Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures ...Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures were prepared through digital light processing(DLP)3D printing,polymer-derived ceramics(PDCs),chemical vapor infiltration(CVI),and oxidation technologies.The incorporation of the CVISiC phase effectively increases the dissipation capability,while the synergistic interaction between the gyroid structure and SiO_(2)phase significantly improves impedance matching performance.The SiOC/SiC/SiO_(2)composite achieved a minimum reflection loss(RL min)of-62.2 d B at 4.3 mm,and the effective absorption bandwidth(EAB)covered the X-band,with a thickness range of 4.1 mm-4.65 mm.The CST simulation results explain the broadband and low-frequency absorption characteristics,with an EAB of 8.4 GHz(9.6-18 GHz)and an RL min of-21.5 dB at 5 GHz.The excellent EM wave attenuation performance is associated primarily with polarization loss,conduction loss,the gyroid structure's enhancement of multiple reflections and scattering of EM waves,and the resonance effect between the structural units.The SiOC/SiC/SiO_(2)composite also demonstrated strong mechanical properties,with a maximum compressive failure strength of 31.6 MPa in the height direction.This work opens novel prospects for the development of multifunctional structural wave-absorbing materials suitable for broadband microwave absorption and load-bearing properties.展开更多
Non-isothermal aging(NIA)treatments have presented significant advantages in improving the comprehensive performance and aging hardening efficiency of the 7000 series aluminum alloys,but there is no attention paid to ...Non-isothermal aging(NIA)treatments have presented significant advantages in improving the comprehensive performance and aging hardening efficiency of the 7000 series aluminum alloys,but there is no attention paid to their composites.This study takes a linear heating aging process as an example to reveal the precipitation behaviors of a 15 vol.%SiC/7085Al composite as well as its impact on mechanical properties using differential scanning calorimetry,transmission electron microscopy,small-angle neutron scattering,hardness measurements,and tensile testing.The results indicated the formation of GP(Ⅰ,Ⅱ)zones,η’andηprecipitates in sequence,leading to the hardness and strength initially increasing and then decreasing with rising NIA temperatures.The maximums were reached at 183℃,corresponding to the appearance ofη’precipitates in large quantities.Owing to the rapid temperature rise during the NIA process,the precipitates entered the coarsening and redissolution stage before they were entirely formed,resulting in reduced peak strength compared to the T6 treatment.The composite exhibited a more significant reduction in strength than the 7085Al alloy because:(i)the annihilation of vacancies suppressed the formation of GPII zones,thereby weakening their transition toη’precipitates;(ii)quenching dislocations promoted the coarsening of precipitates.An improved NIA process,incorporating both heating and cooling aging treatments,was effectively designed with the assistance of in-situ SANS technology to address this issue,which allows for achieving strength comparable to that after the T6 treatment with only 15%of the aging time consumption.This research fills the gap in investigating the NIA precipitation behaviors of aluminum matrix composites,providing guidance for the formulation of NIA schedules.展开更多
The mass of high-speed trains can be reduced using the brake disk prepared with SiC network ceramic frame reinforced 6061 aluminum alloy composite （SiCn/Al）. The thermal and stress analyses of SiCn/Al brake disk dur...The mass of high-speed trains can be reduced using the brake disk prepared with SiC network ceramic frame reinforced 6061 aluminum alloy composite （SiCn/Al）. The thermal and stress analyses of SiCn/Al brake disk during emergency braking at a speed of 300 km/h considering airflow cooling were investigated using finite element （FE） and computational fluid dynamics （CFD） methods. All three modes of heat transfer （conduction, convection and radiation） were analyzed along with the design features of the brake assembly and their interfaces. The results suggested that the higher convection coefficients achieved with airflow cooling will not only reduce the maximum temperature in the braking but also reduce the thermal gradients, since heat will be removed faster from hotter parts of the disk. Airflow cooling should be effective to reduce the risk of hot spot formation and disc thermal distortion. The highest temperature after emergency braking was 461 °C and 359 °C without and with considering airflow cooling, respectively. The equivalent stress could reach 269 MPa and 164 MPa without and with considering airflow cooling, respectively. However, the maximum surface stress may exceed the material yield strength during an emergency braking, which may cause a plastic damage accumulation in a brake disk without cooling. The simulation results are consistent with the experimental results well.展开更多
Al？50%SiC （volume fraction） composites containing different sizesofSiC particles （average sizesof 23, 38 and 75 μm） were prepared by powder metallurgy. The influences of SiC particle sizes and annealing on the p...Al？50%SiC （volume fraction） composites containing different sizesofSiC particles （average sizesof 23, 38 and 75 μm） were prepared by powder metallurgy. The influences of SiC particle sizes and annealing on the propertiesof the compositeswere investigated. The results show that SiC particles are distributed uniformly in the Al matrix. The coarse SiC particles result in higher coefficient of thermal expansion （CTE） and higher thermal conductivity （TC）, while fine SiC particles decrease CTE and improve flexural strength of the composites. The morphology and size of SiC particles in the composite are not influenced by the annealing treatment at 400℃for 6h. However, the CTE and the flexural strength of annealed composites are decreased slightly, and the TCis improved. The TC, CTE and flexural strength of the Al/SiC composite with averageSiC particlesize of75 μm are 156 W/（m·K）, 11.6×10^-6K^-1 and 229 MPa, respectively.展开更多
C/C-ZrC-SiC composites with different ZrC-SiC contents were fabricated by precursor infiltration and pyrolysis. The effect of ceramic content on the microstructure and ablation resistance was investigated. Both the C/...C/C-ZrC-SiC composites with different ZrC-SiC contents were fabricated by precursor infiltration and pyrolysis. The effect of ceramic content on the microstructure and ablation resistance was investigated. Both the C/C-SiC and C/C-ZrC-SiC composites exhibited good ablation resistance under the plasma flame above 2300℃. Withtheincreaseof ZrC content, a continuous oxide layer and a solid Zr-Si-O mesophase were formed during the ablation. And the structure of the formed oxides layer closely linked with the contents of ZrC-SiC ceramics. The solid ZrO2-ZrC and Zr-Si-O mesophase could increase the viscosity of SiO2 moderately and improve the anti-scouring ability. The continuous SiO2-ZrO2-ZrC-SiC layer would serve as a thermal and oxygen barrier for preventing the substratefrom further ablation. The C/C-ZrC-SiC composites with 27.2%ZrC and 7.56%SiC shows superior ablation resistance, and the mass and linear ablation rates are-3.51 mg/s and-1.88 μm/s, respectively.展开更多
The thermophysical properties of the SiC /Al composites mixed with diamond（SiC-Dia/Al） were studied through theoretical calculation and experiments. The thermal conductivity and the thermal expansion coefficient of ...The thermophysical properties of the SiC /Al composites mixed with diamond（SiC-Dia/Al） were studied through theoretical calculation and experiments. The thermal conductivity and the thermal expansion coefficient of the SiC-Dia/Al were calculated by differential effective medium（DEM） theoretical model and extended Turner model, respectively. The microstructure of the SiC-Dia/Al shows that the combination between SiC particles and Al is close, while that between diamond particles and Al is not close. The experimental results of the thermophysical properties of the SiC-Dia/Al are consistent with the calculated ones. The calculation results show that when the volume ratio of the diamond particles to the SiC particles is 3：7, the thermal conductivity and the thermal expansion coefficient can be improved by 39% and 30% compared to SiC/Al composites, respectively. In other words, by adding a small amount of diamond particles, the thermophysical properties of the composites can be improved effectively, while the cost increases little.展开更多
C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl com...C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl composites were also prepared under the same processing condition for comparision. Both kinds of the composites were thermally exposed in vacuum at 800 and 900℃ for different durations in order to study thermal stability of the interfacial zone. With the aids of scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）, the interracial microstructures of the composites were investigated. The results reveal that, although adding the Mo coating, the interfacial reaction product of the SiCf/C/Mo/TiAl composite is the same with that of the SiCf/C/TiA1 composite, which is TiC/Ti2AlC between the coating and the matrix. However, C/Mo duplex coating is more efficient in hindering interfacial reaction than C single coating at 900 ℃ and below. In addition, a new layer of interfacial reaction product was found between Ti2AlC and the matrix after 900 ℃, 200 h thermal exposure, which is rich in V and close to the chemical composition of B2 phase.展开更多
The Al/Si/SiC composites with medium volume fraction for electronic packaging were fabricated by gas pressure infiltration.On the premise of keeping the machinability of the composites,the silicon carbide particles,wh...The Al/Si/SiC composites with medium volume fraction for electronic packaging were fabricated by gas pressure infiltration.On the premise of keeping the machinability of the composites,the silicon carbide particles,which have the similar size with silicon particles（average 13 μm）,were added to replace silicon particles of same volume fraction,and microstructure and properties of the composites were investigated.The results show that reinforcing particles are distributed uniformly and no apparent pores are observed in the composites.It is also observed that higher thermal conductivity（TC） and flexural strength will be obtained with the addition of SiC particles.Meanwhile,coefficient of thermal expansion（CTE） changes smaller than TC.Models for predicting thermal properties were also discussed.Equivalent effective conductivity（EEC） was proposed to make H-J model suitable for hybrid particles and multimodal particle size distribution.展开更多
The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C...The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C composites were investigated in the frequency range of 8.2-12.4 GHz. Both the real and imaginary parts of the complex permittivity decreased after thermal oxidation. The composites after 100 h thermal oxidation showed that reflection loss exceeded-10 d B in the frequency of 9.7-11.9 GHz and the minimum value was-11.4 d B at 11.0 GHz. The flexural strength of composites decreased but fracture behavior was improved obviously after thermal oxidation. These results indicate that the SiCf/SiC composites containing PyC interphase after thermal oxidation possess good microwave absorbing property and fracture behavior.展开更多
The dry friction and wear behaviors of co-continuous composites SiC/Fe–40Cr against SiC/Al 2618 alloy were investigated on a ring-on-ring friction and wear tester at sliding speed of 30-105 m/s under the load of 1.0-...The dry friction and wear behaviors of co-continuous composites SiC/Fe–40Cr against SiC/Al 2618 alloy were investigated on a ring-on-ring friction and wear tester at sliding speed of 30-105 m/s under the load of 1.0-2.5 MPa. The experimental result reveals that the characteristic of two body abrasive wear and oxidation wear mechanisms are present for SiCn/2618 Al composite under higher load and sliding speed. SiC ceramic continuous network as the reinforcement can avoid composite from the third body wear that usually occurs in traditional particle reinforced composite. The mechanically mixed layer (MML) controls greatly the wear rate and friction coefficient of the composites. The composites tested at higher sliding speed exhibit higher value of friction coefficient and fluctuation, which is associated with the intermittent formation and removal of the MML. The wear and stress—strain behaviors of SiCn/Fe–40Cr against SiCn/Al 2168 at 30-105 m/s under 1.0-2.5 MPa were analyzed by finite element method with the software Solidwork2012 Simulation, respectively. The wear and stress–strain behavior of the composite predicted by the FEM correlated well with the experimental results.展开更多
Ceramic matrix composites(CMCs)structural components encounter the dual challenges of severe mechanical conditions and complex electromagnetic environments due to the increasing demand for stealth technology in aerosp...Ceramic matrix composites(CMCs)structural components encounter the dual challenges of severe mechanical conditions and complex electromagnetic environments due to the increasing demand for stealth technology in aerospace field.To address various functional requirements,this study integrates a biomimetic strategy inspired by gradient bamboo vascular bundles with a novel dual-material 3D printing approach.Three distinct bamboo-inspired structural configurations Cf/SiC composites are designed and manufactured,and the effects of these different structural configurations on the CVI process are analyzed.Nanoindentation method is utilized to characterize the relationship between interface bonding strength and mechanical properties.The results reveal that the maximum flexural strength and fracture toughness reach 108.6±5.2 MPa and 16.45±1.52 MPa m1/2,respectively,attributed to the enhanced crack propagation resistance and path caused by the weak fiber-matrix interface.Furthermore,the bio-inspired configuration enhances the dielectric loss and conductivity loss,exhibiting a minimum reflection loss of−24.3 dB with the effective absorption band of 3.89 GHz.This work introduces an innovative biomimetic strategy and 3D printing method for continuous fiber-reinforced ceramic composites,expanding the application of 3D printing technology in the field of CMCs.展开更多
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
The research on high-performance electromagnetic wave absorption materials with high-temperature and oxidative stability in extreme environments is gaining popularity.Herein,the lightweight silicon carbide nanowires(S...The research on high-performance electromagnetic wave absorption materials with high-temperature and oxidative stability in extreme environments is gaining popularity.Herein,the lightweight silicon carbide nanowires(SiC_(nws))/SiC composites are fabricated with in-situ SiC interface on one-dimensional oriented SiC_(nws)skeleton,which collaborative configuration by 3D printing and freeze casting assembly.The con-structed porous structure optimizes the impedance matching degree and scattering intensity,the maximum effective absorption bandwidth(EAB_(max))of 5.9 GHz and the minimum reflection loss(RL_(min))of−41.4 dB can be realized.Considering the inherent oxidation resistance of SiC,the composites present well-maintained absorption performance at 600℃.Even at 1100℃,the EAB_(max)of 4.9 GHz and RLmin of−30.4 dB also demonstrate the high-temperature absorption stability of the composites,indicating exceptional wave absorption properties and thermal stability.The slight attenuation can be attributed to the decrease in impedance matching capability accompanying the elevated dielectric constant.This work clarifies the impact of structure and component synergy on wave absorption behavior,and offers a novel approach to producing high-performance and high-temperature resistance ceramic-based electromagnetic wave absorption materials suitable for extreme environments.展开更多
In a high heat flux ablative environment,the surface temperature of aircraft rises rapidly,leading to traditional high thermal conductivity materials being ineffective at protecting internal metal components.In this s...In a high heat flux ablative environment,the surface temperature of aircraft rises rapidly,leading to traditional high thermal conductivity materials being ineffective at protecting internal metal components.In this study,continuous carbon fiber reinforced Li_(2)O-Al_(2)O_(3)-SiO_(2)(C_(f)/LAS)glass ceramic composites doped with SiC particles(SiC_(p))were prepared by slurry immersion winding and hot pressing sintering.Effect of matrix crystallinity on ablative properties of the composites under ultra-high heat flux was investigated.By utilizing heat absorption and low thermal conductivity characteristics associated with SiO_(2)gasification within composite materials,both surface and internal temperatures of these materials are effectively reduced,thereby ensuring the safe operation of aircraft and electronic devices.Results indicate that the average linear ablation rate of composites doped with 10%(in mass)of SiC_(p)significantly decreases at a heat flux of 20 MW/m^(2).Transmission electron microscope observation reveals that the doped glass matrix exhibits increased crystallinity,reduced internal stress,and minimized lattice distortion,thereby enhancing the composites’high-temperature performance.However,excessive SiC_(p)doping leads to reduced crystallinity and deteriorated ablation performance.Ultimately,the average linear ablation rate of C_(f)/LAS composites with 10%(in mass)SiC_(p)at 20 MW/m^(2)heat flux is comparable to that of commercial carbon/carbon composites,accompanied by providing lower thermal conductivity and higher bending strength.This novel high-performance C_(f)/LAS composite is cost-effective,short-cycled,and suitable for mass production,offering promising potential for widespread application in ablation-resistant components of hypersonic vehicles.展开更多
To meet the increasing demand for advanced materials capable of operation over 2000 ℃ for future thermal protection systems application, C/C-ZrC-SiC composites were fabricated by reactive melt infiltration （RMI） wi...To meet the increasing demand for advanced materials capable of operation over 2000 ℃ for future thermal protection systems application, C/C-ZrC-SiC composites were fabricated by reactive melt infiltration （RMI） with Zr, Si mixed powders as raw materials. The structural evolution and formation mechanism of the C/C- ZrC-SiC composites were discussed, and the mechanical property of the as-prepared material was investigated by compression test. The results showed that after the RMI process, a special structure with ZrC-SiC multi-coating as outer layer and ZrC-SiC-PyC ceramics as inner matrix was formed. ZrC and SiC rich areas were formed in the composites and on the coating surface due to the formation of Zr-Si intermetallic compounds in the RMI process. Mechanical tests showed that the average compression strength of the C/C-ZrC-SiC composites was 133.86 MPa, and the carbon fibers in the composites were not seriously damaged after the RMI process.展开更多
The compression creep deformation of the high volume fraction of SiC particles reinforced AI-Mg-Si composite fabricated by pressure-less infiltration was investigated. The experimental results show that the creep stre...The compression creep deformation of the high volume fraction of SiC particles reinforced AI-Mg-Si composite fabricated by pressure-less infiltration was investigated. The experimental results show that the creep stress exponents are very high at temperatures of 673 K, 723 K and 773 K, and if taking the threshold stress into account, the true stress exponent of minimum creep strain rate is still approximately 5, although the volume fraction of reinforcements is very high. The creep strain rate in the high volume fraction reinforced aluminum alloy matrix composites is controlled by matrix lattice diffusion. It is found that the creep-strengthening effect of high volume fraction of silicon carbide particles is significant, although the particles do not form effective obstacles to dislocation motion.展开更多
Raman spectroscopy was used to measure Raman spectra of the inner SiC fibers and surface C-rich layers of SiC fibers, composite precursors and SiCf/Ni-Cr-Al composites. The residual stresses of the inner SiC fibers an...Raman spectroscopy was used to measure Raman spectra of the inner SiC fibers and surface C-rich layers of SiC fibers, composite precursors and SiCf/Ni-Cr-Al composites. The residual stresses of the inner SiC fibers and surface C-rich layers were calculated, and the effect of the(Al + Al_2O_3) diffusion barrier layer on the interfacial residual stress in the composites was analyzed in combination with the interface microstructure and energy disperse spectroscopy(EDS) elements lining maps. The results show that the existence of(Al + Al_2O_3) diffusion barrier improves the compatibility of the SiCf/Ni-Cr-Al interface,inhibits the adverse interfacial reaction, and relieves the residual stress inside SiC fibers and at the interface of composite material. Heat treatment can reduce the residual stress at the interface. As the heat treatment time increases, the residual stress at the interface decreases.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
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
基金financially supported by National Natural Science Foundation of China(Grant Nos.12141203,52202083,W2421013)the Natural Science Foundation Project of Shaanxi Province(Grant No.2024JC-YBMS-450)+1 种基金the Sichuan Science and Technology Program(Grant No.2024YFHZ0265)the Open Project of High-end Equipment Advanced Materials and Manufacturing Technology Laboratory(Grant No.2023KFKT0005)。
文摘Designing materials with both structural load-bearing capacity and broadband electromagnetic(EM)wave absorption properties remains a significant challenge.In this work,SiOC/SiC/SiO_(2)composite with gyroid structures were prepared through digital light processing(DLP)3D printing,polymer-derived ceramics(PDCs),chemical vapor infiltration(CVI),and oxidation technologies.The incorporation of the CVISiC phase effectively increases the dissipation capability,while the synergistic interaction between the gyroid structure and SiO_(2)phase significantly improves impedance matching performance.The SiOC/SiC/SiO_(2)composite achieved a minimum reflection loss(RL min)of-62.2 d B at 4.3 mm,and the effective absorption bandwidth(EAB)covered the X-band,with a thickness range of 4.1 mm-4.65 mm.The CST simulation results explain the broadband and low-frequency absorption characteristics,with an EAB of 8.4 GHz(9.6-18 GHz)and an RL min of-21.5 dB at 5 GHz.The excellent EM wave attenuation performance is associated primarily with polarization loss,conduction loss,the gyroid structure's enhancement of multiple reflections and scattering of EM waves,and the resonance effect between the structural units.The SiOC/SiC/SiO_(2)composite also demonstrated strong mechanical properties,with a maximum compressive failure strength of 31.6 MPa in the height direction.This work opens novel prospects for the development of multifunctional structural wave-absorbing materials suitable for broadband microwave absorption and load-bearing properties.
基金support of the Na-tional Key R&D Program of China(No.2021YFA1600700)the Na-tional Natural Science Foundation of China(grant Nos.U22A20114,52322106,52192595,and 52301200)+2 种基金the Project funded by China Postdoctoral Science Foundation(No.2023M733573)CSNS Con-sortium on High-performance Materials of Chinese Academy of Sciences(No.JZHKYPT-2021-01)the Natural Science Foun-dation of Liaoning Province(No.2023-BS-020)。
文摘Non-isothermal aging(NIA)treatments have presented significant advantages in improving the comprehensive performance and aging hardening efficiency of the 7000 series aluminum alloys,but there is no attention paid to their composites.This study takes a linear heating aging process as an example to reveal the precipitation behaviors of a 15 vol.%SiC/7085Al composite as well as its impact on mechanical properties using differential scanning calorimetry,transmission electron microscopy,small-angle neutron scattering,hardness measurements,and tensile testing.The results indicated the formation of GP(Ⅰ,Ⅱ)zones,η’andηprecipitates in sequence,leading to the hardness and strength initially increasing and then decreasing with rising NIA temperatures.The maximums were reached at 183℃,corresponding to the appearance ofη’precipitates in large quantities.Owing to the rapid temperature rise during the NIA process,the precipitates entered the coarsening and redissolution stage before they were entirely formed,resulting in reduced peak strength compared to the T6 treatment.The composite exhibited a more significant reduction in strength than the 7085Al alloy because:(i)the annihilation of vacancies suppressed the formation of GPII zones,thereby weakening their transition toη’precipitates;(ii)quenching dislocations promoted the coarsening of precipitates.An improved NIA process,incorporating both heating and cooling aging treatments,was effectively designed with the assistance of in-situ SANS technology to address this issue,which allows for achieving strength comparable to that after the T6 treatment with only 15%of the aging time consumption.This research fills the gap in investigating the NIA precipitation behaviors of aluminum matrix composites,providing guidance for the formulation of NIA schedules.
基金Projects (50872018, 50902018) supported by the National Natural Science Foundation of ChinaProject (1099043) supported by the Science and Technology in Guangxi Province, ChinaProject (090302005) supported by the Basic Research Fund for Northeastern University, China
文摘The mass of high-speed trains can be reduced using the brake disk prepared with SiC network ceramic frame reinforced 6061 aluminum alloy composite （SiCn/Al）. The thermal and stress analyses of SiCn/Al brake disk during emergency braking at a speed of 300 km/h considering airflow cooling were investigated using finite element （FE） and computational fluid dynamics （CFD） methods. All three modes of heat transfer （conduction, convection and radiation） were analyzed along with the design features of the brake assembly and their interfaces. The results suggested that the higher convection coefficients achieved with airflow cooling will not only reduce the maximum temperature in the braking but also reduce the thermal gradients, since heat will be removed faster from hotter parts of the disk. Airflow cooling should be effective to reduce the risk of hot spot formation and disc thermal distortion. The highest temperature after emergency braking was 461 °C and 359 °C without and with considering airflow cooling, respectively. The equivalent stress could reach 269 MPa and 164 MPa without and with considering airflow cooling, respectively. However, the maximum surface stress may exceed the material yield strength during an emergency braking, which may cause a plastic damage accumulation in a brake disk without cooling. The simulation results are consistent with the experimental results well.
基金Project support by the 2015 Shandong Province Project for Outstanding Subject Talent Group,China
文摘Al？50%SiC （volume fraction） composites containing different sizesofSiC particles （average sizesof 23, 38 and 75 μm） were prepared by powder metallurgy. The influences of SiC particle sizes and annealing on the propertiesof the compositeswere investigated. The results show that SiC particles are distributed uniformly in the Al matrix. The coarse SiC particles result in higher coefficient of thermal expansion （CTE） and higher thermal conductivity （TC）, while fine SiC particles decrease CTE and improve flexural strength of the composites. The morphology and size of SiC particles in the composite are not influenced by the annealing treatment at 400℃for 6h. However, the CTE and the flexural strength of annealed composites are decreased slightly, and the TCis improved. The TC, CTE and flexural strength of the Al/SiC composite with averageSiC particlesize of75 μm are 156 W/（m·K）, 11.6×10^-6K^-1 and 229 MPa, respectively.
基金Project(2011CB605801)supported by the National Basic Research Program of ChinaProject(51304249)supported by the National Natural Science Foundation of China+1 种基金Project(2013BAE04B02)supported by the National Key Technology Support Program of ChinaProject(14JJ3023)supported by the Hunan Provincial Science Foundation of China
文摘C/C-ZrC-SiC composites with different ZrC-SiC contents were fabricated by precursor infiltration and pyrolysis. The effect of ceramic content on the microstructure and ablation resistance was investigated. Both the C/C-SiC and C/C-ZrC-SiC composites exhibited good ablation resistance under the plasma flame above 2300℃. Withtheincreaseof ZrC content, a continuous oxide layer and a solid Zr-Si-O mesophase were formed during the ablation. And the structure of the formed oxides layer closely linked with the contents of ZrC-SiC ceramics. The solid ZrO2-ZrC and Zr-Si-O mesophase could increase the viscosity of SiO2 moderately and improve the anti-scouring ability. The continuous SiO2-ZrO2-ZrC-SiC layer would serve as a thermal and oxygen barrier for preventing the substratefrom further ablation. The C/C-ZrC-SiC composites with 27.2%ZrC and 7.56%SiC shows superior ablation resistance, and the mass and linear ablation rates are-3.51 mg/s and-1.88 μm/s, respectively.
文摘The thermophysical properties of the SiC /Al composites mixed with diamond（SiC-Dia/Al） were studied through theoretical calculation and experiments. The thermal conductivity and the thermal expansion coefficient of the SiC-Dia/Al were calculated by differential effective medium（DEM） theoretical model and extended Turner model, respectively. The microstructure of the SiC-Dia/Al shows that the combination between SiC particles and Al is close, while that between diamond particles and Al is not close. The experimental results of the thermophysical properties of the SiC-Dia/Al are consistent with the calculated ones. The calculation results show that when the volume ratio of the diamond particles to the SiC particles is 3：7, the thermal conductivity and the thermal expansion coefficient can be improved by 39% and 30% compared to SiC/Al composites, respectively. In other words, by adding a small amount of diamond particles, the thermophysical properties of the composites can be improved effectively, while the cost increases little.
基金Projects(51201134,51271147)supported by the National Natural Science Foundation of ChinaProject(2015JM5181)supported by the Natural Science Foundation of Shaanxi Province,China+1 种基金Project(115-QP-2014)supported by the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),ChinaProject(3102014JCQ01023)supported by the Fundamental Research Funds for the Central Universities,China
文摘C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl composites were also prepared under the same processing condition for comparision. Both kinds of the composites were thermally exposed in vacuum at 800 and 900℃ for different durations in order to study thermal stability of the interfacial zone. With the aids of scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）, the interracial microstructures of the composites were investigated. The results reveal that, although adding the Mo coating, the interfacial reaction product of the SiCf/C/Mo/TiAl composite is the same with that of the SiCf/C/TiA1 composite, which is TiC/Ti2AlC between the coating and the matrix. However, C/Mo duplex coating is more efficient in hindering interfacial reaction than C single coating at 900 ℃ and below. In addition, a new layer of interfacial reaction product was found between Ti2AlC and the matrix after 900 ℃, 200 h thermal exposure, which is rich in V and close to the chemical composition of B2 phase.
基金Project (60776019) supported by the National Natural Science Foundation of ChinaProject (61-TP-2010) supported by the Research Fund of the State Key Laboratory of Solidification Processing (NWPU),China
文摘The Al/Si/SiC composites with medium volume fraction for electronic packaging were fabricated by gas pressure infiltration.On the premise of keeping the machinability of the composites,the silicon carbide particles,which have the similar size with silicon particles（average 13 μm）,were added to replace silicon particles of same volume fraction,and microstructure and properties of the composites were investigated.The results show that reinforcing particles are distributed uniformly and no apparent pores are observed in the composites.It is also observed that higher thermal conductivity（TC） and flexural strength will be obtained with the addition of SiC particles.Meanwhile,coefficient of thermal expansion（CTE） changes smaller than TC.Models for predicting thermal properties were also discussed.Equivalent effective conductivity（EEC） was proposed to make H-J model suitable for hybrid particles and multimodal particle size distribution.
基金Project(51072165)supported by the National Natural Science Foundation of ChinaProject(201305)supported by the Fund of State Key Laboratory of Solidification Processing,ChinaProjects(2013JK0921,2013JK0922)supported by Shaanxi Provincial Education Department of China
文摘The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C composites were investigated in the frequency range of 8.2-12.4 GHz. Both the real and imaginary parts of the complex permittivity decreased after thermal oxidation. The composites after 100 h thermal oxidation showed that reflection loss exceeded-10 d B in the frequency of 9.7-11.9 GHz and the minimum value was-11.4 d B at 11.0 GHz. The flexural strength of composites decreased but fracture behavior was improved obviously after thermal oxidation. These results indicate that the SiCf/SiC composites containing PyC interphase after thermal oxidation possess good microwave absorbing property and fracture behavior.
基金Project (2012BAE06B01) supported by the Key Technology R&D Program During the 12th Five-Year Plan Period, ChinaProjects(21201030, 51272039, 51032007) supported by the National Natural Science Foundation of ChinaProject (1099043) supported by the Science and Technology in Guangxi Province, China
文摘The dry friction and wear behaviors of co-continuous composites SiC/Fe–40Cr against SiC/Al 2618 alloy were investigated on a ring-on-ring friction and wear tester at sliding speed of 30-105 m/s under the load of 1.0-2.5 MPa. The experimental result reveals that the characteristic of two body abrasive wear and oxidation wear mechanisms are present for SiCn/2618 Al composite under higher load and sliding speed. SiC ceramic continuous network as the reinforcement can avoid composite from the third body wear that usually occurs in traditional particle reinforced composite. The mechanically mixed layer (MML) controls greatly the wear rate and friction coefficient of the composites. The composites tested at higher sliding speed exhibit higher value of friction coefficient and fluctuation, which is associated with the intermittent formation and removal of the MML. The wear and stress—strain behaviors of SiCn/Fe–40Cr against SiCn/Al 2168 at 30-105 m/s under 1.0-2.5 MPa were analyzed by finite element method with the software Solidwork2012 Simulation, respectively. The wear and stress–strain behavior of the composite predicted by the FEM correlated well with the experimental results.
基金supported by The National Key Research and Development Program of China(No.2019YFB1901001).
文摘Ceramic matrix composites(CMCs)structural components encounter the dual challenges of severe mechanical conditions and complex electromagnetic environments due to the increasing demand for stealth technology in aerospace field.To address various functional requirements,this study integrates a biomimetic strategy inspired by gradient bamboo vascular bundles with a novel dual-material 3D printing approach.Three distinct bamboo-inspired structural configurations Cf/SiC composites are designed and manufactured,and the effects of these different structural configurations on the CVI process are analyzed.Nanoindentation method is utilized to characterize the relationship between interface bonding strength and mechanical properties.The results reveal that the maximum flexural strength and fracture toughness reach 108.6±5.2 MPa and 16.45±1.52 MPa m1/2,respectively,attributed to the enhanced crack propagation resistance and path caused by the weak fiber-matrix interface.Furthermore,the bio-inspired configuration enhances the dielectric loss and conductivity loss,exhibiting a minimum reflection loss of−24.3 dB with the effective absorption band of 3.89 GHz.This work introduces an innovative biomimetic strategy and 3D printing method for continuous fiber-reinforced ceramic composites,expanding the application of 3D printing technology in the field of CMCs.
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.
基金supported by the National Key R&D Program of China(No.2022YFB3707700)National Natural Science Foundation of China(No.52302121)+3 种基金Shanghai Sailing Program(No.23YF1454700)Shanghai Natural Science Foundation(No.23ZR1472700)Shanghai Post-doctoral Excellent Program(No.2022664)Shanghai Science and Technology Innovation Action Plan(No.21511104800).
文摘The research on high-performance electromagnetic wave absorption materials with high-temperature and oxidative stability in extreme environments is gaining popularity.Herein,the lightweight silicon carbide nanowires(SiC_(nws))/SiC composites are fabricated with in-situ SiC interface on one-dimensional oriented SiC_(nws)skeleton,which collaborative configuration by 3D printing and freeze casting assembly.The con-structed porous structure optimizes the impedance matching degree and scattering intensity,the maximum effective absorption bandwidth(EAB_(max))of 5.9 GHz and the minimum reflection loss(RL_(min))of−41.4 dB can be realized.Considering the inherent oxidation resistance of SiC,the composites present well-maintained absorption performance at 600℃.Even at 1100℃,the EAB_(max)of 4.9 GHz and RLmin of−30.4 dB also demonstrate the high-temperature absorption stability of the composites,indicating exceptional wave absorption properties and thermal stability.The slight attenuation can be attributed to the decrease in impedance matching capability accompanying the elevated dielectric constant.This work clarifies the impact of structure and component synergy on wave absorption behavior,and offers a novel approach to producing high-performance and high-temperature resistance ceramic-based electromagnetic wave absorption materials suitable for extreme environments.
基金National Natural Science Foundation of China(U23A6014,52103357)。
文摘In a high heat flux ablative environment,the surface temperature of aircraft rises rapidly,leading to traditional high thermal conductivity materials being ineffective at protecting internal metal components.In this study,continuous carbon fiber reinforced Li_(2)O-Al_(2)O_(3)-SiO_(2)(C_(f)/LAS)glass ceramic composites doped with SiC particles(SiC_(p))were prepared by slurry immersion winding and hot pressing sintering.Effect of matrix crystallinity on ablative properties of the composites under ultra-high heat flux was investigated.By utilizing heat absorption and low thermal conductivity characteristics associated with SiO_(2)gasification within composite materials,both surface and internal temperatures of these materials are effectively reduced,thereby ensuring the safe operation of aircraft and electronic devices.Results indicate that the average linear ablation rate of composites doped with 10%(in mass)of SiC_(p)significantly decreases at a heat flux of 20 MW/m^(2).Transmission electron microscope observation reveals that the doped glass matrix exhibits increased crystallinity,reduced internal stress,and minimized lattice distortion,thereby enhancing the composites’high-temperature performance.However,excessive SiC_(p)doping leads to reduced crystallinity and deteriorated ablation performance.Ultimately,the average linear ablation rate of C_(f)/LAS composites with 10%(in mass)SiC_(p)at 20 MW/m^(2)heat flux is comparable to that of commercial carbon/carbon composites,accompanied by providing lower thermal conductivity and higher bending strength.This novel high-performance C_(f)/LAS composite is cost-effective,short-cycled,and suitable for mass production,offering promising potential for widespread application in ablation-resistant components of hypersonic vehicles.
基金supported by the China Postdoctoral Science Foundation(No.2012M511752)the National Basic Research Program of China(No.2011CB605801)+2 种基金the Fundamental Research Funds for the Central Universities(No. 2012QNZT004)the Freedom Explore Program of Central South University,the Open-End Fund for the Valuable and Precision Instruments of Central South University(No.CSUZC2012026)the Postdoctoral Science Foundation of Central South University
文摘To meet the increasing demand for advanced materials capable of operation over 2000 ℃ for future thermal protection systems application, C/C-ZrC-SiC composites were fabricated by reactive melt infiltration （RMI） with Zr, Si mixed powders as raw materials. The structural evolution and formation mechanism of the C/C- ZrC-SiC composites were discussed, and the mechanical property of the as-prepared material was investigated by compression test. The results showed that after the RMI process, a special structure with ZrC-SiC multi-coating as outer layer and ZrC-SiC-PyC ceramics as inner matrix was formed. ZrC and SiC rich areas were formed in the composites and on the coating surface due to the formation of Zr-Si intermetallic compounds in the RMI process. Mechanical tests showed that the average compression strength of the C/C-ZrC-SiC composites was 133.86 MPa, and the carbon fibers in the composites were not seriously damaged after the RMI process.
文摘The compression creep deformation of the high volume fraction of SiC particles reinforced AI-Mg-Si composite fabricated by pressure-less infiltration was investigated. The experimental results show that the creep stress exponents are very high at temperatures of 673 K, 723 K and 773 K, and if taking the threshold stress into account, the true stress exponent of minimum creep strain rate is still approximately 5, although the volume fraction of reinforcements is very high. The creep strain rate in the high volume fraction reinforced aluminum alloy matrix composites is controlled by matrix lattice diffusion. It is found that the creep-strengthening effect of high volume fraction of silicon carbide particles is significant, although the particles do not form effective obstacles to dislocation motion.
基金supported by the National Natural Science Foundation of China(No.51371170)
文摘Raman spectroscopy was used to measure Raman spectra of the inner SiC fibers and surface C-rich layers of SiC fibers, composite precursors and SiCf/Ni-Cr-Al composites. The residual stresses of the inner SiC fibers and surface C-rich layers were calculated, and the effect of the(Al + Al_2O_3) diffusion barrier layer on the interfacial residual stress in the composites was analyzed in combination with the interface microstructure and energy disperse spectroscopy(EDS) elements lining maps. The results show that the existence of(Al + Al_2O_3) diffusion barrier improves the compatibility of the SiCf/Ni-Cr-Al interface,inhibits the adverse interfacial reaction, and relieves the residual stress inside SiC fibers and at the interface of composite material. Heat treatment can reduce the residual stress at the interface. As the heat treatment time increases, the residual stress at the interface decreases.
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.
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.
