Powder metallurgy method was used to prepare copper alloy nanocomposites （CuZr/AlN） with high strength and conductivity. Optical microscopy, high-resolution transmission electron microscopy and other methods were ad...Powder metallurgy method was used to prepare copper alloy nanocomposites （CuZr/AlN） with high strength and conductivity. Optical microscopy, high-resolution transmission electron microscopy and other methods were adopted to study the impact of different sintering technologies on the structural and mechanical properties as well as the impact of solution and aging treatments on the mechanical properties of CuZr/AlN. The result shows that the specimen has a dense structure, and the size of the crystal grain is around 0.2 μm. The Brinell hardness of the specimen increases with the increase in re-pressing pressure and sintering temperature. The Brinell hardness of specimen also increases with the increase in zirconium content. However, above 0.5%（mass fraction） of zirconium content, the Brinell hardness of the nanocomposites is reduced. The buckling strength of the specimens increases with the increase in re-pressing pressure and sintering temperature. The buckling strength is the highest when the zirconium content is 0.5%. The Brinell hardness is lower after solution and aging treatments at 900 ℃. The Brinell hardness of the CuZr/AlN series specimen after the aging treatment at 500 ℃ or 600 ℃ increases. The specimen was also over aged at 700 ℃.展开更多
Multiwalled carbon nanotubes （MWCNTs） reinforced Cu-Sn alloy based nanocomposite was developed by powder metallurgy route. The mass fraction of CNTs was varied from 0 to 2% in a step of 0.5%. The developed nanocompo...Multiwalled carbon nanotubes （MWCNTs） reinforced Cu-Sn alloy based nanocomposite was developed by powder metallurgy route. The mass fraction of CNTs was varied from 0 to 2% in a step of 0.5%. The developed nanocomposites were subjected to density, hardness, electrical conductivity, and friction and wear tests. The results reveal that the density of nanocomposite decreases with the increase of the mass fraction of CNTs. A significant improvement in the hardness is noticed in the nanocomposite with the addition of CNTs. The developed nanocomposites show low coefficient of friction and improved wear resistance when compared with unreinforced alloy. At an applied load of 5 N, the coefficient of friction and wear loss of 2%CNTs reinforced Cu-Sn alloy nanocomposite decrease by 72% and 68%, respectively, compared with those of Cu-Sn alloy. The wear mechanisms of worn surfaces of the composites are reported. In addition, the electrical conductivity reduces with the increase of the content of CNTs.展开更多
Different mass fractions （0, 5%, 10%, and 15%） of the synthesized nano SiC particles reinforced Ti-6Al-4V （Ti64） alloy metal matrix composites （MMCs） were successfully fabricated by the powder metallurgy method....Different mass fractions （0, 5%, 10%, and 15%） of the synthesized nano SiC particles reinforced Ti-6Al-4V （Ti64） alloy metal matrix composites （MMCs） were successfully fabricated by the powder metallurgy method. The effects of addition of SiC particle on the mechanical properties of the composites such as hardness and compressive strength were investigated. The optimum density （93.33%） was obtained at the compaction pressure of 6.035 MPa. Scanning electron microscopic （SEM） observations of the microstructures revealed that the wettability and the bonding force were improved in Ti64 alloy/5% nano SiCp composites. The effect of nano SiCp content in Ti64 alloy/SiCp matrix composite on phase formation was investigated by X-ray diffraction. The correlation between mechanical parameter and phase formation was analyzed. The new phase of brittle interfaced reaction formed in the 10% and 15% SiCp composite specimens and resulted in no beneficial effect on the strength and hardness. The compressive strength and hardness of Ti64 alloy/5% nano SiCp MMCs showed higher values. Hence, 5% SiCp can be considered to be the optimal replacement content for the composite.展开更多
The process of mechanically assisted hydriding and subsequent thermal dehydriding was proposed to produce nanocrystalline Mg and Mg alloy powders using pure Mg and Mg-5.5%Zn-0.6%Zr(mass fraction)(ZK60 Mg) alloy as the...The process of mechanically assisted hydriding and subsequent thermal dehydriding was proposed to produce nanocrystalline Mg and Mg alloy powders using pure Mg and Mg-5.5%Zn-0.6%Zr(mass fraction)(ZK60 Mg) alloy as the starting materal.The hydriding was achieved by room-temperature reaction milling in hydrogen.The dehydriding was carried out by vacuum annealing of the as-milled powders.The microstructure and morphology of both the as-milled and subsequently dehydrided powders were characterized by X-ray diffraction analysis(XRD) ,transmission electron microscopy(TEM) ,and scanning electron microscopy(SEM) ,respectively.The results show that,by reaction milling in hydrogen,both Mg and ZK60 Mg alloy can be fully hydrided to form nanocrystalline MgH2 with an average grain size of 10 nm.After subsequent thermal dehydriding at 300℃,the MgH2 can be turned into Mg again,and the newly formed Mg grains are nanocrystallines,with an average grain size of 25 nm.展开更多
A new process of WC-Co cemented carbide was developed by using nano-grained W（Co, C） composite powders as raw materials processed by high-energy ball milling. X-ray diffraetion（XRD）, differential thermal analysis ...A new process of WC-Co cemented carbide was developed by using nano-grained W（Co, C） composite powders as raw materials processed by high-energy ball milling. X-ray diffraetion（XRD）, differential thermal analysis （DTA）, thermo-gravimetrie （TG） analysis and coercive forces of the sintered samples were adopted to analyze the phase transformation and constitution, and the microstructures of sintered samples were characterized by scanning electron microscopy（SEM）. The results show that the as-milled powders are transformed into transitional phases W2C and η （Co3W3C or Co6W6C） during sintering, and finally transformed into WC and Co phases completely at 1 250℃ for 30 min, and a large number of fibrous WC grains with about 1.2μm in length and 100 nm in radial dimension are formed in the sintered body at 1 300 ℃.展开更多
High temperature treatment of tungsten alloy of W-5wt.% TM （transition metals, TM = Ni, Fe, Cu, Co） nanopowder was run under different temperatures to cover the oxidation rate at different temperatures. The correlat...High temperature treatment of tungsten alloy of W-5wt.% TM （transition metals, TM = Ni, Fe, Cu, Co） nanopowder was run under different temperatures to cover the oxidation rate at different temperatures. The correlation was developed for certain temperatures to find an equation for the relation between time and weight. The thermal treatment was done for different quantities at certain times. The proposed equation studies the correlation between temperature, time, and weight. For each temperature, a number of points were recorded from the measured oxidation curve. The shape of the curves is well-represented in this paper. The final results will present the highest temperature, the maximum weight, and the maximum time for full oxidation at high and low temperatures.展开更多
基金Project(KJ2013A227)supported by the Natural Science Research Key Projects of Anhui Provincial Universities,ChinaProject(51104051)supported by the National Natural Science Foundation of ChinaProject(11C26213401903)supported by Innovation Fund for Small and Medium Technology Based Firms,China
文摘Powder metallurgy method was used to prepare copper alloy nanocomposites （CuZr/AlN） with high strength and conductivity. Optical microscopy, high-resolution transmission electron microscopy and other methods were adopted to study the impact of different sintering technologies on the structural and mechanical properties as well as the impact of solution and aging treatments on the mechanical properties of CuZr/AlN. The result shows that the specimen has a dense structure, and the size of the crystal grain is around 0.2 μm. The Brinell hardness of the specimen increases with the increase in re-pressing pressure and sintering temperature. The Brinell hardness of specimen also increases with the increase in zirconium content. However, above 0.5%（mass fraction） of zirconium content, the Brinell hardness of the nanocomposites is reduced. The buckling strength of the specimens increases with the increase in re-pressing pressure and sintering temperature. The buckling strength is the highest when the zirconium content is 0.5%. The Brinell hardness is lower after solution and aging treatments at 900 ℃. The Brinell hardness of the CuZr/AlN series specimen after the aging treatment at 500 ℃ or 600 ℃ increases. The specimen was also over aged at 700 ℃.
文摘Multiwalled carbon nanotubes （MWCNTs） reinforced Cu-Sn alloy based nanocomposite was developed by powder metallurgy route. The mass fraction of CNTs was varied from 0 to 2% in a step of 0.5%. The developed nanocomposites were subjected to density, hardness, electrical conductivity, and friction and wear tests. The results reveal that the density of nanocomposite decreases with the increase of the mass fraction of CNTs. A significant improvement in the hardness is noticed in the nanocomposite with the addition of CNTs. The developed nanocomposites show low coefficient of friction and improved wear resistance when compared with unreinforced alloy. At an applied load of 5 N, the coefficient of friction and wear loss of 2%CNTs reinforced Cu-Sn alloy nanocomposite decrease by 72% and 68%, respectively, compared with those of Cu-Sn alloy. The wear mechanisms of worn surfaces of the composites are reported. In addition, the electrical conductivity reduces with the increase of the content of CNTs.
基金CISL,Department of Physics,Annamalai University for the support in using AFM and SEM for experimentation
文摘Different mass fractions （0, 5%, 10%, and 15%） of the synthesized nano SiC particles reinforced Ti-6Al-4V （Ti64） alloy metal matrix composites （MMCs） were successfully fabricated by the powder metallurgy method. The effects of addition of SiC particle on the mechanical properties of the composites such as hardness and compressive strength were investigated. The optimum density （93.33%） was obtained at the compaction pressure of 6.035 MPa. Scanning electron microscopic （SEM） observations of the microstructures revealed that the wettability and the bonding force were improved in Ti64 alloy/5% nano SiCp composites. The effect of nano SiCp content in Ti64 alloy/SiCp matrix composite on phase formation was investigated by X-ray diffraction. The correlation between mechanical parameter and phase formation was analyzed. The new phase of brittle interfaced reaction formed in the 10% and 15% SiCp composite specimens and resulted in no beneficial effect on the strength and hardness. The compressive strength and hardness of Ti64 alloy/5% nano SiCp MMCs showed higher values. Hence, 5% SiCp can be considered to be the optimal replacement content for the composite.
基金Project(50574034)supported by the National Natural Science Foundation of ChinaProject(20060213016)supported by Doctoral Education Fund of Ministry of Education of China
文摘The process of mechanically assisted hydriding and subsequent thermal dehydriding was proposed to produce nanocrystalline Mg and Mg alloy powders using pure Mg and Mg-5.5%Zn-0.6%Zr(mass fraction)(ZK60 Mg) alloy as the starting materal.The hydriding was achieved by room-temperature reaction milling in hydrogen.The dehydriding was carried out by vacuum annealing of the as-milled powders.The microstructure and morphology of both the as-milled and subsequently dehydrided powders were characterized by X-ray diffraction analysis(XRD) ,transmission electron microscopy(TEM) ,and scanning electron microscopy(SEM) ,respectively.The results show that,by reaction milling in hydrogen,both Mg and ZK60 Mg alloy can be fully hydrided to form nanocrystalline MgH2 with an average grain size of 10 nm.After subsequent thermal dehydriding at 300℃,the MgH2 can be turned into Mg again,and the newly formed Mg grains are nanocrystallines,with an average grain size of 25 nm.
基金Project (50474049) supported by the National Natural Science Foundation of China
文摘A new process of WC-Co cemented carbide was developed by using nano-grained W（Co, C） composite powders as raw materials processed by high-energy ball milling. X-ray diffraetion（XRD）, differential thermal analysis （DTA）, thermo-gravimetrie （TG） analysis and coercive forces of the sintered samples were adopted to analyze the phase transformation and constitution, and the microstructures of sintered samples were characterized by scanning electron microscopy（SEM）. The results show that the as-milled powders are transformed into transitional phases W2C and η （Co3W3C or Co6W6C） during sintering, and finally transformed into WC and Co phases completely at 1 250℃ for 30 min, and a large number of fibrous WC grains with about 1.2μm in length and 100 nm in radial dimension are formed in the sintered body at 1 300 ℃.
文摘High temperature treatment of tungsten alloy of W-5wt.% TM （transition metals, TM = Ni, Fe, Cu, Co） nanopowder was run under different temperatures to cover the oxidation rate at different temperatures. The correlation was developed for certain temperatures to find an equation for the relation between time and weight. The thermal treatment was done for different quantities at certain times. The proposed equation studies the correlation between temperature, time, and weight. For each temperature, a number of points were recorded from the measured oxidation curve. The shape of the curves is well-represented in this paper. The final results will present the highest temperature, the maximum weight, and the maximum time for full oxidation at high and low temperatures.
