SiCp/2024 aluminum alloy matrix composite was prepared by powder metallurgy method. Effects of heat treatment on the microstructure and mechanical properties of composite were investigated by SEM, EDS, XRD, HREM, tens...SiCp/2024 aluminum alloy matrix composite was prepared by powder metallurgy method. Effects of heat treatment on the microstructure and mechanical properties of composite were investigated by SEM, EDS, XRD, HREM, tensile and hardness tests. The experimental results showed that SiC particles distributed uniformly in the matrix and were in good combination with matrix. The tensile strength and hardness were improved significantly after heat treatment. With the increase of solid solution temperature, the alloy phases dissolved in the matrix gradually. When the solid solution temperature arrived at 505 ℃, the alloy phases dissolved thoroughly, and the composite exhibited the highest tensile strength and hardness（σb=360 MPa, HBS=104）. The main strengthening phase was Al2Cu, which was granular and distributed dispersively in the matrix. Effect of T6 was better than that of T4 at the same solid solution temperature.展开更多
Through the vacuum diffusion bonding for SiCp/ZLl01 aluminum matrix composite, the influence of bonding parameters on the joint properties was reported, with the aim to obtain optimal bonding parameters. The microstru...Through the vacuum diffusion bonding for SiCp/ZLl01 aluminum matrix composite, the influence of bonding parameters on the joint properties was reported, with the aim to obtain optimal bonding parameters. The microstructureof joints was analyzed by means of optical microscope and scanning electron microscope in order to study the relationship between the macro-properties of joints and the microstructures. It was found that diffusion bonding couldbe used for bonding aluminum matrix composites successfully. Meanwhile, the properties of the matrix and the jointwere all affected by some defects such as the reinforcement aggregation in aluminum matrix composites made bystirring casting.展开更多
35% SiCp/2024 Al（volume fraction） composite was prepared by powder metallurgy method. The microstructures of Si Cp/Al interfaces and precipitate phase/Al interfaces were characterized by HRTEM, and the interface con...35% SiCp/2024 Al（volume fraction） composite was prepared by powder metallurgy method. The microstructures of Si Cp/Al interfaces and precipitate phase/Al interfaces were characterized by HRTEM, and the interface conditions were evaluated by tensile modules of elasticity and Brinell hardness measurement. The results show that the overall Si Cp/Al interface condition in this experiment is good and three kinds of Si Cp/Al interfaces are present in the composites, which include vast majority of clean planer interfaces, few slight reaction interfaces and tiny amorphous interfaces. The combination mechanism of Si C and Al in the clean planer interface is the formation of a semi-coherent interface by closely matching of atoms and there are no fixed or preferential crystallographic orientation relationships between Si C and Al. MgAl2O4 spinel particles act as an intermediate to form semi-coherent interface with SiC and Al respectively at the slight reaction interfaces. When the composite is aged at 190 °C for 9 h after being solution-treated at 510 °C for 2 h, numerous discoid-shaped and needle-shaped nanosized precipitates dispersively exist in the composite and are semi-coherent of low mismatch with Al matrix. The Brinell hardness of composites arrives peak value at this time.展开更多
The effects of Ag on the microstructure, mechanical properties, and electrical conductivity of AA2024 aluminum alloy coating were investigated. It was fabricated by friction surfacing as an additive manufacturing proc...The effects of Ag on the microstructure, mechanical properties, and electrical conductivity of AA2024 aluminum alloy coating were investigated. It was fabricated by friction surfacing as an additive manufacturing process. To carry out this investigation, Ag was added by 5.3, 10.6, and 16.0 wt.% to an AA2024 consumable rod by inserting holes in it. It was found that due to the strengthening by solid solution and the formation of precipitates and intermetallic containing Ag, the driving force for grain growth is reduced and consequently the grain size of the coating is decreased. After artificial aging heat treatment, the electrical conductivities of the coatings containing 0 and 16.0 wt.% Ag are increased by 4.15%(IACS) and decreased by 2.15%(IACS), respectively. While considering a linear relationship, it can be proposed that for a 1 wt.% Ag increase, the strength and hardness of the coating will be increased by 1.8% and 1.0%, respectively. It was established that the effect of Al6(Cu,Ag)Mg4 precipitate formation on strengthening is greater than that of Ag-rich intermetallic.展开更多
A study has been made on diffusion bonding of SiCp/2024Ai composites by means of pure Al interlayer. In the condition of TB=843 K, PB=16 MPa, tB= 60 min, the diffusion bonded joint, with a shear strength of 235 MPa, w...A study has been made on diffusion bonding of SiCp/2024Ai composites by means of pure Al interlayer. In the condition of TB=843 K, PB=16 MPa, tB= 60 min, the diffusion bonded joint, with a shear strength of 235 MPa, was obtained when a 15 μm thick interlayer was used. The results of the shear testing and SEM indicate that fracture of the joint presented characteristics of ductile rupture.展开更多
SiCp/2024 matrix composites reinforced with SiC particles and 2219 aluminum alloy were joined via centered electron beam welding and deflection beam welding,respectively,and the microstructures and mechanical properti...SiCp/2024 matrix composites reinforced with SiC particles and 2219 aluminum alloy were joined via centered electron beam welding and deflection beam welding,respectively,and the microstructures and mechanical properties of these joints were investigated.The results revealed that SiC particle segregation was more likely during centered electron beam welding(than during deflection beam welding),and strong interface reactions led to the formation of many Al4C3 brittle intermetallic compounds.Moreover,the tensile strength of the joints was 104 MPa.The interface reaction was restrained via deflection electron beam welding,and only a few Al4C3 intermetallic compounds formed at the top of the joint and heat affected zone of SiCp/Al.Quasi-cleavage fracture occurred at the interface reaction layer of the base metal.Both methods yielded a hardness transition zone near the SiCp/2024 fusion zone,and the brittle intermetallic Al4C3compounds formed in this zone resulted in high hardness.展开更多
In this paper, a new method for welding SiCp/101A was put forward. It is LPI (liquid-phase-impacting) diffusionwelding. Through LPI diffusion welding SiCp/101A aluminum, the effect of welding parameters on the weldedj...In this paper, a new method for welding SiCp/101A was put forward. It is LPI (liquid-phase-impacting) diffusionwelding. Through LPI diffusion welding SiCp/101A aluminum, the effect of welding parameters on the weldedjoint property was investigated, and the optimal welding parameters were brought forward at the same time. Themicrostructure of joint was analyzed by means of optical-microscope, scanning electron microscope in order to studythe relationship between the macro-properties of joint and the microstructure. The results show that LPI diffusionwelding could be used for welding aluminum matrix composites SiCp/101A successfully.展开更多
The effect of non-isothermal aging treatment on microstructure and mechanical properties of in-situ AA2024−Al_(3)NiCu composite fabricated by the stir casting process was examined.The Al_(3)NiCu intermetallic was crea...The effect of non-isothermal aging treatment on microstructure and mechanical properties of in-situ AA2024−Al_(3)NiCu composite fabricated by the stir casting process was examined.The Al_(3)NiCu intermetallic was created by adding 3 wt.%nickel powder during stir casting and homogenization treatment at 500℃ for 24 h after casting.The microstructural results obtained using optical and scanning electron microscope indicate that,after non-isothermal aging treatment,the S-Al_(2)CuMg precipitates become finer,forming a poor zone of this precipitate in the area between the dendrites.Also,adding nickel during stir casting reduces the precipitation rate and the contribution of S-Al_(2)CuMg precipitates in strengthening composite during non-isothermal aging.The maximum hardness,ultimate tensile strength,and toughness achieved in the 3 wt.%nickel-containing sample after non-isothermal aging at 250℃ are(121.30±4.21)HV,(221.67±8.31)MPa,and(1.67±0.08)MJ/m^(3),respectively.The maximum hardness and ultimate tensile strength of AA2024−Al_(3)NiCu composite are decreased by 6%and 4%,respectively,compared to those of nickel-free AA2024 aluminum alloy.展开更多
The liquid-phase-impacting (LPI) diffusion welding mechanism and microstructure of welded joint of aluminum matrixcomposite SiCp/101A have been studied. It shows that by LPl diffusion welding, the interface state betw...The liquid-phase-impacting (LPI) diffusion welding mechanism and microstructure of welded joint of aluminum matrixcomposite SiCp/101A have been studied. It shows that by LPl diffusion welding, the interface state between SiCparticle and matrix is prominent, the harmful microstructure or brittle phase can be restrained from the welded joint.Moreover, the density of dislocation in the matrix near the interface and in the matrix are all so higher than that ofparent composite, the dislocation entwists each other intensively resulted in welding the composite successfully.展开更多
The influences of volume fraction and particle size of SiC particulate reinforcements on the corrosion characteristics of SiCp/2024 Al metal matrix composites in aerated 3.5 wt pct NaCI aqueous solution were investiga...The influences of volume fraction and particle size of SiC particulate reinforcements on the corrosion characteristics of SiCp/2024 Al metal matrix composites in aerated 3.5 wt pct NaCI aqueous solution were investigated. The electrochemical behavior was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy, the general corrosion behavior of the composites was studied further by immersion tests. The results showed that pitting susceptibility was about the same for the composites and the alloy. The corrosion potentials were also independent of SiC phase. The corrosion resistance for the composites decreased as the volume fraction increased or particle size decreased.展开更多
SiCp/Gr/2024Al metal matrix composites were processed by squeeze casting technology. The microstructure of composites was observed by SEM and TEM, and the effects of graphite particulates and SiC particulates on the d...SiCp/Gr/2024Al metal matrix composites were processed by squeeze casting technology. The microstructure of composites was observed by SEM and TEM, and the effects of graphite particulates and SiC particulates on the damping behaviors of composites were also investigated. The results show that the microstructure of composites was dense and homogeneous, without any interfacial reactivity among reinforcement/matrix interfaces. Compared with the damping capacity of 2024A1, the damping capacity of composites was enhanced significantly by addition of SiC or graphite particulates. The main damping mechanisms of SiCp/Al composites were ascribed to the dislocation damping, and those of SiCp/Gr/2024Al were attributed to the intrinsic damping and interface damping.展开更多
The processes of mixed rare earth metal (REM) conversion coatings on 2024 alloy and Al6061/SiC p metal matrix composites (MMC) were introduced. The coatings were examined to be honeycomb like feature by scanning elect...The processes of mixed rare earth metal (REM) conversion coatings on 2024 alloy and Al6061/SiC p metal matrix composites (MMC) were introduced. The coatings were examined to be honeycomb like feature by scanning electron microscope. X ray diffraction analysis revealed that the coatings are amorphous structure. The results of X ray photoelectron spectroscopy indicated that the mixed REM conversion coatings consist predominantly of Ce and O, the contents of other rare earth elements (such as La, Pr) are relatively low, the coatings are about 2～4 μm thickness with excellent adhesion and wearability. The results of mass loss test showed that the mixed REM conversion coatings produce corrosion resistant surface of 2024 alloy and Al6061/SiC p. [展开更多
基金Funded by the National Natural Science Foundation of China(51371077)
文摘SiCp/2024 aluminum alloy matrix composite was prepared by powder metallurgy method. Effects of heat treatment on the microstructure and mechanical properties of composite were investigated by SEM, EDS, XRD, HREM, tensile and hardness tests. The experimental results showed that SiC particles distributed uniformly in the matrix and were in good combination with matrix. The tensile strength and hardness were improved significantly after heat treatment. With the increase of solid solution temperature, the alloy phases dissolved in the matrix gradually. When the solid solution temperature arrived at 505 ℃, the alloy phases dissolved thoroughly, and the composite exhibited the highest tensile strength and hardness（σb=360 MPa, HBS=104）. The main strengthening phase was Al2Cu, which was granular and distributed dispersively in the matrix. Effect of T6 was better than that of T4 at the same solid solution temperature.
基金This work was supported by the National Natural Science Foundation of China (grant No.50171025) and by open project of foundation of National Key Laboratory of Metal Matrix Composite, Shanghai Jiao Tong University.
文摘Through the vacuum diffusion bonding for SiCp/ZLl01 aluminum matrix composite, the influence of bonding parameters on the joint properties was reported, with the aim to obtain optimal bonding parameters. The microstructureof joints was analyzed by means of optical microscope and scanning electron microscope in order to study the relationship between the macro-properties of joints and the microstructures. It was found that diffusion bonding couldbe used for bonding aluminum matrix composites successfully. Meanwhile, the properties of the matrix and the jointwere all affected by some defects such as the reinforcement aggregation in aluminum matrix composites made bystirring casting.
基金Project(51371077)supported by the National Natural Science Foundation of China
文摘35% SiCp/2024 Al（volume fraction） composite was prepared by powder metallurgy method. The microstructures of Si Cp/Al interfaces and precipitate phase/Al interfaces were characterized by HRTEM, and the interface conditions were evaluated by tensile modules of elasticity and Brinell hardness measurement. The results show that the overall Si Cp/Al interface condition in this experiment is good and three kinds of Si Cp/Al interfaces are present in the composites, which include vast majority of clean planer interfaces, few slight reaction interfaces and tiny amorphous interfaces. The combination mechanism of Si C and Al in the clean planer interface is the formation of a semi-coherent interface by closely matching of atoms and there are no fixed or preferential crystallographic orientation relationships between Si C and Al. MgAl2O4 spinel particles act as an intermediate to form semi-coherent interface with SiC and Al respectively at the slight reaction interfaces. When the composite is aged at 190 °C for 9 h after being solution-treated at 510 °C for 2 h, numerous discoid-shaped and needle-shaped nanosized precipitates dispersively exist in the composite and are semi-coherent of low mismatch with Al matrix. The Brinell hardness of composites arrives peak value at this time.
基金funding support of Babol Noshirvani University of Technology,Iran,through Grant Program No.BNUT/370167/99。
文摘The effects of Ag on the microstructure, mechanical properties, and electrical conductivity of AA2024 aluminum alloy coating were investigated. It was fabricated by friction surfacing as an additive manufacturing process. To carry out this investigation, Ag was added by 5.3, 10.6, and 16.0 wt.% to an AA2024 consumable rod by inserting holes in it. It was found that due to the strengthening by solid solution and the formation of precipitates and intermetallic containing Ag, the driving force for grain growth is reduced and consequently the grain size of the coating is decreased. After artificial aging heat treatment, the electrical conductivities of the coatings containing 0 and 16.0 wt.% Ag are increased by 4.15%(IACS) and decreased by 2.15%(IACS), respectively. While considering a linear relationship, it can be proposed that for a 1 wt.% Ag increase, the strength and hardness of the coating will be increased by 1.8% and 1.0%, respectively. It was established that the effect of Al6(Cu,Ag)Mg4 precipitate formation on strengthening is greater than that of Ag-rich intermetallic.
基金the National Advanced Technology "863" Project of China with !No.715-005-0800
文摘A study has been made on diffusion bonding of SiCp/2024Ai composites by means of pure Al interlayer. In the condition of TB=843 K, PB=16 MPa, tB= 60 min, the diffusion bonded joint, with a shear strength of 235 MPa, was obtained when a 15 μm thick interlayer was used. The results of the shear testing and SEM indicate that fracture of the joint presented characteristics of ductile rupture.
基金Project was supported by the National Nature Science Foundation of China(51375115).
文摘SiCp/2024 matrix composites reinforced with SiC particles and 2219 aluminum alloy were joined via centered electron beam welding and deflection beam welding,respectively,and the microstructures and mechanical properties of these joints were investigated.The results revealed that SiC particle segregation was more likely during centered electron beam welding(than during deflection beam welding),and strong interface reactions led to the formation of many Al4C3 brittle intermetallic compounds.Moreover,the tensile strength of the joints was 104 MPa.The interface reaction was restrained via deflection electron beam welding,and only a few Al4C3 intermetallic compounds formed at the top of the joint and heat affected zone of SiCp/Al.Quasi-cleavage fracture occurred at the interface reaction layer of the base metal.Both methods yielded a hardness transition zone near the SiCp/2024 fusion zone,and the brittle intermetallic Al4C3compounds formed in this zone resulted in high hardness.
基金This work was supported by the National Natural Science Foundation of China (No. 90205035, 50171025).
文摘In this paper, a new method for welding SiCp/101A was put forward. It is LPI (liquid-phase-impacting) diffusionwelding. Through LPI diffusion welding SiCp/101A aluminum, the effect of welding parameters on the weldedjoint property was investigated, and the optimal welding parameters were brought forward at the same time. Themicrostructure of joint was analyzed by means of optical-microscope, scanning electron microscope in order to studythe relationship between the macro-properties of joint and the microstructure. The results show that LPI diffusionwelding could be used for welding aluminum matrix composites SiCp/101A successfully.
文摘The effect of non-isothermal aging treatment on microstructure and mechanical properties of in-situ AA2024−Al_(3)NiCu composite fabricated by the stir casting process was examined.The Al_(3)NiCu intermetallic was created by adding 3 wt.%nickel powder during stir casting and homogenization treatment at 500℃ for 24 h after casting.The microstructural results obtained using optical and scanning electron microscope indicate that,after non-isothermal aging treatment,the S-Al_(2)CuMg precipitates become finer,forming a poor zone of this precipitate in the area between the dendrites.Also,adding nickel during stir casting reduces the precipitation rate and the contribution of S-Al_(2)CuMg precipitates in strengthening composite during non-isothermal aging.The maximum hardness,ultimate tensile strength,and toughness achieved in the 3 wt.%nickel-containing sample after non-isothermal aging at 250℃ are(121.30±4.21)HV,(221.67±8.31)MPa,and(1.67±0.08)MJ/m^(3),respectively.The maximum hardness and ultimate tensile strength of AA2024−Al_(3)NiCu composite are decreased by 6%and 4%,respectively,compared to those of nickel-free AA2024 aluminum alloy.
基金This work was supported by the National Natural Science Foundation of China under grant No. 50171025.
文摘The liquid-phase-impacting (LPI) diffusion welding mechanism and microstructure of welded joint of aluminum matrixcomposite SiCp/101A have been studied. It shows that by LPl diffusion welding, the interface state between SiCparticle and matrix is prominent, the harmful microstructure or brittle phase can be restrained from the welded joint.Moreover, the density of dislocation in the matrix near the interface and in the matrix are all so higher than that ofparent composite, the dislocation entwists each other intensively resulted in welding the composite successfully.
文摘The influences of volume fraction and particle size of SiC particulate reinforcements on the corrosion characteristics of SiCp/2024 Al metal matrix composites in aerated 3.5 wt pct NaCI aqueous solution were investigated. The electrochemical behavior was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy, the general corrosion behavior of the composites was studied further by immersion tests. The results showed that pitting susceptibility was about the same for the composites and the alloy. The corrosion potentials were also independent of SiC phase. The corrosion resistance for the composites decreased as the volume fraction increased or particle size decreased.
文摘SiCp/Gr/2024Al metal matrix composites were processed by squeeze casting technology. The microstructure of composites was observed by SEM and TEM, and the effects of graphite particulates and SiC particulates on the damping behaviors of composites were also investigated. The results show that the microstructure of composites was dense and homogeneous, without any interfacial reactivity among reinforcement/matrix interfaces. Compared with the damping capacity of 2024A1, the damping capacity of composites was enhanced significantly by addition of SiC or graphite particulates. The main damping mechanisms of SiCp/Al composites were ascribed to the dislocation damping, and those of SiCp/Gr/2024Al were attributed to the intrinsic damping and interface damping.
文摘The processes of mixed rare earth metal (REM) conversion coatings on 2024 alloy and Al6061/SiC p metal matrix composites (MMC) were introduced. The coatings were examined to be honeycomb like feature by scanning electron microscope. X ray diffraction analysis revealed that the coatings are amorphous structure. The results of X ray photoelectron spectroscopy indicated that the mixed REM conversion coatings consist predominantly of Ce and O, the contents of other rare earth elements (such as La, Pr) are relatively low, the coatings are about 2～4 μm thickness with excellent adhesion and wearability. The results of mass loss test showed that the mixed REM conversion coatings produce corrosion resistant surface of 2024 alloy and Al6061/SiC p. [
