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
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
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
Dry sliding wear behaviour of stir-cast aluminium matrix composites(AMCs)containing LM13 alloy as matrix and ceramic particles as reinforcement was investigated.Two different ceramic particle reinforcements were used ...Dry sliding wear behaviour of stir-cast aluminium matrix composites(AMCs)containing LM13 alloy as matrix and ceramic particles as reinforcement was investigated.Two different ceramic particle reinforcements were used separately:synthetic ceramic particles(B_(4)C),and natural ceramic particles(ilmenite).Optical micrographs showed uniform dispersion of reinforced particles in the matrix material.Reinforced particles refined the grain size of eutectic silicon and changed its morphology to globular type.B_(4)C reinforced composites(BRCs)showed maximum improvement in hardness of AMCs.Ilmenite reinforced composites(IRCs)showed maximum reduction in coefficient of friction values due to strong matrix−reinforcement interfacial bonding caused by the formation of interfacial compounds.Dry sliding wear behaviour of composites was significantly improved as compared to base alloy.The low density and high hardness of B_(4)C particles resulted in high dislocation density around filler particles in BRCs.On the other hand,the low thermal conductivity of ilmenite particles resulted in early oxidation and formation of a tribo-layer on surface of IRCs.So,both types of reinforcements led to the improvement in wear properties of AMCs,though the mechanisms involved were very different.Thus,the low-cost ilmenite particles can be used as alternative fillers to the high-cost B_(4)C particles for processing of wear resistant composites.展开更多
The alumina toughened zirconia(ATZ) ceramic particle reinforced gray iron matrix surface composite was successfully manufactured by pressureless infi ltration. The porous preform played a key role in the infi ltrating...The alumina toughened zirconia(ATZ) ceramic particle reinforced gray iron matrix surface composite was successfully manufactured by pressureless infi ltration. The porous preform played a key role in the infi ltrating progress. The microstructure was observed by scanning electron microscopy(SEM); the phase constitutions was analyzed by X-ray diffraction(XRD); and the hardness and wear resistance of selected specimens were tested by hardness testing machine and abrasion testing machine, respectively. The addition of high carbon ferrochromium powders leads to the formation of white iron during solidifi cation. The wear volume loss rates of ATZ ceramic particle reinforced gray iron matrix surface composite decreases fi rst, and then tends to be stable. The wear resistance of the composite is 2.7 times higher than that of gray iron matrix. The reason is a combination of the surface hardness increase of gray iron matrix and ATZ ceramic particles and alloy carbides protecting effect on gray iron matrix.展开更多
The dry sliding wear behavior of AA6061 matrix composite reinforced with aluminium nitride particles（AlN） produced by stir casting process was investigated. A regression model was developed to predict the wear rate ...The dry sliding wear behavior of AA6061 matrix composite reinforced with aluminium nitride particles（AlN） produced by stir casting process was investigated. A regression model was developed to predict the wear rate of the prepared composite. A four-factor, five-level central composite rotatable design matrix was used to minimize the number of experimental runs. The factors considered in this study were sliding velocity, sliding distance, normal load and mass fraction of AlN reinforcement in the matrix. The developed regression model was validated by statistical software SYSTAT 12 and statistical tools such as analysis of variance（ANOVA） and student＇s t test. It was found that the developed regression model could be effectively used to predict the wear rate at 95% confidence level. The influence of these factors on wear rate of AA6061/AlNp composite was analyzed using the developed regression model and predicted trends were discussed with the aid of worn surface morphologies. The regression model indicated that the wear rate of cast AA6061/AlNp composite decreased with an increase in the mass fraction of AlN and increased with an increase of the sliding velocity, sliding distance and normal load acting on the composite specimen.展开更多
Middle reinforcement content SiCp/Al composites（Vp=30%, 35% and 40%） for precision optical systems applications were fabricated by powder metallurgy technology. The composites were free of porosity and SiC particles...Middle reinforcement content SiCp/Al composites（Vp=30%, 35% and 40%） for precision optical systems applications were fabricated by powder metallurgy technology. The composites were free of porosity and SiC particles distributed uniformly in the composites. The mean linear coefficients of thermal expansion（20-100 ℃） of SiCp/Al composites ranged from 11.6×10-6 to 13.3×10-6 K-1 and decreased with an increase in volume fraction of SiC content. The experimental coeffi cients of thermal expansion agreed well with predicted values based on Kerner＇s model. The Brinell hardness increased from 116 to 147, and the modulus increased from 99 to 112 GPa for the corresponding composites. The tensile strengths were higher than 320 MPa, but no signifi cant increasing trend between tensile strength and SiC content was observed.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
Particle-reinforcing titanium matrix composites(PTMCs)exhibit the sharp raising applications in modern industries owing to its extraordinary physical and mechanical properties.However,the poor grindability and unstabl...Particle-reinforcing titanium matrix composites(PTMCs)exhibit the sharp raising applications in modern industries owing to its extraordinary physical and mechanical properties.However,the poor grindability and unstable grinding processes due to the existence of TiC particles and TiB short fibres inside PTMCs,leading to the sudden grinding burn and low material removal rate.In this work,a novel radial ultrasonic vibration-assisted grinding(RUVAG)device with a special cross structure was developed to improve machining efficiency and avoid grinding burns.Meanwhile,the resonant modal and transient dynamic characteristics of radial ultrasonic vibration system were discussed.Comparative grinding performance experiments were then conducted under the conventional grinding(CG)and RUVAG using mono-layer cubic boron nitride abrasive wheels,in views of the grinding forces and force ratio,grinding temperature,and ground surface morphology.Results show that the ultrasonic vibration direction can be transformed effectively using the special cross structure of vibration converter,and better vibration homogeneity can be obtained.RUVAG has a smaller tangential grinding force by 5.0%–17.2%than that of CG,but a higher normal grinding force of 6.5%–14.9%,owing to the periodic impact of grinding wheels.In addition,RUVAG possesses a remarkable lower grinding temperature in range of 24.2%–51.8%and a higher material removal rate by 2.8 times compared with CG,resulting from the intermittent cutting behavior between the grinding wheel and workpiece.In this case,the sudden burn can be avoided during high-speed grinding processes.Moreover,the proportion of micro-fracture defects on machined surface is slightly increased once the ultrasonic vibration mode is employed because of the periodic impact on reinforced particles,whereas the pull-out defects of reinforced particles are reduced significantly.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
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Dry sliding wear behaviour of stir-cast aluminium matrix composites(AMCs)containing LM13 alloy as matrix and ceramic particles as reinforcement was investigated.Two different ceramic particle reinforcements were used separately:synthetic ceramic particles(B_(4)C),and natural ceramic particles(ilmenite).Optical micrographs showed uniform dispersion of reinforced particles in the matrix material.Reinforced particles refined the grain size of eutectic silicon and changed its morphology to globular type.B_(4)C reinforced composites(BRCs)showed maximum improvement in hardness of AMCs.Ilmenite reinforced composites(IRCs)showed maximum reduction in coefficient of friction values due to strong matrix−reinforcement interfacial bonding caused by the formation of interfacial compounds.Dry sliding wear behaviour of composites was significantly improved as compared to base alloy.The low density and high hardness of B_(4)C particles resulted in high dislocation density around filler particles in BRCs.On the other hand,the low thermal conductivity of ilmenite particles resulted in early oxidation and formation of a tribo-layer on surface of IRCs.So,both types of reinforcements led to the improvement in wear properties of AMCs,though the mechanisms involved were very different.Thus,the low-cost ilmenite particles can be used as alternative fillers to the high-cost B_(4)C particles for processing of wear resistant composites.
基金financially supported by the Scientific Research Fund of Si Chuan Provincial Education Department(No.17ZA0395)the Doctoral Program Foundation of Southwest University of Science and Technology(No.10zx7113)
文摘The alumina toughened zirconia(ATZ) ceramic particle reinforced gray iron matrix surface composite was successfully manufactured by pressureless infi ltration. The porous preform played a key role in the infi ltrating progress. The microstructure was observed by scanning electron microscopy(SEM); the phase constitutions was analyzed by X-ray diffraction(XRD); and the hardness and wear resistance of selected specimens were tested by hardness testing machine and abrasion testing machine, respectively. The addition of high carbon ferrochromium powders leads to the formation of white iron during solidifi cation. The wear volume loss rates of ATZ ceramic particle reinforced gray iron matrix surface composite decreases fi rst, and then tends to be stable. The wear resistance of the composite is 2.7 times higher than that of gray iron matrix. The reason is a combination of the surface hardness increase of gray iron matrix and ATZ ceramic particles and alloy carbides protecting effect on gray iron matrix.
文摘The dry sliding wear behavior of AA6061 matrix composite reinforced with aluminium nitride particles（AlN） produced by stir casting process was investigated. A regression model was developed to predict the wear rate of the prepared composite. A four-factor, five-level central composite rotatable design matrix was used to minimize the number of experimental runs. The factors considered in this study were sliding velocity, sliding distance, normal load and mass fraction of AlN reinforcement in the matrix. The developed regression model was validated by statistical software SYSTAT 12 and statistical tools such as analysis of variance（ANOVA） and student＇s t test. It was found that the developed regression model could be effectively used to predict the wear rate at 95% confidence level. The influence of these factors on wear rate of AA6061/AlNp composite was analyzed using the developed regression model and predicted trends were discussed with the aid of worn surface morphologies. The regression model indicated that the wear rate of cast AA6061/AlNp composite decreased with an increase in the mass fraction of AlN and increased with an increase of the sliding velocity, sliding distance and normal load acting on the composite specimen.
基金Funded by the National Natural Science Foundation of China(51371077)
文摘Middle reinforcement content SiCp/Al composites（Vp=30%, 35% and 40%） for precision optical systems applications were fabricated by powder metallurgy technology. The composites were free of porosity and SiC particles distributed uniformly in the composites. The mean linear coefficients of thermal expansion（20-100 ℃） of SiCp/Al composites ranged from 11.6×10-6 to 13.3×10-6 K-1 and decreased with an increase in volume fraction of SiC content. The experimental coeffi cients of thermal expansion agreed well with predicted values based on Kerner＇s model. The Brinell hardness increased from 116 to 147, and the modulus increased from 99 to 112 GPa for the corresponding composites. The tensile strengths were higher than 320 MPa, but no signifi cant increasing trend between tensile strength and SiC content was observed.
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 Natural Science Foundation of China (Nos. 51921003, 92160301, 52175415 and 52205475)the Science Center for Gas Turbine Project (No. P2022-A-IV-002-001)+3 种基金the Natural Science Foundation of Jiangsu Province (No. BK20210295)the Superior Postdoctoral Project of Jiangsu Province (No. 2022ZB215)the Open Foundation State Key Laboratory of Mechanical Transmissions (No. SKLMT-MSKFKT-202101)the Special Projects for the Reengineering of Industrial Foundation and the High-quality Development of Manufacturing Industry (No. TC210H02X)
文摘Particle-reinforcing titanium matrix composites(PTMCs)exhibit the sharp raising applications in modern industries owing to its extraordinary physical and mechanical properties.However,the poor grindability and unstable grinding processes due to the existence of TiC particles and TiB short fibres inside PTMCs,leading to the sudden grinding burn and low material removal rate.In this work,a novel radial ultrasonic vibration-assisted grinding(RUVAG)device with a special cross structure was developed to improve machining efficiency and avoid grinding burns.Meanwhile,the resonant modal and transient dynamic characteristics of radial ultrasonic vibration system were discussed.Comparative grinding performance experiments were then conducted under the conventional grinding(CG)and RUVAG using mono-layer cubic boron nitride abrasive wheels,in views of the grinding forces and force ratio,grinding temperature,and ground surface morphology.Results show that the ultrasonic vibration direction can be transformed effectively using the special cross structure of vibration converter,and better vibration homogeneity can be obtained.RUVAG has a smaller tangential grinding force by 5.0%–17.2%than that of CG,but a higher normal grinding force of 6.5%–14.9%,owing to the periodic impact of grinding wheels.In addition,RUVAG possesses a remarkable lower grinding temperature in range of 24.2%–51.8%and a higher material removal rate by 2.8 times compared with CG,resulting from the intermittent cutting behavior between the grinding wheel and workpiece.In this case,the sudden burn can be avoided during high-speed grinding processes.Moreover,the proportion of micro-fracture defects on machined surface is slightly increased once the ultrasonic vibration mode is employed because of the periodic impact on reinforced particles,whereas the pull-out defects of reinforced particles are reduced significantly.
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.
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.
