Oxidation behavior of C/C-SiC gradient matrix composites and C/C composites were compared in stationary air. The results show that oxidation threshold of C-SiC materials increases with the amount of SiC particles in t...Oxidation behavior of C/C-SiC gradient matrix composites and C/C composites were compared in stationary air. The results show that oxidation threshold of C-SiC materials increases with the amount of SiC particles in the codeposition matrix. Oxidation rate of C/C-SiC gradient matrix composites is significantly lower than that of C/C material. The micro-oxidation process was observed by SEM.展开更多
The microstructure and rheological behavior of semi-solid Mg2Si/AM60 magnesium matrix composite at steady state were investigated.The results show that the primary α-Mg phases are knapped by mechanical stirring and t...The microstructure and rheological behavior of semi-solid Mg2Si/AM60 magnesium matrix composite at steady state were investigated.The results show that the primary α-Mg phases are knapped by mechanical stirring and the Chinese script type reinforced Mg2Si phases exist in liquid phase and grain boundary.The analysis of apparent viscosity indicates that the apparent viscosity of semi-solid Mg2Si/AM60 magnesium matrix composite at steady state increases with increasing the volume fraction of Mg2Si and solid fraction of primary α-Mg,but decreases with increasing the shearing rate and shearing time,and the apparent viscosity keeps stable when shearing time reaches 300 s.展开更多
The interfacial microstructure and tensile properties of the squeeze cast SiCw/AZ91 Mg composites were characterized. There exist uniform, line and discrete MgO particles at the interface between SiC whisker and magn...The interfacial microstructure and tensile properties of the squeeze cast SiCw/AZ91 Mg composites were characterized. There exist uniform, line and discrete MgO particles at the interface between SiC whisker and magnesium in the composites using acid aluminum phosphate binder. The interfacial reaction products MgO are beneficial to interfacial bonding between SiCw and the Mg matrix. resulting in an improvement of the mechanical properties of the composite.展开更多
In order to improve wear resistance and decrease the cost, carbon and carbon nanotubes reinforced copper matrix composites were fabricated by the power metallurgy method. The effects of carbon （carbon and carbon nano...In order to improve wear resistance and decrease the cost, carbon and carbon nanotubes reinforced copper matrix composites were fabricated by the power metallurgy method. The effects of carbon （carbon and carbon nanotubes） volume fraction and applied load on the friction coefficient and wear rate under dry sliding of the composites were investigated at room temperature. By scanning electron microscopy （SEM）, the worn surfaces and debris were observed, and wear mechanism was also analyzed and discussed. The experimental wear process consists of the run-in, steady wear and severe wear process with the increasing of sliding distance. Both the friction coefficient and wear rate of the composites first decrease and then increase with the increasing of carbon volume fraction. The minimum friction coefficient and wear rate are obtained when carbon is 4.0vo1%. The wear mechanisms of the composites change from the adhesive wear and delamination wear to abrasive wear with the increasing of carbon volume fraction.展开更多
Compression tests on semi-solid SiCp/AZ61 magnesium matrix composites were carried out using Thermecmastor-Z dynamic material testing machine.Influences of strain-rate,strain,temperature and volume fraction of SiC par...Compression tests on semi-solid SiCp/AZ61 magnesium matrix composites were carried out using Thermecmastor-Z dynamic material testing machine.Influences of strain-rate,strain,temperature and volume fraction of SiC particles on flow stress were analyzed.The results show that the flow stress of semi-solid SiCp/AZ61 composites is sensitive to temperature and strain rate.The lower the temperature and the larger the strain rate,the higher the flow stress.Meanwhile the flow stress increases with the increase of the volume fraction of SiC particles.This study helps establish the constitutive model of magnesium matrix composites and offers theoretic and experimental references for its thixoforming.展开更多
Using large strain two dimension axisymmetric elasto plastic finite element method and the modified law of mixture, the effects of thermal residual stresses on the yielding behavior of short fiber reinforced metal mat...Using large strain two dimension axisymmetric elasto plastic finite element method and the modified law of mixture, the effects of thermal residual stresses on the yielding behavior of short fiber reinforced metal matrix composite and their dependencies on the material structure parameters (fiber volume fraction, fiber aspect ratio and fiber end distance) were studied. It is demonstrated that the stress strain partition parameter can be used to describe the stress transfer from the matrix to the fiber. The variation of the second derivation of the stress strain partition parameter can be used to determine the elastic modulus, the proportion limit, the initial and final yield strengths. In the presence of thermal residual stress, these yielding properties are asymmetric and are influenced differently by the material structure parameters under tensile and compressive loadings.展开更多
Non-interlayer liquid phase diffusion welding (China Patent) and laser welding methods for aluminum matrix composite are mainly described in this paper. In the non-interlayer liquid phase diffusion welding, the key pr...Non-interlayer liquid phase diffusion welding (China Patent) and laser welding methods for aluminum matrix composite are mainly described in this paper. In the non-interlayer liquid phase diffusion welding, the key processing parameters affecting the strength of joint is welding temperature. When temperature rises beyond solidus temperature, the bonded line vanishes. The strength of joint reaches the maximum and becomes constant when welding temperature is close to liquid phase temperature. Oxide film in the interface is no longer detected by SEM in the welded joint. With this kind of technique, particle reinforced aluminum matrix composite Al2 O3p/6061Al is welded successfully, and the joint strength is about 80% of the strength of composite (as-casted). In the laser welding, results indicate that because of the huge specific surface area of the reinforcement, the interfacial reaction between the matrix and the reinforcement is restrained intensively at certain laser power and pulsed laser beam. The laser pulse frequency directly affects the reinforcement segregation and the reinforcement distribution in the weld, so that the weldability of the composite could be improved by increasing the laser pulse frequency. The maximum strength of the weld can reach 70% of the strength of the parent.展开更多
The superplastic deformation behavior of titanium alloy matrix composites reinforced with TiB and TiC was studied. Superplastic tension tests under conditions from 750℃ to 1100℃ and initial strain rates ranging from...The superplastic deformation behavior of titanium alloy matrix composites reinforced with TiB and TiC was studied. Superplastic tension tests under conditions from 750℃ to 1100℃ and initial strain rates ranging from 2×10^-2 s^-1 to 10^-4s^-1 were carried out. A maximum elongation of 659% was obtained. The micro-structural evolution was studied by means of optical microscopy （OM） and transmission electron microcopy （TEM）. The deformation mechanism and the effect of reinforcement on superplasticity are also discussed.展开更多
A multi-inclusion cell model is used to investigate the effect of deformation temperature and whisker rotation on the hot compressive behavior of metal matrix composites with misaligned whiskers. Numerical results sho...A multi-inclusion cell model is used to investigate the effect of deformation temperature and whisker rotation on the hot compressive behavior of metal matrix composites with misaligned whiskers. Numerical results show that deformation temperature influences the work-hardening behavior of the matrix and the rotation behavior of the whiskers. With increasing temperature, the work hardening rate of the matrix decreases, but the whisker rotation angle increases. Both whisker rotation and the increase of deformation temperature can induce reductions in the load supported by whisker and the load transferred from matrix to whisker. Additionally, it is found that during large strain deformation at higher temperatures, the enhancing of deformation temperature can reduce the effect of whisker rotation. Meanwhile, the stress-strain behavior of the composite is rather sensitive to deformation temperature. At a relatively lower temperature （150℃）, the composite exhibits work hardening due to the matrix work hardening, but at relatively higher temperatures （300℃ and above）, the composite shows strain softening due to whisker rotation. It is also found that during hot compression at higher temperatures, the softening rate of the composite decreases with increasing temperature. The predicted stress-strain behavior of the composite is approximately in agreement with the experimental results.展开更多
To develop a novel method predicting the viscoelastic behavior of polymer matrix composites according to the viscoelasticity of the matrix, we used the viscoelastic model of the matrix to build new models for unidirec...To develop a novel method predicting the viscoelastic behavior of polymer matrix composites according to the viscoelasticity of the matrix, we used the viscoelastic model of the matrix to build new models for unidirectional composites in both 0° and 90° directions. Viscoelastic parameters for both new models were derived, and the obtained equations shared the same form as the viscoelastic constitutive equation of matrix material. The viscoelastic behaviors of matrix material and unidirectional composites were also tested. Results showed that fitting parameters of creep compliance equation were close to the theoretical values of viscoelastic constitutive parameters of the unidirectional composites, proving the validity of the models. A new method was obtained to predict the viscoelastic property of the unidirectional composites based on the viscoelastic property of composite matrix and elastic property of the unidirectional composites. This method provides a theoretical basis for future studies on the viscoelasticity of composite laminates.展开更多
We studied the characteristics of two-scale pore structure of preform in the deposition process and the mass transfer of reactant gas in dual-scale pores, and observed the physiochemical phenomenon associated with the...We studied the characteristics of two-scale pore structure of preform in the deposition process and the mass transfer of reactant gas in dual-scale pores, and observed the physiochemical phenomenon associated with the reaction. Thereby, we established mathematical models on two scales, respectively, preform and reactor. These models were used for the numerical simulation of the process of ceramic matrix composites densified by isothermal chemical vapor infiltration(ICVI). The models were used to carry out a systematic study on the influence of process conditions and the preform structure on the densification behaviors. The most important findings of our study are that the processing time could be reduced by about 50% without compromising the quality of the material, if the processing temperature is 950-1 000 ℃ for the first 70 hours and then raised to 1 100 ℃.展开更多
文摘Oxidation behavior of C/C-SiC gradient matrix composites and C/C composites were compared in stationary air. The results show that oxidation threshold of C-SiC materials increases with the amount of SiC particles in the codeposition matrix. Oxidation rate of C/C-SiC gradient matrix composites is significantly lower than that of C/C material. The micro-oxidation process was observed by SEM.
基金Project(50765005) supported by the National Natural Science Foundation of Chinasupported by Key Laboratory of Ministry of Education for Conveyance and Equipment (East China Jiaotong University),China
文摘The microstructure and rheological behavior of semi-solid Mg2Si/AM60 magnesium matrix composite at steady state were investigated.The results show that the primary α-Mg phases are knapped by mechanical stirring and the Chinese script type reinforced Mg2Si phases exist in liquid phase and grain boundary.The analysis of apparent viscosity indicates that the apparent viscosity of semi-solid Mg2Si/AM60 magnesium matrix composite at steady state increases with increasing the volume fraction of Mg2Si and solid fraction of primary α-Mg,but decreases with increasing the shearing rate and shearing time,and the apparent viscosity keeps stable when shearing time reaches 300 s.
基金National Natllral S(tience l.'oundation of China (No. 59631080).
文摘The interfacial microstructure and tensile properties of the squeeze cast SiCw/AZ91 Mg composites were characterized. There exist uniform, line and discrete MgO particles at the interface between SiC whisker and magnesium in the composites using acid aluminum phosphate binder. The interfacial reaction products MgO are beneficial to interfacial bonding between SiCw and the Mg matrix. resulting in an improvement of the mechanical properties of the composite.
基金Funded by the National Natural Science Foundation of China (50873047)the Natural Science Foundation of Gansu Province (3ZS061-A25-039)
文摘In order to improve wear resistance and decrease the cost, carbon and carbon nanotubes reinforced copper matrix composites were fabricated by the power metallurgy method. The effects of carbon （carbon and carbon nanotubes） volume fraction and applied load on the friction coefficient and wear rate under dry sliding of the composites were investigated at room temperature. By scanning electron microscopy （SEM）, the worn surfaces and debris were observed, and wear mechanism was also analyzed and discussed. The experimental wear process consists of the run-in, steady wear and severe wear process with the increasing of sliding distance. Both the friction coefficient and wear rate of the composites first decrease and then increase with the increasing of carbon volume fraction. The minimum friction coefficient and wear rate are obtained when carbon is 4.0vo1%. The wear mechanisms of the composites change from the adhesive wear and delamination wear to abrasive wear with the increasing of carbon volume fraction.
基金Projects (50765005,50465003) supported by the National Natural Science Foundation of ChinaProject (S00875) supported by Innovative Group of Science and Technology of College of Jiangxi Province,China
文摘Compression tests on semi-solid SiCp/AZ61 magnesium matrix composites were carried out using Thermecmastor-Z dynamic material testing machine.Influences of strain-rate,strain,temperature and volume fraction of SiC particles on flow stress were analyzed.The results show that the flow stress of semi-solid SiCp/AZ61 composites is sensitive to temperature and strain rate.The lower the temperature and the larger the strain rate,the higher the flow stress.Meanwhile the flow stress increases with the increase of the volume fraction of SiC particles.This study helps establish the constitutive model of magnesium matrix composites and offers theoretic and experimental references for its thixoforming.
文摘Using large strain two dimension axisymmetric elasto plastic finite element method and the modified law of mixture, the effects of thermal residual stresses on the yielding behavior of short fiber reinforced metal matrix composite and their dependencies on the material structure parameters (fiber volume fraction, fiber aspect ratio and fiber end distance) were studied. It is demonstrated that the stress strain partition parameter can be used to describe the stress transfer from the matrix to the fiber. The variation of the second derivation of the stress strain partition parameter can be used to determine the elastic modulus, the proportion limit, the initial and final yield strengths. In the presence of thermal residual stress, these yielding properties are asymmetric and are influenced differently by the material structure parameters under tensile and compressive loadings.
基金supported by the National Natural Science Foundation of China(No.50171025)open project of foundation of National Key Laboratory of Metal Matrix Composite,Shanghai Jiaotong University
文摘Non-interlayer liquid phase diffusion welding (China Patent) and laser welding methods for aluminum matrix composite are mainly described in this paper. In the non-interlayer liquid phase diffusion welding, the key processing parameters affecting the strength of joint is welding temperature. When temperature rises beyond solidus temperature, the bonded line vanishes. The strength of joint reaches the maximum and becomes constant when welding temperature is close to liquid phase temperature. Oxide film in the interface is no longer detected by SEM in the welded joint. With this kind of technique, particle reinforced aluminum matrix composite Al2 O3p/6061Al is welded successfully, and the joint strength is about 80% of the strength of composite (as-casted). In the laser welding, results indicate that because of the huge specific surface area of the reinforcement, the interfacial reaction between the matrix and the reinforcement is restrained intensively at certain laser power and pulsed laser beam. The laser pulse frequency directly affects the reinforcement segregation and the reinforcement distribution in the weld, so that the weldability of the composite could be improved by increasing the laser pulse frequency. The maximum strength of the weld can reach 70% of the strength of the parent.
基金Shanghai RisingStar Program(B type)under Grant No.07QB14001.
文摘The superplastic deformation behavior of titanium alloy matrix composites reinforced with TiB and TiC was studied. Superplastic tension tests under conditions from 750℃ to 1100℃ and initial strain rates ranging from 2×10^-2 s^-1 to 10^-4s^-1 were carried out. A maximum elongation of 659% was obtained. The micro-structural evolution was studied by means of optical microscopy （OM） and transmission electron microcopy （TEM）. The deformation mechanism and the effect of reinforcement on superplasticity are also discussed.
基金This study was financially supported by the National Natural Science Foundation of China (No. 50071008).
文摘A multi-inclusion cell model is used to investigate the effect of deformation temperature and whisker rotation on the hot compressive behavior of metal matrix composites with misaligned whiskers. Numerical results show that deformation temperature influences the work-hardening behavior of the matrix and the rotation behavior of the whiskers. With increasing temperature, the work hardening rate of the matrix decreases, but the whisker rotation angle increases. Both whisker rotation and the increase of deformation temperature can induce reductions in the load supported by whisker and the load transferred from matrix to whisker. Additionally, it is found that during large strain deformation at higher temperatures, the enhancing of deformation temperature can reduce the effect of whisker rotation. Meanwhile, the stress-strain behavior of the composite is rather sensitive to deformation temperature. At a relatively lower temperature （150℃）, the composite exhibits work hardening due to the matrix work hardening, but at relatively higher temperatures （300℃ and above）, the composite shows strain softening due to whisker rotation. It is also found that during hot compression at higher temperatures, the softening rate of the composite decreases with increasing temperature. The predicted stress-strain behavior of the composite is approximately in agreement with the experimental results.
基金Funded by the National High-tech Research and Development Program of China(863 Program)(No.2013AA03 1306)Fundamental Research Funds for the Central Universities(No.WUT:2014-Ia-014)
文摘To develop a novel method predicting the viscoelastic behavior of polymer matrix composites according to the viscoelasticity of the matrix, we used the viscoelastic model of the matrix to build new models for unidirectional composites in both 0° and 90° directions. Viscoelastic parameters for both new models were derived, and the obtained equations shared the same form as the viscoelastic constitutive equation of matrix material. The viscoelastic behaviors of matrix material and unidirectional composites were also tested. Results showed that fitting parameters of creep compliance equation were close to the theoretical values of viscoelastic constitutive parameters of the unidirectional composites, proving the validity of the models. A new method was obtained to predict the viscoelastic property of the unidirectional composites based on the viscoelastic property of composite matrix and elastic property of the unidirectional composites. This method provides a theoretical basis for future studies on the viscoelasticity of composite laminates.
基金Funded by the National Natural Science Foundation of China(No.51472092)
文摘We studied the characteristics of two-scale pore structure of preform in the deposition process and the mass transfer of reactant gas in dual-scale pores, and observed the physiochemical phenomenon associated with the reaction. Thereby, we established mathematical models on two scales, respectively, preform and reactor. These models were used for the numerical simulation of the process of ceramic matrix composites densified by isothermal chemical vapor infiltration(ICVI). The models were used to carry out a systematic study on the influence of process conditions and the preform structure on the densification behaviors. The most important findings of our study are that the processing time could be reduced by about 50% without compromising the quality of the material, if the processing temperature is 950-1 000 ℃ for the first 70 hours and then raised to 1 100 ℃.
文摘作为热结构材料,陶瓷基复合材料(ceramic matrix composites,CMC)在航空航天领域应用潜力巨大。连续纤维的引入解决了陶瓷脆性大的问题,而纤维与基体间微小区域——界面层的设计是保证CMC具有高韧性的关键。一直以来相关研究主要集中于界面层与CMC宏观力学性能之间的关系,受限于表征难以深入研究界面层微区力学行为的困难。随着微纳力学测试与聚焦离子束(focused ion beam,FIB)技术的发展,近些年来对于CMC界面层结合强度以及其失效行为的表征逐渐增多。在此基础上,本文综述CMC中界面层的作用以及界面剪切强度的影响因素与调控机制,同时汇总当下通过直接或间接手段测试界面剪切强度的方法,重点总结微纳力学手段下纤维push-out/push-in以及微柱压缩等方法的适用条件以及差异,报道这些方法在界面区失效机制研究方面的进展,并指明尚存在的一些问题。其中,纤维pushout/push-in可以反映基体应力作用对界面剪切强度的影响,但测试结果可能受到外部因素的影响;而微柱压缩测试则更多地反映界面层本征特性,无法反映基体应力对界面剪切强度的影响,也无法反映纤维拔出过程。最后展望未来的研究方向:进一步拓展界面微区力学行为的表征方法,同时确定微区力学与宏观力学性能间的影响机制并建立模型,最终实现CMC的界面层优化。
