constructi...The interface of ceramic particles and metal matrixes extremely impacts the mechanical properties of particle-reinforced metal matrix composites,especially at elevated temperatures.We provide a strategy for constructing extremely fine,in situ-formed coherent nanolamellar solute-twining architectures in a supersaturated MAX/Ni composite to modify the interface,aiming for higher strengths.Through this unique architecture,a coherent interface of ceramic particles and a metal matrix is formed,with an enormous coherent interface known as a ladder interface.The tensile strength at 1023 K is approximately 1 GPa by forming a thermally stable Schwarz crystal structure(<3 nm).Developing heat-tolerant composites using this architecture may enhance the materials’available properties for high-temperature applications.展开更多
By transforming the governing equations for displacement components into Riccati equations, analytical solutions for displacements, strains and stresses for Representive Volume Elements (RVEs) of particle_ and fiber_r...By transforming the governing equations for displacement components into Riccati equations, analytical solutions for displacements, strains and stresses for Representive Volume Elements (RVEs) of particle_ and fiber_reinforced composites containing inhomo geneous interphases were obtained. The analytical solutions derived here are new and general for power_law variations of the elastic moduli of the inhomogeneous interphases. Given a power exponent, analytical expressions for the bulk moduli of the composites with inho mogeneous interphases can be obtained. By changing the power exponent and the coefficients of the power terms, the solutions derived here can be applied to inhomogeneous interphases with many different property profiles. The results show that the modulus variation and the thickness of the inhomogeneous interphase have great effect on the bulk moduli of the composites. The particle will exhibit a sort of “size effect”, if there is an interphase.展开更多
基金The project, supported by the National Natural Science Foundation of China (19891180, 19925211) and by the Chinese Academy of Sciences (KJ951-1-201) and "Bai Ren" plan
文摘The influences of I,article size on the mechanical properties of the particulate metal matrix composite;are obviously displayed in the experimental observations. However, the phenomenon can not be predicted directly using the conventional elastic-plastic theory. It is because that no length scale parameters are involved in the conventional theory. In the present research, using the strain gradient plasticity theory, a systematic research of the particle size effect in the particulate metal matrix composite is carried out. The roles of many composite factors, such as: the particle size, the Young's modulus of the particle, the particle aspect ratio and volume fraction, as well as the plastic strain hardening exponent of the matrix material, are studied in detail. In order to obtain a general understanding for the composite behavior, two kinds of particle shapes, ellipsoid and cylinder, are considered to check the strength dependence of the smooth or non-smooth particle surface. Finally, the prediction results will be applied to the several experiments about the ceramic particle-reinforced metal-matrix composites. The material length scale parameter is predicted.
基金The financial support from the National Natural Science Foundation of China(Grants Nos.11802007,11872162,and 12002111)the Basic Reserach Program of Taicang(General Program),China(Grant No.TC2020JC11)+1 种基金the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province,China(Grant No.17KJB130002)China Postdoctoral Science Foundation(Grant No.2020M681101)are greatly appreciated.
文摘Micromechanics-based constitutive models offer superior ability to estimate the effective mechanical properties for the composites,which greatly promote the computational efficiency in the multiscale analysis for composite structures.In this work,a thermo-viscoelastic model for particle-reinforced composites is proposed to estimate their thermal-mechanical coupling behaviors in terms of a micromechanics-based homogenization method in the time domain.The matrix and particles of the composites are modeled as“thermo-rheologically complex”viscoelastic materials.The temperature-dependent effective elastic strain energy ratios of particle to composite are proposed to evaluate the contributions of the matrix and particles.The thermo-viscoelastic model for the composites is then formulated by superposing the matrix and particle’s contributions.Finite element simulations based on the representative volume element models are employed to validate the constitutive model under various thermal-mechanical coupling loads.The effects of the loading rate,viscous parameter and particle content on the effective thermal-mechanical responses of the composites are also comprehensively discussed.The experimental data from literature are also employed to verify the constitutive model.The findings show that the proposed thermo-viscoelastic model can accurately predict the thermal-mechanical coupling behaviors for the particle-reinforced composites.
基金Z.F.Yue is grateful to Alexander von Humboldt Foundation for awarding the chance to study and research in Germany. And he is grateful to his host professor, Prof. Dr. Gunther Eggeler, for his invitation, and also to Dr. Malte Probst-Hein for his consiste
文摘A systematical simulation has been carried out on the indentation creep test on particle-reinforced composites. The deformation, failure mechanisms and life are analyzed by three reasonable models. The following five factors have been considered simultaneously: creep property of the particle, creep property of the matrix, the shape of the particle, the volume fraction of the particle and the size (relative size to the particle) of the indentation indenter. For all the cases, the power law respecting to the applied stress can be used to model the steady indentation creep depth rate of the indenter, and the detail expressions have been presented. The computer simulation precision is analyzed by the two-phase model and the three-phase model. Two places of the stress concentration are found in the composites. One is ahead of the indentation indenter, where the high stress state is deduced by the edge of the indenter and will decrease rapidly near to a steady value with the creep time. The other one is at the interface, where the high stress state is deduced by the misfit of material properties between the particles and matrix. It has been found that the creep dissipation energy density other than a stress parameter can be used to be the criterion to model the debonding of the interfaces. With the criterion of the critical creep dissipation energy density, a power law to the applied stress with negative exponent can be used to model the failure life deduced by the debonding of interfaces. The influences of the shape of the particles and the matching of creep properties of particle and matrix can be discussed for the failure. With a crack model, the further growth of interface crack is analyzed, and some important experimental phenomena can be predicted. The failure mechanism which the particle will be punched into matrix has been also discussed. The critical differences between the creep properties of the particles and matrix have been calculated, after a parameter has been defined. In the view of competition of failure mechanisms, the best matching of the creep properties of the two phases and the best shape of the particles are discussed for the composite design.
基金financially supported by the National Natural Science Foundation of China (No. 51505051)the Scientific Research Starting Foundation of Chongqing University of Technology (No. 2012ZD12)the Scientific and Technological Research Program of Chongqing Municipal Education Commission (No. KJ130813)
文摘TiB_2particle-reinforced 7075 Al alloy was synthesized to investigate the effect of TiB_2 particles on microstructure of semisolid 7075 Al alloy slurry. The mean grain size and shape factor of 3 wt% TiB_2/7075 composite could reach 92 lm and 0.64 at 630 ℃ for 23 min,respectively, and for 6 wt% TiB_2/7075 composite, they are100 lm and 0.64 at 630 ℃ for 33 min. The microstructure evolution for TiB_2/7075 composites in semisolid state includes three-stage process. a-Al begins to nucleate and grow up into rosette grains due to a low degree of supercooling at first. Then rosette grains begin to fuse or grow up at different rates. Finally, the dissolution rate and the growth rate of α-Al reach equilibrium.
文摘Al 2O 3 particle-reinforced material (6061 alloy ), which is one of new composites and characterized by high strength and small spe cific gravity, good wear resistance and corrosion resistance, has been widel y used in industry. But it is difficult to machine. Because of electric conducti vity, it can be shaped and processed by electro-machining means. However, this kind of material is mixed with the electrically conductive substances and the di electrically conductive substances, its machining process shows substantially di fferent from the machining of ordinary metal materials. This paper, based on a c ontrast experiment, investigates the machining mechanism and technique by WEDM t o shape the material and gives the optimum selection for the electric paramete rs in operation. The technologic index of shaping the new material by WEDM includes the cutting r ate and the surface roughness. There are a lot of factors that affect the techno logic index of WEDM, in which the electric parameters such as the machining volt age and current as well as the pulse duration, interval and frequency, play an i mportant part. In this experiment, the study focus mainly on the effect of the e lectric parameters on machining process and an orthogonal design is employed to select the proper electric parameters. By experiment, we find how the voltage and current affect machining process and study the removal mechanism by WEDM-HS to machine Al 2O 3 particle-reinforce d material. Besides the machining current and voltage, there are still other fac tors that can affect machining process and state. In order to find out which is the most important factor and to optimize the electric parameters, the orthogona l design has been adopted to perform the experiment. By the analysis to the rela tive differences among different factor levels, the rank of significance for fou r factors is in turn the pulse duration, the voltage, the machining current and the pulse interval. At last we can draw a conclusion that 6061 alloy can be shaped by WEDM-HS, and give the suitable electric parameters to obtain good surface roughness and high machining efficiency.
文摘Mechanical damping of composites reinforced by randomly distributed particles due to interfacial sliding is analyzed. The matrix is elastically isotropic, and the particles are assumed rigid and of identical radii. An auxiliary problem is solved at first for the steady-state response of an infinite matrix containing a single inclusion to a harmonic external load. The result is then used to derive the explicit expression of the specific damping capability of the composite by using Mori-Tanaka＇s mean-field method. Numerical results are given and discussed in detail. It is concluded that the overall damping of the composite depends on several factors, including volume fraction of particles, Poisson＇s ratio of matrix and a dimensionless parameter that incorporates the combined effects of particle size, matrix stiffness, interracial viscosity and vibration frequency. The result is expected to be helpful in tailoring the damping performance of particle-reinforced composites.
基金funded by the National Natural Science Foundation of China(Grant No.12227801).
文摘This paper proposes a state-of-the-art three-dimensional Voronoi cell finite element method(3D VCFEM)aimed at investigating the mechanical properties of particle-reinforced composites(PRCs)in space under different microstructural properties.Firstly,the modified residual energy generalized function of 3D VCFEM was proposed by applying the hybrid stress element method,and the element format of the 3D Voronoi element was constructed.On this basis,the interaction between the matrix and the inclusions was considered,and the higher-order stress function including the interaction stress term was constructed.Secondly,to solve the difficulty of integrating easily due to the complexity and irregularity of the integration region in space,Delaunay tetrahedra were introduced within the 3D Voronoi element for mesh refinement.It simplified the integration process.Finally,to verify the accuracy and efficiency of the 3D VCFEM model,comparative models of 3D VCFENM and FEM were established for analysis and discussion.The stress field and strain field were compared and analyzed for the first time.An example was also given for the presence of a large number of randomly distributed inclusion particles.The results showed that under the same accuracy,3D VCFEM had the advantages of convenient mesh delineation and high computational efficiency compared with FEM,which provided a new way of thinking to analyze the actual PCRs.
基金Supported by the Innovation Fund for Outstanding Scholar of Henan Province (No. 0421000600)
文摘Generally, friction and wear occur on the surface of the materials. It is necessary to investigate the dry sliding friction and wear behavior of surface. In this paper, 3-D topographical parameters were used to investigate the topographical characteristics of dry sliding surfaces for particle-reinforced alu-minum composites on semi-metallic friction material. The experimental results indicate that the surface topography of the particle-reinforced aluminum composites can be divided into two types, the flaking-off pit type and the groove type. The composites whose surface topography is the flaking-off pit type possess superior heat conductivity and bearing area, lower wear rate, and higher friction coefficient than the groove type. Consequently, the flaking-off pit type surface topography is much better than the groove type for particle-reinforced aluminum composites on semi-metallic friction materials in dry sliding.
基金supported by the State Key Laboratory of Powder Metallurgy,China(grant no.2022)Innovation Province Construction Special Project of Hunan(grant no.2020GK4018)+2 种基金the National Natural Science of China(grant no.51771231 and 52020105013)Yubin Ke is grateful for the support from the National Natural Science Foundation of China(grant no.12275154)the Youth Innovation Promotion Association,CAS(no.2020010).
文摘An in situ autogenous particle-reinforced Ti-2.5Zr-2Al-1(Si,C)titanium alloy is prepared by vacuum induction melting.The wide range of an effective strain between 0.2 and 1.2 and the corresponding microstructure are obtained by the double-cone high-throughput compression test and finite element simulation.The deformation mechanism diagram with strains of 0.2-1.2 and strain rates of 0.7-1.5 s^(-1)at 900℃ is constructed.When the strain rate is 1.3 s^(-1),dynamic recovery occurs in the small strain range(<0.377),dynamic recrystallization(DRX)occurs in the medium strain range(0.377-1.182),and deformation instability occurs in the large strain range(>1.182),resulting in the deformation bands.High-angle annular dark field and high-resolution transmission electron microscopy are used to determine the existence of bimodal particle distribution,namely micron-scale TiC particles and nano-scale Ti5Si3 and(Zr,Si)particles.The average radius of the(Zr,Si)nanoparticles measured by small angle neutron scattering is 19.3 nm,and the volume fraction is 0.35%.DRX grains with an average size of 0.49μm are obtained at 900°C,strain rate of 1.3 s^(-1),and strain of about 0.6.Micron-scale particles stimulated DRX nucleation,while nanoscale particles hindered the growth of new grains,resulting in grain refinement.
文摘A new,cost-effective porous polymer composite was developed by reinforcing polypropylene(PP)with cenosphere particles.This study investigates how the composite’s dielectric properties are affected by their porosity.Dielectric constant(ε′)measurements were taken over a range of frequencies at roomtemperature.A theoreticalmodel was developed to explain the electrical conductivity of the porous PP/cenosphere composites.The study thoroughly examined how the inclusion of cenosphere particles influenced key electrical parameters,including dielectric constant,dissipation factor(tanδ),DC(direct current)conductivity,and AC(alternating current)conductivity.The results revealed that increasing the cenosphere content caused a decrease in the dielectric constant,while the dissipation factor increased.The developed porous PP/cenosphere composite exhibits a unique balance of low dielectric constant,lightweight structure making it suitable for several practical applications.Its low dielectric constant and reduced DC conductivity make it an excellent candidate for electronic packaging,insulating layers,and high-frequency components,where minimal energy loss and signal interference are required.The lightweight nature of the cenosphere-reinforced structure also suggests potential use in aerospace and automotive industries for lightweight insulation panels or structural components.Furthermore,its cost-effectiveness and tunable porosity could enable applications in microwave substrates,radar-absorbing materials,and energy-efficient building materials where dielectric control and weight reduction are critical.Additionally,DC conductivity was found to decline with higher cenosphere concentrations.The theoretical model was in good agreement with the experimental data.
基金financially supported by the National Key R&D Program of China(No.2023YFB4604300)the National Natural Sci-ence Foundation of China(No.52205221)+1 种基金the Zhejiang Provincial Natural Science Foundation(No.LY24E050008)the Funda-mental Research Funds for the Provincial Universities of Zhejiang(No.RF-A2023008).
文摘In-situ particle reinforced aluminum composite coatings were fabricated on 7075 aluminum alloy by ultrasonic-assisted laser alloying.The coatings consisted of Fe_(4) Al_(13),TiB_(2),TiC,Cr_(7) C_(3),Cr_(2) B,andα-Al.TiB_(2) and TiC were well bonded to theα-Al interface,with interfacial mismatch rates of 5.8%and 6.8%,re-spectively.Ultrasonic vibration did not alter the phase structure but promoted the synthesis of more in-situ reinforcements and slightly increased surface roughness.Higher ultrasonic power led to increased coating depth and dilution rates due to intensive convection.Compared with the distinct enrichment observed without vibration,ultrasonic assistance resulted in more uniform elemental distributions.The cavitation and acoustic flow effects refined the intermetallic compounds and in-situ reinforcements,im-proving their distribution.An ultrasonic power exceeding 3,000 W further broke needle-like intermetallic compounds into finer particles.The ultrasonic-assisted coatings presented higher and more uniform mi-crohardness values and superior wear resistance.The primary wear mechanism for all the coatings was abrasive wear,whereas the coatings without ultrasonic vibration exhibited more severe wear.
基金Project supported by the Special Funding Support for the Development of 1500 Meter Subsea Christmas Tree and Control System,China。
文摘Improving interfacial bonding and alloying design are effective strategies for enhancing mechanical properties of particle-reinforced steel matrix composites(SMCs).This study prepared SMCs with uniformly distributed TiC_(P)in matrix using master alloying method.The TiC(002)/Fe(011)interface model was established based on the orientation relationship of(011)_(Fe)//(002)_(TiC),and[100]_(Fe)//[100]_(TiC).The effects of single and co-doping of alloying elements(Mn,Cr,Mo,Ni,Cu and Si)on the interface bonding behavior of TiC/Fe in composites were investigated in conjunction with first principles.The results demonstrate that the interface between TiC and matrix is continuous and stable.Compared to the undoped TiC/Fe interface,single-doping Mn,Cr,and Mo can improve the stability of TiC/Fe interface and enhance tensile strength.Conversely,single-doping with Ni,Cu,and Si reduced the interface stability and marginally reduces tensile strength.Relative to the undoped and singly Ni-doped TiC/Fe interfaces,the co-doping Ni-Mo boosts binding energy and separation work at the TiC/Fe interface,which is conducive to the interface bonding between TiC_(P)and matrix,and thus improves the mechanical properties of composites.Thus,in the alloying design of TiC particle reinforced low-alloy SMCs,incorporating Mn,Cr,Mo,and Ni into matrix can enhance the overall mechanical properties of composites.
基金Project(51271076)supported by the National Natural Science Foundation of China
文摘Hot compression tests of the extruded 7075Al/15%SiC (volume fraction) particle reinforced composite prepared by spray deposition were performed on Gleeble?1500 system in the temperature range of 300?450 °C and strain rate range of 0.001?1 s?1. The results indicate that the true stress?true strain curve almost exhibits rapid flow softening phenomenon without an obvious work hardening, and the stress decreases with increasing temperature and decreasing strain rate. Moreover, the stress levels are higher at temperature below 400 °C but lower at 450 °C compared with the spray deposited 7075Al alloy. Superplastic deformation characteristics are found at temperature of 450 °C and strain rate range of 0.001?0.1 s?1 with corresponding strain rate sensitivity of 0.72. The optimum parameters of hot working are determined to be temperature of 430?450 °C and strain rate of 0.001?0.05 s?1 based on processing map and optical microstructural observation.
基金financially supported by the National Science and Technology Major Project of China (No. 2012ZX04010-081)the National High-Tech Research and Development Program of China (No. 2013AA040404)
文摘In this work, an in situ synthesized TiC-reinforced metal matrix composite （MMC） coating of approximately 350-400μm thickness was fabricated on a gray cast iron （GCI） substrate by plasma transferred arc （PTA） surface alloying of Ti-Fe alloy powder. Microhard- ness tests showed that the surface hardness increased approximately four-fold after the alloying treatment. The microstructure of the MMC coating was mainly composed of residual austenite, acicular martensite, and eutectic ledeburite. Scanning electron microscopy （SEM） and X-ray diffraction analyzes revealed that the in situ TiC particles, which were formed by direct reaction of Ti with carbon originally contained in the GCI, was uniformly distributed at the boundary of residual anstenite in the alloying zone. Pin-on-disc high-temperature wear tests were performed on samples both with and without the MMC coating at room temperature and at elevated temperatures （473 K and 623 K）, and the wear behavior and mechanism were investigated. The results showed that, after the PTA alloying treatment, the wear resistance of the sam- ples improved significantly. On the basis of our analysis of the composite coatings by optical microscopy, SEM with energy-dispersive X-ray spectroscopy, and microhardness measurements, we attributed this improvement of wear resistance to the transformation of the microstruc- ture and to the presence of TiC particles.
基金The investigation has been carried out within the SB RAS Program Ⅲ.20.2 for Basic Researchat partial financial support of the RFBR Grant No.11-08-12069-ofi-m-2011+1 种基金the Project No.5 of the Belarus NASSB RAS Program for Joint Basic Research
文摘The results of a theoretical study on the influence of strength of interphase boundaries in metal-ceramic composite on macroscopical characteristics of composite response such as strength, deformation capacity, fracture energy and fracture pattern are presented. The study was conducted by means of computer-aided simulation by means of movable cellular automaton method taking account of a developed ＂mesoscopical＂ structural model of particle-reinforced composite. The strength of interphase boundaries is found to be a key structural factor determining not only the strength properties of metal-ceramic composite, but also the pattern and rate of fracture. The principles for achievement of the high-strength values of particle/binder interfaces in the metal-ceramic composition due to the formation of the wide transition zones （areas of variable chemical composition） at the interphase boundaries are discussed. Simulation results confirm that such transition zones provide a change in fracture mechanism and make the achievement of a high-strength and a high deformation capacity of metal-ceramic composite possible.
文摘Interactions between Zn-Al alloy and Al2O 3p/6061Al composite with the aid of ultrasonic vibration in air were investigated. For the composite without degassed treatment, the molten Zn-Al alloy cannot spread along the surface of the composite when the ultrasonic vibration amplitude is lower than 10μm. Instead, it undermines the substrate oxide layer and propagates along the substrate metal-substrate oxide interface, and penetrates into the composite at the same time. The penetration of the Zn-Al alloy into the composite makes the microstructure of the penetration zone unconsolidated. As the ultrasonic vibration amplitude increases, the spreading area of the molten Zn-Al alloy increases and the mass transfer at the interaction interface between the Zn-Al alloy and the composite intensifies. The porosity at the interaction interface results from the gas escaping from the base material by which the undermining phenomenon and the penetration of elements Zn, Cu into the composite is favoured. When the composite is degassed, the undermining zone and the penetration zone become significantly limited and the penetration zone remains consolidated. Only limited base metal melts during interaction, which is accompanied with fewer reinforcements and primary α-Al dendrites in the solidified Zn-Al alloy.
基金The work supported by the LNM, Institute of Mechanics, Chinese Academy of Sciencesthe National Natural Science Foundation of China
文摘Micromechanical theory is applied to study the nonlinear elastic and viscoelastic constitutive relations of polymeric matrix filled with high rigidity solid particles. It is shown that Eshelby's method can be extended to the case of nonlinear matrix and Eshelby's tensor still exists provided that Poisson's ratio of the nonlinear matrix assumes constant value in deforming process and the rigidity of elastic filling particles is much higher than that of the matrix. A new method for averaging process is proposed to overcome the difficulty that occured in applying the ordinary equivalent inclusion method or the seff-consistant method to nonlinear matrices. A rather simple constitutive equation is obtained finally and the strengthening effect of solid particles to composites is investigated.
文摘A new method was applied to produce an Al-0.5wt%Ti-0.3wt%Zr/5vol%B_4C composite via stir casting with the aim of characterizing the microstructure of the resulting composite. For the production of the composite, large B4 C particles（larger than 75 μm） with no pre-heating were added to the stirred melt. Reflected-light microscopy, X-ray diffraction, scanning electron microscopy, field-emission scanning electron microscopy, laser particle size analysis, and image analysis using the Clemex software were performed on the cast samples for microstructural analysis and phase detection. The results revealed that as a consequence of thermal shock, B_4 C particle breakage occurred in the melt. The mechanism proposed for this phenomenon is that the exerted thermal shock in combination with the low thermal shock resistance of B_4 C and large size of the added B_4 C particles were the three key parameters responsible for B_4 C particle breakage. This breakage introduced small particles with sizes less than 10 μm and with no contamination on their surfaces into the melt. The mean particle distance measured via image analysis was approximately 60 μm. The coefficient of variation index, which was used as a measure of particle distribution homogeneity, showed some variations, indicating a relatively homogeneous distribution.
基金supported financially by the Beijing Natural Science Foundation(No.2212046)the National Natural Science Foundation of China(Nos.51871011 and 51572017)+2 种基金the Research Fund for Commercialization of Major Scientific and Technological Achievements of Hebei Province(No.22281006Z)the Beijing Government Funds for the Constructive Project of Central UniversitiesThe financial supports by them are greatly appreciated.
文摘The interface of ceramic particles and metal matrixes extremely impacts the mechanical properties of particle-reinforced metal matrix composites,especially at elevated temperatures.We provide a strategy for constructing extremely fine,in situ-formed coherent nanolamellar solute-twining architectures in a supersaturated MAX/Ni composite to modify the interface,aiming for higher strengths.Through this unique architecture,a coherent interface of ceramic particles and a metal matrix is formed,with an enormous coherent interface known as a ladder interface.The tensile strength at 1023 K is approximately 1 GPa by forming a thermally stable Schwarz crystal structure(<3 nm).Developing heat-tolerant composites using this architecture may enhance the materials’available properties for high-temperature applications.
文摘By transforming the governing equations for displacement components into Riccati equations, analytical solutions for displacements, strains and stresses for Representive Volume Elements (RVEs) of particle_ and fiber_reinforced composites containing inhomo geneous interphases were obtained. The analytical solutions derived here are new and general for power_law variations of the elastic moduli of the inhomogeneous interphases. Given a power exponent, analytical expressions for the bulk moduli of the composites with inho mogeneous interphases can be obtained. By changing the power exponent and the coefficients of the power terms, the solutions derived here can be applied to inhomogeneous interphases with many different property profiles. The results show that the modulus variation and the thickness of the inhomogeneous interphase have great effect on the bulk moduli of the composites. The particle will exhibit a sort of “size effect”, if there is an interphase.
