Volume 41,Issue 12,2012 Table of Contents
2012, 41(12):2069-2074.
Abstract:
The nanocrystalline Mg2Ni-type alloys with the compositions of Mg20Ni10-xCux (x=0, 1, 2, 3, 4) were synthesized by melt spinning technique. The microstructures of the alloys were characterized by XRD, SEM and HRTEM. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system, and their hydriding and dehydriding kinetics were measured by an automatically controlled Sievert's apparatus. The results show that all the as-spun alloys hold a typical nanocrystalline structure. The substitution of Cu for Ni improves the electrochemical hydrogen storage performances of the alloys significantly, involving both the discharge capacity and the electrochemical cycle stability. Furthermore, the hydrogen absorption capacity of the alloy first increases and then decreases with the rising of Cu content, but the hydrogen desorption capacity grows dramatically for the same reason
The nanocrystalline Mg2Ni-type alloys with the compositions of Mg20Ni10-xCux (x=0, 1, 2, 3, 4) were synthesized by melt spinning technique. The microstructures of the alloys were characterized by XRD, SEM and HRTEM. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system, and their hydriding and dehydriding kinetics were measured by an automatically controlled Sievert's apparatus. The results show that all the as-spun alloys hold a typical nanocrystalline structure. The substitution of Cu for Ni improves the electrochemical hydrogen storage performances of the alloys significantly, involving both the discharge capacity and the electrochemical cycle stability. Furthermore, the hydrogen absorption capacity of the alloy first increases and then decreases with the rising of Cu content, but the hydrogen desorption capacity grows dramatically for the same reason
2012, 41(12):2075-2080.
Abstract:
The isothermal oxidation behavior of a new Ni-Cr-W base superalloy Ni-20Cr-18W at 1100 oC has been investigated by analytical electron microscopy, scanning electron microscope coupled with energy dispersive spectrum and X-ray diffraction. Oxidation kinetics was evaluated from measurements of mass change, metal loss and internal penetration. Initially, the mixtural oxide scale is composed of hexagonal Cr2O3, cubic NiO and spinel-type (Ni，Mn，Cr)3O4 isomorphous with M3O4 at the initial stage of oxidation. After long-term oxidation, the oxide scale turns from mono-layer to double-layer. There is a consecutive Cr2O3 scale at inner adherent layer, and a compact NiO scale at outer layer which can restrain the inner Cr2O3 volatilization. At the same time, the oxidation void has formed between the oxide scale and interface of the alloy (scale/metal interface), and the inner oxidation of Al element happens at this place
The isothermal oxidation behavior of a new Ni-Cr-W base superalloy Ni-20Cr-18W at 1100 oC has been investigated by analytical electron microscopy, scanning electron microscope coupled with energy dispersive spectrum and X-ray diffraction. Oxidation kinetics was evaluated from measurements of mass change, metal loss and internal penetration. Initially, the mixtural oxide scale is composed of hexagonal Cr2O3, cubic NiO and spinel-type (Ni，Mn，Cr)3O4 isomorphous with M3O4 at the initial stage of oxidation. After long-term oxidation, the oxide scale turns from mono-layer to double-layer. There is a consecutive Cr2O3 scale at inner adherent layer, and a compact NiO scale at outer layer which can restrain the inner Cr2O3 volatilization. At the same time, the oxidation void has formed between the oxide scale and interface of the alloy (scale/metal interface), and the inner oxidation of Al element happens at this place
2012, 41(12):2081-2085.
Abstract:
The isothermal oxidation behavior of a new Ni-Cr-W base superalloy Ni-20Cr-18W at 1100 oC has been investigated by analytical electron microscopy, scanning electron microscope coupled with energy dispersive spectrum and X-ray diffraction. Oxidation kinetics was evaluated from measurements of mass change, metal loss and internal penetration. Initially, the mixtural oxide scale is composed of hexagonal Cr2O3, cubic NiO and spinel-type (Ni，Mn，Cr)3O4 isomorphous with M3O4 at the initial stage of oxidation. After long-term oxidation, the oxide scale turns from mono-layer to double-layer. There is a consecutive Cr2O3 scale at inner adherent layer, and a compact NiO scale at outer layer which can restrain the inner Cr2O3 volatilization. At the same time, the oxidation void has formed between the oxide scale and interface of the alloy (scale/metal interface), and the inner oxidation of Al element happens at this place
The isothermal oxidation behavior of a new Ni-Cr-W base superalloy Ni-20Cr-18W at 1100 oC has been investigated by analytical electron microscopy, scanning electron microscope coupled with energy dispersive spectrum and X-ray diffraction. Oxidation kinetics was evaluated from measurements of mass change, metal loss and internal penetration. Initially, the mixtural oxide scale is composed of hexagonal Cr2O3, cubic NiO and spinel-type (Ni，Mn，Cr)3O4 isomorphous with M3O4 at the initial stage of oxidation. After long-term oxidation, the oxide scale turns from mono-layer to double-layer. There is a consecutive Cr2O3 scale at inner adherent layer, and a compact NiO scale at outer layer which can restrain the inner Cr2O3 volatilization. At the same time, the oxidation void has formed between the oxide scale and interface of the alloy (scale/metal interface), and the inner oxidation of Al element happens at this place
2012, 41(12):2086-2090.
Abstract:
The first-principles were employed investigate the structure properties, elastic constant and electronic structure of two phases of the RuB2 (orthorhombic and hexagonal phase). The lattice parameter and volume of the two RuB2 phases are in good agreement with experimental values. The calculated elastic constants indicate that the RuB2 exhibits excellent mechanical properties. The electronic structure shows that hybridization occurs between Ru (d states) and B (p states) and form Ru-B covalent bonding forms. The results reveal that the hexagonal RuB2 is a stable phase at ground state
The first-principles were employed investigate the structure properties, elastic constant and electronic structure of two phases of the RuB2 (orthorhombic and hexagonal phase). The lattice parameter and volume of the two RuB2 phases are in good agreement with experimental values. The calculated elastic constants indicate that the RuB2 exhibits excellent mechanical properties. The electronic structure shows that hybridization occurs between Ru (d states) and B (p states) and form Ru-B covalent bonding forms. The results reveal that the hexagonal RuB2 is a stable phase at ground state
2012, 41(12):2091-2094.
Abstract:
Two kinds of copper oxide with different particle sizes and 1.5 μm tungsten trioxide powder were employed to prepare the high-purity CuWO4 powder. By two stage hydrogen-reduction of the CuWO4 at 360 and 750 ℃ respectively and continuously, nano-composite powder of tungsten coated copper was synthesized. Micro-morphology, crystallization-components and grain-size of the products were investigated by scanning electron microscope (SEM), X-ray diffract meter (XRD) and transmission electric microscope (TEM) and laser particle size analyzer (LPSA) was also applied to measure the particle-size of CuWO4. The W film thickness of nano-composite powder synthesized by smaller-sized CuWO4 is thinner than that made from bigger-sized CuWO4. The average particle size of nano-composite powder of tungsten coated copper is about 50 nm under the two-stage hydrogen reduction
Two kinds of copper oxide with different particle sizes and 1.5 μm tungsten trioxide powder were employed to prepare the high-purity CuWO4 powder. By two stage hydrogen-reduction of the CuWO4 at 360 and 750 ℃ respectively and continuously, nano-composite powder of tungsten coated copper was synthesized. Micro-morphology, crystallization-components and grain-size of the products were investigated by scanning electron microscope (SEM), X-ray diffract meter (XRD) and transmission electric microscope (TEM) and laser particle size analyzer (LPSA) was also applied to measure the particle-size of CuWO4. The W film thickness of nano-composite powder synthesized by smaller-sized CuWO4 is thinner than that made from bigger-sized CuWO4. The average particle size of nano-composite powder of tungsten coated copper is about 50 nm under the two-stage hydrogen reduction
2012, 41(12):2095-2099.
Abstract:
Morphologies, microstructure and composition distribution of the magnesium anode materials were studied by metallographic microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The corrosion behavior and electrochemical properties of Mg alloy were also investigated by constant current method, potential polarization, and drainage. The results show that Sn and Pb can restrain β-Mg17Al12 phase precipitation along the grain boundary and Mg-Al-Pb-Sn magnesium alloys have uniform and fine grain size. With the content of tin increasing, the content of particle Mg2Sn phase increases. After uniform heat treatment, most of β-Mg17Al12 phase dissolve, while most of Mg2Sn and Mg2Pb do not dissolve. The tin can improve self-corrosion potential and reduce release hydrogen rate. Magnesium anode has high discharge potential and current efficiency with 2wt% tin. With the current density increasing, the release hydrogen rate improves, owing to negative variance effect of magnesium alloys. The current efficiency is up to 88% at 10 mA/cm2. The main composition of the corrosion products are Mg(OH)2, SnO2 and MgSnO3 that are easier to peel off , which leads to more negative and stable work potential and can accelerate reaction continuously.
Morphologies, microstructure and composition distribution of the magnesium anode materials were studied by metallographic microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The corrosion behavior and electrochemical properties of Mg alloy were also investigated by constant current method, potential polarization, and drainage. The results show that Sn and Pb can restrain β-Mg17Al12 phase precipitation along the grain boundary and Mg-Al-Pb-Sn magnesium alloys have uniform and fine grain size. With the content of tin increasing, the content of particle Mg2Sn phase increases. After uniform heat treatment, most of β-Mg17Al12 phase dissolve, while most of Mg2Sn and Mg2Pb do not dissolve. The tin can improve self-corrosion potential and reduce release hydrogen rate. Magnesium anode has high discharge potential and current efficiency with 2wt% tin. With the current density increasing, the release hydrogen rate improves, owing to negative variance effect of magnesium alloys. The current efficiency is up to 88% at 10 mA/cm2. The main composition of the corrosion products are Mg(OH)2, SnO2 and MgSnO3 that are easier to peel off , which leads to more negative and stable work potential and can accelerate reaction continuously.
2012, 41(12):2100-2104.
Abstract:
The phase transformation process of dynamic model of L12 and DO22 phase in Ni64Al21V15 alloy at 1150 K was studied by micro-phase field model. The migration of Al, V and Ni atoms in the two phases in the different lattice faces and at different sites was analyzed, and its evolution was researched. The results show that there are two types of crystallographic orientation relationship between L12 and DO22: (001)L12→(001)DO22 and (001)L12→(100)DO22. In the structure transformation form L12 to DO22, the atomic ordering is proceeded on each plane as the atoms migrate between different planes, Al and V occupy the β and β1 sites prior to others, Ni occupy the α1 and β2 sites, and the nonordered domain gradually transforms to the L12 structure. Then, the atomic ordering is proceeded on each plane as the atoms migrate on planes only, Al occupy the β1 and α1 sites, V occupy the β and β2 sites, Ni mainly occupy the α1 site, and L12 structure transforms into DO22 structure
The phase transformation process of dynamic model of L12 and DO22 phase in Ni64Al21V15 alloy at 1150 K was studied by micro-phase field model. The migration of Al, V and Ni atoms in the two phases in the different lattice faces and at different sites was analyzed, and its evolution was researched. The results show that there are two types of crystallographic orientation relationship between L12 and DO22: (001)L12→(001)DO22 and (001)L12→(100)DO22. In the structure transformation form L12 to DO22, the atomic ordering is proceeded on each plane as the atoms migrate between different planes, Al and V occupy the β and β1 sites prior to others, Ni occupy the α1 and β2 sites, and the nonordered domain gradually transforms to the L12 structure. Then, the atomic ordering is proceeded on each plane as the atoms migrate on planes only, Al occupy the β1 and α1 sites, V occupy the β and β2 sites, Ni mainly occupy the α1 site, and L12 structure transforms into DO22 structure
2012, 41(12):2105-2108.
Abstract:
The direct cladding of Al2O3-13wt%TiO2 coating on Ti-6Al-4V alloy substrate was performed with coaxial laser cladding. OM and EMPA were used to examine the dilution characters, microstructure and element distribution of the cross-sections of cladding samples. The results show that after the irradiation the dilution zone (DZ) is likely to form the distinct pattern that at the edges of single clad pass the ceramic coating penetrates into the substrate, while in the middle of the pass the melting metal protrudes from the substrate into the ceramic coating. Moreover, there are many ceramic particles distributing in the DZ zone, and the layer is prone to produce more cracks with the cluster formation of the ceramic particles. The coating with low dilution and no obvious cracks is obtained by optimizing the processing parameters
The direct cladding of Al2O3-13wt%TiO2 coating on Ti-6Al-4V alloy substrate was performed with coaxial laser cladding. OM and EMPA were used to examine the dilution characters, microstructure and element distribution of the cross-sections of cladding samples. The results show that after the irradiation the dilution zone (DZ) is likely to form the distinct pattern that at the edges of single clad pass the ceramic coating penetrates into the substrate, while in the middle of the pass the melting metal protrudes from the substrate into the ceramic coating. Moreover, there are many ceramic particles distributing in the DZ zone, and the layer is prone to produce more cracks with the cluster formation of the ceramic particles. The coating with low dilution and no obvious cracks is obtained by optimizing the processing parameters
2012, 41(12):2109-2112.
Abstract:
Through cross-rolling, cold deep drawing and analysis of mechanical properties and microstructure, the microstructure evolution and cold deep drawing performance of molybdenum strip for liquid crystal display (LCD) backlight were investigated. The results show that 0.2 mm thick molybdenum strip of high quality and high deep drawing performance was fabricated by low temperature cross-rolling twice and cold cross-rolling once. The molybdenum strip has weak anisotropy and good mechanical properties. The small molybdenum cup with 2.0 mm outside diameter and 10 mm height was prepared by multi-pass continuous cold deep drawing. The microstructure of entire cross-section of molybdenum cup is fibrous elongated grains which are staggered overlapped each other. The thickness reduction ratio is the largest at bottom corner of the cup, namely the "danger zone". The prepared molybdenum strip is suitable for LCD backlight light
Through cross-rolling, cold deep drawing and analysis of mechanical properties and microstructure, the microstructure evolution and cold deep drawing performance of molybdenum strip for liquid crystal display (LCD) backlight were investigated. The results show that 0.2 mm thick molybdenum strip of high quality and high deep drawing performance was fabricated by low temperature cross-rolling twice and cold cross-rolling once. The molybdenum strip has weak anisotropy and good mechanical properties. The small molybdenum cup with 2.0 mm outside diameter and 10 mm height was prepared by multi-pass continuous cold deep drawing. The microstructure of entire cross-section of molybdenum cup is fibrous elongated grains which are staggered overlapped each other. The thickness reduction ratio is the largest at bottom corner of the cup, namely the "danger zone". The prepared molybdenum strip is suitable for LCD backlight light
2012, 41(12):2113-2117.
Abstract:
A 2024 aluminum alloy tube was prepared by friction stir welding and spinning. The bulging performance and circumferential thickness distribution of the welded tube with different strength matching coefficients were investigated by the hydro bulging experiment. The deformation behaviors and the stress and strain history of the welded tube during hydro-bulging were investigated by finite element analysis (FEA) and mechanics analysis. The results indicate that the welded tube with high strength matching coefficient shows higher bulge ratio and more uniform circumferential thickness distribution than that with low strength matching coefficient. The results of FEA and mechanics analysis show that the equivalent stress on the weld is higher than that of the base material and the strain state of the weld is biaxial tension for the welded tube with high strength matching coefficient. On the contrary, the equivalent stress on the weld is lower than that of the base material for the welded tube with low strength matching coefficient, and the tensile strain occurs in the circumferential of the weld, while the compressive strain firstly occurs in the axial direction of the weld and then gradually transforms to tensile strain. The welded tubes with high strength matching coefficient possess high formability during hydro bulging for that the welds with high strength promote the deformation of the base material
A 2024 aluminum alloy tube was prepared by friction stir welding and spinning. The bulging performance and circumferential thickness distribution of the welded tube with different strength matching coefficients were investigated by the hydro bulging experiment. The deformation behaviors and the stress and strain history of the welded tube during hydro-bulging were investigated by finite element analysis (FEA) and mechanics analysis. The results indicate that the welded tube with high strength matching coefficient shows higher bulge ratio and more uniform circumferential thickness distribution than that with low strength matching coefficient. The results of FEA and mechanics analysis show that the equivalent stress on the weld is higher than that of the base material and the strain state of the weld is biaxial tension for the welded tube with high strength matching coefficient. On the contrary, the equivalent stress on the weld is lower than that of the base material for the welded tube with low strength matching coefficient, and the tensile strain occurs in the circumferential of the weld, while the compressive strain firstly occurs in the axial direction of the weld and then gradually transforms to tensile strain. The welded tubes with high strength matching coefficient possess high formability during hydro bulging for that the welds with high strength promote the deformation of the base material
2012, 41(12):2118-2122.
Abstract:
a-In2Se3 is one of the A2IIIB3IV type semiconductors with a wide band gap. A proper co-doping of Cu and Te leads to the formation of slab Cu2Se, which accounts for the reduction of band gap Eg, with its value decreasing from 1.32 eV for the intrinsic a-In2Se3 to 1.14 eV. This reduction of band gap is responsible for the remarkable improvement in thermoelectric properties, with the maximum power factor p increasing from 0.76′10-4 to 2.8×10-4 W·m-1·K-2 and the highest ZT value from 0.25 to 0.63. A proper co-doping results in a change in morphology from the amorphous-like structure represented by In2Se3 to the visible polycrystalline form, observed using HRTEM, and this change is directly related to the moderate enhancement of lattice thermal conductivity above 500 K
a-In2Se3 is one of the A2IIIB3IV type semiconductors with a wide band gap. A proper co-doping of Cu and Te leads to the formation of slab Cu2Se, which accounts for the reduction of band gap Eg, with its value decreasing from 1.32 eV for the intrinsic a-In2Se3 to 1.14 eV. This reduction of band gap is responsible for the remarkable improvement in thermoelectric properties, with the maximum power factor p increasing from 0.76′10-4 to 2.8×10-4 W·m-1·K-2 and the highest ZT value from 0.25 to 0.63. A proper co-doping results in a change in morphology from the amorphous-like structure represented by In2Se3 to the visible polycrystalline form, observed using HRTEM, and this change is directly related to the moderate enhancement of lattice thermal conductivity above 500 K
2012, 41(12):2123-2126.
Abstract:
By means of rapid water cooling to retain the microstructure state at high temperature, the phase transformation in TC6 titanium alloy during heating and cooling processes within the two phase field was investigated. The results show that with increasing the temperature during the heating process, the secondary α dissolves within a range of temperature between 700 and 850 °C but the primary α dissolves at 900 °C. The results of energy spectrum analysis show that Al element concentration in primary α is higher than that in secondary α, that is to say, primary α is more stable than secondary α at high temperature. During the cooling process, the primary α grows up preferentially at a higher temperature, while due to the formation of secondary α through nucleation and growth, it precipitates at a relatively lower temperature, and the secondary α precipitates can slow down the growth of the primary α. Furthermore, with reducing the holding temperature, the precipitation temperature of secondary α gradually decreases
By means of rapid water cooling to retain the microstructure state at high temperature, the phase transformation in TC6 titanium alloy during heating and cooling processes within the two phase field was investigated. The results show that with increasing the temperature during the heating process, the secondary α dissolves within a range of temperature between 700 and 850 °C but the primary α dissolves at 900 °C. The results of energy spectrum analysis show that Al element concentration in primary α is higher than that in secondary α, that is to say, primary α is more stable than secondary α at high temperature. During the cooling process, the primary α grows up preferentially at a higher temperature, while due to the formation of secondary α through nucleation and growth, it precipitates at a relatively lower temperature, and the secondary α precipitates can slow down the growth of the primary α. Furthermore, with reducing the holding temperature, the precipitation temperature of secondary α gradually decreases
2012, 41(12):2127-2130.
Abstract:
Ni-20Cr-4Mo-0.15C and Ni-20Cr-4Mo-0.15C-12.85TiC-3TiN (wt%) alloys were prepared by powder metallurgy method, in order to investigate the effect of Ti(C,N) on microstructure, mechanical properties and oxidation resistance at 800 °C of Ni-based superalloys. Results show that due to the addition of 12.85wt% TiC and 3wt% TiN, the formed Ti(C,N) particles dispersed within grains and at grain boundaries of austenite matrix, therefore austenite grains became fine. The density of supralloys decreased from 8.38 to 7.5 g/cm3, the hardness increased from 1850 to 3430 MPa, and the tensile strength increased from 752 to 1192 MPa. In addition, the superalloys still exhibited good oxidation resistance in air at 800 °C, and the oxide scale formed mainly consisted of α-Cr2O3 and TiO2
Ni-20Cr-4Mo-0.15C and Ni-20Cr-4Mo-0.15C-12.85TiC-3TiN (wt%) alloys were prepared by powder metallurgy method, in order to investigate the effect of Ti(C,N) on microstructure, mechanical properties and oxidation resistance at 800 °C of Ni-based superalloys. Results show that due to the addition of 12.85wt% TiC and 3wt% TiN, the formed Ti(C,N) particles dispersed within grains and at grain boundaries of austenite matrix, therefore austenite grains became fine. The density of supralloys decreased from 8.38 to 7.5 g/cm3, the hardness increased from 1850 to 3430 MPa, and the tensile strength increased from 752 to 1192 MPa. In addition, the superalloys still exhibited good oxidation resistance in air at 800 °C, and the oxide scale formed mainly consisted of α-Cr2O3 and TiO2
2012, 41(12):2135-2138.
Abstract:
Improvement and enhancement of wear resistance of TC4 alloy surface is one of the key technology to be used as tubing materials. Cu coating on TC4 alloy surface was prepared by the electroplating technology of sulfate. The tribological and wear properties of TC4 alloy substrate and Cu coating were investigated. The morphologies of the wear scars, wear rate and friction coefficient were analyzed by SEM, EDS and STM, and the wear mechanism was discussed. The results show that the Cu plating on TC4 alloy can greatly improve and enhance its wear resistance, and the wear resistance of the Cu plating is obviously better than that of TC4 alloy substrate. The wearing track of TC4 alloy is of the furrow morphology, and its wear mechanism is delamination abrasion and adhesive abrasion. The wearing track of Cu plating shows the morphology of plastic deformation caused by adherent copper debris being pressed, and its wearing mechanism includes delamination abrasion and fatigue abrasion.
Improvement and enhancement of wear resistance of TC4 alloy surface is one of the key technology to be used as tubing materials. Cu coating on TC4 alloy surface was prepared by the electroplating technology of sulfate. The tribological and wear properties of TC4 alloy substrate and Cu coating were investigated. The morphologies of the wear scars, wear rate and friction coefficient were analyzed by SEM, EDS and STM, and the wear mechanism was discussed. The results show that the Cu plating on TC4 alloy can greatly improve and enhance its wear resistance, and the wear resistance of the Cu plating is obviously better than that of TC4 alloy substrate. The wearing track of TC4 alloy is of the furrow morphology, and its wear mechanism is delamination abrasion and adhesive abrasion. The wearing track of Cu plating shows the morphology of plastic deformation caused by adherent copper debris being pressed, and its wearing mechanism includes delamination abrasion and fatigue abrasion.
2012, 41(12):2139-2143.
Abstract:
The process of melt infiltration of WCu alloy was simulated by the finite element software. A spherical particle skeleton model was established according to the distributing morphology of W particles. The pressure and the velocity vector distribution of copper liquid in the flow path were analyzed in isodiametric and non-isodiametric porous system. The relationship between the depth and time of infiltration in the porous system is obtained when the average particle size of W powder is 5 μm, which is in good agreement with experimental values
The process of melt infiltration of WCu alloy was simulated by the finite element software. A spherical particle skeleton model was established according to the distributing morphology of W particles. The pressure and the velocity vector distribution of copper liquid in the flow path were analyzed in isodiametric and non-isodiametric porous system. The relationship between the depth and time of infiltration in the porous system is obtained when the average particle size of W powder is 5 μm, which is in good agreement with experimental values
2012, 41(12):2144-2148.
Abstract:
In order to study the pore formation mechanism of die cast magnesium alloy during fusion welding, local re-melting of die cast magnesium alloy AZ91D of 6 mm thickness utilizing laser has been conducted. Microstructure and pore morphology of base metal have been observed adopting OM and SEM. The size of pores has been measured by particle size analysis software Nano measure 2.1. The formation mechanism of various kinds of pores was analyzed. The results indicate that the porosity increases with the increase of laser power. Small pores, resulted from hydrogen, have smooth inner wall and inverted-trumpet shape. Large pores have irregular shapes and hackly inner wall with obvious traces scoured by metal. These pores are developed by shrinkage blowhole of base metal. Mathematical model on relationship of pore in re-melted zone associated with that in the molten pool was established
In order to study the pore formation mechanism of die cast magnesium alloy during fusion welding, local re-melting of die cast magnesium alloy AZ91D of 6 mm thickness utilizing laser has been conducted. Microstructure and pore morphology of base metal have been observed adopting OM and SEM. The size of pores has been measured by particle size analysis software Nano measure 2.1. The formation mechanism of various kinds of pores was analyzed. The results indicate that the porosity increases with the increase of laser power. Small pores, resulted from hydrogen, have smooth inner wall and inverted-trumpet shape. Large pores have irregular shapes and hackly inner wall with obvious traces scoured by metal. These pores are developed by shrinkage blowhole of base metal. Mathematical model on relationship of pore in re-melted zone associated with that in the molten pool was established
2012, 41(12):2149-2153.
Abstract:
The burn resistant coating with the thickness of 0.2~0.4 mm was prepared on Ti40 titanium substrates by plasma spraying. The microstructure and the cross section morphology of the Ti-based alloys and the burn resistant coating were characterized by OM and SEM. The oxidation resistance properties of substrates and burn resistant coating at 600 °C were studied. Results show that the Ti-based alloys with burn resistant coating were oxidized continuously in 600 °C static air for 100 h, and afterwards that the mass gain is decreased by 76% and the oxidation rate is decreased by 92% with contrast to the no-coating Ti-based alloys. It is shown that the oxidation resistance is improved by 12 times. In addition, the burn resistant coating is fully perfect after oxidation test, so it is concluded that the burn resistant coating can provide excellent oxidation resistance and be applied to the titanium fire resistance for titanium alloy parts in aero-engine
The burn resistant coating with the thickness of 0.2~0.4 mm was prepared on Ti40 titanium substrates by plasma spraying. The microstructure and the cross section morphology of the Ti-based alloys and the burn resistant coating were characterized by OM and SEM. The oxidation resistance properties of substrates and burn resistant coating at 600 °C were studied. Results show that the Ti-based alloys with burn resistant coating were oxidized continuously in 600 °C static air for 100 h, and afterwards that the mass gain is decreased by 76% and the oxidation rate is decreased by 92% with contrast to the no-coating Ti-based alloys. It is shown that the oxidation resistance is improved by 12 times. In addition, the burn resistant coating is fully perfect after oxidation test, so it is concluded that the burn resistant coating can provide excellent oxidation resistance and be applied to the titanium fire resistance for titanium alloy parts in aero-engine
2012, 41(12):2154-2156.
Abstract:
Double glow plasma surface metallurgy technology was used on the surfaces of Q235 Steel to form W-Mo-Y alloying layer. The distribution of alloying elements in the diffusion layer was analyzed. The diffusion coefficient and diffusion activation energy of tungsten and molybdenum atoms were calculated to analyze the effect of RE (Y) on the atomic diffusion of W and Mo. The results show that RE (Y) addition increases the diffusion coefficient of molybdenum atoms by 1.89 times in the diffusion layer, but reduces the diffusion coefficient of tungsten atoms by 0.89 time in average. RE (Y) addition decreases the diffusion activation energy of molybdenum atoms by 5737.72, 6511.72 and 7853.38 J/mol in the diffusion layer from the surface of 12~15, 24~25 and 35~36 μm, while increases the diffusion activation energy of tungsten atoms by 998.5, 106.37 and 2904.56 J/ mol. It is indicated that RE (Y) has a catalytic effect on molybdenum atoms but plays no obvious catalytic role in the diffusion of tungsten atoms
Double glow plasma surface metallurgy technology was used on the surfaces of Q235 Steel to form W-Mo-Y alloying layer. The distribution of alloying elements in the diffusion layer was analyzed. The diffusion coefficient and diffusion activation energy of tungsten and molybdenum atoms were calculated to analyze the effect of RE (Y) on the atomic diffusion of W and Mo. The results show that RE (Y) addition increases the diffusion coefficient of molybdenum atoms by 1.89 times in the diffusion layer, but reduces the diffusion coefficient of tungsten atoms by 0.89 time in average. RE (Y) addition decreases the diffusion activation energy of molybdenum atoms by 5737.72, 6511.72 and 7853.38 J/mol in the diffusion layer from the surface of 12~15, 24~25 and 35~36 μm, while increases the diffusion activation energy of tungsten atoms by 998.5, 106.37 and 2904.56 J/ mol. It is indicated that RE (Y) has a catalytic effect on molybdenum atoms but plays no obvious catalytic role in the diffusion of tungsten atoms
2012, 41(12):2157-2162.
Abstract:
Pd-AgNbO3 photocatalysts were synthesized by an impregnation method. X-ray powder diffraction (XRD), scanning electronic microscope (SEM) and energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectra (XPS) and diffuse reflectance spectra (DRS) were employed to investigate the structure, morphology and photocatalytic properties of the photocatalysts. The photocatalytic activity of the samples was evaluated by degradation of methylene blue dye (MB). The mechanism of enhancing photocatalytic activity was also discussed. The results indicate that Pd loading could not change the crystal structure and surface property of the AgNbO3. The DRS analysis indicates that Pd loading increases the ability of visible light absorption of the catalysts. The Pd-AgNbO3 photocatalysts present the enhanced photocatalytic activity compared with the pure AgNbO3. The photocatalytic efficiency is the highest when the sample with 0.8wt% Pd was calcined at 400 °C for 3 h and the MB degradation rate is 92.2%. The photocatalytic degradation of MB over the samples follows pseudo-first-order kinetics
Pd-AgNbO3 photocatalysts were synthesized by an impregnation method. X-ray powder diffraction (XRD), scanning electronic microscope (SEM) and energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectra (XPS) and diffuse reflectance spectra (DRS) were employed to investigate the structure, morphology and photocatalytic properties of the photocatalysts. The photocatalytic activity of the samples was evaluated by degradation of methylene blue dye (MB). The mechanism of enhancing photocatalytic activity was also discussed. The results indicate that Pd loading could not change the crystal structure and surface property of the AgNbO3. The DRS analysis indicates that Pd loading increases the ability of visible light absorption of the catalysts. The Pd-AgNbO3 photocatalysts present the enhanced photocatalytic activity compared with the pure AgNbO3. The photocatalytic efficiency is the highest when the sample with 0.8wt% Pd was calcined at 400 °C for 3 h and the MB degradation rate is 92.2%. The photocatalytic degradation of MB over the samples follows pseudo-first-order kinetics
2012, 41(12):2163-2168.
Abstract:
The microstructure evolution of coherent precipitates was simulated with the phase-field model by computer and the influence of different strain energy on the precipitation morphology was also discussed. Results show that when the coherent strain energy is 0, spherical-shaped precipitates or flocculent structure distribute randomly with isotropic morphology. With the elastic strain energy increasing, the arrangement orientation increases, quasi-periodical macro lattice structures and sandwich-shaped structures are formed with anisotropic morphology. The simulation results are in good agreement with the experimental
The microstructure evolution of coherent precipitates was simulated with the phase-field model by computer and the influence of different strain energy on the precipitation morphology was also discussed. Results show that when the coherent strain energy is 0, spherical-shaped precipitates or flocculent structure distribute randomly with isotropic morphology. With the elastic strain energy increasing, the arrangement orientation increases, quasi-periodical macro lattice structures and sandwich-shaped structures are formed with anisotropic morphology. The simulation results are in good agreement with the experimental
2012, 41(12):2169-2172.
Abstract:
SiO2/Ag composite material was synthesized with polyvinylpyrrolidone (PVP) as both the reductant and stabilizing agent. The particle size and quantity of silver nanoparticles on silica spheres could be changed with [Ag(NH3)2]+ ions of different concentrations. Transmission electron microscope (TEM) and scanning electron microscope (SEM) analysis were used to characterize the SiO2/Ag composite material. Results show that the silver is deposited on silica spheres as polycrystalline nanoparticles. Raman spectrometer measurement shows that surface enhanced Raman scattering (SERS) performance is improved by increasing the quantity of silver deposition on silica.
SiO2/Ag composite material was synthesized with polyvinylpyrrolidone (PVP) as both the reductant and stabilizing agent. The particle size and quantity of silver nanoparticles on silica spheres could be changed with [Ag(NH3)2]+ ions of different concentrations. Transmission electron microscope (TEM) and scanning electron microscope (SEM) analysis were used to characterize the SiO2/Ag composite material. Results show that the silver is deposited on silica spheres as polycrystalline nanoparticles. Raman spectrometer measurement shows that surface enhanced Raman scattering (SERS) performance is improved by increasing the quantity of silver deposition on silica.
2012, 41(12):2173-2177.
Abstract:
The precursor powder of AgCl prepared by solid state reaction milling and different dry processes were mixed with Ag nanopowder in a certain ratio, prilled, pressed into a mold and then sintered, and finally a composite Ag/AgCl porous electrode was obtained. The electrode was characterized by SEM, XRD, electrochemical workstation and electrical noise test set. The influence of the porous structure of the electrode was discussed on the polarization properties, short-term stability and electrochemical noise. Results show that the precursor powder of AgCl prepared by freeze-drying method has excellent dispersivity and uniform size. The prepared composite Ag/AgCl electrode presents a porous structure with large exchange current density and good consistency. The potential difference of the two like electrodes is about –0.2744 mV. The electrode possesses good short term stability, with a potential difference drift less than 0.0477 mV/24 h. The voltage noise density of electrode is down to nV/Hz1/2 level at 1 Hz
The precursor powder of AgCl prepared by solid state reaction milling and different dry processes were mixed with Ag nanopowder in a certain ratio, prilled, pressed into a mold and then sintered, and finally a composite Ag/AgCl porous electrode was obtained. The electrode was characterized by SEM, XRD, electrochemical workstation and electrical noise test set. The influence of the porous structure of the electrode was discussed on the polarization properties, short-term stability and electrochemical noise. Results show that the precursor powder of AgCl prepared by freeze-drying method has excellent dispersivity and uniform size. The prepared composite Ag/AgCl electrode presents a porous structure with large exchange current density and good consistency. The potential difference of the two like electrodes is about –0.2744 mV. The electrode possesses good short term stability, with a potential difference drift less than 0.0477 mV/24 h. The voltage noise density of electrode is down to nV/Hz1/2 level at 1 Hz
2012, 41(12):2178-2184.
Abstract:
A precise and efficient 3D-FE model of the porthole extrusion process for AZ31 Mg alloy thin-walled tube, used to manufacture towers antenna in battlefield, was developed in the DEFORM-3D software environment. And the influencing laws of ram speed on the load, welding pressure and the peak temperature of billet at die export were investigated and revealed by comprehensive numerical simulations. With integrated consideration of the extrusion load, quality of welding area and surface quality of the extruded tube, it is proposed that the optimum ram speed range is about 3.5~7 mm/s for the extrusion of AZ31 Mg alloy thin-walled tube on a 2000 t extrusion machine
A precise and efficient 3D-FE model of the porthole extrusion process for AZ31 Mg alloy thin-walled tube, used to manufacture towers antenna in battlefield, was developed in the DEFORM-3D software environment. And the influencing laws of ram speed on the load, welding pressure and the peak temperature of billet at die export were investigated and revealed by comprehensive numerical simulations. With integrated consideration of the extrusion load, quality of welding area and surface quality of the extruded tube, it is proposed that the optimum ram speed range is about 3.5~7 mm/s for the extrusion of AZ31 Mg alloy thin-walled tube on a 2000 t extrusion machine
2012, 41(12):2185-2190.
Abstract:
By measuring the creep curves at medium temperature and high stress of a nickel-base single crystal superalloy and analyzing the microstructure and dislocation configuration diffraction after creep fracture, the microstructure evolution and deformation mechanism of the single crystal alloy were researched. The results show that the alloy creep activation energy Q is (462 ± 20) kJ/mol under the medium temperature and high stress conditions, and the apparent stress exponent na is 4.34, indicating that the alloy possesses better creep resistance in the measuring temperature and stress range. Dislocation diffraction contrast analysis indicates that the super dislocations <110> that cut into g￠ phase both slip in the {100} cube slip systems and in the {111} octahedral slip systems during creep. The dislocations of movement meet and a dislocation reaction can occur to form a super dislocation which can cross slip to the cube {100} slip plane. A reaction can occur for the motion dislocation which meet in two different six-sided {100} slip planes, and the resulting dislocation can move in the {111} octahedral slip systems
By measuring the creep curves at medium temperature and high stress of a nickel-base single crystal superalloy and analyzing the microstructure and dislocation configuration diffraction after creep fracture, the microstructure evolution and deformation mechanism of the single crystal alloy were researched. The results show that the alloy creep activation energy Q is (462 ± 20) kJ/mol under the medium temperature and high stress conditions, and the apparent stress exponent na is 4.34, indicating that the alloy possesses better creep resistance in the measuring temperature and stress range. Dislocation diffraction contrast analysis indicates that the super dislocations <110> that cut into g￠ phase both slip in the {100} cube slip systems and in the {111} octahedral slip systems during creep. The dislocations of movement meet and a dislocation reaction can occur to form a super dislocation which can cross slip to the cube {100} slip plane. A reaction can occur for the motion dislocation which meet in two different six-sided {100} slip planes, and the resulting dislocation can move in the {111} octahedral slip systems
2012, 41(12):2191-2194.
Abstract:
Ti12LC low cost titanium alloys (Ti-4.5Al-1.5Fe-6.8Mo) were prepared by molten salt electrolysis with the mixed oxides as raw materials, and the electrolysis process was studied. The CaTiO3 and low valence oxide Ti6O, Ti2O and Ca2Al2O5 were formed firstly during the reaction. With the deoxy time increasing, the content of low valence titanium oxides increases, followed by appearing of the metal molybdenum. The final electrolytic product is the Ti12LC. The molybdenum is reduced prior to Ti and Al, because the theoretic reduction voltage of MoO2 is lower than that of TiO2 and Al2O3. The molybdenum can dissolve infinitely in b-Ti so the molybdenum exists in Ti in the form of solid solution. Although the theoretic reduction voltage of Fe2O3 is lower, the iron is not detected due to the low content. The surface of electrolytic product was analyzed by BEIs. It is found that the morphology of the electrolytic product is similar to that of Ti12LC titanium alloy
Ti12LC low cost titanium alloys (Ti-4.5Al-1.5Fe-6.8Mo) were prepared by molten salt electrolysis with the mixed oxides as raw materials, and the electrolysis process was studied. The CaTiO3 and low valence oxide Ti6O, Ti2O and Ca2Al2O5 were formed firstly during the reaction. With the deoxy time increasing, the content of low valence titanium oxides increases, followed by appearing of the metal molybdenum. The final electrolytic product is the Ti12LC. The molybdenum is reduced prior to Ti and Al, because the theoretic reduction voltage of MoO2 is lower than that of TiO2 and Al2O3. The molybdenum can dissolve infinitely in b-Ti so the molybdenum exists in Ti in the form of solid solution. Although the theoretic reduction voltage of Fe2O3 is lower, the iron is not detected due to the low content. The surface of electrolytic product was analyzed by BEIs. It is found that the morphology of the electrolytic product is similar to that of Ti12LC titanium alloy
2012, 41(12):2195-2198.
Abstract:
W-30Re heavy alloy was prepared by spark plasma sintering (SPS) technology. The effects of sintering temperature on density, hardness, microstructure and fracture mode of the alloy were investigated. Results show that the SPS technique could prepare W-30Re heavy alloy with fine grains and homogeneous microstructure in a relatively short period of time. With the increase of sintering temperature, the density and hardness of the sintered alloy always increase, and the number of binder phases in the alloy increases. The fracture mode of the alloy transfers from typical brittle intergranular fracture to more and more cleavage fracture and ductile tearing of binding phase
W-30Re heavy alloy was prepared by spark plasma sintering (SPS) technology. The effects of sintering temperature on density, hardness, microstructure and fracture mode of the alloy were investigated. Results show that the SPS technique could prepare W-30Re heavy alloy with fine grains and homogeneous microstructure in a relatively short period of time. With the increase of sintering temperature, the density and hardness of the sintered alloy always increase, and the number of binder phases in the alloy increases. The fracture mode of the alloy transfers from typical brittle intergranular fracture to more and more cleavage fracture and ductile tearing of binding phase
2012, 41(12):2199-2204.
Abstract:
The Mg2Ni-type Mg2-xLaxNi (x=0, 0.2, 0.4, 0.6) hydrogen storage alloys were synthesized by casting and direct melt quenching technique. The microstructures of the as-cast and spun alloys were investigated by XRD, SEM and HRTEM. The gaseous hydrogen storage kinetics of the alloys was measured using an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the alloys was tested by constant current to charge and discharge the electrode. The results show that the substitution of La for Mg visibly alters the phase composition of the alloys. For x≤0.2, the substitution leads to formation of a small amount of secondary phases LaMg3 and La2Mg17 without changing major phase Mg2Ni. But the major phase of the alloys are changed to the (La, Mg)Ni3+LaMg3 phases by increasing La content to x≥0.4. The as-spun alloys substituted by La hold an evident amorphous structure, meaning the substitution of La for Mg facilitates the glass formation of the Mg2Ni-type alloy. The gaseous and electrochemical hydrogen storage kinetics of the alloys are sensitive to both the amount of La substitution and the melt spinning technology. The appropriate melt spinning process can significantly ameliorate the gaseous and electrochemical hydrogen storage kinetics of the alloys, whereas the melt spinning technology, by which the optimal hydrogen storage kinetics of the alloy can be yielded, is associated with the chemical composition of the alloy
The Mg2Ni-type Mg2-xLaxNi (x=0, 0.2, 0.4, 0.6) hydrogen storage alloys were synthesized by casting and direct melt quenching technique. The microstructures of the as-cast and spun alloys were investigated by XRD, SEM and HRTEM. The gaseous hydrogen storage kinetics of the alloys was measured using an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the alloys was tested by constant current to charge and discharge the electrode. The results show that the substitution of La for Mg visibly alters the phase composition of the alloys. For x≤0.2, the substitution leads to formation of a small amount of secondary phases LaMg3 and La2Mg17 without changing major phase Mg2Ni. But the major phase of the alloys are changed to the (La, Mg)Ni3+LaMg3 phases by increasing La content to x≥0.4. The as-spun alloys substituted by La hold an evident amorphous structure, meaning the substitution of La for Mg facilitates the glass formation of the Mg2Ni-type alloy. The gaseous and electrochemical hydrogen storage kinetics of the alloys are sensitive to both the amount of La substitution and the melt spinning technology. The appropriate melt spinning process can significantly ameliorate the gaseous and electrochemical hydrogen storage kinetics of the alloys, whereas the melt spinning technology, by which the optimal hydrogen storage kinetics of the alloy can be yielded, is associated with the chemical composition of the alloy
2012, 41(12):2205-2209.
Abstract:
A new continuous casting method for production of bulk metallic glass (BMG) was proposed. An intermittent withdrawal procedure, in which a withdrawal cycle was employed, was adopted for the continuous casting of BMG. A Zr-based bulk glassy alloy rod with a diameter of 10 mm and a length of 60 cm was prepared using this method. The glassy nature of the rod was identified by optical microscopy, X-ray diffraction and differential scanning calorimetry. The continuous cooling transformation curve of the glassy alloy was adopted for the discussion of cooling history of the continuous cast. The newly developed continuous casting method can be used for the massive production of bulk glassy alloys, and it can effectively reduce production costs and accelerate the development and application of metallic glasses
A new continuous casting method for production of bulk metallic glass (BMG) was proposed. An intermittent withdrawal procedure, in which a withdrawal cycle was employed, was adopted for the continuous casting of BMG. A Zr-based bulk glassy alloy rod with a diameter of 10 mm and a length of 60 cm was prepared using this method. The glassy nature of the rod was identified by optical microscopy, X-ray diffraction and differential scanning calorimetry. The continuous cooling transformation curve of the glassy alloy was adopted for the discussion of cooling history of the continuous cast. The newly developed continuous casting method can be used for the massive production of bulk glassy alloys, and it can effectively reduce production costs and accelerate the development and application of metallic glasses
2012, 41(12):2210-2214.
Abstract:
The opposed jet milling processing on tungsten powder was studied. The results show that after grinding by the jet milling, the particle size distribution range becomes narrower, the values of d10, d50 and d90 decrease from 2.02, 4.43 and 9.95 μm to 1.79, 3.02 and 5.54 μm respectively, and the specific surface area increases from 1.754 m2/g to 2.569 m2/g. The SEM observation shows that the original agglomerations in the tungsten powder disappear and the morphology of the tungsten powder becomes spherical or nearly spherical with good dispersivity. XRD indicates that there is no new impurity involved. In addition, processing parameters have an important influence on powder performance, and once more time grinding can get more uniform particle size, more regular morphology and much better dispersing capability
The opposed jet milling processing on tungsten powder was studied. The results show that after grinding by the jet milling, the particle size distribution range becomes narrower, the values of d10, d50 and d90 decrease from 2.02, 4.43 and 9.95 μm to 1.79, 3.02 and 5.54 μm respectively, and the specific surface area increases from 1.754 m2/g to 2.569 m2/g. The SEM observation shows that the original agglomerations in the tungsten powder disappear and the morphology of the tungsten powder becomes spherical or nearly spherical with good dispersivity. XRD indicates that there is no new impurity involved. In addition, processing parameters have an important influence on powder performance, and once more time grinding can get more uniform particle size, more regular morphology and much better dispersing capability
2012, 41(12):2215-2218.
Abstract:
SmCo5 nanoparticles are one of the most important binary transition metal-rare earth systems for magnetic materials. SmCo5 nanoparticles were fabricated by a four-stage route. At first, pH value of mixed aqueous soluble with SmCl3 and CoCl2 was adjusted using NaOH. Secondly, two soluble metal-salts were forced hydrolysis to oxides under atmospheric refluxing at 80 °C. Then, oxide nanoparticles with a ca average size of 20 nm were prepared at 150 °C for 9 h through a convenient hydrothermal process. Finally, the SmCo5 nanoparticles were attained via hydrothermally prepared nanoparticles deoxidized using Na under the hydrogen stream at 400 °C. The SmCo5 nanoparticles are superparamagnetic at 300 K while the particles are ferromagnetic with Hc of 4.16×104 A/m at 5 K
SmCo5 nanoparticles are one of the most important binary transition metal-rare earth systems for magnetic materials. SmCo5 nanoparticles were fabricated by a four-stage route. At first, pH value of mixed aqueous soluble with SmCl3 and CoCl2 was adjusted using NaOH. Secondly, two soluble metal-salts were forced hydrolysis to oxides under atmospheric refluxing at 80 °C. Then, oxide nanoparticles with a ca average size of 20 nm were prepared at 150 °C for 9 h through a convenient hydrothermal process. Finally, the SmCo5 nanoparticles were attained via hydrothermally prepared nanoparticles deoxidized using Na under the hydrogen stream at 400 °C. The SmCo5 nanoparticles are superparamagnetic at 300 K while the particles are ferromagnetic with Hc of 4.16×104 A/m at 5 K
2012, 41(12):2219-2222.
Abstract:
Microstructure evolution and phase transformation of β phase Ti40 alloy before and after hydrogenation were investigated by XRD, OM, SEM, EDX and TEM. The results show that the amount of matrix β phase decreases while the modified β with the same bcc structure but different elemental composition increases gradually as the hydrogen content increases; the small particles of η phase appear around the grain boundaries when the hydrogen content reaches above 0.3%. The structure of η phase is fcc and the lattice constant is 0.4377 nm. The composition of η phase is Ti: V: Cr = 38.10: 35.16: 26.66. The hydrogenation and phase transformation of Ti40 alloy can be concluded as β→βH for low hydrogen content (≤0.2wt%) and β→βH+modified β+η for high hydrogen content (>0.3wt%)
Microstructure evolution and phase transformation of β phase Ti40 alloy before and after hydrogenation were investigated by XRD, OM, SEM, EDX and TEM. The results show that the amount of matrix β phase decreases while the modified β with the same bcc structure but different elemental composition increases gradually as the hydrogen content increases; the small particles of η phase appear around the grain boundaries when the hydrogen content reaches above 0.3%. The structure of η phase is fcc and the lattice constant is 0.4377 nm. The composition of η phase is Ti: V: Cr = 38.10: 35.16: 26.66. The hydrogenation and phase transformation of Ti40 alloy can be concluded as β→βH for low hydrogen content (≤0.2wt%) and β→βH+modified β+η for high hydrogen content (>0.3wt%)
2012, 41(12):2223-2227.
Abstract:
Based on the Hertz equation, an equivalent film thickness method using spherical indentation was proposed to determine the modulus of thin films by means of modifying the mechanical model of flat cylindrical indentation. The FEM results verified by RW model show that the?error of the proposed model is less than?RW model when?the elastic modulus of film?is greater than that of the substrate; on the contrary, the results of the present method still agree well with the theoretic value while the indentation is much deeper. Therefore this model could be used to the instance that the indentation is more severe. In addition, the influences of yield strength of thin films and radius of the ball on the results were studied. It is found that the greater the yield strength of the thin films is, the smaller the error derived by proposed model is. At the same time, with the increase of the indenter radius, the error is greater under the same indentation depth. Furthermore, the influence of the radius on the modulus is smaller when the indentation is shallow. The proposed model is verified by indentation experiment on TiN/sapphire with Spherical indenter and Berkovich indenter
Based on the Hertz equation, an equivalent film thickness method using spherical indentation was proposed to determine the modulus of thin films by means of modifying the mechanical model of flat cylindrical indentation. The FEM results verified by RW model show that the?error of the proposed model is less than?RW model when?the elastic modulus of film?is greater than that of the substrate; on the contrary, the results of the present method still agree well with the theoretic value while the indentation is much deeper. Therefore this model could be used to the instance that the indentation is more severe. In addition, the influences of yield strength of thin films and radius of the ball on the results were studied. It is found that the greater the yield strength of the thin films is, the smaller the error derived by proposed model is. At the same time, with the increase of the indenter radius, the error is greater under the same indentation depth. Furthermore, the influence of the radius on the modulus is smaller when the indentation is shallow. The proposed model is verified by indentation experiment on TiN/sapphire with Spherical indenter and Berkovich indenter
2012, 41(12):2228-2232.
Abstract:
AgTiB2 contact material with different additives was prepared by high-energy milling and powder metallurgy. The effects of WO3, Al, Bi2O3 addition and WO3+Bi2O3, WO3+Al composite additions on the microstructure and properties of AgTiB2 were investigated. The morphology of milled powders and the microstructure of AgTiB2 composite with different additives were characterized by scanning electron microscope equipped with energy disperse spectroscopy, and the hardness and electrical conductivity were tested. The results show that WO3 single addition and WO3+Al, WO3+Bi2O3 composite additions can improve the densification of AgTiB2. In comparison with those of Ag/TiB2 composite without any additive, the hardness and electrical conductivity of the AgTiB2 composite materials with WO3 single addition and WO3+Al composite addition are increased, whose hardness values are 1253 and 1022 MPa respectively, and the electrical conductivity are 78.62%IACS and 14.91%IACS, respectively. The hardness and electrical conductivity of the AgTiB2 composite materials with Bi2O3+WO3 composite addition are 786 MPa and 16.12%IACS, respectively
AgTiB2 contact material with different additives was prepared by high-energy milling and powder metallurgy. The effects of WO3, Al, Bi2O3 addition and WO3+Bi2O3, WO3+Al composite additions on the microstructure and properties of AgTiB2 were investigated. The morphology of milled powders and the microstructure of AgTiB2 composite with different additives were characterized by scanning electron microscope equipped with energy disperse spectroscopy, and the hardness and electrical conductivity were tested. The results show that WO3 single addition and WO3+Al, WO3+Bi2O3 composite additions can improve the densification of AgTiB2. In comparison with those of Ag/TiB2 composite without any additive, the hardness and electrical conductivity of the AgTiB2 composite materials with WO3 single addition and WO3+Al composite addition are increased, whose hardness values are 1253 and 1022 MPa respectively, and the electrical conductivity are 78.62%IACS and 14.91%IACS, respectively. The hardness and electrical conductivity of the AgTiB2 composite materials with Bi2O3+WO3 composite addition are 786 MPa and 16.12%IACS, respectively
2012, 41(12):2233-2237.
Abstract:
The mechanism of the direct electrochemical reduction of solid oxides Tb2O3-Dy2O3-Fe2O3 was studied by cyclic voltammetry and chronoamperometry measurements. The reduction process was then proved by the constant potential electrolysis for different time. Five cathodic current peaks in the cyclic voltammogram were observed, supporting a mechanism of five-step processes for the electrochemical reduction of Tb2O3-Dy2O3-Fe2O3. The first peak represented the electrochemical reduction reaction of Fe2O3→Fe, while other peaks could be confirmed as the electrochemical reduction reactions between Fe and Tb2O3 as well as Dy2O3. The following electrochemical reduction sequence was confirmed by XRD analysis. Firstly Fe2O3 was electrolyzed to form Fe, then intermetallic Tb-Fe and Dy-Fe were electrolyzed from Fe and Tb2O3 as well as Dy2O3, and finally they were alloyed to form TbDyFe2. The above electrochemical reduction results could be explained by a theory of “diffusion at triplephase boundary lines”, and hereby the triplephase boundary lines were Fe|Fe2O3|CaCl2 and Tb-Dy-Fe|Tb2O3-Dy2O3|CaCl2 in the electro-reduction process
The mechanism of the direct electrochemical reduction of solid oxides Tb2O3-Dy2O3-Fe2O3 was studied by cyclic voltammetry and chronoamperometry measurements. The reduction process was then proved by the constant potential electrolysis for different time. Five cathodic current peaks in the cyclic voltammogram were observed, supporting a mechanism of five-step processes for the electrochemical reduction of Tb2O3-Dy2O3-Fe2O3. The first peak represented the electrochemical reduction reaction of Fe2O3→Fe, while other peaks could be confirmed as the electrochemical reduction reactions between Fe and Tb2O3 as well as Dy2O3. The following electrochemical reduction sequence was confirmed by XRD analysis. Firstly Fe2O3 was electrolyzed to form Fe, then intermetallic Tb-Fe and Dy-Fe were electrolyzed from Fe and Tb2O3 as well as Dy2O3, and finally they were alloyed to form TbDyFe2. The above electrochemical reduction results could be explained by a theory of “diffusion at triplephase boundary lines”, and hereby the triplephase boundary lines were Fe|Fe2O3|CaCl2 and Tb-Dy-Fe|Tb2O3-Dy2O3|CaCl2 in the electro-reduction process
2012, 41(12):2238-2241.
Abstract:
Zr-4 alloy was hot rolled to 2.2 mm thickness at 800 and 960 °C respectively, then cold rolled to 1.2 mm by a strip roller after interannealing, and finally cold rolled to 0.6 mm strips by the strip roller again after interannealing. The effect of rolling technology on the texture orientation factor of Zr-4 alloy strips was discussed, and the corrosion performance was tested in super-heated steam at 400 °C, 10.3 MPa for 72 h for the same-thickness rolled strips prepared at different cogging temperatures. Results show that in the same cold rolling deformation, transverse texture of the strip hot rolled at 960 °C is always more than that of the strip hot rolled at 800 °C, while the normal texture of the strip rolled at 960 °C is always less than that of the strip hot rolled at 800 °C. After hot rolling, the more cold rolling deformation causes less transverse texture but more normal texture. Corrosion performance in stream of 0.6 mm Zr-4 alloy strip rolled at 800 °C is better than that of the strip rolled at 960 °C. Therefore, it is possible to control and calculate the texture orientation factor of the Zr-4 alloy strips while attention should be paid to the effect of rolling technology on corrosion performance
Zr-4 alloy was hot rolled to 2.2 mm thickness at 800 and 960 °C respectively, then cold rolled to 1.2 mm by a strip roller after interannealing, and finally cold rolled to 0.6 mm strips by the strip roller again after interannealing. The effect of rolling technology on the texture orientation factor of Zr-4 alloy strips was discussed, and the corrosion performance was tested in super-heated steam at 400 °C, 10.3 MPa for 72 h for the same-thickness rolled strips prepared at different cogging temperatures. Results show that in the same cold rolling deformation, transverse texture of the strip hot rolled at 960 °C is always more than that of the strip hot rolled at 800 °C, while the normal texture of the strip rolled at 960 °C is always less than that of the strip hot rolled at 800 °C. After hot rolling, the more cold rolling deformation causes less transverse texture but more normal texture. Corrosion performance in stream of 0.6 mm Zr-4 alloy strip rolled at 800 °C is better than that of the strip rolled at 960 °C. Therefore, it is possible to control and calculate the texture orientation factor of the Zr-4 alloy strips while attention should be paid to the effect of rolling technology on corrosion performance
2012, 41(12):2243-2248.
Abstract:
For the welding problem which requires immediate solution before engineering, the recent research and development in welding technology of Fe3Al based alloys are summarized through 3 aspects including fusion welding, solid phase welding and infrared brazing. The microstructure and mechanical properties of the weld joint after different welding procedures are illustrated. Problems during welding procedure and the corresponding resolving measures are also discussed. At last, the future trends of welding technology are prospected.
For the welding problem which requires immediate solution before engineering, the recent research and development in welding technology of Fe3Al based alloys are summarized through 3 aspects including fusion welding, solid phase welding and infrared brazing. The microstructure and mechanical properties of the weld joint after different welding procedures are illustrated. Problems during welding procedure and the corresponding resolving measures are also discussed. At last, the future trends of welding technology are prospected.
2012, 41(12):2249-2253.
Abstract:
CuxBi2Se3 is yielded by chemical intercalating copper at the interlayer of topological insulator Bi2Se3 with layered grapheme like structure, and it is termed as topological superconductor due to the appearance of superconductivity with 12 at%~15 at% copper at 3.8 ~4.2 K temperature. CuxBi2Se3 is time-reversal-invariant superconductor and fully gapped in the bulk but has protected gapless surface Andreev bound states, and it has a three-dimensional Dirac band structure due to strong spin-orbit coupling. A superconducting energy gap leads to a state supporting Majorana fermions which are of difficulty to be detected, and thus it cannot be attracted or repelled by the ambient particles or atoms; then it is fault-resistant against the frail quantum state from disorder or impurities, which possibly provide a new venue for realizing proposals for spintronics and topological quantum computation. In this paper, the theoretical and experimental study concerning the new quantum material were reviewed firstly, the doping characters together with antisite defect features were analyzed in detail from the perspective of material science secondly, and the scientific statement of improving the physical and chemical performance by reducing the concentration of antisite defect and doping suitable elements were presented lastly
CuxBi2Se3 is yielded by chemical intercalating copper at the interlayer of topological insulator Bi2Se3 with layered grapheme like structure, and it is termed as topological superconductor due to the appearance of superconductivity with 12 at%~15 at% copper at 3.8 ~4.2 K temperature. CuxBi2Se3 is time-reversal-invariant superconductor and fully gapped in the bulk but has protected gapless surface Andreev bound states, and it has a three-dimensional Dirac band structure due to strong spin-orbit coupling. A superconducting energy gap leads to a state supporting Majorana fermions which are of difficulty to be detected, and thus it cannot be attracted or repelled by the ambient particles or atoms; then it is fault-resistant against the frail quantum state from disorder or impurities, which possibly provide a new venue for realizing proposals for spintronics and topological quantum computation. In this paper, the theoretical and experimental study concerning the new quantum material were reviewed firstly, the doping characters together with antisite defect features were analyzed in detail from the perspective of material science secondly, and the scientific statement of improving the physical and chemical performance by reducing the concentration of antisite defect and doping suitable elements were presented lastly
2012, 41(12):2254-2260.
Abstract:
Precious metals are the most active component in the automobile catalyst. Accurate determination of Pt, Pd and Rh is important for controlling the cost of catalyst, ensuring the performance of catalyst and the recovery from exhausted catalyst. The sampling, dissolution and analysis methods of automobile catalyst were introduced.
Precious metals are the most active component in the automobile catalyst. Accurate determination of Pt, Pd and Rh is important for controlling the cost of catalyst, ensuring the performance of catalyst and the recovery from exhausted catalyst. The sampling, dissolution and analysis methods of automobile catalyst were introduced.
