Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal s...Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles.Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements,was favorable for the formation of in-situ synthesized carbide particles.In this paper,rare earth oxide(RE2O3) was added into t...展开更多
Higher-order multiscale structures are proposed to predict the effective elastic properties of 3-phase particle reinforced composites by considering the probabilistic spherical particles spatial distribution,the parti...Higher-order multiscale structures are proposed to predict the effective elastic properties of 3-phase particle reinforced composites by considering the probabilistic spherical particles spatial distribution,the particle interactions,and utilizing homogenization with ensemble volume average approach.The matrix material,spherical particles with radius a1,and spherical particles with radius a2,are denoted as the 0th phase,the 1st phase,and the 2nd phase,respectively.Particularly,the two inhomogeneity phases are different particle sizes and the same elastic material properties.Improved higher-order(in ratio of spherical particle sizes to the distance between the centers of spherical particles)bounds on effective elastic properties of 3-phase particle reinforced proposed Formulation II and Formulation I derive composites.As a special case,i.e.,particle size of the 1st phase is the same as that of the 2nd phase,the proposed formulations reduce to 2-phase formulas.Our theoretical predictions demonstrate excellent agreement with selected experimental data.In addition,several numerical examples are presented to demonstrate the competence of the proposed frameworks.展开更多
Effects of diffusion welding process parameters on strength of welded joint based on particle reinforced aluminium matrix composite Al 2O 3p /6061Al have been studied through comparing with aluminium matrix allo...Effects of diffusion welding process parameters on strength of welded joint based on particle reinforced aluminium matrix composite Al 2O 3p /6061Al have been studied through comparing with aluminium matrix alloy. The mechanism for loss of joint strength has been analyzed. It should be pointed out that key processing parameters affecting the strength of joint was welding temperature. The high quality joint can be successfully obtained with appropriate diffusion welding parameters.展开更多
The mechanisms of interfacial debonding of particle reinforcedrheological materials are studied. Based on an energy criterion, asimple formula of local critical stress for interfacial debonding isderived and expressed...The mechanisms of interfacial debonding of particle reinforcedrheological materials are studied. Based on an energy criterion, asimple formula of local critical stress for interfacial debonding isderived and expressed in terms of the interfacial energy. Theparticle size effect on interface debond- ing can then be analyzedeasily owing to the fact that critical stress is inverselyproportional to the square root of particle radius. By takingPP/CaCO_3 system as an example, the present energy criterion iscompared with the mechanical debonding criterion, and it is foundthat under the condition that bond strength is equal to matrixstrength and particle radius not over 0.2μm, the mechanicaldebonding cri- terion can be automatically satisfied if the energycirterion is satisfied.展开更多
This paper provides a comprehensive review of research progress in particle-reinforced Mg matrix composites prepared via powder metallurgy.The article discusses different strategies,such as micro-sized,nano-sized part...This paper provides a comprehensive review of research progress in particle-reinforced Mg matrix composites prepared via powder metallurgy.The article discusses different strategies,such as micro-sized,nano-sized particles,and multi-particle hybridization,which has been employed to enhance the performance of the composites.In addition,a range of preparation techniques that optimize the dispersion of the reinforcing particles are summarized.The paper also highlights how the different configurations between the reinforcements and matrix alloy impact the composites’performance.Finally,the article outlines the prospects of particles reinforced Mg matrix composites fabricated via powder metallurgy and recommends modification methods that could be explored to further develop these materials for various applications.展开更多
Tungsten(W)particle-reinforced nickel(Ni)-based composites were fabricated via laser-direct energy de-position(L-DED).The influence of the W particle size on the microstructure and mechanical properties of the deposit...Tungsten(W)particle-reinforced nickel(Ni)-based composites were fabricated via laser-direct energy de-position(L-DED).The influence of the W particle size on the microstructure and mechanical properties of the deposited samples was systematically studied.The results indicate that refining the W particle size could refine theγ-Ni grains and subgrains,thin the(Ni,Cr)_(4)W interface layer,and increase the disloca-tion density of the intergranular matrix,thus improving the tensile strength and elongation of the L-DED samples.As W particle size decreased from 75 to 150μm to 6.5-12μm,the tensile strength and elonga-tion of the deposited samples increased by 150 MPa and 2.9 times to 1347.6±15.7 MPa and 17.5±0.4%,respectively.Based on the properties of the interface(Ni,Cr)_(4)W,a load-transfer efficiency factor suitable for this composite was proposed and the load-transfer strengthening formula was optimized.A quanti-tative analysis of the strengthening mechanisms was established considering load-transfer strengthening,Hall-Petch strengthening,thermal-mismatch strengthening,and solid-solution strengthening.The calcu-lated contribution of each strengthening mechanism to the yield strength and theoretical calculations were in good agreement with the experimental data.The article breaks the bottleneck of poor plasticity of W particle-reinforced Ni-based composites prepared by L-DED and provides a theoretical basis for the construction design of W particle-reinforced Ni-based composites with excellent mechanical properties.展开更多
The fabrication of copper (Cu) and copper matrix silicon carbide (Cu/SiCp) particulate composites via the sinter-forging process was investigated. Sintering and sinter-forging processes were performed under an ine...The fabrication of copper (Cu) and copper matrix silicon carbide (Cu/SiCp) particulate composites via the sinter-forging process was investigated. Sintering and sinter-forging processes were performed under an inert Ar atmosphere. The influence of sinter-forging time, temperature, and compressive stress on the relative density and hardness of the prepared samples was systematically investigated and subsequently compared with that of the samples prepared by the conventional sintering process. The relative density and hardness of the composites were enhanced when they were prepared by the sinter-forging process. The relative density values of all Cu/SiCp composite samples were observed to decrease with the increase in SiC content.展开更多
This article focuses on the microstructural evolution and wear behavior of 50wt%WC reinforced Ni-based composites prepared onto 304 stainless steel substrates by vacuum sintering at different sintering temperatures. T...This article focuses on the microstructural evolution and wear behavior of 50wt%WC reinforced Ni-based composites prepared onto 304 stainless steel substrates by vacuum sintering at different sintering temperatures. The microstructure and chemical composition of the coatings were investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning and transmission electron microscopy (SEM and TEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The wear resistance of the coatings was tested by thrust washer testing. The mechanisms of the decomposition, dissolution, and precipitation of primary carbides, and their influences on the wear resistance have been discussed. The results indicate that the coating sintered at 1175℃ is composed of fine WC particles, coarse M6C (M=Ni, Fe, Co, etc.) carbides, and discrete borides dispersed in solid solution. Upon increasing the sintering temperature to 1225℃, the microstructure reveals few incompletely dissolved WC particles trapped in larger M6C, Cr-rich lamellar M23C6, and M3C2 in the austenite matrix. M23C6 and M3C2 precipitates are formed in both the γ/M6C grain boundary and the matrix. These large-sized and lamellar brittle phases tend to weaken the wear resistance of the composite coatings. The wear behavior is controlled simultaneously by both abrasive wear and adhesive wear. Among them, abrasive wear plays a major role in the wear process of the coating sintered at 1175℃, while the effect of adhesive wear is predominant in the coating sintered at 1225℃.展开更多
Pure Cu composites reinforced with diamond particles were fabricated by a high pressure and high temperature (HPHT) infiltration technique. Their microstructural evolution and thermal conductivity were presented as ...Pure Cu composites reinforced with diamond particles were fabricated by a high pressure and high temperature (HPHT) infiltration technique. Their microstructural evolution and thermal conductivity were presented as a function of sintering parameters (temperature, pressure, and time). The improvement in interfacial bonding strength and the maximum thermM conductivity of 750 W/(m.K) were achieved at the optimal sintering parameters of 1200℃, 6 GPa and 10 min. It is found that the thermal conductivity of the composites depends strongly on sintering pressure. When the sintering pressure is above 6 GPa, the diamond skeleton is detected, which greatly contributes to the excellent thermal conductivity.展开更多
The 6351 wrought aluminum alloy and K2TiF6-CaF2-LiCl components were selected as raw materials to fabricate in situ Al3Ti particulate reinforced aluminum alloy at 720℃via direct melt reaction method with electromagne...The 6351 wrought aluminum alloy and K2TiF6-CaF2-LiCl components were selected as raw materials to fabricate in situ Al3Ti particulate reinforced aluminum alloy at 720℃via direct melt reaction method with electromagnetic stirring(EMS).CaF2 and LiCl acted as fluxes to lower the reaction temperature of the system.It is shown that the electromagnetic stirring and fluxes accelerate the emulsion process of K2TiF6.Optical microscopy,scanning electron microscopy,transmission electron microscopy and energy dispersive spectrum were utilized to analyze the microstructure and components of composites.Compared to composites fabricated without EMS and fluxes,the sizes of endogenetic Al3Ti are refined from 10-15μm to 2-4μm,which are often accompanied with silicon element.The morphology of Al3Ti or Al3TiSi0.22 exhibits triangle,quadrilateral and other clumpy patterns. Because of the Ca elements from CaF2,the sizes of Mg2Si decrease from 8-10μm to 1-2μm due to the formation of Ca2Si.展开更多
A mixture of NiCrSiB alloy powder and tantalum (Ta) powder was used as laser clad material to improve abrasive wear resistance of the Ni-based coating. The microstructure and wear resistance of the coating were inve...A mixture of NiCrSiB alloy powder and tantalum (Ta) powder was used as laser clad material to improve abrasive wear resistance of the Ni-based coating. The microstructure and wear resistance of the coating were investigated. Addition of Ta element works to suppress the growth of coarse M7C3 carbide in the coating, resulting in a decrease in aspect ratio of coarse carbide. In the abrasive wear test, in situ synthesized TaC particles well bond with Ni-based matrix, and are hardly pull out from wear surface. Grooves on the worn surface of NiCrSiB coating are much deeper and sharper than those in the NiCrSiB+Ta composite coating. Also, a weight loss of the composite coating is much lower than that of the NiCrSiB coating. The wear resistance of the laser clad Ni-based coating is enhanced to a much greater extent through the addition of Ta. This is attributed to the in situ synthesized hard TaC particles of nearly equiaxed shape, the Ni-based matrix strengthened by Ta and the decrease in aspect ratio of the coarse brittle carbides.展开更多
Particulate reinforced metallic matrix composites have attracted considerable attention due to their lightweight, high strength, high specific modulus, and good wear resistance. A1/B4C composite strips were produced i...Particulate reinforced metallic matrix composites have attracted considerable attention due to their lightweight, high strength, high specific modulus, and good wear resistance. A1/B4C composite strips were produced in this work by a modified accumulative roll bonding process where the strips were rotated 90° around the normal direction between successive passes. Transmission electron microscopy and X-ray diffraction analyses reveal the development of nanostructures in the Al matrix after seven passes. It is found that the B4C reinforcement distribution in the matrix is improved by progression of the process. Additionally, the tensile yield strength and elongation of the processed materials are increased with the increase of passes.展开更多
The key factor in semi-solid metal processing is the solid fraction at the forming temperature because it affects the microstructure and mechanical properties of the thixoformed components. Though an enormous amount o...The key factor in semi-solid metal processing is the solid fraction at the forming temperature because it affects the microstructure and mechanical properties of the thixoformed components. Though an enormous amount of data exists on the solid fraction-temperature re- lationship in A356 alloy, information regarding the solid fraction evolution characteristics of A356-TiB2 composites is scarce. The present article establishes the temperature-solid fraction correlation in A356 alloy and A356-xTiB2 (x = 2.5wt% and 5wt%) composites using dif- ferential thermal analysis (DTA). The DTA results indicate that the solidification characteristics of the composites exhibited a variation of 2℃ and 3℃ in liquidus temperatures and a variation of 3℃ and 5℃ in solidus temperatures with respect to the base alloy. Moreover, the eutectic growth temperature and the solid fraction(fs) vs. temperature characteristics of the composites were found to be higher than those of the base alloy. The investigation revealed that in-situ formed TiB2 particles in the molten metal introduced more nucleation sites and reduced undercooling.展开更多
Effects of diffusion welding parameters on strength of welded joint based on particle reinforced alumini- um matrix composite Al2O3p/6061Al were studied by comparing with aluminium matrix alloy,Mecha- nism for ...Effects of diffusion welding parameters on strength of welded joint based on particle reinforced alumini- um matrix composite Al2O3p/6061Al were studied by comparing with aluminium matrix alloy,Mecha- nism for the loss of joint strength was analyzed.It was pointed out that the key processing parameters affecting the strength of joint was the welding temperature.The high quality joint can be successfully obtained with appropriate diffusion welding parameters.展开更多
The distribution of stress and strain fields in a micro-structuralarea of a particle reinforced composite is studied by a combinationof experimental and numerical method (hybrid method). With the ex-perimental values ...The distribution of stress and strain fields in a micro-structuralarea of a particle reinforced composite is studied by a combinationof experimental and numerical method (hybrid method). With the ex-perimental values of displacements in a micro-region as the boundaryloading condition, strain and stress fields inside the micro-regionare calculated by the finite element method under tow different kindsof model- ing, namely, as pale stress and plane strain condition. Thedifferences between the two kinds of modeling conditions as appliedto micro-structural areas are discussed.展开更多
We introduce an improved bond-based peridynamic(BPD)model for simulating brittle fracture in particle reinforced composites based on a micromodulus correction approach.In the peridynamic(PD)constitutive model of parti...We introduce an improved bond-based peridynamic(BPD)model for simulating brittle fracture in particle reinforced composites based on a micromodulus correction approach.In the peridynamic(PD)constitutive model of particle reinforced composites,three kinds of interactive bond forces are considered,and precise definition of mechanical properties for PD bonds is essential for the fracture analysis in particle reinforced composites.A new micromodulus model of PD bonds for particle reinforced composites is proposed based on the equivalence between the elastic strain energy density of classical continuum mechanics and peridynamic model and the harmonic average approach.The damage of particle reinforced composites is defined locally at the level of pairwise bond,and the critical stretch criterion is described as a function of fracture energy based on the composite failure theory.The algorithm procedure for the improved BPD model based on the finite element/discontinuous Galerkin finite element method is brought forward in detail.Several numerical examples are performed to test the feasibility and effectiveness of the proposed model and algorithm in analysis of elastic deformation,crack nucleation and propagation in particle reinforced composites.Additionally,the impact of distribution,shape and size of particles on the fractures of composite materials are also investigated.Numerical results demonstrate that the improved BPD model can effectively be used to analyze the fracture in particle reinforced composites.展开更多
In order to improve the mechanical properties of MGH956 alloy fusion weZding joint, two kinds of self-made materials were used as filler materials to MGH956 alloy for TIG welding respectively. Microstracture and tensi...In order to improve the mechanical properties of MGH956 alloy fusion weZding joint, two kinds of self-made materials were used as filler materials to MGH956 alloy for TIG welding respectively. Microstracture and tensile fracture of joints were researched by scanning electron microscope(SEM). Reinforced particles were researched by SEM, X-ray diffraction ( XRD ) and energy dispersive X-ray spectrometry (EDS). These results were compared with joint which is filled with base materials. The results show that new reinforced phases such as TiC, TiN, Ni3Al and A1Ni are produced in the weld metal zone with two kinds of self-made materials as filler materials. The size of these reinforcements is about 1 μm, and the distribution of particles is very uniform in the matrix. The number of pores is reduced. Agglomerate Al-Y-O composite oxides are correspondingly decreased compared to the joint filled with base material. Thus, welded joint perormanee is enhanced. The average room temperature tensile strength of joints are 581 MPa and 607 MPa respectively. The fracture of joints both in general exhibit brittle fracture.展开更多
The characterization of reinforcement in 15% SiC particles reinforced AI matrix composites processed by powder metallurgy route was studied by statistical method. During the analysis, a new approach for the estimation...The characterization of reinforcement in 15% SiC particles reinforced AI matrix composites processed by powder metallurgy route was studied by statistical method. During the analysis, a new approach for the estimation of the characterization of reinforcement was presented. The mathematic software MATLAB was used to calculate the area and perimeter of reinforcement, in which the image processing technique was applied. Based on the calculation, the fractal dimension, shape factor, reinforcement size distribution and reinforcement distribution were investigated. The results show that the reinforcement shape is similar to rectangle; the reinforcement size distribution is broad with the' range of 1-12 μm; the topography of reinforcement is smooth; and the reinforcement distribution is inhomogeneous. Furthermore, the cell model based on the statistical characterization was established and tested.展开更多
Al_(2)O_(3) particles reinforced hypereutectic Al-Si composites were prepared by in situ Fe_(2)O_(3)/Al reaction system.The thermodynamic analysis and microstructure evolution were investigated by differential scannin...Al_(2)O_(3) particles reinforced hypereutectic Al-Si composites were prepared by in situ Fe_(2)O_(3)/Al reaction system.The thermodynamic analysis and microstructure evolution were investigated by differential scanning calorimetry,optical microscope,scanning electronic microscopy and transmission electron microscope.Results show that the reaction between Fe_(2)O_(3) and Al is spontaneous which can be separated into two steps at different temperatures.The in situ Al_(2)O_(3) particles in nano size distribute on the Al matrix accompanied with long needle-shapedβFe-rich intermetallic phase.With different content of Mn addition,βphase can be modified toα-Al15(Mn,Fe)3Si2 andδ-Al4(Fe,Mn)Si2.Both tensile strength and elongation results at room temperature and 300℃reveal that the optimal Fe-rich intermetallic phase is finer Chinese-script and polyhedralαphase with a Mn/Fe mass ratio 0.5 for the composites.Both in situ Al_(2)O_(3) particles andα-Fe phases contribute to the properties improvement of the composites。展开更多
The Ti_(p)/ZX60 composites with different Ti_(p) contents were prepared by semi-solid stirring casting.After extrusion,the microstructure,work hardening and softening behavior of the Ti_(p)/ZX60 composites were analyz...The Ti_(p)/ZX60 composites with different Ti_(p) contents were prepared by semi-solid stirring casting.After extrusion,the microstructure,work hardening and softening behavior of the Ti_(p)/ZX60 composites were analyzed compared with the ZX60(Mg-6Zn-0.2Ca)alloy.The results showed that the addition of Ti_(p) could not only promote the nucleation of dynamic recrystallized(DRXed)grains,but also be propitious to the refinement of DRXed grains.With increasing Ti_(p) content,the size of DRXed grains decreased accompanied with increasing volume fraction of DRXed grains.As the Ti_(p) content increased to 15 vol.%,the average size and volume fraction of DRXed grains reached to~0.32μm and 93.2%,respectively.Besides,both the strength and elongation were improved by the addition of Ti_(p).With increasing content of Ti_(p),a substantial increase in the strength was achieved with little change in the elongation.However,the elongation decreased sharply when the Ti_(p) content further increased to 15 vol.%.The addition of Ti_(p) led to an increase in the work hardening rate,which gradually increased with increasing Ti_(p) content.However,the softening rate did not demonstrate the same tendency with increasing Ti_(p) content.Unlike the conventional ceramic particles,the Ti_(p) can be deformed in coordination with the matrix alloy,which imparted a higher softening rate to the matrix alloy.Even though the softening rate improved as the Ti_(p) content increased from 5 to 10 vol.%,it dropped deeply as the Ti_(p) content increased to 15 vol.%owing to the fracture of Ti_(p) during extrusion.展开更多
文摘Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles.Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements,was favorable for the formation of in-situ synthesized carbide particles.In this paper,rare earth oxide(RE2O3) was added into t...
基金This work was in part sponsored by the 2015-2016 California State University Long Beach Research,Scholarship and Creative Activity(RSCA)Award。
文摘Higher-order multiscale structures are proposed to predict the effective elastic properties of 3-phase particle reinforced composites by considering the probabilistic spherical particles spatial distribution,the particle interactions,and utilizing homogenization with ensemble volume average approach.The matrix material,spherical particles with radius a1,and spherical particles with radius a2,are denoted as the 0th phase,the 1st phase,and the 2nd phase,respectively.Particularly,the two inhomogeneity phases are different particle sizes and the same elastic material properties.Improved higher-order(in ratio of spherical particle sizes to the distance between the centers of spherical particles)bounds on effective elastic properties of 3-phase particle reinforced proposed Formulation II and Formulation I derive composites.As a special case,i.e.,particle size of the 1st phase is the same as that of the 2nd phase,the proposed formulations reduce to 2-phase formulas.Our theoretical predictions demonstrate excellent agreement with selected experimental data.In addition,several numerical examples are presented to demonstrate the competence of the proposed frameworks.
文摘Effects of diffusion welding process parameters on strength of welded joint based on particle reinforced aluminium matrix composite Al 2O 3p /6061Al have been studied through comparing with aluminium matrix alloy. The mechanism for loss of joint strength has been analyzed. It should be pointed out that key processing parameters affecting the strength of joint was welding temperature. The high quality joint can be successfully obtained with appropriate diffusion welding parameters.
基金the Nationai Natural Science Foundation of China(19632030 and 19872007)Natural Science Foundation of Jiangsu Province
文摘The mechanisms of interfacial debonding of particle reinforcedrheological materials are studied. Based on an energy criterion, asimple formula of local critical stress for interfacial debonding isderived and expressed in terms of the interfacial energy. Theparticle size effect on interface debond- ing can then be analyzedeasily owing to the fact that critical stress is inverselyproportional to the square root of particle radius. By takingPP/CaCO_3 system as an example, the present energy criterion iscompared with the mechanical debonding criterion, and it is foundthat under the condition that bond strength is equal to matrixstrength and particle radius not over 0.2μm, the mechanicaldebonding cri- terion can be automatically satisfied if the energycirterion is satisfied.
基金supports of the National Natural Science Foundation of China (Nos.U2241231 and 51631006).
文摘This paper provides a comprehensive review of research progress in particle-reinforced Mg matrix composites prepared via powder metallurgy.The article discusses different strategies,such as micro-sized,nano-sized particles,and multi-particle hybridization,which has been employed to enhance the performance of the composites.In addition,a range of preparation techniques that optimize the dispersion of the reinforcing particles are summarized.The paper also highlights how the different configurations between the reinforcements and matrix alloy impact the composites’performance.Finally,the article outlines the prospects of particles reinforced Mg matrix composites fabricated via powder metallurgy and recommends modification methods that could be explored to further develop these materials for various applications.
基金supported by the Key Projects of the National Natural Science Foundation of China(Nos.92066201 and 92266101)the Jiangxi Provincial Key R&D Programme Projects(No.20212BBE51011).
文摘Tungsten(W)particle-reinforced nickel(Ni)-based composites were fabricated via laser-direct energy de-position(L-DED).The influence of the W particle size on the microstructure and mechanical properties of the deposited samples was systematically studied.The results indicate that refining the W particle size could refine theγ-Ni grains and subgrains,thin the(Ni,Cr)_(4)W interface layer,and increase the disloca-tion density of the intergranular matrix,thus improving the tensile strength and elongation of the L-DED samples.As W particle size decreased from 75 to 150μm to 6.5-12μm,the tensile strength and elonga-tion of the deposited samples increased by 150 MPa and 2.9 times to 1347.6±15.7 MPa and 17.5±0.4%,respectively.Based on the properties of the interface(Ni,Cr)_(4)W,a load-transfer efficiency factor suitable for this composite was proposed and the load-transfer strengthening formula was optimized.A quanti-tative analysis of the strengthening mechanisms was established considering load-transfer strengthening,Hall-Petch strengthening,thermal-mismatch strengthening,and solid-solution strengthening.The calcu-lated contribution of each strengthening mechanism to the yield strength and theoretical calculations were in good agreement with the experimental data.The article breaks the bottleneck of poor plasticity of W particle-reinforced Ni-based composites prepared by L-DED and provides a theoretical basis for the construction design of W particle-reinforced Ni-based composites with excellent mechanical properties.
文摘The fabrication of copper (Cu) and copper matrix silicon carbide (Cu/SiCp) particulate composites via the sinter-forging process was investigated. Sintering and sinter-forging processes were performed under an inert Ar atmosphere. The influence of sinter-forging time, temperature, and compressive stress on the relative density and hardness of the prepared samples was systematically investigated and subsequently compared with that of the samples prepared by the conventional sintering process. The relative density and hardness of the composites were enhanced when they were prepared by the sinter-forging process. The relative density values of all Cu/SiCp composite samples were observed to decrease with the increase in SiC content.
基金financial support of the Program for Changjiang Scholars and Innovative Research Team (PCSIRT) in Chinese Universities (No. IRT1146)
文摘This article focuses on the microstructural evolution and wear behavior of 50wt%WC reinforced Ni-based composites prepared onto 304 stainless steel substrates by vacuum sintering at different sintering temperatures. The microstructure and chemical composition of the coatings were investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning and transmission electron microscopy (SEM and TEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The wear resistance of the coatings was tested by thrust washer testing. The mechanisms of the decomposition, dissolution, and precipitation of primary carbides, and their influences on the wear resistance have been discussed. The results indicate that the coating sintered at 1175℃ is composed of fine WC particles, coarse M6C (M=Ni, Fe, Co, etc.) carbides, and discrete borides dispersed in solid solution. Upon increasing the sintering temperature to 1225℃, the microstructure reveals few incompletely dissolved WC particles trapped in larger M6C, Cr-rich lamellar M23C6, and M3C2 in the austenite matrix. M23C6 and M3C2 precipitates are formed in both the γ/M6C grain boundary and the matrix. These large-sized and lamellar brittle phases tend to weaken the wear resistance of the composite coatings. The wear behavior is controlled simultaneously by both abrasive wear and adhesive wear. Among them, abrasive wear plays a major role in the wear process of the coating sintered at 1175℃, while the effect of adhesive wear is predominant in the coating sintered at 1225℃.
基金supported by the National Natural Science Foundation of China (No. 50971020)the National High-Tech Research and Development Program of China (No. 2008AA03Z505)
文摘Pure Cu composites reinforced with diamond particles were fabricated by a high pressure and high temperature (HPHT) infiltration technique. Their microstructural evolution and thermal conductivity were presented as a function of sintering parameters (temperature, pressure, and time). The improvement in interfacial bonding strength and the maximum thermM conductivity of 750 W/(m.K) were achieved at the optimal sintering parameters of 1200℃, 6 GPa and 10 min. It is found that the thermal conductivity of the composites depends strongly on sintering pressure. When the sintering pressure is above 6 GPa, the diamond skeleton is detected, which greatly contributes to the excellent thermal conductivity.
基金Project(2007AA03Z548)supported by the National High-Tech Research and Development Program of ChinaProject(207038)supported by the Key Program of Ministry of Education of China+3 种基金Project(06-D-021)supported by the Talents Peak in Six Key Fields of Jiangsu Province in ChinaProject(07JDG084)supported by the Technical Enablement Foundation for the Super Special Talents of Jiangsu UniversityProject(20071108)supported by the Technical Enablement Foundation of Ministry of Education for the Returned ScholarsProject(20060299006)supported by the PhD Programs Foundation of Ministry of Education of China
文摘The 6351 wrought aluminum alloy and K2TiF6-CaF2-LiCl components were selected as raw materials to fabricate in situ Al3Ti particulate reinforced aluminum alloy at 720℃via direct melt reaction method with electromagnetic stirring(EMS).CaF2 and LiCl acted as fluxes to lower the reaction temperature of the system.It is shown that the electromagnetic stirring and fluxes accelerate the emulsion process of K2TiF6.Optical microscopy,scanning electron microscopy,transmission electron microscopy and energy dispersive spectrum were utilized to analyze the microstructure and components of composites.Compared to composites fabricated without EMS and fluxes,the sizes of endogenetic Al3Ti are refined from 10-15μm to 2-4μm,which are often accompanied with silicon element.The morphology of Al3Ti or Al3TiSi0.22 exhibits triangle,quadrilateral and other clumpy patterns. Because of the Ca elements from CaF2,the sizes of Mg2Si decrease from 8-10μm to 1-2μm due to the formation of Ca2Si.
基金Funded by the National Natural Science Foundation of China(Nos. 50675136 and 50375096)the Scholastic Foundation of Nanchang University (Nos. Z02887 and 06300971)
文摘A mixture of NiCrSiB alloy powder and tantalum (Ta) powder was used as laser clad material to improve abrasive wear resistance of the Ni-based coating. The microstructure and wear resistance of the coating were investigated. Addition of Ta element works to suppress the growth of coarse M7C3 carbide in the coating, resulting in a decrease in aspect ratio of coarse carbide. In the abrasive wear test, in situ synthesized TaC particles well bond with Ni-based matrix, and are hardly pull out from wear surface. Grooves on the worn surface of NiCrSiB coating are much deeper and sharper than those in the NiCrSiB+Ta composite coating. Also, a weight loss of the composite coating is much lower than that of the NiCrSiB coating. The wear resistance of the laser clad Ni-based coating is enhanced to a much greater extent through the addition of Ta. This is attributed to the in situ synthesized hard TaC particles of nearly equiaxed shape, the Ni-based matrix strengthened by Ta and the decrease in aspect ratio of the coarse brittle carbides.
文摘Particulate reinforced metallic matrix composites have attracted considerable attention due to their lightweight, high strength, high specific modulus, and good wear resistance. A1/B4C composite strips were produced in this work by a modified accumulative roll bonding process where the strips were rotated 90° around the normal direction between successive passes. Transmission electron microscopy and X-ray diffraction analyses reveal the development of nanostructures in the Al matrix after seven passes. It is found that the B4C reinforcement distribution in the matrix is improved by progression of the process. Additionally, the tensile yield strength and elongation of the processed materials are increased with the increase of passes.
基金financial support from the Indian Institute of Technology Bhubaneswar under the SEED project grant for fabricating the "cooling slope casting" experimental setupthe support extended by Central Research Facility (CRF), Indian Institute of Technology Kharagpur, toward the facility for conducting DTA experiments
文摘The key factor in semi-solid metal processing is the solid fraction at the forming temperature because it affects the microstructure and mechanical properties of the thixoformed components. Though an enormous amount of data exists on the solid fraction-temperature re- lationship in A356 alloy, information regarding the solid fraction evolution characteristics of A356-TiB2 composites is scarce. The present article establishes the temperature-solid fraction correlation in A356 alloy and A356-xTiB2 (x = 2.5wt% and 5wt%) composites using dif- ferential thermal analysis (DTA). The DTA results indicate that the solidification characteristics of the composites exhibited a variation of 2℃ and 3℃ in liquidus temperatures and a variation of 3℃ and 5℃ in solidus temperatures with respect to the base alloy. Moreover, the eutectic growth temperature and the solid fraction(fs) vs. temperature characteristics of the composites were found to be higher than those of the base alloy. The investigation revealed that in-situ formed TiB2 particles in the molten metal introduced more nucleation sites and reduced undercooling.
文摘Effects of diffusion welding parameters on strength of welded joint based on particle reinforced alumini- um matrix composite Al2O3p/6061Al were studied by comparing with aluminium matrix alloy,Mecha- nism for the loss of joint strength was analyzed.It was pointed out that the key processing parameters affecting the strength of joint was the welding temperature.The high quality joint can be successfully obtained with appropriate diffusion welding parameters.
基金the National Natural Science Foundation of China(19972046)National Overseas Study Foundation
文摘The distribution of stress and strain fields in a micro-structuralarea of a particle reinforced composite is studied by a combinationof experimental and numerical method (hybrid method). With the ex-perimental values of displacements in a micro-region as the boundaryloading condition, strain and stress fields inside the micro-regionare calculated by the finite element method under tow different kindsof model- ing, namely, as pale stress and plane strain condition. Thedifferences between the two kinds of modeling conditions as appliedto micro-structural areas are discussed.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDC06030102)the Aeronautical Science Foundation of China(2020001053002)+1 种基金the National Key R&D Program of China(2020YFA0713603)National Natural Science Foundation of China(11872016,51739007).
文摘We introduce an improved bond-based peridynamic(BPD)model for simulating brittle fracture in particle reinforced composites based on a micromodulus correction approach.In the peridynamic(PD)constitutive model of particle reinforced composites,three kinds of interactive bond forces are considered,and precise definition of mechanical properties for PD bonds is essential for the fracture analysis in particle reinforced composites.A new micromodulus model of PD bonds for particle reinforced composites is proposed based on the equivalence between the elastic strain energy density of classical continuum mechanics and peridynamic model and the harmonic average approach.The damage of particle reinforced composites is defined locally at the level of pairwise bond,and the critical stretch criterion is described as a function of fracture energy based on the composite failure theory.The algorithm procedure for the improved BPD model based on the finite element/discontinuous Galerkin finite element method is brought forward in detail.Several numerical examples are performed to test the feasibility and effectiveness of the proposed model and algorithm in analysis of elastic deformation,crack nucleation and propagation in particle reinforced composites.Additionally,the impact of distribution,shape and size of particles on the fractures of composite materials are also investigated.Numerical results demonstrate that the improved BPD model can effectively be used to analyze the fracture in particle reinforced composites.
文摘In order to improve the mechanical properties of MGH956 alloy fusion weZding joint, two kinds of self-made materials were used as filler materials to MGH956 alloy for TIG welding respectively. Microstracture and tensile fracture of joints were researched by scanning electron microscope(SEM). Reinforced particles were researched by SEM, X-ray diffraction ( XRD ) and energy dispersive X-ray spectrometry (EDS). These results were compared with joint which is filled with base materials. The results show that new reinforced phases such as TiC, TiN, Ni3Al and A1Ni are produced in the weld metal zone with two kinds of self-made materials as filler materials. The size of these reinforcements is about 1 μm, and the distribution of particles is very uniform in the matrix. The number of pores is reduced. Agglomerate Al-Y-O composite oxides are correspondingly decreased compared to the joint filled with base material. Thus, welded joint perormanee is enhanced. The average room temperature tensile strength of joints are 581 MPa and 607 MPa respectively. The fracture of joints both in general exhibit brittle fracture.
文摘The characterization of reinforcement in 15% SiC particles reinforced AI matrix composites processed by powder metallurgy route was studied by statistical method. During the analysis, a new approach for the estimation of the characterization of reinforcement was presented. The mathematic software MATLAB was used to calculate the area and perimeter of reinforcement, in which the image processing technique was applied. Based on the calculation, the fractal dimension, shape factor, reinforcement size distribution and reinforcement distribution were investigated. The results show that the reinforcement shape is similar to rectangle; the reinforcement size distribution is broad with the' range of 1-12 μm; the topography of reinforcement is smooth; and the reinforcement distribution is inhomogeneous. Furthermore, the cell model based on the statistical characterization was established and tested.
基金Funded by the National Natural Science Foundation of China(No.51201071)the National Natural Science Foundation of Jiangsu Province(No.BK20161270)Jiangsu Overseas Visiting Scholar Program for University Prominent Young&Middle-aged Teachers and Presidents(2018)。
文摘Al_(2)O_(3) particles reinforced hypereutectic Al-Si composites were prepared by in situ Fe_(2)O_(3)/Al reaction system.The thermodynamic analysis and microstructure evolution were investigated by differential scanning calorimetry,optical microscope,scanning electronic microscopy and transmission electron microscope.Results show that the reaction between Fe_(2)O_(3) and Al is spontaneous which can be separated into two steps at different temperatures.The in situ Al_(2)O_(3) particles in nano size distribute on the Al matrix accompanied with long needle-shapedβFe-rich intermetallic phase.With different content of Mn addition,βphase can be modified toα-Al15(Mn,Fe)3Si2 andδ-Al4(Fe,Mn)Si2.Both tensile strength and elongation results at room temperature and 300℃reveal that the optimal Fe-rich intermetallic phase is finer Chinese-script and polyhedralαphase with a Mn/Fe mass ratio 0.5 for the composites.Both in situ Al_(2)O_(3) particles andα-Fe phases contribute to the properties improvement of the composites。
基金supported financially by the National Natural Science Foundation of China (Nos.52271109 and 52001223)the authors also thank the Support from the"the National Key Research and Development Program for Young Scientists" (No.2021YFB3703300)the Special Fund Project for Guiding Local Science and Technology Development by the Central Government (No.YDZJSX2021B019).
文摘The Ti_(p)/ZX60 composites with different Ti_(p) contents were prepared by semi-solid stirring casting.After extrusion,the microstructure,work hardening and softening behavior of the Ti_(p)/ZX60 composites were analyzed compared with the ZX60(Mg-6Zn-0.2Ca)alloy.The results showed that the addition of Ti_(p) could not only promote the nucleation of dynamic recrystallized(DRXed)grains,but also be propitious to the refinement of DRXed grains.With increasing Ti_(p) content,the size of DRXed grains decreased accompanied with increasing volume fraction of DRXed grains.As the Ti_(p) content increased to 15 vol.%,the average size and volume fraction of DRXed grains reached to~0.32μm and 93.2%,respectively.Besides,both the strength and elongation were improved by the addition of Ti_(p).With increasing content of Ti_(p),a substantial increase in the strength was achieved with little change in the elongation.However,the elongation decreased sharply when the Ti_(p) content further increased to 15 vol.%.The addition of Ti_(p) led to an increase in the work hardening rate,which gradually increased with increasing Ti_(p) content.However,the softening rate did not demonstrate the same tendency with increasing Ti_(p) content.Unlike the conventional ceramic particles,the Ti_(p) can be deformed in coordination with the matrix alloy,which imparted a higher softening rate to the matrix alloy.Even though the softening rate improved as the Ti_(p) content increased from 5 to 10 vol.%,it dropped deeply as the Ti_(p) content increased to 15 vol.%owing to the fracture of Ti_(p) during extrusion.