Volume 40,Issue 2,2011 Table of Contents
2011, 40(2):189-194.
Abstract:
AB5-type rare-earth nickel (RE-Ni) based hydrogen storage alloys and AB3-type La-Mg-Ni based hydrogen storage alloys were prepared by vacuum medium-frequency induction melting in argon atmosphere. Industrial offgas was simulated by the mixed gas including H2, N2 and CH4. The purity of hydrogen separated by rare-earth hydrogen storage alloys and anti-poison and anti-pulverization properties of the alloys in the process of hydrogen absorption and desorption were studied. The results show that AB5-type RE-Ni based hydrogen storage alloys are possessed of the single structure with CaCu5-type, and AB3-type La-Mg-Ni based hydrogen storage alloys are possessed of the multi-phase structure with (La,Mg)Ni3, LaNi5 and LaNi2 phase. The hydrogen storage alloys will be poisoned by impurity gas in the separation of hydrogen, resulting in lower speed rate of hydrogen absorption and lesser capacity of hydrogen absorption. The anti-pulverization property of La-Mg-Ni based alloys is better than that of LaNi5 alloy and its complex alloy. LaNi3.7Mn0.4Al0.3Fe0.4Co0.2 alloy is considered as better alloy to separate hydrogen from the mixed gas, considering the purity of separated hydrogen, anti-poison and anti-pulverization property of the alloy. The hydrogen purity of 90.7% can be achieved.
AB5-type rare-earth nickel (RE-Ni) based hydrogen storage alloys and AB3-type La-Mg-Ni based hydrogen storage alloys were prepared by vacuum medium-frequency induction melting in argon atmosphere. Industrial offgas was simulated by the mixed gas including H2, N2 and CH4. The purity of hydrogen separated by rare-earth hydrogen storage alloys and anti-poison and anti-pulverization properties of the alloys in the process of hydrogen absorption and desorption were studied. The results show that AB5-type RE-Ni based hydrogen storage alloys are possessed of the single structure with CaCu5-type, and AB3-type La-Mg-Ni based hydrogen storage alloys are possessed of the multi-phase structure with (La,Mg)Ni3, LaNi5 and LaNi2 phase. The hydrogen storage alloys will be poisoned by impurity gas in the separation of hydrogen, resulting in lower speed rate of hydrogen absorption and lesser capacity of hydrogen absorption. The anti-pulverization property of La-Mg-Ni based alloys is better than that of LaNi5 alloy and its complex alloy. LaNi3.7Mn0.4Al0.3Fe0.4Co0.2 alloy is considered as better alloy to separate hydrogen from the mixed gas, considering the purity of separated hydrogen, anti-poison and anti-pulverization property of the alloy. The hydrogen purity of 90.7% can be achieved.
2011, 40(2):195-200.
Abstract:
To perform molecular dynamics (MD) simulation of self-radiation effects in Ga-stabilized δ-Pu alloys, spectral representation 7Fg (9Fg), 2Pu (4Pu) and 1Sg (3Sg) of Pu, Ga and He atoms are resolved into the direct sum of Pu2 (D∞h)，PuGa (C∞v)，Ga2 (D∞h)，PuHe (C∞v)，GaHe (C∞v)，He2 (D∞h) according to atomic and molecular reaction statics, respectively. All possible electronic states can be derived by the direct product and reduction operation. The Pu-Pu, Pu-Ga, Pu-He, Ga-Ga, Ga-He and He-He potential data have been implemented ab initio calculation using relativistic alloy effective core potential (RECP) for Pu atom, 6-311G* all electron basis sets for Ga atom and He atom with Becke-3 hybrid functional (B3LYP). Interatomic potentials and electron states of the corresponding molecular have been obtained.
To perform molecular dynamics (MD) simulation of self-radiation effects in Ga-stabilized δ-Pu alloys, spectral representation 7Fg (9Fg), 2Pu (4Pu) and 1Sg (3Sg) of Pu, Ga and He atoms are resolved into the direct sum of Pu2 (D∞h)，PuGa (C∞v)，Ga2 (D∞h)，PuHe (C∞v)，GaHe (C∞v)，He2 (D∞h) according to atomic and molecular reaction statics, respectively. All possible electronic states can be derived by the direct product and reduction operation. The Pu-Pu, Pu-Ga, Pu-He, Ga-Ga, Ga-He and He-He potential data have been implemented ab initio calculation using relativistic alloy effective core potential (RECP) for Pu atom, 6-311G* all electron basis sets for Ga atom and He atom with Becke-3 hybrid functional (B3LYP). Interatomic potentials and electron states of the corresponding molecular have been obtained.
2011, 40(2):201-205.
Abstract:
The hot rolled and cold rolled-annealed plates of Al-Mg-Sc alloys were welded by friction stir welding. The hardness distribution and the tensile properties of welded joints were measured; the relationships between the microstructure and the properties of the welded joints were studied by means of optical microscopy and transmission electron microscopy. The results show that the welding coefficients of two plates are as high as 92%, the hardness and strength of their weld nugget zones are the lowest, and the fracture of their welded joints happens at weld nugget zones during tensile testing. The decrease of the substructure strengthening caused by the partial recrystallization and the loss of precipitation strengthening from Al3(Sc,Zr) particles result in the decline of hardness and strength of Al-Mg-Sc alloy welded joints.
The hot rolled and cold rolled-annealed plates of Al-Mg-Sc alloys were welded by friction stir welding. The hardness distribution and the tensile properties of welded joints were measured; the relationships between the microstructure and the properties of the welded joints were studied by means of optical microscopy and transmission electron microscopy. The results show that the welding coefficients of two plates are as high as 92%, the hardness and strength of their weld nugget zones are the lowest, and the fracture of their welded joints happens at weld nugget zones during tensile testing. The decrease of the substructure strengthening caused by the partial recrystallization and the loss of precipitation strengthening from Al3(Sc,Zr) particles result in the decline of hardness and strength of Al-Mg-Sc alloy welded joints.
2011, 40(2):206-208.
Abstract:
Mechanical properties of (Zr41.2Ti13.8Cu12.5Ni10Be22.5)100-xNbx bulk metallic glass (BMG) matrix composites reinforced by tungsten fiber (Wf) were investigated by X-ray diffraction, scanning electron microscope (SEM) and so on. The results show that the matrix of the prepared composites remain amorphous after adding Nb with x=1, 3, 5 and 7, at%, and the compressive yield strength and plastic strain increase with the increase of Nb content. The composites with x=7 possess the excellent comprehensive properties, whose compressive yield strength and plastic strain reach 2450 MPa and 20%, respectively.
Mechanical properties of (Zr41.2Ti13.8Cu12.5Ni10Be22.5)100-xNbx bulk metallic glass (BMG) matrix composites reinforced by tungsten fiber (Wf) were investigated by X-ray diffraction, scanning electron microscope (SEM) and so on. The results show that the matrix of the prepared composites remain amorphous after adding Nb with x=1, 3, 5 and 7, at%, and the compressive yield strength and plastic strain increase with the increase of Nb content. The composites with x=7 possess the excellent comprehensive properties, whose compressive yield strength and plastic strain reach 2450 MPa and 20%, respectively.
2011, 40(2):209-214.
Abstract:
E. coli and S. aureus were used as model for testing antimicrobial activity, and L-929 cell line was selected for toxicity evaluation by cellular mitochondrial function (MTT assay). The results show that silver nanoparticles (Ag NPs) can significantly increase antibacterial activity with the increasing of concentration of the silver nanoparticles. The lowest effective concentration of silver nanoparticles (30×10-6) which leads to more than 50% of inhibition in liquid medium and agar plate on bacterias is still satisfactory but will produce potential cytotoxicity. Even at 3×10-6 concentration of silver nanoparticles the cytotoxicity still exists with 2 grade which represents 26%-50% of cell growth inhibited, and 30×10-6 displays similar impact.
E. coli and S. aureus were used as model for testing antimicrobial activity, and L-929 cell line was selected for toxicity evaluation by cellular mitochondrial function (MTT assay). The results show that silver nanoparticles (Ag NPs) can significantly increase antibacterial activity with the increasing of concentration of the silver nanoparticles. The lowest effective concentration of silver nanoparticles (30×10-6) which leads to more than 50% of inhibition in liquid medium and agar plate on bacterias is still satisfactory but will produce potential cytotoxicity. Even at 3×10-6 concentration of silver nanoparticles the cytotoxicity still exists with 2 grade which represents 26%-50% of cell growth inhibited, and 30×10-6 displays similar impact.
2011, 40(2):215-219.
Abstract:
Nanostructured Ag with different morphologies and structures was prepared by replacement reaction (Zn versus AgNO3). The influence of AgNO3 concentration on the growth speed, the morphology and the structure of the nanostructured Ag was investigated. Experimental results show that the growth speed, morphologies and structures of the nanostructured Ag strongly depend on AgNO3 concentration and reaction time. The growth speed is mainly dependent on the AgNO3 concentration; the higher the concentration, the faster the growth speed. When the AgNO3 concentration is 5 mmol/L, Ag fractal forms at the beginning stage, but the fractal transforms to dendrite consisting of nanoparticles and to monocrystal at last as the reaction proceeds. When the concentration is in the range of 20-100 mmol/L, the products are all Ag dendrites, but the dendrites consist of nanoparticles when the concentration is below 40 mmol/L while they are monocrystal when the concentration is above 60 mmol/L. Ag nanostructures with different morphologies and structures can be prepared by controlling AgNO3 concentration and reaction time.
Nanostructured Ag with different morphologies and structures was prepared by replacement reaction (Zn versus AgNO3). The influence of AgNO3 concentration on the growth speed, the morphology and the structure of the nanostructured Ag was investigated. Experimental results show that the growth speed, morphologies and structures of the nanostructured Ag strongly depend on AgNO3 concentration and reaction time. The growth speed is mainly dependent on the AgNO3 concentration; the higher the concentration, the faster the growth speed. When the AgNO3 concentration is 5 mmol/L, Ag fractal forms at the beginning stage, but the fractal transforms to dendrite consisting of nanoparticles and to monocrystal at last as the reaction proceeds. When the concentration is in the range of 20-100 mmol/L, the products are all Ag dendrites, but the dendrites consist of nanoparticles when the concentration is below 40 mmol/L while they are monocrystal when the concentration is above 60 mmol/L. Ag nanostructures with different morphologies and structures can be prepared by controlling AgNO3 concentration and reaction time.
2011, 40(2):220-224.
Abstract:
Isothermal compression deformation tests were conducted for Ti600 alloy column samples by Gleeble-1500 thermal simulator. According to the obtained experimental data (deformation temperatures of 800-1100 oC and strain rates of 0.01-10 s-1), the high temperature constitutive relationship model for the alloy was built based on the BP neural network. Results show that the constitutive relationship model of BP neural network is of high prediction accuracy, which can describe the complicated nonlinear relationship of thermodynamical parameters well. Therefore it provides a more convenient and more effective way to establish the model of constitutive relationship for titanium alloys.
Isothermal compression deformation tests were conducted for Ti600 alloy column samples by Gleeble-1500 thermal simulator. According to the obtained experimental data (deformation temperatures of 800-1100 oC and strain rates of 0.01-10 s-1), the high temperature constitutive relationship model for the alloy was built based on the BP neural network. Results show that the constitutive relationship model of BP neural network is of high prediction accuracy, which can describe the complicated nonlinear relationship of thermodynamical parameters well. Therefore it provides a more convenient and more effective way to establish the model of constitutive relationship for titanium alloys.
2011, 40(2):225-230.
Abstract:
Titanium alloys’ properties are sensitive to the microstructure very much, which have nonlinear interactive relationship with the microstructral characteristics. In this study, a model was developed for the prediction of the correlation between microstructure and tensile properties in titanium alloys using artificial neural network (ANN). The inputs of the neural network were quantificational microstructure parameters, including thickness of α-laths, volume fraction of α-laths and Ferret Ratio. The outputs of the model were the tensile properties, including ultimate strength, yield strength, elongation and reduction of area. The model was based on back-error propagation (BP) neural network, and trained with the data collected from isothermal compression experiments of Ti17 alloys. A very good performance of the neural network was achieved such as prediction accuracy and generalization ability. Bayesian regularization and gradient descent learning method can solve the super-fitting problem of high-accuracy training and low-accuracy prediction of traditional BP artificial neural network. The model can be used for prediction of tensile properties of Ti17 alloys according to its microstructural features. Modeling this correlation is fairly necessary to build a robust expert database in titanium expert system.
Titanium alloys’ properties are sensitive to the microstructure very much, which have nonlinear interactive relationship with the microstructral characteristics. In this study, a model was developed for the prediction of the correlation between microstructure and tensile properties in titanium alloys using artificial neural network (ANN). The inputs of the neural network were quantificational microstructure parameters, including thickness of α-laths, volume fraction of α-laths and Ferret Ratio. The outputs of the model were the tensile properties, including ultimate strength, yield strength, elongation and reduction of area. The model was based on back-error propagation (BP) neural network, and trained with the data collected from isothermal compression experiments of Ti17 alloys. A very good performance of the neural network was achieved such as prediction accuracy and generalization ability. Bayesian regularization and gradient descent learning method can solve the super-fitting problem of high-accuracy training and low-accuracy prediction of traditional BP artificial neural network. The model can be used for prediction of tensile properties of Ti17 alloys according to its microstructural features. Modeling this correlation is fairly necessary to build a robust expert database in titanium expert system.
2011, 40(2):231-235.
Abstract:
Incremental step strain-rate test in the temperature range of 700-800 oC and the strain rate range of 5′10-4–1′10-2 s-1 were conducted for investigation of high temperature deformation behavior of Ti-29Nb-13Ta-5Zr (Ti-29-13), as well as another typical β titanium alloy Ti-15V-3Cr-3Sn-3Al (Ti-15-3). Results show there exist discontinuous yielding phenomenon in both alloys and the subgrain behavior is different between them. The strain to failure of Ti-29-13 is lower than that of Ti-15-3. In the deformation of Ti-29-13, the stress exponent is near 3.3, which is almost constant, and the deformation activation energy is 152-161 kJ/mol; while in the deformation of Ti-15-3, the stress exponent at the temperatures higher than 730 oC is 2.3-2.5, and the deformation activation energy is 173-176 kJ/mol.
Incremental step strain-rate test in the temperature range of 700-800 oC and the strain rate range of 5′10-4–1′10-2 s-1 were conducted for investigation of high temperature deformation behavior of Ti-29Nb-13Ta-5Zr (Ti-29-13), as well as another typical β titanium alloy Ti-15V-3Cr-3Sn-3Al (Ti-15-3). Results show there exist discontinuous yielding phenomenon in both alloys and the subgrain behavior is different between them. The strain to failure of Ti-29-13 is lower than that of Ti-15-3. In the deformation of Ti-29-13, the stress exponent is near 3.3, which is almost constant, and the deformation activation energy is 152-161 kJ/mol; while in the deformation of Ti-15-3, the stress exponent at the temperatures higher than 730 oC is 2.3-2.5, and the deformation activation energy is 173-176 kJ/mol.
2011, 40(2):236-238.
Abstract:
Using the model of cluster + glue atom, the ternary bulk metallic glasses (BMG) in Fe-B-Y system was designed, choosing the close-packed Archimedes octahedral antiprism CN-10 Fe8B3 as basic cluster and Y as glue atom. 3at%Nb was added as minor alloying element to form quaternary BMG. Ni was used to substitute for Fe, and a quinary BMG, [(Fe100-xNix)8B3-Y]97-Nb3, was formed. Results show that when Ni is less than 30at% the BMG with diameter of 2 mm can be obtained and the alloy [(Fe94Ni6)8B3-Y]97-Nb3 has the biggest Tg, Tx and Trg which are 884 K, 972 K and 0.634, respectively.
Using the model of cluster + glue atom, the ternary bulk metallic glasses (BMG) in Fe-B-Y system was designed, choosing the close-packed Archimedes octahedral antiprism CN-10 Fe8B3 as basic cluster and Y as glue atom. 3at%Nb was added as minor alloying element to form quaternary BMG. Ni was used to substitute for Fe, and a quinary BMG, [(Fe100-xNix)8B3-Y]97-Nb3, was formed. Results show that when Ni is less than 30at% the BMG with diameter of 2 mm can be obtained and the alloy [(Fe94Ni6)8B3-Y]97-Nb3 has the biggest Tg, Tx and Trg which are 884 K, 972 K and 0.634, respectively.
11 Rotary Bending High Cycle Fatigue Behavior of Single Crystal Superalloy DD499 in <111> Orientation
2011, 40(2):239-242.
Abstract:
Smooth and notched specimens of single crystal superalloy DD499 in <111> orientation were subjected to rotary bending high cycle fatigue loading at temperatures of 700 and 900 oC in ambient atmosphere. The results show that both fatigue strength and notch sensitivity of smooth specimens of <111>-oriented DD499 alloy are increased at elevated temperature; the fatigue strength of smooth specimens are 355 MPa at 700 oC, and 400 MPa at 900 oC. High cycle fatigue failure of smooth specimens of DD499 alloy at different temperatures is in the form of cleavage fracture with multiple crack initiation sites, which was evidently observed along {111} glide plane. However, for the notched specimens, the cracks propagate towards the central area from notched roots at 700 oC, and cleavage rupture characteristics is just like that of the smooth specimens at 900 oC.
Smooth and notched specimens of single crystal superalloy DD499 in <111> orientation were subjected to rotary bending high cycle fatigue loading at temperatures of 700 and 900 oC in ambient atmosphere. The results show that both fatigue strength and notch sensitivity of smooth specimens of <111>-oriented DD499 alloy are increased at elevated temperature; the fatigue strength of smooth specimens are 355 MPa at 700 oC, and 400 MPa at 900 oC. High cycle fatigue failure of smooth specimens of DD499 alloy at different temperatures is in the form of cleavage fracture with multiple crack initiation sites, which was evidently observed along {111} glide plane. However, for the notched specimens, the cracks propagate towards the central area from notched roots at 700 oC, and cleavage rupture characteristics is just like that of the smooth specimens at 900 oC.
2011, 40(2):243-246.
Abstract:
Interfacial residual stress distribution of SiC/Ti-6Al-4V composite was simulated by a three-dimensional finite element method. The effects of fiber arrays on interfacial residual stresses were discussed. Results show that the fiber array has great influences on radial, axial and circumferential residual stress. Among them hexagonal fiber array is an ideal arrangement pattern due to uniform distribution of interfacial residual stresses along the circumferential direction and low circumferential residual stress, which makes it difficult to generate radial crack.
Interfacial residual stress distribution of SiC/Ti-6Al-4V composite was simulated by a three-dimensional finite element method. The effects of fiber arrays on interfacial residual stresses were discussed. Results show that the fiber array has great influences on radial, axial and circumferential residual stress. Among them hexagonal fiber array is an ideal arrangement pattern due to uniform distribution of interfacial residual stresses along the circumferential direction and low circumferential residual stress, which makes it difficult to generate radial crack.
2011, 40(2):247-250.
Abstract:
The filling process and solidification of TiAl based alloy blade by suction casting was studied via numerical simulation. The shrinkage defect of TiAl based alloy blade casting was predicted using FEM software ProCAST. The results indicate the cold shut will be decreased with the increase of graphite suction opening diameter and the pouring temperature. With the decrease of the coefficient of heat transfer, the cold shut is reduced. The TiAl blades are obtained by this method. The simulated result tallies well with the actual cast experiment, and lays down a foundation for improving the cast technology of the TiAl based alloy casting.
The filling process and solidification of TiAl based alloy blade by suction casting was studied via numerical simulation. The shrinkage defect of TiAl based alloy blade casting was predicted using FEM software ProCAST. The results indicate the cold shut will be decreased with the increase of graphite suction opening diameter and the pouring temperature. With the decrease of the coefficient of heat transfer, the cold shut is reduced. The TiAl blades are obtained by this method. The simulated result tallies well with the actual cast experiment, and lays down a foundation for improving the cast technology of the TiAl based alloy casting.
2011, 40(2):251-254.
Abstract:
Al86Fe10Zr4 amorphous ribbons were prepared by melt spinning. The amorphous characteristics and crystallization behavior of the amorphous ribbons was investigated by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that the as-spun ribbons are in fully amorphous state. The DSC trace reveals that two-step crystallization occurs in the amorphous ribbon during the heating scanning, and the onset temperatures of the first and the second crystallization are about 603 and 718 K, respectively. The activation energies for the two-step crystallization are 273 and 239 kJ/mol, respectively. Furthermore, the effect of crystallization on the electrochemical properties was examined. The results indicate that the partially crystallized ribbon exhibits better corrosion resistance than that of the fully amorphous ribbon, while the fully crystallization deteriorates the corrosion resistance of the amorphous ribbon.
Al86Fe10Zr4 amorphous ribbons were prepared by melt spinning. The amorphous characteristics and crystallization behavior of the amorphous ribbons was investigated by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that the as-spun ribbons are in fully amorphous state. The DSC trace reveals that two-step crystallization occurs in the amorphous ribbon during the heating scanning, and the onset temperatures of the first and the second crystallization are about 603 and 718 K, respectively. The activation energies for the two-step crystallization are 273 and 239 kJ/mol, respectively. Furthermore, the effect of crystallization on the electrochemical properties was examined. The results indicate that the partially crystallized ribbon exhibits better corrosion resistance than that of the fully amorphous ribbon, while the fully crystallization deteriorates the corrosion resistance of the amorphous ribbon.
2011, 40(2):255-258.
Abstract:
Diamond-like carbon (DLC) films were prepared on medical Ti6Al4V alloy by ion beam sputtering deposition technology. The morphology, microstructure and tribological properties of the films were characterized using atomic force microscopy (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and UMT-2 universal micro-tribometer. The corrosion resistance in Hank’s solution of the films and the uncoated sample was evaluated by means of potentiodynamic polarization techniques. The results indicate that the carbon films have typical diamond-like characteristics. The surface roughness and morphology are also significantly influenced by the substrate bias. The film grown at –100 V bias has optimal properties such as high sp3/sp2 ratio of carbon bonding, low roughness of 6.5 nm and excellent friction behavior. Electrochemical measurements show that the DLC films markedly improve the corrosion resistance of the Ti6Al4V alloy.
Diamond-like carbon (DLC) films were prepared on medical Ti6Al4V alloy by ion beam sputtering deposition technology. The morphology, microstructure and tribological properties of the films were characterized using atomic force microscopy (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and UMT-2 universal micro-tribometer. The corrosion resistance in Hank’s solution of the films and the uncoated sample was evaluated by means of potentiodynamic polarization techniques. The results indicate that the carbon films have typical diamond-like characteristics. The surface roughness and morphology are also significantly influenced by the substrate bias. The film grown at –100 V bias has optimal properties such as high sp3/sp2 ratio of carbon bonding, low roughness of 6.5 nm and excellent friction behavior. Electrochemical measurements show that the DLC films markedly improve the corrosion resistance of the Ti6Al4V alloy.
2011, 40(2):259-264.
Abstract:
The substitution behavior of Cr atom in Ni75CrxAl25-x alloy at 873 K was simulated by a microscopic phase-field model. During the precipitation progress, Cr atoms substitute for the Al sublattices partially to form Ni3Al1-xCrx phases (L12 structure). The limits of occupation probabilities of Cr atoms in L12 phases are lower. Cr atom concentration approaches the saturation value in L12 phases when Cr content exceeds 3%. At the ordering domain interface of L12 phases, Cr atoms substitute for the Al sublattices completely, and the stable D022 phases are formed. The final precipitates are mix phases of Ni3Al-Ni3Cr.
The substitution behavior of Cr atom in Ni75CrxAl25-x alloy at 873 K was simulated by a microscopic phase-field model. During the precipitation progress, Cr atoms substitute for the Al sublattices partially to form Ni3Al1-xCrx phases (L12 structure). The limits of occupation probabilities of Cr atoms in L12 phases are lower. Cr atom concentration approaches the saturation value in L12 phases when Cr content exceeds 3%. At the ordering domain interface of L12 phases, Cr atoms substitute for the Al sublattices completely, and the stable D022 phases are formed. The final precipitates are mix phases of Ni3Al-Ni3Cr.
2011, 40(2):265-268.
Abstract:
The morphology of primary Al3(Sc, Zr) particles in as-cast microstructure of Al-Zn-Mg-Cu-Zr-Sc alloys and the grain refinement mechanism of Sc on as-cast microstructure of Al-Zn-Mg-Cu-Zr alloys were investigated by optical microscope, scanning electron microscope (SEM) and energy spectrum analysis. Primary Al3(Sc, Zr) particles precipitated from the melt is an effective nucleating agent of α(Al) matrix with metastable Al3Zr (L12) as nucleation. The particle is of layered construction. Sc and Zr in primary Al3(Sc, Zr) particles distributed interleavingly with the Zr-rich core. Adding 0.20wt%-0.60wt% Sc to Al-9.0Zn-2.5Mg-2.5Cu-0.15Zr alloys, coarse dendrite was changed into fine equiaxed grains. The higher content of Sc of alloys is, the finer as-cast grain is.
The morphology of primary Al3(Sc, Zr) particles in as-cast microstructure of Al-Zn-Mg-Cu-Zr-Sc alloys and the grain refinement mechanism of Sc on as-cast microstructure of Al-Zn-Mg-Cu-Zr alloys were investigated by optical microscope, scanning electron microscope (SEM) and energy spectrum analysis. Primary Al3(Sc, Zr) particles precipitated from the melt is an effective nucleating agent of α(Al) matrix with metastable Al3Zr (L12) as nucleation. The particle is of layered construction. Sc and Zr in primary Al3(Sc, Zr) particles distributed interleavingly with the Zr-rich core. Adding 0.20wt%-0.60wt% Sc to Al-9.0Zn-2.5Mg-2.5Cu-0.15Zr alloys, coarse dendrite was changed into fine equiaxed grains. The higher content of Sc of alloys is, the finer as-cast grain is.
2011, 40(2):269-274.
Abstract:
A new kind of adsorbent was prepared from the bark of black wattle being rich of tannin; furthermore, the cross-linking reaction of formaldehyde was used to immobilize tannin in situ to get the adsorbent. The adsorption property of this new adsorbent to ions of light rare earth such as La3+, Pr3+ and Nd3+ (RE3+) in aqueous solution was investigated. Results show that the optimum pH value of this adsorbent to La3+ is about 5.0, while the optimum value of Pr3+ and Nd3+ is about 5.5. The equilibrium adsorption capacity will decline significantly when the pH value of reaction system is changed from the optimum pH value. Compared with the effect of pH value, the influence of the temperature on the equilibrium adsorption capacity is weaker, and at 303 K the equilibrium adsorption capacity of this adsorbent to RE3+ is optimal. At 303 K and the optimum pH value, when the initial concentration of RE3+ solution is 5.0 mmol·L-1 and the dosage of adsorbent is 0.10 g, the equilibrium adsorption capacity of this adsorbent to La3+, Pr3+ and Nd3+ are 217.26, 228.56 and 329.76 mg·g-1, respectively. The adsorption isotherm can be described by the Freundlich equation. This adsorption kinetics data of this adsorbent to RE3+ is fitted with the pseudo-second-order rate model well and the equilibrium adsorption capacities calculated by the model are consistent with the experimental data with the warps in 7%.
A new kind of adsorbent was prepared from the bark of black wattle being rich of tannin; furthermore, the cross-linking reaction of formaldehyde was used to immobilize tannin in situ to get the adsorbent. The adsorption property of this new adsorbent to ions of light rare earth such as La3+, Pr3+ and Nd3+ (RE3+) in aqueous solution was investigated. Results show that the optimum pH value of this adsorbent to La3+ is about 5.0, while the optimum value of Pr3+ and Nd3+ is about 5.5. The equilibrium adsorption capacity will decline significantly when the pH value of reaction system is changed from the optimum pH value. Compared with the effect of pH value, the influence of the temperature on the equilibrium adsorption capacity is weaker, and at 303 K the equilibrium adsorption capacity of this adsorbent to RE3+ is optimal. At 303 K and the optimum pH value, when the initial concentration of RE3+ solution is 5.0 mmol·L-1 and the dosage of adsorbent is 0.10 g, the equilibrium adsorption capacity of this adsorbent to La3+, Pr3+ and Nd3+ are 217.26, 228.56 and 329.76 mg·g-1, respectively. The adsorption isotherm can be described by the Freundlich equation. This adsorption kinetics data of this adsorbent to RE3+ is fitted with the pseudo-second-order rate model well and the equilibrium adsorption capacities calculated by the model are consistent with the experimental data with the warps in 7%.
2011, 40(2):275-278.
Abstract:
Melt-spun Y1.7Er0.3Fe17 ribbons were prepared at the wheel speed of 20 m/s. The crystal structure, the magnetic entropy change and three-dimensional atomic mapping of the ribbons were investigated. The results indicate that the melt-spun Y1.7Er0.3Fe17 ribbons crystallize in the hexagonal Th2Zn17 structure, and the lattice parameters of main phase Y2Fe17 in the melt-spun Y1.7Er0.3Fe17 ribbons decrease compared with the standard PDF card (48-1454). The Curie temperature of melt-spun Y1.7Er0.3Fe17 ribbons is about 308 K, which is close to room temperature, and the maximum magnetic entropy change for a field change of 0-1.5 T is 2.10 J·kg-1·K-1. Three elements (Y, Er and Fe) uniformly distributed in the three-dimensional space except in the grain boundary with lower Fe content.
Melt-spun Y1.7Er0.3Fe17 ribbons were prepared at the wheel speed of 20 m/s. The crystal structure, the magnetic entropy change and three-dimensional atomic mapping of the ribbons were investigated. The results indicate that the melt-spun Y1.7Er0.3Fe17 ribbons crystallize in the hexagonal Th2Zn17 structure, and the lattice parameters of main phase Y2Fe17 in the melt-spun Y1.7Er0.3Fe17 ribbons decrease compared with the standard PDF card (48-1454). The Curie temperature of melt-spun Y1.7Er0.3Fe17 ribbons is about 308 K, which is close to room temperature, and the maximum magnetic entropy change for a field change of 0-1.5 T is 2.10 J·kg-1·K-1. Three elements (Y, Er and Fe) uniformly distributed in the three-dimensional space except in the grain boundary with lower Fe content.
2011, 40(2):279-284.
Abstract:
The trace elements Hf-, Zr- and Ta-containing phases in the mother alloy, plasma rotating electrode processing (PREP) powders and hot isostatic pressed (HIPed) state of a new third generation nickel-based powder metallurgy (P/M) superalloy were studied. The results show that the trace elements Hf, Zr and Ta mainly exist as MC-type carbides which locate between the dendrites and in the shape of block, strip and butterfly. The carbides in PREP powders can be broadly divided into two groups. One is rich in Ti, Ta and Nb, and the other contains the elements of Ta, Hf and Zr. The two types of carbides both contain a certain amount of non-carbide forming elements Co and Ni, weak carbide forming elements Cr and Mo, and locate between the dendrites or cellulars and in the shape of block and granular. In addition, the analysis of HIPed alloy show that the trace elements Hf, Ta and Zr mainly exist as intragranular and grain boundary MC carbides. All of these indicate that the trace elements Hf, Zr and Ta are in the survival of MC-type carbides and with the genetic characteristic. Carbides and γ' phase of HIPed alloy contain less Ta compared with PREP powders.
The trace elements Hf-, Zr- and Ta-containing phases in the mother alloy, plasma rotating electrode processing (PREP) powders and hot isostatic pressed (HIPed) state of a new third generation nickel-based powder metallurgy (P/M) superalloy were studied. The results show that the trace elements Hf, Zr and Ta mainly exist as MC-type carbides which locate between the dendrites and in the shape of block, strip and butterfly. The carbides in PREP powders can be broadly divided into two groups. One is rich in Ti, Ta and Nb, and the other contains the elements of Ta, Hf and Zr. The two types of carbides both contain a certain amount of non-carbide forming elements Co and Ni, weak carbide forming elements Cr and Mo, and locate between the dendrites or cellulars and in the shape of block and granular. In addition, the analysis of HIPed alloy show that the trace elements Hf, Ta and Zr mainly exist as intragranular and grain boundary MC carbides. All of these indicate that the trace elements Hf, Zr and Ta are in the survival of MC-type carbides and with the genetic characteristic. Carbides and γ' phase of HIPed alloy contain less Ta compared with PREP powders.
2011, 40(2):285-288.
Abstract:
The low-frequency damping characteristics of a new kind of titanium alloy TNCH-Z after different heat treatment were investigated by means of DMA (dynamic mechanical thermal analysis) with the frequency, strain and temperature varying. And audio internal friction was measured. The results show that the damping performance of the alloy is increased greatly with strain amplitude increasing under low-frequency at room temperature. The damping capacity of the alloy is decreased with the frequency increasing. Due to the martensitic transformation, the alloy is sensitive to temperature change. Between –50 oC and 100 oC, the internal friction peak value (tan φ) is 0.08 (heating)/0.09 (cooling). The value of internal friction in the martensitic is higher than that in the mother phase. Because of the influence of the heat treatment system, the internal friction peak of the alloy is wide and the temperature is increased. The audio internal friction reaches to the 10-2 level.
The low-frequency damping characteristics of a new kind of titanium alloy TNCH-Z after different heat treatment were investigated by means of DMA (dynamic mechanical thermal analysis) with the frequency, strain and temperature varying. And audio internal friction was measured. The results show that the damping performance of the alloy is increased greatly with strain amplitude increasing under low-frequency at room temperature. The damping capacity of the alloy is decreased with the frequency increasing. Due to the martensitic transformation, the alloy is sensitive to temperature change. Between –50 oC and 100 oC, the internal friction peak value (tan φ) is 0.08 (heating)/0.09 (cooling). The value of internal friction in the martensitic is higher than that in the mother phase. Because of the influence of the heat treatment system, the internal friction peak of the alloy is wide and the temperature is increased. The audio internal friction reaches to the 10-2 level.
22 Modeling the High-Temperature Constitutive Relationship of Ti-22Al-25Nb Alloy Based on Fuzzy Theory
2011, 40(2):289-293.
Abstract:
The hot deformation characteristics of Ti-22Al-25Nb alloy were studied in the temperature range of 940-1030 oC and strain rate range of 0.001-10 s-1 using Gleeble 1500 thermal simulator. Based on the results obtained from the experiment for the complex flow deformation behavior, a constitutive model of Ti-22Al-25Nb alloy was established with the help of the fuzzy set theory. Simultaneously, a kind of fuzzy dynamic linear model was put forward to extract the feature of sample data for the complicated nonlinear relationship of thermodynamic parameters. Compared with the experimental value, the results of this study indicate that the method is feasible to construct a constitutive relationship model for this alloy and high in the degree of fitting. It can be used to make up for the limitations that traditional regression can not reflect the whole deformation process. It is not only a wide prospect of application but also a convenient way to characterize the constitutive model for Ti-22Al-25Nb alloy.
The hot deformation characteristics of Ti-22Al-25Nb alloy were studied in the temperature range of 940-1030 oC and strain rate range of 0.001-10 s-1 using Gleeble 1500 thermal simulator. Based on the results obtained from the experiment for the complex flow deformation behavior, a constitutive model of Ti-22Al-25Nb alloy was established with the help of the fuzzy set theory. Simultaneously, a kind of fuzzy dynamic linear model was put forward to extract the feature of sample data for the complicated nonlinear relationship of thermodynamic parameters. Compared with the experimental value, the results of this study indicate that the method is feasible to construct a constitutive relationship model for this alloy and high in the degree of fitting. It can be used to make up for the limitations that traditional regression can not reflect the whole deformation process. It is not only a wide prospect of application but also a convenient way to characterize the constitutive model for Ti-22Al-25Nb alloy.
23 Effects of Cu/Ni Multilayer Film on Fretting Wear and Fretting Fatigue Resistance of Ti811 Alloys
2011, 40(2):294-300.
Abstract:
The Cu/Ni multilayer films with modulation period thickness of 20-1200 nm were prepared on Ti811 titanium alloy surface by ion assisted magnetron sputtering deposition (IAD) technique. The structure, bonding strength, micro-hardness and ductility of the films were analyzed. The effects of the Cu/Ni multilayer films with different modulation periods on the fretting wear (FW) property and fretting fatigue (FF) resistance of the titanium alloy substrate at room temperature were investigated. The results indicate that the IAD technique can prepare Cu/Ni multilayer films with high density, small grain size, high bonding strength and excellent lubricating properties. Therefore, the Cu/Ni multilayer films could improve the resistance of fretting wear and fretting fatigue of the Ti811 alloy at room temperature. The FF resistance of the titanium alloy substrate is increased non-monotonously with increasing of the modulation period thickness of the Cu/Ni multilayer films. The Cu/Ni multilayer films with modulation period thickness of 200 nm have the highest FF resistance among the prepared Cu/Ni multilayer films for its comprehensive properties with high toughness, high strength and good lubricating action.
The Cu/Ni multilayer films with modulation period thickness of 20-1200 nm were prepared on Ti811 titanium alloy surface by ion assisted magnetron sputtering deposition (IAD) technique. The structure, bonding strength, micro-hardness and ductility of the films were analyzed. The effects of the Cu/Ni multilayer films with different modulation periods on the fretting wear (FW) property and fretting fatigue (FF) resistance of the titanium alloy substrate at room temperature were investigated. The results indicate that the IAD technique can prepare Cu/Ni multilayer films with high density, small grain size, high bonding strength and excellent lubricating properties. Therefore, the Cu/Ni multilayer films could improve the resistance of fretting wear and fretting fatigue of the Ti811 alloy at room temperature. The FF resistance of the titanium alloy substrate is increased non-monotonously with increasing of the modulation period thickness of the Cu/Ni multilayer films. The Cu/Ni multilayer films with modulation period thickness of 200 nm have the highest FF resistance among the prepared Cu/Ni multilayer films for its comprehensive properties with high toughness, high strength and good lubricating action.
2011, 40(2):301-306.
Abstract:
TiAl based alloy with ultrafine grain structure were prepared by mechanical alloying and spark plasma sintering (SPS). And high temperature cycle oxidation behavior was tested by DSC. The effects of mechanical alloying on the fine-grain microstructure and high temperature oxidation resistance were investigated. Result show that the fine microstructure is attributed to ball milling. Fine and nodular TiAl and Ti3Al phases are formed after ball milling and SPS. Fine microstructure display higher oxidation resistance under high temperature cycle oxidation condition. The oxidation resistance of TiAl based alloy is improved with Nb content increasing. The oxidation rate is the fastest in the heating stage.
TiAl based alloy with ultrafine grain structure were prepared by mechanical alloying and spark plasma sintering (SPS). And high temperature cycle oxidation behavior was tested by DSC. The effects of mechanical alloying on the fine-grain microstructure and high temperature oxidation resistance were investigated. Result show that the fine microstructure is attributed to ball milling. Fine and nodular TiAl and Ti3Al phases are formed after ball milling and SPS. Fine microstructure display higher oxidation resistance under high temperature cycle oxidation condition. The oxidation resistance of TiAl based alloy is improved with Nb content increasing. The oxidation rate is the fastest in the heating stage.
2011, 40(2):307-310.
Abstract:
The solidification microstructure evolution of Ni-based superalloy DZ125 with melt superheating time was investigated. The results show that the dendrite arms are evidently refined and the segregation is reduced with the increase of melt superheating time when the melt superheating time is less than 30 min. However, further prolonging melt superheating time, the dendrite arms become coarser lightly. The morphology of carbide presents from script-like to blocky and nodule when the melt superheating time increases from 15 to 30 min. But when melt superheating treatment time is prolonged to 60 min, the morphology of carbide is still mainly blocky and nodule. The reason of solidification microstructure evolution is the change of melt structure with the prolonging of melt superheating time.
The solidification microstructure evolution of Ni-based superalloy DZ125 with melt superheating time was investigated. The results show that the dendrite arms are evidently refined and the segregation is reduced with the increase of melt superheating time when the melt superheating time is less than 30 min. However, further prolonging melt superheating time, the dendrite arms become coarser lightly. The morphology of carbide presents from script-like to blocky and nodule when the melt superheating time increases from 15 to 30 min. But when melt superheating treatment time is prolonged to 60 min, the morphology of carbide is still mainly blocky and nodule. The reason of solidification microstructure evolution is the change of melt structure with the prolonging of melt superheating time.
2011, 40(2):311-315.
Abstract:
Magnetic composite nanoparticles Fe3O4/Pt were prepared via ultrasonic irradiation to the mixed solution of hexachloroplatinum acid hydrate solution and (3-aminopropyl)triethoxysilane (APTES)-coated Fe3O4 nanoparticles and subsequent dropping addition of hydrozine hydrate. The morphology, microstructure, composition and magnetic properties of the Fe3O4/Pt nanoparticles were characterized by ultraviolet-visible spectroscopy (UV-Vis), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID) magnetometry. Results show that Fe3O4/Pt nanoparticles obtained under the conditions possess saturation magnetization intensity of about 17.2 (A·m2)/kg, and their average diameter is about 50 nm.
Magnetic composite nanoparticles Fe3O4/Pt were prepared via ultrasonic irradiation to the mixed solution of hexachloroplatinum acid hydrate solution and (3-aminopropyl)triethoxysilane (APTES)-coated Fe3O4 nanoparticles and subsequent dropping addition of hydrozine hydrate. The morphology, microstructure, composition and magnetic properties of the Fe3O4/Pt nanoparticles were characterized by ultraviolet-visible spectroscopy (UV-Vis), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID) magnetometry. Results show that Fe3O4/Pt nanoparticles obtained under the conditions possess saturation magnetization intensity of about 17.2 (A·m2)/kg, and their average diameter is about 50 nm.
2011, 40(2):316-320.
Abstract:
Using slurry pack cementation mixture with TiO2 as titanizing source, pure Al powder as reducer, NH4Cl as activator, Al2O3 as inert additive and albumen (egg white) as cohesive agent, electroplated specimens with a layer of electroplating nickel originally deposited on copper were titanized to prepare Ti-Al coating. The effect of CeO2 oxides on the microstructures and high temperature oxidation resistance of Ti-Al coating were studied. The results show that the phases of the coating are transformed from Ni-Ti to Ni-Al intermetallics, and the process of slurry pack cementation are also changed from the titanizing-base dual process to the aluminizing process after adding CeO2 oxides. The oxidation mass gain of Ti-Al coating is decreased from 1/10 of that of pure copper to 1/28. The oxide is primarily composed of TiO2, Al2O3 and a small amount of NiO. The oxide layer is dense without cracks and pores, which improves the high temperature oxidation resistance.
Using slurry pack cementation mixture with TiO2 as titanizing source, pure Al powder as reducer, NH4Cl as activator, Al2O3 as inert additive and albumen (egg white) as cohesive agent, electroplated specimens with a layer of electroplating nickel originally deposited on copper were titanized to prepare Ti-Al coating. The effect of CeO2 oxides on the microstructures and high temperature oxidation resistance of Ti-Al coating were studied. The results show that the phases of the coating are transformed from Ni-Ti to Ni-Al intermetallics, and the process of slurry pack cementation are also changed from the titanizing-base dual process to the aluminizing process after adding CeO2 oxides. The oxidation mass gain of Ti-Al coating is decreased from 1/10 of that of pure copper to 1/28. The oxide is primarily composed of TiO2, Al2O3 and a small amount of NiO. The oxide layer is dense without cracks and pores, which improves the high temperature oxidation resistance.
2011, 40(2):321-324.
Abstract:
Melt hydrogenation was presented based on thermal hydrogenation processing (THP). Titanium alloy was melted in H2/Ar gaseous mixture. Part of hydrogen was absorbed by the alloy after cooling. Compared with THP, the hydrogenation process was very fast because of the big diffusion coefficient in melt alloy. The relationship between hydrogen content in TC21 alloy and partial pressure of H2 was deduced based on Sievert’s law. It is found that the grain size and microhardness of TC21 alloy are decreased with more hydrogen. With the hydrogen content further increasing, α" phase and twining structure is detected in the alloy.
Melt hydrogenation was presented based on thermal hydrogenation processing (THP). Titanium alloy was melted in H2/Ar gaseous mixture. Part of hydrogen was absorbed by the alloy after cooling. Compared with THP, the hydrogenation process was very fast because of the big diffusion coefficient in melt alloy. The relationship between hydrogen content in TC21 alloy and partial pressure of H2 was deduced based on Sievert’s law. It is found that the grain size and microhardness of TC21 alloy are decreased with more hydrogen. With the hydrogen content further increasing, α" phase and twining structure is detected in the alloy.
2011, 40(2):325-330.
Abstract:
Dynamic recrystallization microstructure evolution of titanium alloy TA15 was investigated during deformation at 1050 oC and different strain rates. The dynamic recrystallization kinetics, nucleation rate and grain size evolution were discussed. Results show that with different strain rates there are two types of dynamic recrystallization, i.e. the continuous and the discontinuous. According to the dynamic analysis, at the strain rates of 0.01, 0.1 and 1 s-1, the corresponded dynamic recrystallization steady strains are 1.26, 1.57 and 2.93, indicating higher strain rates lead to higher steady strain. It is hard to reach steady stage at higher strain rates while the nucleation is obviously higher than that at lower strain rates. At lower strain rate, a slight increment of strain rates can greatly decrease the grain size; however, at higher strain rates, the grain size is little dependent on the strain rates. Therefore, refinement of structure can be obtained by the continuous dynamic recrystallization at high strain rate and large strain.
Dynamic recrystallization microstructure evolution of titanium alloy TA15 was investigated during deformation at 1050 oC and different strain rates. The dynamic recrystallization kinetics, nucleation rate and grain size evolution were discussed. Results show that with different strain rates there are two types of dynamic recrystallization, i.e. the continuous and the discontinuous. According to the dynamic analysis, at the strain rates of 0.01, 0.1 and 1 s-1, the corresponded dynamic recrystallization steady strains are 1.26, 1.57 and 2.93, indicating higher strain rates lead to higher steady strain. It is hard to reach steady stage at higher strain rates while the nucleation is obviously higher than that at lower strain rates. At lower strain rate, a slight increment of strain rates can greatly decrease the grain size; however, at higher strain rates, the grain size is little dependent on the strain rates. Therefore, refinement of structure can be obtained by the continuous dynamic recrystallization at high strain rate and large strain.
2011, 40(2):331-334.
Abstract:
The fracture mechanisms of Al-Cu-Li-Zr-Ce alloys aged for different time were studied by means of semi-quantity method. The effects of aging time and stress state of the crack tip on the fracture mechanisms were discussed. The results show that in the initial cracking area, with longer aging time the delamination percentage increases, the dimple percentage decreases, and even quasi-cleavage character appears. In the stable crack growth area, the delamination is the main fracture mechanism. However, in the near unstable crack growth area, the delamination percentage decreases and the quasi-cleavage become the main fracture mechanism gradually. The delamination thickness decreases with aging time prolonging and crack growing. The formation and propagation of the delamination cracks are significantly dependent on the main crack growth and the aging time of alloys. The higher delamination percentage leads to higher values both of toughness and strength.
The fracture mechanisms of Al-Cu-Li-Zr-Ce alloys aged for different time were studied by means of semi-quantity method. The effects of aging time and stress state of the crack tip on the fracture mechanisms were discussed. The results show that in the initial cracking area, with longer aging time the delamination percentage increases, the dimple percentage decreases, and even quasi-cleavage character appears. In the stable crack growth area, the delamination is the main fracture mechanism. However, in the near unstable crack growth area, the delamination percentage decreases and the quasi-cleavage become the main fracture mechanism gradually. The delamination thickness decreases with aging time prolonging and crack growing. The formation and propagation of the delamination cracks are significantly dependent on the main crack growth and the aging time of alloys. The higher delamination percentage leads to higher values both of toughness and strength.
2011, 40(2):335-338.
Abstract:
Metal injection molding (MIM) was used to fabricate porous titanium with sodium chloride (NaCl) as spacer-holder. The effects of sintering temperature, particle size and amount of the spacer-holder on porosity, microstructure and mechanical properties were investigated. The results show that the porosity of porous titanium decreases while the compressive strength and elastic modulus increases with the increasing of sintering temperature. The pore size of porous titanium decreases with the granularity of NaCl decreasing, and the porosity increases with the addition of spacer-holder. The optimum sintering temperature of MIM porous titanium implant is 1100-1200 oC, and the optimum granularity of NaCl is 150-250 μm.
Metal injection molding (MIM) was used to fabricate porous titanium with sodium chloride (NaCl) as spacer-holder. The effects of sintering temperature, particle size and amount of the spacer-holder on porosity, microstructure and mechanical properties were investigated. The results show that the porosity of porous titanium decreases while the compressive strength and elastic modulus increases with the increasing of sintering temperature. The pore size of porous titanium decreases with the granularity of NaCl decreasing, and the porosity increases with the addition of spacer-holder. The optimum sintering temperature of MIM porous titanium implant is 1100-1200 oC, and the optimum granularity of NaCl is 150-250 μm.
2011, 40(2):339-342.
Abstract:
Mg-Zr-O films for plasma display panels (PDPs) were deposited on glass substrates by magnetron sputtering method. The effects of Zr doping on both the discharge properties (firing voltage and the minimum sustaining voltage) and the microstructure of the Mg-Zr-O films were investigated. The results show that the deposited Mg-Zr-O films retain the NaCl-type structure as the pure MgO crystal. The grain of the films is very fine. The doped Zr exists in the form of Zr4+ substitution solution in MgO crystal. When the Zr concentration is about 2.03at%, the Mg-Zr-O films have the strongest (200) preferred orientation and the minimum surface roughness. The firing voltage and the minimum sustaining voltage of Mg-Zr-O protective films are reduced at most by about 25 and 15 V, respectively, compared with those of the pure MgO film.
Mg-Zr-O films for plasma display panels (PDPs) were deposited on glass substrates by magnetron sputtering method. The effects of Zr doping on both the discharge properties (firing voltage and the minimum sustaining voltage) and the microstructure of the Mg-Zr-O films were investigated. The results show that the deposited Mg-Zr-O films retain the NaCl-type structure as the pure MgO crystal. The grain of the films is very fine. The doped Zr exists in the form of Zr4+ substitution solution in MgO crystal. When the Zr concentration is about 2.03at%, the Mg-Zr-O films have the strongest (200) preferred orientation and the minimum surface roughness. The firing voltage and the minimum sustaining voltage of Mg-Zr-O protective films are reduced at most by about 25 and 15 V, respectively, compared with those of the pure MgO film.
2011, 40(2):343-346.
Abstract:
Gold nanoparticles were prepared in PEG10000/Vc/HAuCl4 system with Vc as the reducing agent. Then gold-platinum bimetallic nanoparticles with different Pt/Au ratio were formed using a simple gold seed-mediated growth method by controlling the mass ratio of HAuCl4/H2PtCl6. Their electrocatalysis effects on H2O-2 electrochemical oxidation were studied. Results of Uv-visible spectra (Uv-vis), transmission electronic microscopy (TEM), X-ray diffraction (XRD) and selected area electron diffraction (SAED) show that Au-Pt bimetallic nanoparticles are of face-centered cubic structure. The electrochemical performance of Au-Pt/glassy carbon (GC) electrode was investigated by cyclic voltammetry method. The result indicates that the Au-Pt/GC electrode has good electrocatalytic activity for H2O2 oxidation. The catalytic efficiency is increased with more Pt content in Au-Pt alloys.
Gold nanoparticles were prepared in PEG10000/Vc/HAuCl4 system with Vc as the reducing agent. Then gold-platinum bimetallic nanoparticles with different Pt/Au ratio were formed using a simple gold seed-mediated growth method by controlling the mass ratio of HAuCl4/H2PtCl6. Their electrocatalysis effects on H2O-2 electrochemical oxidation were studied. Results of Uv-visible spectra (Uv-vis), transmission electronic microscopy (TEM), X-ray diffraction (XRD) and selected area electron diffraction (SAED) show that Au-Pt bimetallic nanoparticles are of face-centered cubic structure. The electrochemical performance of Au-Pt/glassy carbon (GC) electrode was investigated by cyclic voltammetry method. The result indicates that the Au-Pt/GC electrode has good electrocatalytic activity for H2O2 oxidation. The catalytic efficiency is increased with more Pt content in Au-Pt alloys.
2011, 40(2):347-351.
Abstract:
Cylindrical rod-like specimens with various diameters for Zr65Cu27.5Al7.5 alloy were prepared by arc-melting and Cu-mold casting under different hydrostatic pressures. The influences of hydrostatic pressure on the alloy’s glass-forming ability (GFA) and mechanical properties were investigated. Results show that the alloy’s GFA presents sensitive response to the variation of hydrostatic pressure at kPa level, and lower or higher pressures can decrease the GFA. The sensitive hydrostatic pressure dependence of GFA is related with the microstructures of primary phases.
Cylindrical rod-like specimens with various diameters for Zr65Cu27.5Al7.5 alloy were prepared by arc-melting and Cu-mold casting under different hydrostatic pressures. The influences of hydrostatic pressure on the alloy’s glass-forming ability (GFA) and mechanical properties were investigated. Results show that the alloy’s GFA presents sensitive response to the variation of hydrostatic pressure at kPa level, and lower or higher pressures can decrease the GFA. The sensitive hydrostatic pressure dependence of GFA is related with the microstructures of primary phases.
2011, 40(2):352-356.
Abstract:
Fe and He atoms were introduced into aluminum via ion implantation, and the effect of Fe-doping on the ion-implantation helium behavior in aluminum was studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and thermal helium desorption spectrometry (THDS). The results indicate that the doped Fe mainly exist in the form of atomic clusters in the matrix, and the behavior of surface blistering and thermal helium desorption has a close dependence on the doped-Fe and its dose. Small dose of Fe doping will result in effective resistance of surface blistering and delay of gas release, while large dose doping can deteriorate the irradiation damage, leading to flaking and even repeated flaking on the surface, and the enhancement of gas release in lower temperature range. The reasons are interpreted as following: when small dose of Fe are implanted in aluminum, second phase precipitates of high He trapping ability will form in the matrix, restraining the mobility and the growth of helium bubbles. Consequently, the microstructural evolution and gas release character are affected. However, the resistance effect will be weakened when large dose of Fe is doped in aluminum.
Fe and He atoms were introduced into aluminum via ion implantation, and the effect of Fe-doping on the ion-implantation helium behavior in aluminum was studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and thermal helium desorption spectrometry (THDS). The results indicate that the doped Fe mainly exist in the form of atomic clusters in the matrix, and the behavior of surface blistering and thermal helium desorption has a close dependence on the doped-Fe and its dose. Small dose of Fe doping will result in effective resistance of surface blistering and delay of gas release, while large dose doping can deteriorate the irradiation damage, leading to flaking and even repeated flaking on the surface, and the enhancement of gas release in lower temperature range. The reasons are interpreted as following: when small dose of Fe are implanted in aluminum, second phase precipitates of high He trapping ability will form in the matrix, restraining the mobility and the growth of helium bubbles. Consequently, the microstructural evolution and gas release character are affected. However, the resistance effect will be weakened when large dose of Fe is doped in aluminum.
2011, 40(2):357-361.
Abstract:
Room temperature deformation behavior of the hydrogenated TC16 alloys was investigated by quasistatic compression and dynamic compression tests. Microstructure evolution and phase compositions of the hydrogenated TC16 alloys were analyzed by OM, XRD, etc. The results show that the addition of hydrogen decreases the phase transition temperature and promotes the formation of the metastable β phase. In static tests, the deformation limit decreases at first and then increases with the increase of the hydrogen concentration and the deformation rate. For the specimens containing 0.6wt% H deformed at 100 mm/min, the deformation limit reaches or even exceeds that of the initial alloy and the flow stress is decreased by about 200 MPa. In dynamic compression tests, clear dynamic softening occurs and the flow stress exhibits the character of the high temperature deformation.
Room temperature deformation behavior of the hydrogenated TC16 alloys was investigated by quasistatic compression and dynamic compression tests. Microstructure evolution and phase compositions of the hydrogenated TC16 alloys were analyzed by OM, XRD, etc. The results show that the addition of hydrogen decreases the phase transition temperature and promotes the formation of the metastable β phase. In static tests, the deformation limit decreases at first and then increases with the increase of the hydrogen concentration and the deformation rate. For the specimens containing 0.6wt% H deformed at 100 mm/min, the deformation limit reaches or even exceeds that of the initial alloy and the flow stress is decreased by about 200 MPa. In dynamic compression tests, clear dynamic softening occurs and the flow stress exhibits the character of the high temperature deformation.
2011, 40(2):362-366.
Abstract:
WCu composite powders were prepared by the sol-gel method with Cu(NO3)2·3H2O and (NH4)6H2W12O40·5H2O as raw materials and citric acid as chelating reagent. The composition, morphology and particle size of the powders were studied by XRD and TEM. TEM observation results show that the particle size of WCu powders is about 100 nm after reduction and the W grains were covered homogeneously by Cu on the surface. The reduction behavior and mechanism of the oxide powders were analyzed systematically. Temperature programmed reduction (TPR) result indicates that the appropriate two-step reduction temperatures are 500 and 700 oC. The FT-IR analyses reveal that the bond of W-O-W is weakened due to the bond of Cu-O-W, leading to the increase of the reduction properties of the WCu composite oxide powders.
WCu composite powders were prepared by the sol-gel method with Cu(NO3)2·3H2O and (NH4)6H2W12O40·5H2O as raw materials and citric acid as chelating reagent. The composition, morphology and particle size of the powders were studied by XRD and TEM. TEM observation results show that the particle size of WCu powders is about 100 nm after reduction and the W grains were covered homogeneously by Cu on the surface. The reduction behavior and mechanism of the oxide powders were analyzed systematically. Temperature programmed reduction (TPR) result indicates that the appropriate two-step reduction temperatures are 500 and 700 oC. The FT-IR analyses reveal that the bond of W-O-W is weakened due to the bond of Cu-O-W, leading to the increase of the reduction properties of the WCu composite oxide powders.
2011, 40(2):367-371.
Abstract:
Nd0.75Mg0.25(Ni0.8Co0.2)3.5 hydrogen storage alloys were prepared by mid-frequency induction melting, and were annealed at 850, 900 and 950 oC for 7 h in 0.03 MPa argon atmosphere. The electrochemical properties, hydrogen storage properties and microstructure of the alloys were investigated. The results show that annealing has little influence on the variation of phase composition in the alloys, and the main phases are Ce2Ni7 type (Nd,Mg)2(Ni,Co)7 phase and CaCu5 type NdNi5 phase. Average grain size and element homogenization of the alloys increase with increasing the annealing temperature, the area of phase interface and the grain stress decrease, and hydrogen storage capacity increases. Simultaneously, the loss of Mg element in the alloys decreases the hydrogen storage capacity owing to higher annealing temperature. So Nd0.75Mg0.25-(Ni0.8Co0.2)3.5 alloy annealed at 900 oC exhibit better hydrogen storage properties; the max discharge capacity of alloy electrode is about 359 mAh/g, the capacity retention rates is about 90.3% after 100 cycles, and the hydrogen absorption capacity is about 1.65 wt%.
Nd0.75Mg0.25(Ni0.8Co0.2)3.5 hydrogen storage alloys were prepared by mid-frequency induction melting, and were annealed at 850, 900 and 950 oC for 7 h in 0.03 MPa argon atmosphere. The electrochemical properties, hydrogen storage properties and microstructure of the alloys were investigated. The results show that annealing has little influence on the variation of phase composition in the alloys, and the main phases are Ce2Ni7 type (Nd,Mg)2(Ni,Co)7 phase and CaCu5 type NdNi5 phase. Average grain size and element homogenization of the alloys increase with increasing the annealing temperature, the area of phase interface and the grain stress decrease, and hydrogen storage capacity increases. Simultaneously, the loss of Mg element in the alloys decreases the hydrogen storage capacity owing to higher annealing temperature. So Nd0.75Mg0.25-(Ni0.8Co0.2)3.5 alloy annealed at 900 oC exhibit better hydrogen storage properties; the max discharge capacity of alloy electrode is about 359 mAh/g, the capacity retention rates is about 90.3% after 100 cycles, and the hydrogen absorption capacity is about 1.65 wt%.
2011, 40(2):372-376.
Abstract:
As the primary active components of automotive three-way catalysts, precious metals play an important role in purifying auto-exhaust. However, the charge of the precious metals in their precursor compounds, the bond intensities between precious metals and the ligands, the precursors solution pH values and whether other ions exist in them or not, directly influence dispersion of the precious metals on the modified material and interaction between the precursor and the material after activation treatment. Consequently they affect the performance standards of the catalyst activity, high-temperature stability, durability and so on. According to the review of the precious metals precursor researches at home and abroad, the important effects of the species and applied conditions of precious metals precursors on the catalyst performance are clarified, and it is thought that making full use of them to guide the high cost-effective catalytic material development are of great importance.
As the primary active components of automotive three-way catalysts, precious metals play an important role in purifying auto-exhaust. However, the charge of the precious metals in their precursor compounds, the bond intensities between precious metals and the ligands, the precursors solution pH values and whether other ions exist in them or not, directly influence dispersion of the precious metals on the modified material and interaction between the precursor and the material after activation treatment. Consequently they affect the performance standards of the catalyst activity, high-temperature stability, durability and so on. According to the review of the precious metals precursor researches at home and abroad, the important effects of the species and applied conditions of precious metals precursors on the catalyst performance are clarified, and it is thought that making full use of them to guide the high cost-effective catalytic material development are of great importance.
