A novel technique for fabricating TiB_2/Al composites in molten aluminum was introduced. The formation mechanism of brittleAl,Ti particulates up to 30 m in size produced in the composites was studied and a method of e...A novel technique for fabricating TiB_2/Al composites in molten aluminum was introduced. The formation mechanism of brittleAl,Ti particulates up to 30 m in size produced in the composites was studied and a method of eliminating them was proposed. The resultsshow that (l) the brittle Al,Ti particulates are always present in the composites when the molar ratio of Ti to B 'T,:nB is l:2; and (2) theformation of the brittle Al,Ti phase can be avoided entirely from the final product by using a proper 'T,:nB of l:4 in the Ti-B-Al preforms.In the former case, the tensile elongation of the composite is only 4%, much lower than the value of pure aluminum (20%). In the latercase, the tensile elongation of this composite is 10%, higher than the value of the composite with a lot ofAl,Ti (4%), whereas the ultimatetensile stfength of the former is nearly that of the later.展开更多
In situ Al2O3 whiskers reinforced Ti-Al intermetallic composites were fabricated at ~1200℃ by reaction sintering of cold-consolidated fillets consisting mainly of Ti, Al, and different additives. The phases and micro...In situ Al2O3 whiskers reinforced Ti-Al intermetallic composites were fabricated at ~1200℃ by reaction sintering of cold-consolidated fillets consisting mainly of Ti, Al, and different additives. The phases and microstructures of the sintered composites were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The process of synthesis was investigated using differential thermal analysis (DTA). The effects of processing parameters and additives on the microstructures of the composites and the development of whisker were examined. It is found that the morphology of the whisker is strongly influenced by the additives, the exothermal reaction process, and the processing parameters.展开更多
Aluminum matrix composites reinforced by in situ Al2O3 and Al3Zr particles are fabricated from A356-Zr(CO3)2 system via magnetochemistry reaction,and the morphologies,sizes and distributions of the in situ particles a...Aluminum matrix composites reinforced by in situ Al2O3 and Al3Zr particles are fabricated from A356-Zr(CO3)2 system via magnetochemistry reaction,and the morphologies,sizes and distributions of the in situ particles as well as the microstructures,mechanical mechanisms of the composites are investigated by XRD,SEM,TEM and in situ tensile tests.The results indicate that with the pulsed magnetic field assistance,the morphologies of the in situ particles are mainly with ball-shape,the sizes are in nanometer scale and the distributions in the matrix are uniform.The interfaces between the in situ particles and the aluminum matrix are net and no interfacial outgrowth is observed.These are due to the strong vibration induced by the applied magnetic field in the aluminum melt,which in turn,accelerates the melt reactions.The effects of the magnetic field on the above contributions are discussed in detail.展开更多
The effect of high-speed direct-chill(DC) casting on the microstructure and mechanical properties of Al–Mg_2Si in situ composites and AA6061 alloy was investigated. The microstructural evolution of the Al–Mg_2Si com...The effect of high-speed direct-chill(DC) casting on the microstructure and mechanical properties of Al–Mg_2Si in situ composites and AA6061 alloy was investigated. The microstructural evolution of the Al–Mg_2Si composites and AA6061 alloy was examined by optical microscopy, field-emission scanning electron microscopy(FE-SEM) and transmission electron microscopy(TEM). The results revealed that an increase of the casting speed substantially refined the primary Mg_2Si particles(from 28 to 12 μm), the spacing of eutectic Mg_2Si(from 3 to 0.5 μm), and the grains of AA6061 alloy(from 102 to 22 μm). The morphology of the eutectic Mg_2Si transformed from lamellar to rod-like and fibrous with increasing casting speed. The tensile tests showed that the yield strength, tensile strength, and elongation improved at higher casting speeds because of refinement of the Mg_2Si phase and the grains in the Al–Mg_2Si composites and the AA6061 alloy. High-speed DC casting is demonstrated to be an effective method to improve the mechanical properties of Al–Mg_2Si composites and AA6061 alloy billets.展开更多
Al2O3 particle-reinforced ZL109 composite was prepared by in situ reaction between CuO and Al2O3 . The microstructure was observed by means of OM, SEM and TEM. The Al2O3 particles in sub-micron sizes distribute unifo...Al2O3 particle-reinforced ZL109 composite was prepared by in situ reaction between CuO and Al2O3 . The microstructure was observed by means of OM, SEM and TEM. The Al2O3 particles in sub-micron sizes distribute uniformly in the matrix, and the Cu displaced from the in situ reaction forms net-like alloy phases with other alloy elements. The hardness and the tensile strength of the composites at room temperature have a slight increase as compared to that of the matrix. However, the tensile strength at 350℃ has reached 90.23 MPa, or 16.92 MPa higher than that of the matrix. The mechanism of the reaction in the CuO/AI system was studied by using of differential scanning calorimetry（DSC） and thermodynamic calculation. The reaction between CuO and Al involves two steps. First, CuO reacts with Al to form Cu20 and Al2O3 at the melting temperature of the matrix alloy, and second, Cu20 reacts with Al to form Cu and Al2O3 at a higher temperature. At ZL109 casting temperature of 750- 780 ℃, the second step can also take place because of the effect of exothermic reaction of the first step.展开更多
The in-situ forming TiB_2 reinforced Al composite was favorably prepared by reaction- sintering of pure Al,Ti and B powders under vacuum.The TiB_2 is of submicrosize and free from lattice defect in the main.A superior...The in-situ forming TiB_2 reinforced Al composite was favorably prepared by reaction- sintering of pure Al,Ti and B powders under vacuum.The TiB_2 is of submicrosize and free from lattice defect in the main.A superior room,temperature strength and modulus, as well as good elevated temperature properties were obtained as comparison with that of pure Al.展开更多
Al 2O 3/Al composite was fabricated by the reaction between SiO 2 and molten aluminum.The microstructures of the composite obtained under different reaction conditions were analyzed. The formation mechanism of the ...Al 2O 3/Al composite was fabricated by the reaction between SiO 2 and molten aluminum.The microstructures of the composite obtained under different reaction conditions were analyzed. The formation mechanism of the composite microstructure was discussed. Results show that the reaction kinetics is influenced remarkably by the reaction temperature, reaction time and the quantity of SiO 2.The morphologies of Al 2O 3 have different features,depending on the reaction temperature.The composite has equiaxed Al 2O 3 grains when materials reacted below 1200℃,and the composite is composed of a large number of fine Al 2O 3 grains and aluminum.The composite has a frame shaped Al 2O 3 microstructure at the reaction temperature of above 1250℃.展开更多
Obtaining an appropriate grain size is crucial for Al alloys or Al matrix composites prior to processing,as it significantly influences the mechanical properties of components and workability during the manufacturing ...Obtaining an appropriate grain size is crucial for Al alloys or Al matrix composites prior to processing,as it significantly influences the mechanical properties of components and workability during the manufacturing process.TiB_(2)particles are exceptional grain refiners in Al and serve as excellent reinforcement particles for particulate-reinforced aluminum matrix composites.However,the optimal particle content for achieving excellent refinement and strengthening effects depends on the matrix composition and requires further investigation.Additionally,homogenization is essential for mitigating the element segregation in the ingot.Although it is anticipated that adding suitable particles can effectively inhibit undesired grain growth during homogenization,comprehensive investigations on this aspect are currently lacking.Therefore,TiB_(2)/2219Al matrix composites with varying reinforcement contents(0,1,3,5 wt%)were fabricated through traditional casting followed by homogenization treatment to address these research gaps.The effects of reinforcement content and homogenization treatment on the microstructure and mechanical properties of in-situ TiB_(2)/2219Al composites were investigated.The results demonstrate a gradual strengthening of the refining effect with increasing particle concentration.Moreover,composites containing 3 wt%TiB_(2)particles exhibit superior comprehensive mechanical properties in both as-cast and homogenized state.Additionally,potential orientation relationships are observed and calculated between undissolved Al_(2)Cu eutectic phase and submicron or nanometer-sized TiB_(2)particles,resulting in a mixture structure with enhanced bonding strength.This mixture structure is continuously distributed along grain boundaries during solidification,forming a three-dimensional cellular network that acts as primary retarding forces for grain growth during homogenization.Furthermore,the established homogenization kinetic equations were further utilized to analyze the correlation between homogenization time and grain size,as well as the influence of homogenization temperature.展开更多
利用Fe Ti B熔体反应制备了TiB2颗粒增强铁基复合材料,研究了该材料的显微组织。热力学分析表明,Fe Ti B熔体具有反应生成TiB2的可能性。试验结果表明,TiB2颗粒均匀分布于α Fe晶粒中,晶内TiB2粒子平均间距大于晶界。TiB2粒子尺寸大多为...利用Fe Ti B熔体反应制备了TiB2颗粒增强铁基复合材料,研究了该材料的显微组织。热力学分析表明,Fe Ti B熔体具有反应生成TiB2的可能性。试验结果表明,TiB2颗粒均匀分布于α Fe晶粒中,晶内TiB2粒子平均间距大于晶界。TiB2粒子尺寸大多为1～6μm,形状大多为接近等轴的多面体。展开更多
文摘A novel technique for fabricating TiB_2/Al composites in molten aluminum was introduced. The formation mechanism of brittleAl,Ti particulates up to 30 m in size produced in the composites was studied and a method of eliminating them was proposed. The resultsshow that (l) the brittle Al,Ti particulates are always present in the composites when the molar ratio of Ti to B 'T,:nB is l:2; and (2) theformation of the brittle Al,Ti phase can be avoided entirely from the final product by using a proper 'T,:nB of l:4 in the Ti-B-Al preforms.In the former case, the tensile elongation of the composite is only 4%, much lower than the value of pure aluminum (20%). In the latercase, the tensile elongation of this composite is 10%, higher than the value of the composite with a lot ofAl,Ti (4%), whereas the ultimatetensile stfength of the former is nearly that of the later.
基金This work was supported by the National Natural Science Foundation of China (No. 50432010, 50372037).
文摘In situ Al2O3 whiskers reinforced Ti-Al intermetallic composites were fabricated at ~1200℃ by reaction sintering of cold-consolidated fillets consisting mainly of Ti, Al, and different additives. The phases and microstructures of the sintered composites were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The process of synthesis was investigated using differential thermal analysis (DTA). The effects of processing parameters and additives on the microstructures of the composites and the development of whisker were examined. It is found that the morphology of the whisker is strongly influenced by the additives, the exothermal reaction process, and the processing parameters.
基金Project(2007AA03Z548) supported by High-Tech Research and Development Program of ChinaProject(50971066) supported by the National Natural Science Foundation of ChinaProject(1283000349) supported by the Jiangsu University Research Fund for Advanced Scholars,China
文摘Aluminum matrix composites reinforced by in situ Al2O3 and Al3Zr particles are fabricated from A356-Zr(CO3)2 system via magnetochemistry reaction,and the morphologies,sizes and distributions of the in situ particles as well as the microstructures,mechanical mechanisms of the composites are investigated by XRD,SEM,TEM and in situ tensile tests.The results indicate that with the pulsed magnetic field assistance,the morphologies of the in situ particles are mainly with ball-shape,the sizes are in nanometer scale and the distributions in the matrix are uniform.The interfaces between the in situ particles and the aluminum matrix are net and no interfacial outgrowth is observed.These are due to the strong vibration induced by the applied magnetic field in the aluminum melt,which in turn,accelerates the melt reactions.The effects of the magnetic field on the above contributions are discussed in detail.
基金financially supported by the Science and Technology Program of Guangzhou,China(No.2015B090926013)Postdoctoral Science Foundation of China(No.2015M581348)+1 种基金Postdoctoral Science Foundation of Northeastern University(No.20150302)the Doctoral Foundation of Chinese Ministry of Education(No.20130042130001)
文摘The effect of high-speed direct-chill(DC) casting on the microstructure and mechanical properties of Al–Mg_2Si in situ composites and AA6061 alloy was investigated. The microstructural evolution of the Al–Mg_2Si composites and AA6061 alloy was examined by optical microscopy, field-emission scanning electron microscopy(FE-SEM) and transmission electron microscopy(TEM). The results revealed that an increase of the casting speed substantially refined the primary Mg_2Si particles(from 28 to 12 μm), the spacing of eutectic Mg_2Si(from 3 to 0.5 μm), and the grains of AA6061 alloy(from 102 to 22 μm). The morphology of the eutectic Mg_2Si transformed from lamellar to rod-like and fibrous with increasing casting speed. The tensile tests showed that the yield strength, tensile strength, and elongation improved at higher casting speeds because of refinement of the Mg_2Si phase and the grains in the Al–Mg_2Si composites and the AA6061 alloy. High-speed DC casting is demonstrated to be an effective method to improve the mechanical properties of Al–Mg_2Si composites and AA6061 alloy billets.
文摘Al2O3 particle-reinforced ZL109 composite was prepared by in situ reaction between CuO and Al2O3 . The microstructure was observed by means of OM, SEM and TEM. The Al2O3 particles in sub-micron sizes distribute uniformly in the matrix, and the Cu displaced from the in situ reaction forms net-like alloy phases with other alloy elements. The hardness and the tensile strength of the composites at room temperature have a slight increase as compared to that of the matrix. However, the tensile strength at 350℃ has reached 90.23 MPa, or 16.92 MPa higher than that of the matrix. The mechanism of the reaction in the CuO/AI system was studied by using of differential scanning calorimetry（DSC） and thermodynamic calculation. The reaction between CuO and Al involves two steps. First, CuO reacts with Al to form Cu20 and Al2O3 at the melting temperature of the matrix alloy, and second, Cu20 reacts with Al to form Cu and Al2O3 at a higher temperature. At ZL109 casting temperature of 750- 780 ℃, the second step can also take place because of the effect of exothermic reaction of the first step.
文摘The in-situ forming TiB_2 reinforced Al composite was favorably prepared by reaction- sintering of pure Al,Ti and B powders under vacuum.The TiB_2 is of submicrosize and free from lattice defect in the main.A superior room,temperature strength and modulus, as well as good elevated temperature properties were obtained as comparison with that of pure Al.
文摘Al 2O 3/Al composite was fabricated by the reaction between SiO 2 and molten aluminum.The microstructures of the composite obtained under different reaction conditions were analyzed. The formation mechanism of the composite microstructure was discussed. Results show that the reaction kinetics is influenced remarkably by the reaction temperature, reaction time and the quantity of SiO 2.The morphologies of Al 2O 3 have different features,depending on the reaction temperature.The composite has equiaxed Al 2O 3 grains when materials reacted below 1200℃,and the composite is composed of a large number of fine Al 2O 3 grains and aluminum.The composite has a frame shaped Al 2O 3 microstructure at the reaction temperature of above 1250℃.
基金supported by the National Key Research and Development Program of China(No.2022YFB3400142)the National Natural Science Foundation of China(Nos.52174356,52022017,51927801,51971051,51901034 and U22A20174)+3 种基金the Science and Technology Plan Project of Liaoning Province(Nos.2022010005-JH6/1001 and 2022JH2/1013)the Innovation Foundation of Science and Technology of Dalian(Nos.2020JJ25CY002 and 2020J12GX037)the Major Science and Technology Projects of Longmen Laboratory(No.231100220400)the Fundamental Research Funds for the Central Universities.
文摘Obtaining an appropriate grain size is crucial for Al alloys or Al matrix composites prior to processing,as it significantly influences the mechanical properties of components and workability during the manufacturing process.TiB_(2)particles are exceptional grain refiners in Al and serve as excellent reinforcement particles for particulate-reinforced aluminum matrix composites.However,the optimal particle content for achieving excellent refinement and strengthening effects depends on the matrix composition and requires further investigation.Additionally,homogenization is essential for mitigating the element segregation in the ingot.Although it is anticipated that adding suitable particles can effectively inhibit undesired grain growth during homogenization,comprehensive investigations on this aspect are currently lacking.Therefore,TiB_(2)/2219Al matrix composites with varying reinforcement contents(0,1,3,5 wt%)were fabricated through traditional casting followed by homogenization treatment to address these research gaps.The effects of reinforcement content and homogenization treatment on the microstructure and mechanical properties of in-situ TiB_(2)/2219Al composites were investigated.The results demonstrate a gradual strengthening of the refining effect with increasing particle concentration.Moreover,composites containing 3 wt%TiB_(2)particles exhibit superior comprehensive mechanical properties in both as-cast and homogenized state.Additionally,potential orientation relationships are observed and calculated between undissolved Al_(2)Cu eutectic phase and submicron or nanometer-sized TiB_(2)particles,resulting in a mixture structure with enhanced bonding strength.This mixture structure is continuously distributed along grain boundaries during solidification,forming a three-dimensional cellular network that acts as primary retarding forces for grain growth during homogenization.Furthermore,the established homogenization kinetic equations were further utilized to analyze the correlation between homogenization time and grain size,as well as the influence of homogenization temperature.
文摘利用Fe Ti B熔体反应制备了TiB2颗粒增强铁基复合材料,研究了该材料的显微组织。热力学分析表明,Fe Ti B熔体具有反应生成TiB2的可能性。试验结果表明,TiB2颗粒均匀分布于α Fe晶粒中,晶内TiB2粒子平均间距大于晶界。TiB2粒子尺寸大多为1～6μm,形状大多为接近等轴的多面体。
