A suitable combustion synthesis and densification process was designed to fabricate dense NiAl/ TiB2 composites from Ni-Al- Ti-B system. Combustion synthesis processing and microstructure characteristics of products w...A suitable combustion synthesis and densification process was designed to fabricate dense NiAl/ TiB2 composites from Ni-Al- Ti-B system. Combustion synthesis processing and microstructure characteristics of products were studied in detail. The results show that the amount of TiB2 ceramics has a great influence on the combustion synthesis processing and microstructure; with the increase of the amount of TiB2 ceramics, the combustion temperature and combustion velocity increase rapidly. The volume of synthesized products and the grain size of ceramics particle size are also affected by the amount of TiB2 ceramics. TiB2 ceramics fiber can be produced in this synthesis system. The dense NiAl/ TiB2 composites with residual porosity of no more than 1% are fabricated by the combustion synthesis and hot pressing, the mechanical properties of the dense NiAl/ TiB2 composites increase with increase of the amount of TiB2 ceramics.展开更多
Ni-50at.%A1 matrix composites containing 0 to 20v.% TiB_(2) particles have been successfully fabricated by HPES technique. The results show that the Vickers hardness at room temperature and the compressive yield stren...Ni-50at.%A1 matrix composites containing 0 to 20v.% TiB_(2) particles have been successfully fabricated by HPES technique. The results show that the Vickers hardness at room temperature and the compressive yield strength from room temperature to 1000℃ of the composites increase with increasing volume fraction of the strengthening phase. Especially, the yield strength of NiAl-20TiB_(2) was approximately twice as high as that of unreinforced NiAl. The ductility of the composites at room temperature is also superior to the monolithic NiAl.展开更多
TiC-TiB2-Cu composites were produced by self-propagating high-temperature synthesis combined with pseudo hot isostatic pressing using Ti, B4C and Cu powders. The microstructure and mechanical properties of the composi...TiC-TiB2-Cu composites were produced by self-propagating high-temperature synthesis combined with pseudo hot isostatic pressing using Ti, B4C and Cu powders. The microstructure and mechanical properties of the composites were investigated. The X-ray diffraction （XRD） and scanning electron microscopy （SEM） results showed that the final products were only TiC, TiB2 and Cu phases. The clubbed TiB2 grains and spheroidal or irregular TiC grains were found in the microstructure of synthesized products. The reaction temperature and grain size of TiB2 and TiC particles decreased with increasing Cu content. The introduction of Cu into the composites resulted in a drastic increase in the relative density and flexual strength, and the maximum values were obtained with the addition of 20 wt pct, while the fracture toughness was the best when Cu content was 40 wt pct.展开更多
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
Reaction-milled NiAl-TiB2 composite was fabricated by mechanical alloying elemental powders and hot pressing. TiB2 particles are distributed mostly in grain boundaries of the matrix. The compressive strain to failure ...Reaction-milled NiAl-TiB2 composite was fabricated by mechanical alloying elemental powders and hot pressing. TiB2 particles are distributed mostly in grain boundaries of the matrix. The compressive strain to failure of the composite at RT is about twice that of cast NiAl. The compressive yield stress at high temperatures is about 4.5 times higher than that of extruded NiAl, and is also much stronger than XD NiAl-TiB2 composites. Deformation behavior between 1000~1100℃ with different strain rates has been investigated展开更多
A NiAl/TiB2 nanocomposite is synthesized by mechanical alloying elemental powders. Upon milling for a certain time, an abrupt exothermic reaction occurs and a large amount of NiAl and TiB2 compounds form simultaneousl...A NiAl/TiB2 nanocomposite is synthesized by mechanical alloying elemental powders. Upon milling for a certain time, an abrupt exothermic reaction occurs and a large amount of NiAl and TiB2 compounds form simultaneously. It is suggested that two separate chemical reactions,i.e. Ni+Al →NiAl and Ti+2B→TiB2, are involved during the exothermic reaction. Additionof Ti and B to Ni-Al system impedes the structural evolution of Ni and Al powders and delays the abrupt reaction. The final products are equilibrium phases without any metastable phases formed. This type of reaction is suggested to be suitable for alloy systems with two large heatrelease reactions.展开更多
14% and 20% (volume fraction) TiB2p/6061Al composites were fabricated by pressure infiltration method, and then were extruded. The microstructure and properties of TiB2p/Al composites before and after extrusion were s...14% and 20% (volume fraction) TiB2p/6061Al composites were fabricated by pressure infiltration method, and then were extruded. The microstructure and properties of TiB2p/Al composites before and after extrusion were studied by TEM, SEM and tensile method. The results show that TiB2 particles employed are equiaxed polyhedrals and are well wetted with the aluminum alloy. Hot extruding is effective in eliminating defects such as pores, which are induced in the fabrication process. After T6 treatment and extrusion treatment, elastic modulus, tensile strength and elongation of 14%TiB2p/6061Al composites are 107 GPa, 364.1 MPa and 9.25%, respectively. While those of 20%TiB2p/6061Al composites are 120 GPa, 472.6 MPa and 9.79%, respectively, which show high strength and plasticity. A lot of dimples and a few cracked particles are observed on the fracture surfaces of the composites, which indicates good plasticity of the composites. The high strength and plasticity of TiB2p/6061Al composites are attributed to good bonding between TiB2 particles and aluminum alloy.展开更多
TiB2/ZL114 composites with the density of 2.733 g/cm^3 were fabricated through reaction of K2TiF4 and KBF4 （LSM method）. The composites were characterized by X-ray diffraction （XRD） and scanning electron microsco...TiB2/ZL114 composites with the density of 2.733 g/cm^3 were fabricated through reaction of K2TiF4 and KBF4 （LSM method）. The composites were characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM）. The internal friction measurements were performed on DTM-II-J dynamic modulus damping analyzer and the mechanisms were investigated. Experimental results indicate that reinforced particles are well-distributed in the matrix and the internal friction value of TiB2/ZL114 composites is up to a maximum of 9.04×10^-3, almost twice that of ZL114. The internal friction results form dislocation vibration within the material, the sliding of grain boundary and phase interface, and together with the micro-plastic deformation caused by difference in coefficients of thermal expansion and elasticity modulus of various phases. The average internal friction values of samples with the sizes of 40 mm×4 mm×2 mm, 40 mm×8 mm×2 mm and 40 mm×25 mm×2 mm are 8.83 ×10^-3, 8.89 × 10^-3, and 8.93× 10^-3, respectively. Thus, the developed composites are of low density, high internal friction, and the sizes of samples have no relation to the internal friction behavior.展开更多
Ceramic tapes, containing Al2O3-25 wt pct TiB2(B) and Al2O3-25 wt pct nano-TiC (c), have been obtained by tape casting process. Numerous tapes (about 60～80 tapes) were prepared by stacking in turn the composition (B)...Ceramic tapes, containing Al2O3-25 wt pct TiB2(B) and Al2O3-25 wt pct nano-TiC (c), have been obtained by tape casting process. Numerous tapes (about 60～80 tapes) were prepared by stacking in turn the composition (B) and (C), laminating under 10 MPa pressure, eliminating the solvent and burning out the polymer additives. The final green bodies were hot pressed at 1750℃ and 30 MPa. The composite has a bending strength of 568 MPa and a fracture toughness of 5.8 M Pa·m1/2. SEM analysis exhibits that Al2O3 particle growth was inhibited by TiC particles in C. but TiB2 particles could not hinder Al2O3 growth in B. The curves of GTA indicates that all organic additives could be removed completely above 600℃展开更多
Aluminum alloys are used frequently in aerospace and ship building industry. Due to poor wear and corrosion resistance, conventional aluminum alloys are replaced by metal matrix composites (MMC). Aluminum alloy matrix...Aluminum alloys are used frequently in aerospace and ship building industry. Due to poor wear and corrosion resistance, conventional aluminum alloys are replaced by metal matrix composites (MMC). Aluminum alloy matrix reinforced with ceramic particles (TiB2) has importance in industry where components slide each other. The main task is to produce MMCs with low cost effective way to meet the requirement. In this study, an attempt is made to produce AA6061/TiB2 MMCs with different volume fractions of ceramic particles using friction stir processing technique. The dry sliding wear behavior of composites was investigated using pin on disc method. The lowest wear resistance has obtained for 8% composite. The corrosion of composites was analyzed by salt spray method. It was found that wear and corrosion resistance was increased with increase of reinforcement which was higher for 8% composite.展开更多
TiB2 and Dy2O3 were used as codeposited particles in the preparation of Ni-TiB2-Dy2O3 composite coatings to improve its performance. Ni-TiB2-Dy2O3 composite coatings were prepared by electrodeposition method with a ni...TiB2 and Dy2O3 were used as codeposited particles in the preparation of Ni-TiB2-Dy2O3 composite coatings to improve its performance. Ni-TiB2-Dy2O3 composite coatings were prepared by electrodeposition method with a nickel cetyltrimethylammonium bromide and hexadecylpyridinium bromide solution containing TiB2 and Dy2O3 particles. The content of codeposited TiB2 and Dy2O3 in the composite coatings was controlled by adding TiB2 and Dy2O3 particles of different concentrations into the solution, respectively. The effects of TiB2 and Dy2O3 content on microhardness, wear mass loss and friction coefficients of composite coatings were investigated. The composite coatings were characterized by X-ray diffraction （XRD）, inductively coupled plasma-atomic emission spectrometer （ICP-AES） and scanning electron microscopy （SEM） techniques. Ni-TiBE-Dy2O3 composite coatings showed higher microhardness, lower wear mass loss and friction coefficient compared with those of the pure Ni coating and Ni-TiB2 composite coatings. The wear mass loss of Ni-TiB2-Dy2O3 composite coatings was 9 and 1.57 times lower than that of the pure Ni coating and Ni-TiB2 composite coatings, respectively. The friction coefficient of pure Ni coating, Ni-TiB2 and Ni-TiB2-Dy2O3 composite coatings were 0.723, 0.815 and 0.619, respectively. Ni-TiBE-Dy2O3 composite coatings displayed the least friction coefficient among the three coatings. Dy2O3 particles in composite coatings might serve as a solid lubricant between contact surfaces to decrease the friction coefficient and abate the wear of the composite coatings. The loading-bearing capacity and the wear-reducing effect of the Dy2O3 particles were closely related to the content of Dy2O3 particles in the composite coatings.展开更多
文摘A suitable combustion synthesis and densification process was designed to fabricate dense NiAl/ TiB2 composites from Ni-Al- Ti-B system. Combustion synthesis processing and microstructure characteristics of products were studied in detail. The results show that the amount of TiB2 ceramics has a great influence on the combustion synthesis processing and microstructure; with the increase of the amount of TiB2 ceramics, the combustion temperature and combustion velocity increase rapidly. The volume of synthesized products and the grain size of ceramics particle size are also affected by the amount of TiB2 ceramics. TiB2 ceramics fiber can be produced in this synthesis system. The dense NiAl/ TiB2 composites with residual porosity of no more than 1% are fabricated by the combustion synthesis and hot pressing, the mechanical properties of the dense NiAl/ TiB2 composites increase with increase of the amount of TiB2 ceramics.
文摘Ni-50at.%A1 matrix composites containing 0 to 20v.% TiB_(2) particles have been successfully fabricated by HPES technique. The results show that the Vickers hardness at room temperature and the compressive yield strength from room temperature to 1000℃ of the composites increase with increasing volume fraction of the strengthening phase. Especially, the yield strength of NiAl-20TiB_(2) was approximately twice as high as that of unreinforced NiAl. The ductility of the composites at room temperature is also superior to the monolithic NiAl.
基金The work was supported by the Foundation of Aerospace Innovation Fund and the National Natural Science Foundation of China(No.90505015)the Foundation of National Key Laboratory for Remanufacturing.
文摘TiC-TiB2-Cu composites were produced by self-propagating high-temperature synthesis combined with pseudo hot isostatic pressing using Ti, B4C and Cu powders. The microstructure and mechanical properties of the composites were investigated. The X-ray diffraction （XRD） and scanning electron microscopy （SEM） results showed that the final products were only TiC, TiB2 and Cu phases. The clubbed TiB2 grains and spheroidal or irregular TiC grains were found in the microstructure of synthesized products. The reaction temperature and grain size of TiB2 and TiC particles decreased with increasing Cu content. The introduction of Cu into the composites resulted in a drastic increase in the relative density and flexual strength, and the maximum values were obtained with the addition of 20 wt pct, while the fracture toughness was the best when Cu content was 40 wt pct.
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.
文摘Reaction-milled NiAl-TiB2 composite was fabricated by mechanical alloying elemental powders and hot pressing. TiB2 particles are distributed mostly in grain boundaries of the matrix. The compressive strain to failure of the composite at RT is about twice that of cast NiAl. The compressive yield stress at high temperatures is about 4.5 times higher than that of extruded NiAl, and is also much stronger than XD NiAl-TiB2 composites. Deformation behavior between 1000~1100℃ with different strain rates has been investigated
文摘A NiAl/TiB2 nanocomposite is synthesized by mechanical alloying elemental powders. Upon milling for a certain time, an abrupt exothermic reaction occurs and a large amount of NiAl and TiB2 compounds form simultaneously. It is suggested that two separate chemical reactions,i.e. Ni+Al →NiAl and Ti+2B→TiB2, are involved during the exothermic reaction. Additionof Ti and B to Ni-Al system impedes the structural evolution of Ni and Al powders and delays the abrupt reaction. The final products are equilibrium phases without any metastable phases formed. This type of reaction is suggested to be suitable for alloy systems with two large heatrelease reactions.
基金Project(NCET-07-0234) supported by Program for New Century Excellent Talents in UniversityProject(20060400813) supported by China Postdoctoral Science Foundation
文摘14% and 20% (volume fraction) TiB2p/6061Al composites were fabricated by pressure infiltration method, and then were extruded. The microstructure and properties of TiB2p/Al composites before and after extrusion were studied by TEM, SEM and tensile method. The results show that TiB2 particles employed are equiaxed polyhedrals and are well wetted with the aluminum alloy. Hot extruding is effective in eliminating defects such as pores, which are induced in the fabrication process. After T6 treatment and extrusion treatment, elastic modulus, tensile strength and elongation of 14%TiB2p/6061Al composites are 107 GPa, 364.1 MPa and 9.25%, respectively. While those of 20%TiB2p/6061Al composites are 120 GPa, 472.6 MPa and 9.79%, respectively, which show high strength and plasticity. A lot of dimples and a few cracked particles are observed on the fracture surfaces of the composites, which indicates good plasticity of the composites. The high strength and plasticity of TiB2p/6061Al composites are attributed to good bonding between TiB2 particles and aluminum alloy.
基金financial support from the National Natural Science Foundation of China (No.50864002)from the Innovation Project of Guangxi Graduate Education (No.2008105930805M076)
文摘TiB2/ZL114 composites with the density of 2.733 g/cm^3 were fabricated through reaction of K2TiF4 and KBF4 （LSM method）. The composites were characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM）. The internal friction measurements were performed on DTM-II-J dynamic modulus damping analyzer and the mechanisms were investigated. Experimental results indicate that reinforced particles are well-distributed in the matrix and the internal friction value of TiB2/ZL114 composites is up to a maximum of 9.04×10^-3, almost twice that of ZL114. The internal friction results form dislocation vibration within the material, the sliding of grain boundary and phase interface, and together with the micro-plastic deformation caused by difference in coefficients of thermal expansion and elasticity modulus of various phases. The average internal friction values of samples with the sizes of 40 mm×4 mm×2 mm, 40 mm×8 mm×2 mm and 40 mm×25 mm×2 mm are 8.83 ×10^-3, 8.89 × 10^-3, and 8.93× 10^-3, respectively. Thus, the developed composites are of low density, high internal friction, and the sizes of samples have no relation to the internal friction behavior.
文摘Ceramic tapes, containing Al2O3-25 wt pct TiB2(B) and Al2O3-25 wt pct nano-TiC (c), have been obtained by tape casting process. Numerous tapes (about 60～80 tapes) were prepared by stacking in turn the composition (B) and (C), laminating under 10 MPa pressure, eliminating the solvent and burning out the polymer additives. The final green bodies were hot pressed at 1750℃ and 30 MPa. The composite has a bending strength of 568 MPa and a fracture toughness of 5.8 M Pa·m1/2. SEM analysis exhibits that Al2O3 particle growth was inhibited by TiC particles in C. but TiB2 particles could not hinder Al2O3 growth in B. The curves of GTA indicates that all organic additives could be removed completely above 600℃
文摘Aluminum alloys are used frequently in aerospace and ship building industry. Due to poor wear and corrosion resistance, conventional aluminum alloys are replaced by metal matrix composites (MMC). Aluminum alloy matrix reinforced with ceramic particles (TiB2) has importance in industry where components slide each other. The main task is to produce MMCs with low cost effective way to meet the requirement. In this study, an attempt is made to produce AA6061/TiB2 MMCs with different volume fractions of ceramic particles using friction stir processing technique. The dry sliding wear behavior of composites was investigated using pin on disc method. The lowest wear resistance has obtained for 8% composite. The corrosion of composites was analyzed by salt spray method. It was found that wear and corrosion resistance was increased with increase of reinforcement which was higher for 8% composite.
基金Project(51272141)supported by the National Natural Science Foundation of ChinaProject(ts20110828)supported by the Taishan Scholars Project of Shandong Province,ChinaProject(2015AA034404)supported by the Ministry of Science and Technology of China
基金supported by the Science Technology Foundation of Shanghai (072305113)the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning and Science Technology Foundation of Shanghai Institute of Technology (KJ2008-07)
文摘TiB2 and Dy2O3 were used as codeposited particles in the preparation of Ni-TiB2-Dy2O3 composite coatings to improve its performance. Ni-TiB2-Dy2O3 composite coatings were prepared by electrodeposition method with a nickel cetyltrimethylammonium bromide and hexadecylpyridinium bromide solution containing TiB2 and Dy2O3 particles. The content of codeposited TiB2 and Dy2O3 in the composite coatings was controlled by adding TiB2 and Dy2O3 particles of different concentrations into the solution, respectively. The effects of TiB2 and Dy2O3 content on microhardness, wear mass loss and friction coefficients of composite coatings were investigated. The composite coatings were characterized by X-ray diffraction （XRD）, inductively coupled plasma-atomic emission spectrometer （ICP-AES） and scanning electron microscopy （SEM） techniques. Ni-TiBE-Dy2O3 composite coatings showed higher microhardness, lower wear mass loss and friction coefficient compared with those of the pure Ni coating and Ni-TiB2 composite coatings. The wear mass loss of Ni-TiB2-Dy2O3 composite coatings was 9 and 1.57 times lower than that of the pure Ni coating and Ni-TiB2 composite coatings, respectively. The friction coefficient of pure Ni coating, Ni-TiB2 and Ni-TiB2-Dy2O3 composite coatings were 0.723, 0.815 and 0.619, respectively. Ni-TiBE-Dy2O3 composite coatings displayed the least friction coefficient among the three coatings. Dy2O3 particles in composite coatings might serve as a solid lubricant between contact surfaces to decrease the friction coefficient and abate the wear of the composite coatings. The loading-bearing capacity and the wear-reducing effect of the Dy2O3 particles were closely related to the content of Dy2O3 particles in the composite coatings.
