The 2024Al/Gr/SiC hybrid composite plates with 5%-10% SiC particles （volume fraction） and 3%-6% flaky graphite （Gr） （volume fraction） were fabricated by vacuum hot pressing and hot extrusion processing. The effe...The 2024Al/Gr/SiC hybrid composite plates with 5%-10% SiC particles （volume fraction） and 3%-6% flaky graphite （Gr） （volume fraction） were fabricated by vacuum hot pressing and hot extrusion processing. The effects of SiC and Gr on the microstructures and mechanical properties of the composites aged at 160, 175 and 190℃ were studied by optical microscopy, scanning electron microscopy （SEM）, and hardness and tensile tests. The results indicate that the SiC particles have a more obvious effect on accelerating the aging response as compared with the Gr. Both the tensile strength and elongation are reduced by the Gr and SiC particles added into the matrix, while the Gr has a more negative influence on the elongation than the SiC particles. The tensile strength （ab）, yield stress （as） and elongation （δ） of the 2024Al/3Gr/10SiC composite aged at 165℃ for 8 h are 387 MPa, 280.3 MPa and 5.7%, respectively. The hybrid composites are characterized by ductile fracture, which is associated with the ductile fracture of the matrix and the tearing of the interface between the matrix and the particles.展开更多
In this study, a multilayer Al/Ni/Cu composite reinforced with Si C particles was produced using an accumulative roll bonding(ARB) process with different cycles. The microstructure and mechanical properties of this co...In this study, a multilayer Al/Ni/Cu composite reinforced with Si C particles was produced using an accumulative roll bonding(ARB) process with different cycles. The microstructure and mechanical properties of this composite were investigated using optical and scanning microscopy and hardness and tensile testing. The results show that by increasing the applied strain, the Al/Ni/Cu multilayer composite converted from layer features to near a particle-strengthening characteristic. After the fifth ARB cycle, a composite with a uniform distribution of reinforcements(Cu, Ni, and SiC) was fabricated. The tensile strength of the composite increased from the initial sandwich structure to the first ARB cycle and then decreased from the first to the third ARB cycle. Upon reaching five ARB cycles, the tensile strength of the composite increased again. The variation in the elongation of the composite exhibited a tendency similar to that of its tensile strength. It is observed that with increasing strain, the microhardness values of the Al, Cu, and Ni layers increased, and that the dominant fracture mechanisms of Al and Cu were dimple formation and ductile fracture. In contrast, brittle fracture in specific plains was the main characteristic of Ni fractures.展开更多
Sessile drop technique was used to investigate the influence of Ti on the wetting behaviour of copper alloy on SiC substrate. A low contact angle of 15- for Cu alloy on SiC substrate is obtained at the temperature of ...Sessile drop technique was used to investigate the influence of Ti on the wetting behaviour of copper alloy on SiC substrate. A low contact angle of 15- for Cu alloy on SiC substrate is obtained at the temperature of 1 100 ℃. The interfacial energy is lowered by the segregation of Ti and the formation of reaction product TiC, resulting in the significant enhancement of wettability. Ti is found to almost completely segregate to Cu/SiC interface. This agrees well with a coverage of 99.8%Ti at the Cu/SiC interface predicted from a simple model based on Gibbs adsorption isotherm. SiCp/Cu composites are produced by pressureless infiltration of copper alloy into Ti-activated SiC preform. The volume fraction of SiC reaches 57%. The densification achieves 97.5%. The bending strength varies from 150 MPa to 250 MPa and increases with decreasing particle size.展开更多
SiC/Cu composites were prepared by hot pressing. The high temperature tribological properties of the composites were investigated. XRD, SEM techniques were carried out to characterize the samples. It is found that the...SiC/Cu composites were prepared by hot pressing. The high temperature tribological properties of the composites were investigated. XRD, SEM techniques were carried out to characterize the samples. It is found that the friction coefficient of SiC/Cu composites increases with the increasing SiC content. The SiC reinforcement particles are worn down other than removed by pulling out during the wear test. Oxidation of Cu debris leads to the smooth contacting surface. Ring crack is formed under the cyclic wear test. The crack propagates through the damaged matrix and along the brittle interface between SiC particles and Cu matrix.展开更多
The thermal conductivity of diamond hybrid SiC/Cu,diamond/Cu and SiC/Cu composite were calculated by using the extended differential effective medium (DEM) theoretical model in this paper.The effects of the particle v...The thermal conductivity of diamond hybrid SiC/Cu,diamond/Cu and SiC/Cu composite were calculated by using the extended differential effective medium (DEM) theoretical model in this paper.The effects of the particle volume fraction,the particle size and the volume ratio of the diamond particles to the total particles on the thermal conductivity of the composite were studied.The DEM theoretical calculation results show that,for the diamond hybrid SiC/Cu composite,when the particle volume fraction is above 46% and the volume ratio of the diamond particles to the SiC particles is above 13:12,the thermal conductivity of the composite can reach 500 W·m-1·K-1.The thermal conduc-tivity of the composite has little change when the particle size is above 200μm.The experimental results show that Ti can improve the wettability of the SiC and Cu.The thermal conductivity of the diamond hybrid SiCTi/Cu is almost two times better than that of the diamond hybrid SiC/Cu.It is feasible to predict the thermal conductivity of the composite by DEM theoretical model.展开更多
To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8＋20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by las...To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8＋20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM （scanning electron microscopy）, EDS （energy dispersive X-ray spectroscopy）, XRD （X-ray diffraction） and TEM （transmission electron microscopy） techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.展开更多
SiC composites and 40 Cr Steels were joined with Ag-Cu-Ti solder in order to develop a new method of joining ceramics to metal. Effects of solder component and process parameters on the joining strength were investiga...SiC composites and 40 Cr Steels were joined with Ag-Cu-Ti solder in order to develop a new method of joining ceramics to metal. Effects of solder component and process parameters on the joining strength were investigated. The results show that some chemical reactions occur on the jointing interface between ceramics and metal. Higher joining strength is achieved when titanium is 0.2% (mass fraction) in the solder. The thickness of solder also affects the joining characteristics, and 0.2-0.3 mm. thickness of solder is the most suitable.展开更多
文摘The 2024Al/Gr/SiC hybrid composite plates with 5%-10% SiC particles （volume fraction） and 3%-6% flaky graphite （Gr） （volume fraction） were fabricated by vacuum hot pressing and hot extrusion processing. The effects of SiC and Gr on the microstructures and mechanical properties of the composites aged at 160, 175 and 190℃ were studied by optical microscopy, scanning electron microscopy （SEM）, and hardness and tensile tests. The results indicate that the SiC particles have a more obvious effect on accelerating the aging response as compared with the Gr. Both the tensile strength and elongation are reduced by the Gr and SiC particles added into the matrix, while the Gr has a more negative influence on the elongation than the SiC particles. The tensile strength （ab）, yield stress （as） and elongation （δ） of the 2024Al/3Gr/10SiC composite aged at 165℃ for 8 h are 387 MPa, 280.3 MPa and 5.7%, respectively. The hybrid composites are characterized by ductile fracture, which is associated with the ductile fracture of the matrix and the tearing of the interface between the matrix and the particles.
文摘In this study, a multilayer Al/Ni/Cu composite reinforced with Si C particles was produced using an accumulative roll bonding(ARB) process with different cycles. The microstructure and mechanical properties of this composite were investigated using optical and scanning microscopy and hardness and tensile testing. The results show that by increasing the applied strain, the Al/Ni/Cu multilayer composite converted from layer features to near a particle-strengthening characteristic. After the fifth ARB cycle, a composite with a uniform distribution of reinforcements(Cu, Ni, and SiC) was fabricated. The tensile strength of the composite increased from the initial sandwich structure to the first ARB cycle and then decreased from the first to the third ARB cycle. Upon reaching five ARB cycles, the tensile strength of the composite increased again. The variation in the elongation of the composite exhibited a tendency similar to that of its tensile strength. It is observed that with increasing strain, the microhardness values of the Al, Cu, and Ni layers increased, and that the dominant fracture mechanisms of Al and Cu were dimple formation and ductile fracture. In contrast, brittle fracture in specific plains was the main characteristic of Ni fractures.
基金Project(2006AA03Z557) supported by The High-tech Research and Development Program of ChinaProject(2006CB605207) supported by the National Basic Research Program of ChinaProject(I2P407) supported by MOE Program For Changjiang Scholars and Innovative Research Team in University
文摘Sessile drop technique was used to investigate the influence of Ti on the wetting behaviour of copper alloy on SiC substrate. A low contact angle of 15- for Cu alloy on SiC substrate is obtained at the temperature of 1 100 ℃. The interfacial energy is lowered by the segregation of Ti and the formation of reaction product TiC, resulting in the significant enhancement of wettability. Ti is found to almost completely segregate to Cu/SiC interface. This agrees well with a coverage of 99.8%Ti at the Cu/SiC interface predicted from a simple model based on Gibbs adsorption isotherm. SiCp/Cu composites are produced by pressureless infiltration of copper alloy into Ti-activated SiC preform. The volume fraction of SiC reaches 57%. The densification achieves 97.5%. The bending strength varies from 150 MPa to 250 MPa and increases with decreasing particle size.
基金Funded by the National Natural Scince Foundation of China (50972132)the Science Fund for Distinguished Young Scholars of Henan Province(512002200)
文摘SiC/Cu composites were prepared by hot pressing. The high temperature tribological properties of the composites were investigated. XRD, SEM techniques were carried out to characterize the samples. It is found that the friction coefficient of SiC/Cu composites increases with the increasing SiC content. The SiC reinforcement particles are worn down other than removed by pulling out during the wear test. Oxidation of Cu debris leads to the smooth contacting surface. Ring crack is formed under the cyclic wear test. The crack propagates through the damaged matrix and along the brittle interface between SiC particles and Cu matrix.
基金financially supported by High-Technology Research and Development Program of China (No.2008AA03Z505)
文摘The thermal conductivity of diamond hybrid SiC/Cu,diamond/Cu and SiC/Cu composite were calculated by using the extended differential effective medium (DEM) theoretical model in this paper.The effects of the particle volume fraction,the particle size and the volume ratio of the diamond particles to the total particles on the thermal conductivity of the composite were studied.The DEM theoretical calculation results show that,for the diamond hybrid SiC/Cu composite,when the particle volume fraction is above 46% and the volume ratio of the diamond particles to the SiC particles is above 13:12,the thermal conductivity of the composite can reach 500 W·m-1·K-1.The thermal conduc-tivity of the composite has little change when the particle size is above 200μm.The experimental results show that Ti can improve the wettability of the SiC and Cu.The thermal conductivity of the diamond hybrid SiCTi/Cu is almost two times better than that of the diamond hybrid SiC/Cu.It is feasible to predict the thermal conductivity of the composite by DEM theoretical model.
基金supported by the Open Fund of the State Key Laboratory of Advanced Welding Production Technology in Harbin Institute of Technology,Chinathe Open Fund of the State Key Laboratory of Materials Processing and Die&Mould Technology in Huazhong University of Science and Technology,China
文摘To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8＋20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM （scanning electron microscopy）, EDS （energy dispersive X-ray spectroscopy）, XRD （X-ray diffraction） and TEM （transmission electron microscopy） techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.
文摘SiC composites and 40 Cr Steels were joined with Ag-Cu-Ti solder in order to develop a new method of joining ceramics to metal. Effects of solder component and process parameters on the joining strength were investigated. The results show that some chemical reactions occur on the jointing interface between ceramics and metal. Higher joining strength is achieved when titanium is 0.2% (mass fraction) in the solder. The thickness of solder also affects the joining characteristics, and 0.2-0.3 mm. thickness of solder is the most suitable.
