The researchers made magnesium aluminum composite panels by asymmetric metal packaging and studied rolling temperature,holding time,and high temperature heat treatment,such as short time and low temperatures over long...The researchers made magnesium aluminum composite panels by asymmetric metal packaging and studied rolling temperature,holding time,and high temperature heat treatment,such as short time and low temperatures over long periods of time parameters under the new preparation method.We tested the new magnesium aluminum composite panels’tensing properties and bending performance by using scanning electric mirror and EDS.It is concluded that the new magnesium aluminum composite panels’elongation is 24%under the tensile strength of 260 MPa.Regarding performance when compared with other methods,traditional magnesium aluminum composite panels’elongation is 10%,which shows its advanced nature.At the same time,bending performance test showed that the combination of the composite board has higher performance,offering the reference value for the preparation of magnesium–aluminum composite plate.展开更多
The fabrication of AlN-TiC/Al composites by carbon- and nitrogen-containing gas injection into Al-Mg-Ti melts was studied. It was shown that AlN and TiC particles could be formed by the in situ reaction of mixture gas...The fabrication of AlN-TiC/Al composites by carbon- and nitrogen-containing gas injection into Al-Mg-Ti melts was studied. It was shown that AlN and TiC particles could be formed by the in situ reaction of mixture gas （N2 ＋ C2H2 ＋ NH3） with Al-Mg-Ti melts. The condition for the formation of AlN was that the treatment temperature must be higher than 1373 K, and the amounts of AlN and TiC increased with the increase of the treatment temperature and the gas injection time It was considered that AlN was formed by the direct reaction of Al with nitrogen-containing gas at the interface of the gas bubble and the melt. However, the mechanism of TiC formation is a combination mechanism of solution-precipitation and solid-liquid reaction.展开更多
The key factor in semi-solid metal processing is the solid fraction at the forming temperature because it affects the microstructure and mechanical properties of the thixoformed components. Though an enormous amount o...The key factor in semi-solid metal processing is the solid fraction at the forming temperature because it affects the microstructure and mechanical properties of the thixoformed components. Though an enormous amount of data exists on the solid fraction-temperature re- lationship in A356 alloy, information regarding the solid fraction evolution characteristics of A356-TiB2 composites is scarce. The present article establishes the temperature-solid fraction correlation in A356 alloy and A356-xTiB2 （x = 2.5wt% and 5wt%） composites using dif- ferential thermal analysis （DTA）. The DTA results indicate that the solidification characteristics of the composites exhibited a variation of 2℃ and 3℃ in liquidus temperatures and a variation of 3℃ and 5℃ in solidus temperatures with respect to the base alloy. Moreover, the eutectic growth temperature and the solid fraction（fs） vs. temperature characteristics of the composites were found to be higher than those of the base alloy. The investigation revealed that in-situ formed TiB2 particles in the molten metal introduced more nucleation sites and reduced undercooling.展开更多
A novel technique in which TiC particulate are prepared by an in situ reaction in molten aluminum was introduced for producing TiC/Al composite. In order to reveal the characteristics of the technique, the formation m...A novel technique in which TiC particulate are prepared by an in situ reaction in molten aluminum was introduced for producing TiC/Al composite. In order to reveal the characteristics of the technique, the formation mechanism of TiC particulate prepared by this method was studied. Both theoretical and experimental results show that the TiC particulate is formed by a diffusion mechanism when the molar fraction of aluminum in the preforms is higher than 20.02%. On the contrary, the TiC particulate is formed by a solution-precipitation mechanism when the fraction of aluminum in the preforms is lower than 20.02%.展开更多
Al-based composites reinforced with A1-Ti intermetallic compounds/Ti metal hierarchically spherical agents were successfully fabricated by powder metallurgy. This kind of structure produces strongly bonded interfaces ...Al-based composites reinforced with A1-Ti intermetallic compounds/Ti metal hierarchically spherical agents were successfully fabricated by powder metallurgy. This kind of structure produces strongly bonded interfaces as well as soft/hard/soft transition regions between the matrix and reinforced agents, which are beneficial to load transfer during deformation. As expected, the resultant composites exhibit promising mechanical properties at ambient temperature. The underlying mechanism was also discussed in this paper.展开更多
Ti_(3)AlC_(2)-reinforced Ag-based composites,which are used as sliding current collectors,electrical contacts,and electrode materials,exhibit remarkable performances.However,the interfacial reactions between Ag and Ti...Ti_(3)AlC_(2)-reinforced Ag-based composites,which are used as sliding current collectors,electrical contacts,and electrode materials,exhibit remarkable performances.However,the interfacial reactions between Ag and Ti_(3)AlC_(2) significantly degrade the electrical and thermal properties of these composites.To diminish these interfacial reactions,we fabricated carbon-coated Ti_(3)AlC_(2) particles(C@Ti_(3)AlC_(2))as reinforcement and prepared Ag–10wt%C@Ti_(3)AlC_(2) composites with carbon-layer thicknesses ranging from 50–200 nm.Compared with the uncoated Ag–Ti_(3)AlC_(2) composite,Ag–C@Ti_(3)AlC_(2) was found to have a better distribution of Ti_(3)AlC_(2) particles.With increases in the carbon-layer thickness,the Vickers hardness value and relative density of Ag–C@Ti_(3)AlC_(2) gradually decreases.With a carbon-layer thickness of 150 nm,we obtained the lowest resistivity of Ag–C@Ti_(3)AlC_(2) of 29.4135.5×10^(−9)Ω·m,which is half that of Ag–Ti_(3)AlC_(2)(66.7×10^(−9)Ω·m).The thermal conductivity of Ag–C@Ti_(3)AlC_(2) reached a maximum value of 135.5 W·m^(−1)·K^(−1) with a 200-nm carbon coating(~1.8 times that of Ag–Ti_(3)AlC_(2)).These results indicate that the carbon-coating method is a feasible strategy for improving the performance of Ag–C@Ti_(3)AlC_(2) composites.展开更多
Aluminum foam is a light weight material with good mechanical and energy absorption properties. In this study, aluminum foam composite was fabricated using aluminum powder 6061 and silicon carbide (SiC) powder. Titani...Aluminum foam is a light weight material with good mechanical and energy absorption properties. In this study, aluminum foam composite was fabricated using aluminum powder 6061 and silicon carbide (SiC) powder. Titanium hydride (TiH2) was used as the foaming agent. Cold compact followed by hot pressing (sintering) was used to produce the composite precursor. Foaming was carried out, following the sintering process, by heating the aluminum composite precursor to a temperature above the melting point of aluminum (Al). The linear expansion of the foam and the percent porosity were found to increase as the SiC percentage decreased from 10 to 4%, whereas the density got lower. The percent porosity and linear expansion were both found to increase as the percentage of the foaming agent was increased from 0.5 to 1.5%. Compression stress was evaluated for two different porosity values (40% and 47%), and found to be higher for the samples with lower percent porosity at the same strain value. Effect of shape memory alloy fiber, made of nickel and titanium (NiTi), on the mechanical properties was also investigated. The compression stress was higher, in the densification region, for the samples in which NiTi was used.展开更多
This paper considers the technique of obtaining boride-containing nanostructured composite materials by the method of self-propagating high-temperature synthesis (SHS). It is shown that the selection of regimes and co...This paper considers the technique of obtaining boride-containing nanostructured composite materials by the method of self-propagating high-temperature synthesis (SHS). It is shown that the selection of regimes and conditions of reactions allows receiving materials on the basis of titanium and chromium borides as well as aluminum oxide with finely dispersed structure and high mechanical properties.展开更多
TiN- Al2O3 composite powder was prepared by aluminothermic reduction- nitridation method with starting materials of aluminum-containing dross and rutile,and metallic aluminum in the aluminum-containing dross as reduce...TiN- Al2O3 composite powder was prepared by aluminothermic reduction- nitridation method with starting materials of aluminum-containing dross and rutile,and metallic aluminum in the aluminum-containing dross as reducer. The influences of synthesis temperature（600-1 400 ℃） and aluminum-containing dross addition（20% lower than theoretical value,theoretical value,20% higher than theoretical value,and 50% higher than theoretical value） on phase compositions and microstructure of the composites were investigated,and the reaction mechanism was analyzed. The results show that（1） TiN- Al2O3 composite powder can be synthesized under the experimental conditions; the main phases are TiN,α-Al2O3,a little bytownite,and MgAl2O4;（2）enhancing synthesis temperature or increasing aluminumcontaining dross addition favors the reaction of aluminothermic reduction- nitridation;（3） in the synthesized products,α-Al2O3 is platy or columnar; TiN is sub-micron granular,which reinforces and toughens the composite.展开更多
Two types of titanium/steel composite plates with the same thickness were manufactured by parallel explosive welding and double vertical explosive welding and rolling, respectively. The comparative analysis of microst...Two types of titanium/steel composite plates with the same thickness were manufactured by parallel explosive welding and double vertical explosive welding and rolling, respectively. The comparative analysis of microstructure showed that the interface of double vertical explosive welding plate （B plate） tended to be straight while the interface of parallel explosive welding plate （A plate） was wavy bonding. Defects near the interface of B plate were extruded, and the thickness of the diffusion layer of B plate was thicker under the effects of preheating temperature and press-working. Comparative tests of mechanical properties indicated that the tensile shear strength of B plate was lower while its micro-hardness was higher. Specimens of these two types of plates were neither separated nor cracked after bending up to 180° in the three-point bending test. From the microstructural observation of tensile fracture characteristics, A plate had strong toughness fracture while B plate had mainly ductile fracture with cleavage fracture as the supplement. Macroscopically, the tensile strength of the latter was 7.9% less than that of the former. However, both satisfied the Chinese standard of tensile strength.展开更多
基金the Shanxi Province University Science and Technology innovation project(2014108).
文摘The researchers made magnesium aluminum composite panels by asymmetric metal packaging and studied rolling temperature,holding time,and high temperature heat treatment,such as short time and low temperatures over long periods of time parameters under the new preparation method.We tested the new magnesium aluminum composite panels’tensing properties and bending performance by using scanning electric mirror and EDS.It is concluded that the new magnesium aluminum composite panels’elongation is 24%under the tensile strength of 260 MPa.Regarding performance when compared with other methods,traditional magnesium aluminum composite panels’elongation is 10%,which shows its advanced nature.At the same time,bending performance test showed that the combination of the composite board has higher performance,offering the reference value for the preparation of magnesium–aluminum composite plate.
文摘The fabrication of AlN-TiC/Al composites by carbon- and nitrogen-containing gas injection into Al-Mg-Ti melts was studied. It was shown that AlN and TiC particles could be formed by the in situ reaction of mixture gas （N2 ＋ C2H2 ＋ NH3） with Al-Mg-Ti melts. The condition for the formation of AlN was that the treatment temperature must be higher than 1373 K, and the amounts of AlN and TiC increased with the increase of the treatment temperature and the gas injection time It was considered that AlN was formed by the direct reaction of Al with nitrogen-containing gas at the interface of the gas bubble and the melt. However, the mechanism of TiC formation is a combination mechanism of solution-precipitation and solid-liquid reaction.
基金financial support from the Indian Institute of Technology Bhubaneswar under the SEED project grant for fabricating the "cooling slope casting" experimental setupthe support extended by Central Research Facility (CRF), Indian Institute of Technology Kharagpur, toward the facility for conducting DTA experiments
文摘The key factor in semi-solid metal processing is the solid fraction at the forming temperature because it affects the microstructure and mechanical properties of the thixoformed components. Though an enormous amount of data exists on the solid fraction-temperature re- lationship in A356 alloy, information regarding the solid fraction evolution characteristics of A356-TiB2 composites is scarce. The present article establishes the temperature-solid fraction correlation in A356 alloy and A356-xTiB2 （x = 2.5wt% and 5wt%） composites using dif- ferential thermal analysis （DTA）. The DTA results indicate that the solidification characteristics of the composites exhibited a variation of 2℃ and 3℃ in liquidus temperatures and a variation of 3℃ and 5℃ in solidus temperatures with respect to the base alloy. Moreover, the eutectic growth temperature and the solid fraction（fs） vs. temperature characteristics of the composites were found to be higher than those of the base alloy. The investigation revealed that in-situ formed TiB2 particles in the molten metal introduced more nucleation sites and reduced undercooling.
文摘A novel technique in which TiC particulate are prepared by an in situ reaction in molten aluminum was introduced for producing TiC/Al composite. In order to reveal the characteristics of the technique, the formation mechanism of TiC particulate prepared by this method was studied. Both theoretical and experimental results show that the TiC particulate is formed by a diffusion mechanism when the molar fraction of aluminum in the preforms is higher than 20.02%. On the contrary, the TiC particulate is formed by a solution-precipitation mechanism when the fraction of aluminum in the preforms is lower than 20.02%.
文摘Al-based composites reinforced with A1-Ti intermetallic compounds/Ti metal hierarchically spherical agents were successfully fabricated by powder metallurgy. This kind of structure produces strongly bonded interfaces as well as soft/hard/soft transition regions between the matrix and reinforced agents, which are beneficial to load transfer during deformation. As expected, the resultant composites exhibit promising mechanical properties at ambient temperature. The underlying mechanism was also discussed in this paper.
基金financial support of the National Natural Science Foundation of China(Nos.51731004 and 51671054)the Natural Science Foundation of Jiangsu Province(No.BK20181285)the Fundamental Research Funds for the Central Universities,China(No.2242019K 40056).
文摘Ti_(3)AlC_(2)-reinforced Ag-based composites,which are used as sliding current collectors,electrical contacts,and electrode materials,exhibit remarkable performances.However,the interfacial reactions between Ag and Ti_(3)AlC_(2) significantly degrade the electrical and thermal properties of these composites.To diminish these interfacial reactions,we fabricated carbon-coated Ti_(3)AlC_(2) particles(C@Ti_(3)AlC_(2))as reinforcement and prepared Ag–10wt%C@Ti_(3)AlC_(2) composites with carbon-layer thicknesses ranging from 50–200 nm.Compared with the uncoated Ag–Ti_(3)AlC_(2) composite,Ag–C@Ti_(3)AlC_(2) was found to have a better distribution of Ti_(3)AlC_(2) particles.With increases in the carbon-layer thickness,the Vickers hardness value and relative density of Ag–C@Ti_(3)AlC_(2) gradually decreases.With a carbon-layer thickness of 150 nm,we obtained the lowest resistivity of Ag–C@Ti_(3)AlC_(2) of 29.4135.5×10^(−9)Ω·m,which is half that of Ag–Ti_(3)AlC_(2)(66.7×10^(−9)Ω·m).The thermal conductivity of Ag–C@Ti_(3)AlC_(2) reached a maximum value of 135.5 W·m^(−1)·K^(−1) with a 200-nm carbon coating(~1.8 times that of Ag–Ti_(3)AlC_(2)).These results indicate that the carbon-coating method is a feasible strategy for improving the performance of Ag–C@Ti_(3)AlC_(2) composites.
文摘Aluminum foam is a light weight material with good mechanical and energy absorption properties. In this study, aluminum foam composite was fabricated using aluminum powder 6061 and silicon carbide (SiC) powder. Titanium hydride (TiH2) was used as the foaming agent. Cold compact followed by hot pressing (sintering) was used to produce the composite precursor. Foaming was carried out, following the sintering process, by heating the aluminum composite precursor to a temperature above the melting point of aluminum (Al). The linear expansion of the foam and the percent porosity were found to increase as the SiC percentage decreased from 10 to 4%, whereas the density got lower. The percent porosity and linear expansion were both found to increase as the percentage of the foaming agent was increased from 0.5 to 1.5%. Compression stress was evaluated for two different porosity values (40% and 47%), and found to be higher for the samples with lower percent porosity at the same strain value. Effect of shape memory alloy fiber, made of nickel and titanium (NiTi), on the mechanical properties was also investigated. The compression stress was higher, in the densification region, for the samples in which NiTi was used.
文摘This paper considers the technique of obtaining boride-containing nanostructured composite materials by the method of self-propagating high-temperature synthesis (SHS). It is shown that the selection of regimes and conditions of reactions allows receiving materials on the basis of titanium and chromium borides as well as aluminum oxide with finely dispersed structure and high mechanical properties.
文摘TiN- Al2O3 composite powder was prepared by aluminothermic reduction- nitridation method with starting materials of aluminum-containing dross and rutile,and metallic aluminum in the aluminum-containing dross as reducer. The influences of synthesis temperature（600-1 400 ℃） and aluminum-containing dross addition（20% lower than theoretical value,theoretical value,20% higher than theoretical value,and 50% higher than theoretical value） on phase compositions and microstructure of the composites were investigated,and the reaction mechanism was analyzed. The results show that（1） TiN- Al2O3 composite powder can be synthesized under the experimental conditions; the main phases are TiN,α-Al2O3,a little bytownite,and MgAl2O4;（2）enhancing synthesis temperature or increasing aluminumcontaining dross addition favors the reaction of aluminothermic reduction- nitridation;（3） in the synthesized products,α-Al2O3 is platy or columnar; TiN is sub-micron granular,which reinforces and toughens the composite.
基金This project was sponsored by the National Natural Science Foundation of China （No. 51541112） and Special Fund Achievement Transformation Projects in Jiangsu of China （No. BA2012030）.
文摘Two types of titanium/steel composite plates with the same thickness were manufactured by parallel explosive welding and double vertical explosive welding and rolling, respectively. The comparative analysis of microstructure showed that the interface of double vertical explosive welding plate （B plate） tended to be straight while the interface of parallel explosive welding plate （A plate） was wavy bonding. Defects near the interface of B plate were extruded, and the thickness of the diffusion layer of B plate was thicker under the effects of preheating temperature and press-working. Comparative tests of mechanical properties indicated that the tensile shear strength of B plate was lower while its micro-hardness was higher. Specimens of these two types of plates were neither separated nor cracked after bending up to 180° in the three-point bending test. From the microstructural observation of tensile fracture characteristics, A plate had strong toughness fracture while B plate had mainly ductile fracture with cleavage fracture as the supplement. Macroscopically, the tensile strength of the latter was 7.9% less than that of the former. However, both satisfied the Chinese standard of tensile strength.
