Volume 41,Issue 8,2012 Table of Contents
2012, 41(8):1317-1322.
Abstract:
Hot compression tests were conducted using a Gleeble–3500 thermomechanical simulator to investigate the effect of hot deformation conditions on dynamic recrystallization (DRX) of GH690 alloy. The results show that the DRX process of GH690 alloy is controlled by deformation temperature and strain rate. Under the investigated condition at a constant strain rate ranging from 0.001 to 1 s-1, the temperature needed for fully dynamic recrystallization increases with the increases of strain rate, and the size of dynamically recrystallized grain is greatly affected by the increase of deformation temperature. The values of critical strain for the initiation of DRX can be determined from the strain-stress curves, and a equation related to the Zener-Hollomon Parameter is as follows: εc =1.135×10-3Z0.14233. A discontinuous dynamic recrystallization (DDRX) mechanism with nucleation of bulging of the original grain boundaries is the operating nucleation mechanism of DRX of GH690 alloy. A continuous dynamic recrystallization (CDRX) with subgrain rotation, which can only be considered as an assistant nucleation mechanism of DRX, occurs simultaneously with the DDRX
Hot compression tests were conducted using a Gleeble–3500 thermomechanical simulator to investigate the effect of hot deformation conditions on dynamic recrystallization (DRX) of GH690 alloy. The results show that the DRX process of GH690 alloy is controlled by deformation temperature and strain rate. Under the investigated condition at a constant strain rate ranging from 0.001 to 1 s-1, the temperature needed for fully dynamic recrystallization increases with the increases of strain rate, and the size of dynamically recrystallized grain is greatly affected by the increase of deformation temperature. The values of critical strain for the initiation of DRX can be determined from the strain-stress curves, and a equation related to the Zener-Hollomon Parameter is as follows: εc =1.135×10-3Z0.14233. A discontinuous dynamic recrystallization (DDRX) mechanism with nucleation of bulging of the original grain boundaries is the operating nucleation mechanism of DRX of GH690 alloy. A continuous dynamic recrystallization (CDRX) with subgrain rotation, which can only be considered as an assistant nucleation mechanism of DRX, occurs simultaneously with the DDRX
2012, 41(8):1323-1326.
Abstract:
The effect of the Li-site, Fe-site and co-doping in LiFePO4 on the electronic properties and local structural stability has been calculated by first principle plane-wave pseudopotential method. Our calculation shows that Li-site doped (Li0.75Na0.25)FePO4 exhibit better electronic conductivity than Fe-site doped Li(Fe0.75Mn0.25)PO4 cathode material, the local structural stability is reverse. But the Li-site and Fe-site co-doped (Li0.75Na0.25)(Fe0.75Mn0.25)PO4 possesses double optimization, which is probably ascribed to the interaction between Na-2p electron states and Li-s electron states. Meanwhile, large charges are transferred from the other atoms to lithium atoms in the co-doping LiFePO4 materials based on difference of charge density, this will result in the improvement of intrinsic electronic conductivity
The effect of the Li-site, Fe-site and co-doping in LiFePO4 on the electronic properties and local structural stability has been calculated by first principle plane-wave pseudopotential method. Our calculation shows that Li-site doped (Li0.75Na0.25)FePO4 exhibit better electronic conductivity than Fe-site doped Li(Fe0.75Mn0.25)PO4 cathode material, the local structural stability is reverse. But the Li-site and Fe-site co-doped (Li0.75Na0.25)(Fe0.75Mn0.25)PO4 possesses double optimization, which is probably ascribed to the interaction between Na-2p electron states and Li-s electron states. Meanwhile, large charges are transferred from the other atoms to lithium atoms in the co-doping LiFePO4 materials based on difference of charge density, this will result in the improvement of intrinsic electronic conductivity
2012, 41(8):1327-1330.
Abstract:
VO2 films on muscovite substrate were fabricated by inorganic sol-gel method and the following thermal treatment. The films were characterized by X-ray diffraction，scanning electron microscope (SEM), fourier transform infrared spectrophotometer (FTIR) and color difference (?E*). The FTIR result shows that the film has an infrared transmittance switching efficiency of 77% in the metal-insulator transition. The color changing properties indicate that the film color reversibly changes from khaki to yellow-green as the temperature changes. The relationship between ?E* and the temperature presents a hysteresis loop, which is in accordance with the infrared optical switching properties. The maximum of ?E* during the film metal-insulator transition is 11.31
VO2 films on muscovite substrate were fabricated by inorganic sol-gel method and the following thermal treatment. The films were characterized by X-ray diffraction，scanning electron microscope (SEM), fourier transform infrared spectrophotometer (FTIR) and color difference (?E*). The FTIR result shows that the film has an infrared transmittance switching efficiency of 77% in the metal-insulator transition. The color changing properties indicate that the film color reversibly changes from khaki to yellow-green as the temperature changes. The relationship between ?E* and the temperature presents a hysteresis loop, which is in accordance with the infrared optical switching properties. The maximum of ?E* during the film metal-insulator transition is 11.31
2012, 41(8):1331-1335.
Abstract:
Two methods for stripping of anodic oxide films formed on titanium alloys Ti-6.5Al-1Mo-1V-2Zr without hydrofluoric acid or fluoride were studied: ⅰ using hydrogen peroxide with sulfuric acid and ⅱ using hydrogen peroxide with sodium hydroxide. The morphologies and microstructures of the oxide films before and after stripping were compared by SEM and Raman spectroscopy. The surface topography and roughness of the samples were detected by AFM. The results show that the oxide films can be stripped both by the two methods and the stripping process is affected by the microstructure of the matrix material obviously. β or platelet α phases are more affected by the solution ⅰ while globular α phase is preferentially dissolved by the solution ⅱ. The surface stripped by solution ⅱ is flatter than that by solution ⅰ. Compared to solution ⅰ, solution ⅱ presents better environmental friendly result and lower cost
Two methods for stripping of anodic oxide films formed on titanium alloys Ti-6.5Al-1Mo-1V-2Zr without hydrofluoric acid or fluoride were studied: ⅰ using hydrogen peroxide with sulfuric acid and ⅱ using hydrogen peroxide with sodium hydroxide. The morphologies and microstructures of the oxide films before and after stripping were compared by SEM and Raman spectroscopy. The surface topography and roughness of the samples were detected by AFM. The results show that the oxide films can be stripped both by the two methods and the stripping process is affected by the microstructure of the matrix material obviously. β or platelet α phases are more affected by the solution ⅰ while globular α phase is preferentially dissolved by the solution ⅱ. The surface stripped by solution ⅱ is flatter than that by solution ⅰ. Compared to solution ⅰ, solution ⅱ presents better environmental friendly result and lower cost
2012, 41(8):1336-1340.
Abstract:
In order to understand the effects of Re and Ru additions on solidification characteristics of nickel base single crystal superalloys, four nickel base single crystal superalloys containing different contents of Re and Ru, were produced by dual heating zone melting and liquid-metal cooling (LMC) directional solidification technique at the withdraw rate of 2 μm/s, and a planar solid/liquid interface was obtained. The equilibrium partition coefficients of each element and solidification characteristic temperatures of experimental alloys were also obtained. Results show that with the increasing of Re content, the segregation degree of high segregation elements Re, W and Ta decreases, the liquidus temperature decreases initially and then increases, while the solidus temperature decreases continuously. The addition of Ru has little influence on the partition of other elements, and slightly lowers the liquidus temperature and solidus temperature of superalloys. In addition, we can effectively forecast the segregation degree of elements and solidification defects of non-equilibrium directional solidified superalloys on the basis of equilibrium partition coefficients and solidification characteristic temperatures
In order to understand the effects of Re and Ru additions on solidification characteristics of nickel base single crystal superalloys, four nickel base single crystal superalloys containing different contents of Re and Ru, were produced by dual heating zone melting and liquid-metal cooling (LMC) directional solidification technique at the withdraw rate of 2 μm/s, and a planar solid/liquid interface was obtained. The equilibrium partition coefficients of each element and solidification characteristic temperatures of experimental alloys were also obtained. Results show that with the increasing of Re content, the segregation degree of high segregation elements Re, W and Ta decreases, the liquidus temperature decreases initially and then increases, while the solidus temperature decreases continuously. The addition of Ru has little influence on the partition of other elements, and slightly lowers the liquidus temperature and solidus temperature of superalloys. In addition, we can effectively forecast the segregation degree of elements and solidification defects of non-equilibrium directional solidified superalloys on the basis of equilibrium partition coefficients and solidification characteristic temperatures
2012, 41(8):1341-1345.
Abstract:
Using density functional theory (DFT) within the scheme of the linearized augmented plane wave and the improved local orbital (APW+lo), we investigated the newly discovered FeAs layered compounds LaOFeAs, SrFe2As2, CaFe2As2, LiFeAs, NaFeAs and FeSe. We report the crystal structures, magnetism, and electronic properties of these Fe-based materials. The results reveal a close correlation of the superconductivity of these FeAs superconductors with the lattice geometry formation and magnetism of their parent compounds. The maximal critical temperatures Tc could simultaneously increase with the decrease of distortion of the FeAs4 tetrahedrons and the increase of interlayer distance L between two [FeAs] layers. We have further found that the magnetism is mainly attributed to Fe moment, and As 4p and Fe 3d hybrid states affect the physical natures, which are the common feature in these Fe-pnictide superconductors
Using density functional theory (DFT) within the scheme of the linearized augmented plane wave and the improved local orbital (APW+lo), we investigated the newly discovered FeAs layered compounds LaOFeAs, SrFe2As2, CaFe2As2, LiFeAs, NaFeAs and FeSe. We report the crystal structures, magnetism, and electronic properties of these Fe-based materials. The results reveal a close correlation of the superconductivity of these FeAs superconductors with the lattice geometry formation and magnetism of their parent compounds. The maximal critical temperatures Tc could simultaneously increase with the decrease of distortion of the FeAs4 tetrahedrons and the increase of interlayer distance L between two [FeAs] layers. We have further found that the magnetism is mainly attributed to Fe moment, and As 4p and Fe 3d hybrid states affect the physical natures, which are the common feature in these Fe-pnictide superconductors
2012, 41(8):1346-1350.
Abstract:
Back－Propagation artificial neural network (BP ANN) module with Trainrp algorithm was used to predict annealing parameter and hardness of HANA-4(Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr)and HANA-6(Zr-1.1Nb-0.05Cu). In this module, chemical compositions, annealing temperature and annealing time were employed as input units while hardness was employed as output unit. The optimal network architecture was considered to be 3-7-1 with momentum factor and learning rate all chosen to be 0.6, respectively. The result of ANN module shows that the biggest relative error (RE) is 7%, and the correlation coefficients (R-value) is 0.98534. The result strongly indicates that the ANN model is an efficient tool to provide annealing parameter. Moreover, Sensitivity analysis (SA) shows that annealing temperature and annealing time are the most important parameters to the ANN model accuracy, the effect of chemical compositions is very small
Back－Propagation artificial neural network (BP ANN) module with Trainrp algorithm was used to predict annealing parameter and hardness of HANA-4(Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr)and HANA-6(Zr-1.1Nb-0.05Cu). In this module, chemical compositions, annealing temperature and annealing time were employed as input units while hardness was employed as output unit. The optimal network architecture was considered to be 3-7-1 with momentum factor and learning rate all chosen to be 0.6, respectively. The result of ANN module shows that the biggest relative error (RE) is 7%, and the correlation coefficients (R-value) is 0.98534. The result strongly indicates that the ANN model is an efficient tool to provide annealing parameter. Moreover, Sensitivity analysis (SA) shows that annealing temperature and annealing time are the most important parameters to the ANN model accuracy, the effect of chemical compositions is very small
2012, 41(8):1351-1356.
Abstract:
Based on the similar physical simulation theory, we investigated the physical simulation similar regulation during Ti alloy melt filling flow in centrifugal field. And by means of similar physical simulation method, the variation of flow was studied during Ti alloy melt filling flow in centrifugal field. The results show that the melt flow meets both Cn criterion and Reynolds criterion in the centrifugal field upon filling, model fluid fill the mould along the back wall of cross gate, the free surface of fluid is a regular curved surface in the spindle centers, the cross section of fluid decreases with increasing of rotation speed and filling length. At the same time, the higher the rotation speed, the smaller the filling speed and length
Based on the similar physical simulation theory, we investigated the physical simulation similar regulation during Ti alloy melt filling flow in centrifugal field. And by means of similar physical simulation method, the variation of flow was studied during Ti alloy melt filling flow in centrifugal field. The results show that the melt flow meets both Cn criterion and Reynolds criterion in the centrifugal field upon filling, model fluid fill the mould along the back wall of cross gate, the free surface of fluid is a regular curved surface in the spindle centers, the cross section of fluid decreases with increasing of rotation speed and filling length. At the same time, the higher the rotation speed, the smaller the filling speed and length
2012, 41(8):1357-1361.
Abstract:
Using the Gleeble-1500D simulator, the high-temperature plastic deformation behavior and processing map of W-75%Cu composite were investigated at 650~950 ℃ with the strain rate of 0.01~5 s-1 and total strain of 0.7. The results show that the softening mechanism of dynamic recrystallization is a feature of high-temperature flow stress-strain curves of W-75%Cu composite, and the peak stress increases with the decrease of deformation temperature or the increase of strain rate. Based on the true stress-strain curves, the established constitutive equation represents the high-temperature flow behavior of W-75%Cu composite, and the calculated results of the flow stress are in good agreement with the experimental results of the high-temperature deformation of W-75%Cu composite. Meanwhile, the obtained processing map of Dynamic Material Modeling is used to analyze the deformation mechanism and the destabilization mechanism of W-75%Cu composite, the optimal deformation processing parameters of the deformation temperatures range and the strain rates range are 800~950 ℃ and 0.01~0.1 s-1, respectively
Using the Gleeble-1500D simulator, the high-temperature plastic deformation behavior and processing map of W-75%Cu composite were investigated at 650~950 ℃ with the strain rate of 0.01~5 s-1 and total strain of 0.7. The results show that the softening mechanism of dynamic recrystallization is a feature of high-temperature flow stress-strain curves of W-75%Cu composite, and the peak stress increases with the decrease of deformation temperature or the increase of strain rate. Based on the true stress-strain curves, the established constitutive equation represents the high-temperature flow behavior of W-75%Cu composite, and the calculated results of the flow stress are in good agreement with the experimental results of the high-temperature deformation of W-75%Cu composite. Meanwhile, the obtained processing map of Dynamic Material Modeling is used to analyze the deformation mechanism and the destabilization mechanism of W-75%Cu composite, the optimal deformation processing parameters of the deformation temperatures range and the strain rates range are 800~950 ℃ and 0.01~0.1 s-1, respectively
2012, 41(8):1362-1366.
Abstract:
Tensile properties and SEM analysis were carried out in a modeling specimen of cooling turbine blade with [001] orientation. Three factors including temperatures, thickness and cooling holes were considered to study the influences on the mechanics properties. The results show that when the temperature is higher than 850 ℃, the ultimate strength and yield strength decrease with the increment of temperature, while for the elongation and area reduction, they increase. Also, the ultimate strength and yield strength of the 2.0 mm thick specimens are higher than those of the 1.5 mm thick specimens, the same results for the elongation and area reduction. Because of the stress and strain concentrations, not only the ultimate strength and yield strength of the specimens with cooling holes are lower than those of specimens without cooling holes, but also for the percentages of elongation and area reduction. Furthermore, from the SEM analysis of the fracture faces, we conclude that at 850 ℃ the fracture surfaces are made up of smooth sloping planes, while at 980 ℃ the fracture surfaces are mainly made up of dimples
Tensile properties and SEM analysis were carried out in a modeling specimen of cooling turbine blade with [001] orientation. Three factors including temperatures, thickness and cooling holes were considered to study the influences on the mechanics properties. The results show that when the temperature is higher than 850 ℃, the ultimate strength and yield strength decrease with the increment of temperature, while for the elongation and area reduction, they increase. Also, the ultimate strength and yield strength of the 2.0 mm thick specimens are higher than those of the 1.5 mm thick specimens, the same results for the elongation and area reduction. Because of the stress and strain concentrations, not only the ultimate strength and yield strength of the specimens with cooling holes are lower than those of specimens without cooling holes, but also for the percentages of elongation and area reduction. Furthermore, from the SEM analysis of the fracture faces, we conclude that at 850 ℃ the fracture surfaces are made up of smooth sloping planes, while at 980 ℃ the fracture surfaces are mainly made up of dimples
2012, 41(8):1367-1370.
Abstract:
The behavior and mechanism of extraction of Palladium(Ⅱ)with unsymmetrical sulfoxide BSO were studied. The results show that the percentage extraction of Pd(Ⅱ) achieves 99.8% from 0.1 mol·L-1 HCl media with 0.3 mol·L-1 BSO-kerosene (their phase ratio 1:1) as an extractant after 5 min extraction vibration. The structure of the complex was discussed by slope analysis method and FT-IR spectra. When HCl concentration is less than 0.3 mol·L-1, BSO acts as a neutral ligand coordinated with Pd(Ⅱ) and the composition of complex is [PdCl2·2BSO](0). When HCl concentration ranges from 1.0 mol·L-1 to 4.0 mol·L-1 , the reaction of extracting of Pd(Ⅱ) is acid ion association extraction and the composition of complex may be [H+·hH2O·(BSO)2]2·[PdCl42- ] (0)
The behavior and mechanism of extraction of Palladium(Ⅱ)with unsymmetrical sulfoxide BSO were studied. The results show that the percentage extraction of Pd(Ⅱ) achieves 99.8% from 0.1 mol·L-1 HCl media with 0.3 mol·L-1 BSO-kerosene (their phase ratio 1:1) as an extractant after 5 min extraction vibration. The structure of the complex was discussed by slope analysis method and FT-IR spectra. When HCl concentration is less than 0.3 mol·L-1, BSO acts as a neutral ligand coordinated with Pd(Ⅱ) and the composition of complex is [PdCl2·2BSO](0). When HCl concentration ranges from 1.0 mol·L-1 to 4.0 mol·L-1 , the reaction of extracting of Pd(Ⅱ) is acid ion association extraction and the composition of complex may be [H+·hH2O·(BSO)2]2·[PdCl42- ] (0)
12 Study on Spectra Characteristics of Newly-Developed Eu or Gd Co-doped Ce:YAG Phosphor for White-LED
Hua Wei
,
Xiang Weidong
,
Dong Yongjun
,
Liang Xiaojuan
,
Yang Fan
,
Jin Huaidong
,
Liang Xu
,
Lü Chunyan
2012, 41(8):1371-1375.
Abstract:
The growth and spectra characteristics of Eu,Ce and Gd,Ce co-doped YAG single crystals phosphor used for white LED were investigated. Eu,Ce:YAG and Gd,Ce:YAG single crystals were grown by Czochralski method, and their luminescence properties were studied in terms of absorption, emission and excitation spectra. Date analysis reveals that a broad emission band range from 480-650 nm can be produced with blue light excitation. Eu3+ or Gd3+ co-doped ions could affect the emission properties of Ce:YAG crystal: Eu3+ ions co-doping will have the Ce3+ ions luminous quenching effect. On the contrary, Gd3+ ions, which is substituted at the Y site, would shift the emission spectra of Ce:YAG crystal to the red spectra
The growth and spectra characteristics of Eu,Ce and Gd,Ce co-doped YAG single crystals phosphor used for white LED were investigated. Eu,Ce:YAG and Gd,Ce:YAG single crystals were grown by Czochralski method, and their luminescence properties were studied in terms of absorption, emission and excitation spectra. Date analysis reveals that a broad emission band range from 480-650 nm can be produced with blue light excitation. Eu3+ or Gd3+ co-doped ions could affect the emission properties of Ce:YAG crystal: Eu3+ ions co-doping will have the Ce3+ ions luminous quenching effect. On the contrary, Gd3+ ions, which is substituted at the Y site, would shift the emission spectra of Ce:YAG crystal to the red spectra
2012, 41(8):1376-1380.
Abstract:
Based on the microscopic phase field model, the precipitation process of Ni-Al-V alloy was simulated. The composition distribution and the evolution of order-disordering interface and ordered heterointerface formed between DO22 and L12 phase were studied. The results show that the degree and the preference of segregation or the depletion of alloying elements are related with the atomic structure of interfaces. Ni and Al segregate, V depletes at the order-disorder interface formed between DO22 and disorder phases. Ni and Al deplete, V segregates at the order-disorder interface formed between L12 and disorder phases. At the ordered heterointerfaces, V segregates at the DO22 side of the interface but depletes at the L12 side of the interface, Al depletes at the DO22 side of the interface but segregates at the L12 side of the interface. The distribution of Ni at the ordered heterointerface is related with the formation process of the interface. The preferences of segregation or the depletion of alloy elements remain unchanged, but the distribution of alloy elements becomes sharp during the evolution of interface
Based on the microscopic phase field model, the precipitation process of Ni-Al-V alloy was simulated. The composition distribution and the evolution of order-disordering interface and ordered heterointerface formed between DO22 and L12 phase were studied. The results show that the degree and the preference of segregation or the depletion of alloying elements are related with the atomic structure of interfaces. Ni and Al segregate, V depletes at the order-disorder interface formed between DO22 and disorder phases. Ni and Al deplete, V segregates at the order-disorder interface formed between L12 and disorder phases. At the ordered heterointerfaces, V segregates at the DO22 side of the interface but depletes at the L12 side of the interface, Al depletes at the DO22 side of the interface but segregates at the L12 side of the interface. The distribution of Ni at the ordered heterointerface is related with the formation process of the interface. The preferences of segregation or the depletion of alloy elements remain unchanged, but the distribution of alloy elements becomes sharp during the evolution of interface
2012, 41(8):1381-1384.
Abstract:
采用热压缩试验方法，对Ti-5553钛合金的动态再结晶行为进行研究。结果表明，在温度800～860 ℃、应变速率0.01～10 s-1的范围内，Ti-5553合金在高温、低应变速率变形时，晶界弓出形核是其主要的动态再结晶形核机制；在低温、高应变速率、大变形量变形时，位错塞积形核是主要的动态再结晶形核机制。在非均匀变形的条件下材料产生绝热剪切现象，其形核主要以亚晶吞并长大形核机制进行
采用热压缩试验方法，对Ti-5553钛合金的动态再结晶行为进行研究。结果表明，在温度800～860 ℃、应变速率0.01～10 s-1的范围内，Ti-5553合金在高温、低应变速率变形时，晶界弓出形核是其主要的动态再结晶形核机制；在低温、高应变速率、大变形量变形时，位错塞积形核是主要的动态再结晶形核机制。在非均匀变形的条件下材料产生绝热剪切现象，其形核主要以亚晶吞并长大形核机制进行
2012, 41(8):1385-1389.
Abstract:
The nano-SiO2 particle reinforced NiTi matrix composites (SiO2%=1%~4%, mass fraction) were fabricated by Spark Plasma Sintering (SPS) method, and the effects of the contents of SiO2 nano-particles on the microstructure, the phase transformation points, the mechanical properties and the fracture feature were investigated. The results indicate that the microstructures of the composites mainly consist of the phases of B2-NiTi, B19'-NiTi, Ni3Ti, Ti2Ni and SiO2, and the SiO2 particles are evenly dispersed in NiTi matrix. The addition of SiO2 reduces the phase transformation point of Mf, As and Af, but has no strong influence on Ms. The SiO2 particles can obviously improve the strength of NiTi alloy, but with the increase of SiO2 particles, the fracture mode of the alloy changes from ductile fracture to brittle fracture. More over, the composites containing SiO2 exhibit higher deformation recovery and better superelasticity than that of NiTi alloy in the deformation within 6%
The nano-SiO2 particle reinforced NiTi matrix composites (SiO2%=1%~4%, mass fraction) were fabricated by Spark Plasma Sintering (SPS) method, and the effects of the contents of SiO2 nano-particles on the microstructure, the phase transformation points, the mechanical properties and the fracture feature were investigated. The results indicate that the microstructures of the composites mainly consist of the phases of B2-NiTi, B19'-NiTi, Ni3Ti, Ti2Ni and SiO2, and the SiO2 particles are evenly dispersed in NiTi matrix. The addition of SiO2 reduces the phase transformation point of Mf, As and Af, but has no strong influence on Ms. The SiO2 particles can obviously improve the strength of NiTi alloy, but with the increase of SiO2 particles, the fracture mode of the alloy changes from ductile fracture to brittle fracture. More over, the composites containing SiO2 exhibit higher deformation recovery and better superelasticity than that of NiTi alloy in the deformation within 6%
2012, 41(8):1390-1394.
Abstract:
(La0.6Ce0.4)65Al10Cu25 bulk metallic glasses (BMGs) were prepared by copper-mold casting. The crystallization behavior and thermal stability of (La0.6Ce0.4)65Al10Cu25 were investigated by X-ray diffraction and differential scanning caloricity (DSC). The isothermal kinetics was evaluated by the Johnson–Mehl–Avrami equation. The calculated Avrami exponents were in the range of 2.39 to 3.38. The average values of local Avrami exponents show that the value of n is about 3 at the initial stage; in the middle crystallization stage, the value of n changes from 2.5 to 3.5. In this stage, for 2.5
(La0.6Ce0.4)65Al10Cu25 bulk metallic glasses (BMGs) were prepared by copper-mold casting. The crystallization behavior and thermal stability of (La0.6Ce0.4)65Al10Cu25 were investigated by X-ray diffraction and differential scanning caloricity (DSC). The isothermal kinetics was evaluated by the Johnson–Mehl–Avrami equation. The calculated Avrami exponents were in the range of 2.39 to 3.38. The average values of local Avrami exponents show that the value of n is about 3 at the initial stage; in the middle crystallization stage, the value of n changes from 2.5 to 3.5. In this stage, for 2.5
2012, 41(8):1395-1399.
Abstract:
La0.75Mg0..25Ni3.5-xMnx (x=0,0.05,0.1,0.15,0.2) alloy ingots were prepared by induction melting. The effect of Mn substitution for Ni on the phase structure and the electrochemical characteristics of hydrogen storage alloys was studied. XRD analysis shows that the La0.75Mg0.25Ni3.5-xMnx consists of La2Ni7 phase, and LaNi5 phase with CaCu5 type appears when Mn is added. LaNi5 phase disappears with Mn higher content from x=0.15 to x=0.2. The electrochemical analysis shows that the substitutions lower the maximum electrochemical discharge capacity, the high rate dischargeability, and the exchange current density and have a little effect on the activation property. The replacements of Ni by Mn have a little effect on the cyclic stability and limiting current density (IL).
La0.75Mg0..25Ni3.5-xMnx (x=0,0.05,0.1,0.15,0.2) alloy ingots were prepared by induction melting. The effect of Mn substitution for Ni on the phase structure and the electrochemical characteristics of hydrogen storage alloys was studied. XRD analysis shows that the La0.75Mg0.25Ni3.5-xMnx consists of La2Ni7 phase, and LaNi5 phase with CaCu5 type appears when Mn is added. LaNi5 phase disappears with Mn higher content from x=0.15 to x=0.2. The electrochemical analysis shows that the substitutions lower the maximum electrochemical discharge capacity, the high rate dischargeability, and the exchange current density and have a little effect on the activation property. The replacements of Ni by Mn have a little effect on the cyclic stability and limiting current density (IL).
2012, 41(8):1400-1404.
Abstract:
A pulse current auxiliary superplastic forming (PCASF) is developed to solve the problems of high energy consumption and low efficiency of Ti-6Al-4V alloy superplastic forming. In this process, the sheet was connected in series with a pulse current circuit and heated directly by the pulse current. Through the pulse current heating experiment, the effects of the average current density on the temperature and the rate of temperature rise have been studied. The result indicates that the heating time is reduced from tens of minutes to dozens of seconds, and the energy consumption is reduced to 20% compared to the traditional process. Thus the heating efficiency is improved and the energy consumption is reduced greatly. The green superplastic forming technology with the merit of energy conservation becomes possible. The double hemisphere structure of Ti-6Al-4V alloy has been formed by PCASF and its deformation mechanism has been studied
A pulse current auxiliary superplastic forming (PCASF) is developed to solve the problems of high energy consumption and low efficiency of Ti-6Al-4V alloy superplastic forming. In this process, the sheet was connected in series with a pulse current circuit and heated directly by the pulse current. Through the pulse current heating experiment, the effects of the average current density on the temperature and the rate of temperature rise have been studied. The result indicates that the heating time is reduced from tens of minutes to dozens of seconds, and the energy consumption is reduced to 20% compared to the traditional process. Thus the heating efficiency is improved and the energy consumption is reduced greatly. The green superplastic forming technology with the merit of energy conservation becomes possible. The double hemisphere structure of Ti-6Al-4V alloy has been formed by PCASF and its deformation mechanism has been studied
2012, 41(8):1405-1408.
Abstract:
LiBH4/Li3AlH6 hydrogen storage composite was prepared by ball-milling, and its hydrogen storage properties and mechanism were studied by TG/DSC/MS and XRD analysis. The activation energies of the dehydrogenation reactions were calculated. The experimental results show that LiBH4-Li3AlH6 composite dehydrogenates shows three reactions: (1) Li3AlH6 decomposes with hydrogen desorption and formation of Al; (2) part of Al reacts with LBH4 with hydrogen desorption; (3) Al reacts with LiH. The total hydrogen desorption capacity reaches 8.5 wt%. And the mechanism of hydrogen desorption process of LiBH4-Li3AlH6 composite was discussed
LiBH4/Li3AlH6 hydrogen storage composite was prepared by ball-milling, and its hydrogen storage properties and mechanism were studied by TG/DSC/MS and XRD analysis. The activation energies of the dehydrogenation reactions were calculated. The experimental results show that LiBH4-Li3AlH6 composite dehydrogenates shows three reactions: (1) Li3AlH6 decomposes with hydrogen desorption and formation of Al; (2) part of Al reacts with LBH4 with hydrogen desorption; (3) Al reacts with LiH. The total hydrogen desorption capacity reaches 8.5 wt%. And the mechanism of hydrogen desorption process of LiBH4-Li3AlH6 composite was discussed
2012, 41(8):1409-1412.
Abstract:
The dynamic mechanical properties of a model binary Cu64Zr36 metallic glass under axial compression were obtained by molecular dynamics (MD) simulation. Cooling rate, strain rate, surrounding temperature and initial crack were investigated. In the simulation, EAM potential function was adopted to describe the relationship between atoms. Results show that the elastic modulus and the compressive strength of the metallic glass are twice more than those of the crystal metal. A main shear is generated in the specimen prepared at a slow cooling rate because of the rearrangement of atoms, while in the specimen prepared at fast cooling rate no atom rearrangement takes place. The elastic modulus, falling stress and flow stress are non-sensitive to strain rate. However, they decrease with increasing of surrounding temperature. The specimens with initial cracks show highly localized shear bands which are generated from the crack tip and propagate at the angle of 45o away from the loading direction
The dynamic mechanical properties of a model binary Cu64Zr36 metallic glass under axial compression were obtained by molecular dynamics (MD) simulation. Cooling rate, strain rate, surrounding temperature and initial crack were investigated. In the simulation, EAM potential function was adopted to describe the relationship between atoms. Results show that the elastic modulus and the compressive strength of the metallic glass are twice more than those of the crystal metal. A main shear is generated in the specimen prepared at a slow cooling rate because of the rearrangement of atoms, while in the specimen prepared at fast cooling rate no atom rearrangement takes place. The elastic modulus, falling stress and flow stress are non-sensitive to strain rate. However, they decrease with increasing of surrounding temperature. The specimens with initial cracks show highly localized shear bands which are generated from the crack tip and propagate at the angle of 45o away from the loading direction
Li Chunguang
,
Sun Xiaguang
,
Deng Shengtao
,
Guan Junqiang
,
Xiao Chengjun
,
Wan Xiaobo
,
Zhu Sihua
,
Li Jianfeng
,
Du Shejun
,
Wang Tiancheng
,
Zhang Fengshou
,
Liu Xianghong
,
Feng Yong
2012, 41(8):1413-1416.
Abstract:
The Nb3Sn strands over 1500 m piece length by Rod Restack Process (RRP) for high field magnet were fabricated by Western Superconducting Technologies Co., Ltd. (WST). The distributing Nb barriers were employed around each sub-element in the process, which not only protect the Cu stabilization from the pollution of Sn, but also contribute to the critical current for forming A15 phase Nb3Sn during the reaction. Meanwhile, Nb-47wt%Ti filaments were adopted to replace some of Nb as the resource of Ti adding in the process, lowering the production price the commercial Nb-47wt%Ti. The testing results show that the Ic of the strands with better stability is 514 A at 12 T, 4.2 K, 0.1 μV/cm with the heat treatment of 640 ℃, 60 h and the RRR value is 148. While the Ic is 599 A with the heat treatment of 665 ℃, 60 h and RRR value is 3.77. The success choosing of barrier and Ti doping make it possible to develop higher quality strands, including long piece length and high critical current
The Nb3Sn strands over 1500 m piece length by Rod Restack Process (RRP) for high field magnet were fabricated by Western Superconducting Technologies Co., Ltd. (WST). The distributing Nb barriers were employed around each sub-element in the process, which not only protect the Cu stabilization from the pollution of Sn, but also contribute to the critical current for forming A15 phase Nb3Sn during the reaction. Meanwhile, Nb-47wt%Ti filaments were adopted to replace some of Nb as the resource of Ti adding in the process, lowering the production price the commercial Nb-47wt%Ti. The testing results show that the Ic of the strands with better stability is 514 A at 12 T, 4.2 K, 0.1 μV/cm with the heat treatment of 640 ℃, 60 h and the RRR value is 148. While the Ic is 599 A with the heat treatment of 665 ℃, 60 h and RRR value is 3.77. The success choosing of barrier and Ti doping make it possible to develop higher quality strands, including long piece length and high critical current
2012, 41(8):1417-1420.
Abstract:
The dehydriding processes and kinetics of nanocrystalline hydrided Mg and AZ31 Mg alloy powders at different temperatures have been studied. By theoretical analysis of the experimental data of the pyrolytic dehydriding reaction and fitting them with the Johnson-Mehl-Avrami (JMA) equation, the kinetic equation and the corresponding kinetic parameters including the reaction order, the reaction rate constant, and the reaction activation energy have been obtained. Furthermore, the reason why there is difference in dehydriding kinetics between the hydrided Mg and AZ31 Mg alloy powders has been interpreted referring to the thermodynamic and kinetic factors.
The dehydriding processes and kinetics of nanocrystalline hydrided Mg and AZ31 Mg alloy powders at different temperatures have been studied. By theoretical analysis of the experimental data of the pyrolytic dehydriding reaction and fitting them with the Johnson-Mehl-Avrami (JMA) equation, the kinetic equation and the corresponding kinetic parameters including the reaction order, the reaction rate constant, and the reaction activation energy have been obtained. Furthermore, the reason why there is difference in dehydriding kinetics between the hydrided Mg and AZ31 Mg alloy powders has been interpreted referring to the thermodynamic and kinetic factors.
2012, 41(8):1421-1425.
Abstract:
The growth law of tin whiskers on the surface of the oxidized CeSn3, LaSn3, (La0.4Ce0.6)Sn3 and ErSn3 precipitates was investigated during the aging. The results indicate that during aging at room temperature, rapid tin whisker growth was found on all of the oxidized RE-Sn surfaces, hillocks and kinked whiskers were easily formed on the oxidized LaSn3 surface, needle-like and kinked whiskers were easily formed on the oxidized CeSn3 and (La0.4Ce0.6)Sn3 surfaces, especially, large sized rod-like and stick-like whiskers were easily formed on the surface of the oxidized ErSn3 phase. During aging at 150 ℃, no whiskers were found on the surfaces of the oxidized CeSn3, LaSn3, (La0.4Ce0.6)Sn3 phases. However, a great number of thread-like whiskers were formed over the whole surface of the oxidized ErSn3 phase. In conclusion, the oxidation tendency of RE-Sn phases dominates the growth law of whisker on the oxidized RE-Sn surface
The growth law of tin whiskers on the surface of the oxidized CeSn3, LaSn3, (La0.4Ce0.6)Sn3 and ErSn3 precipitates was investigated during the aging. The results indicate that during aging at room temperature, rapid tin whisker growth was found on all of the oxidized RE-Sn surfaces, hillocks and kinked whiskers were easily formed on the oxidized LaSn3 surface, needle-like and kinked whiskers were easily formed on the oxidized CeSn3 and (La0.4Ce0.6)Sn3 surfaces, especially, large sized rod-like and stick-like whiskers were easily formed on the surface of the oxidized ErSn3 phase. During aging at 150 ℃, no whiskers were found on the surfaces of the oxidized CeSn3, LaSn3, (La0.4Ce0.6)Sn3 phases. However, a great number of thread-like whiskers were formed over the whole surface of the oxidized ErSn3 phase. In conclusion, the oxidation tendency of RE-Sn phases dominates the growth law of whisker on the oxidized RE-Sn surface
2012, 41(8):1426-1430.
Abstract:
Analysis on the influence of deformation temperature, strain rate and deformation degree on the microstructure after solution treatment was carried out, and a predicting model for the recrystallization volume and average grain size of the microstructure was established by a three-layer feed-forward artificial neural network with a back-propagation learning rule. The results indicate that under the condition of the same cooling and heat treatment rules, the deformation parameters such as deformation temperature, deformation degree and strain rate have important influence on the microstructures evolution after hot deformation and solution treatment of TB8 titanium alloy. A larger deformation degree, a lower temperature and an appropriate strain rate are required to acquire the microstructure with homogeneous and fine grains. The close agreement of the predicted results with measured ones shows that the neural network is able to successfully predict the variation of the microstructure with the hot deformation parameters. The above results can provide the determining of reasonable hot forming process with a scientific base.
Analysis on the influence of deformation temperature, strain rate and deformation degree on the microstructure after solution treatment was carried out, and a predicting model for the recrystallization volume and average grain size of the microstructure was established by a three-layer feed-forward artificial neural network with a back-propagation learning rule. The results indicate that under the condition of the same cooling and heat treatment rules, the deformation parameters such as deformation temperature, deformation degree and strain rate have important influence on the microstructures evolution after hot deformation and solution treatment of TB8 titanium alloy. A larger deformation degree, a lower temperature and an appropriate strain rate are required to acquire the microstructure with homogeneous and fine grains. The close agreement of the predicted results with measured ones shows that the neural network is able to successfully predict the variation of the microstructure with the hot deformation parameters. The above results can provide the determining of reasonable hot forming process with a scientific base.
2012, 41(8):1431-1434.
Abstract:
Dispersion strengthened tungsten with nano-tantalum carbide (TaC) was prepared by Spark Plasma Sintering (SPS) process at 1700 ℃ for 1 min. The results show that the grain size of tungsten will be larger if the particle size of tungsten powder is larger. When the particle size of tungsten powder is 3 μm, the grain size of tungsten is 22.19 μm. And then, with the increase of TaC content, the grain size of tungsten will be finer. When the particle size of tungsten powder is 200 nm and the content of TaC is 4%, the grain size of sintered tungsten is about 5.91 μm. It also can be seen that TaC is spherical, it exists at grain boundaries of the sintered tungsten. Some transgranular fracture can be seen in fracture surface of pure tungsten by SPS, but it is mainly intergranular fracture in fracture surface of dispersion strengthened tungsten with nano-tantalum carbide
Dispersion strengthened tungsten with nano-tantalum carbide (TaC) was prepared by Spark Plasma Sintering (SPS) process at 1700 ℃ for 1 min. The results show that the grain size of tungsten will be larger if the particle size of tungsten powder is larger. When the particle size of tungsten powder is 3 μm, the grain size of tungsten is 22.19 μm. And then, with the increase of TaC content, the grain size of tungsten will be finer. When the particle size of tungsten powder is 200 nm and the content of TaC is 4%, the grain size of sintered tungsten is about 5.91 μm. It also can be seen that TaC is spherical, it exists at grain boundaries of the sintered tungsten. Some transgranular fracture can be seen in fracture surface of pure tungsten by SPS, but it is mainly intergranular fracture in fracture surface of dispersion strengthened tungsten with nano-tantalum carbide
2012, 41(8):1435-1438.
Abstract:
Fe3Al porous materials were fabricated by the powder metallurgy method with Cr-modified Fe3Al pre-alloy powder as starting material. The effects of oxidation temperature and time, and cooling rate on properties of oxidation scales of Fe3Al porous materials were researched. The results show that oxidation mass gain is increased with the temperature increasing. Oxidation kinetics of Fe3Al porous materials follows the fourth power rules. The oxidation scales with small grain size have completely covered the sintered neck of Fe3Al porous materials after 9 h oxidation in atmosphere at 800 oC. The grains become coarse with higher temperature and longer time. The cracks have appeared on oxidation scales after 5 h oxidation in atmosphere at 900 oC. Cooling rate has little effect on mass gain and the cracks do not appear due to the unmatched thermal expansion coefficient.
Fe3Al porous materials were fabricated by the powder metallurgy method with Cr-modified Fe3Al pre-alloy powder as starting material. The effects of oxidation temperature and time, and cooling rate on properties of oxidation scales of Fe3Al porous materials were researched. The results show that oxidation mass gain is increased with the temperature increasing. Oxidation kinetics of Fe3Al porous materials follows the fourth power rules. The oxidation scales with small grain size have completely covered the sintered neck of Fe3Al porous materials after 9 h oxidation in atmosphere at 800 oC. The grains become coarse with higher temperature and longer time. The cracks have appeared on oxidation scales after 5 h oxidation in atmosphere at 900 oC. Cooling rate has little effect on mass gain and the cracks do not appear due to the unmatched thermal expansion coefficient.
2012, 41(8):1439-1442.
Abstract:
The thermal decomposition behavior of YBCO-TFA precursors was investigated by thermogravimetric and differential scanning calorimetry analysis (TG-DSC), in-situ Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction analysis (XRD). The results show that the thermal decomposition of YBCO-TFA precursors occurred mainly in the range of 230~250 oC, and the residues were identified as BaF2, CuO, Y2O3, YBaF and other unidentified noncrystalline materials. The studies of the mechanism of thermal decomposition are beneficial to optimize the thermal decomposition processes and to achieve high critical current YBCO coated conductors
The thermal decomposition behavior of YBCO-TFA precursors was investigated by thermogravimetric and differential scanning calorimetry analysis (TG-DSC), in-situ Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction analysis (XRD). The results show that the thermal decomposition of YBCO-TFA precursors occurred mainly in the range of 230~250 oC, and the residues were identified as BaF2, CuO, Y2O3, YBaF and other unidentified noncrystalline materials. The studies of the mechanism of thermal decomposition are beneficial to optimize the thermal decomposition processes and to achieve high critical current YBCO coated conductors
28 Electrical Property of Nanocomposite Ag/SnO2 Electrical Contact Material Prepared by Plasma Spraying
Jiang Fengyang
,
Wang Junbo
,
Fu Chong
,
Yang Minge
,
He Xinhai
,
Su Xiaolei
,
Ding Bingjun
,
Liu Jiangnan
2012, 41(8):1443-1446.
Abstract:
Nanocomposite Ag/SnO2 coating was prepared on pure Cu-surface by plasma spraying using the Ag-12%SnO2 mixed powder fabricated by chemical coprecipitation and high-energy ball milling. The physical property and electrical property were tested in vacuum the surface structure was observed and analyzed by SEM. The results show that the thicker nanocomposite Ag/SnO2 coating is, the smaller density is, the larger resistivity is, the higher the breakdown strength is. The hardness is related to the distribution of SnO2. The distribution of breakdown strength values is connected with coating surface roughness. The arc of nanocomposite Ag/SnO2 coating is dispersive and the arc erosion rate is low
Nanocomposite Ag/SnO2 coating was prepared on pure Cu-surface by plasma spraying using the Ag-12%SnO2 mixed powder fabricated by chemical coprecipitation and high-energy ball milling. The physical property and electrical property were tested in vacuum the surface structure was observed and analyzed by SEM. The results show that the thicker nanocomposite Ag/SnO2 coating is, the smaller density is, the larger resistivity is, the higher the breakdown strength is. The hardness is related to the distribution of SnO2. The distribution of breakdown strength values is connected with coating surface roughness. The arc of nanocomposite Ag/SnO2 coating is dispersive and the arc erosion rate is low
Guo Yuanjun
,
Ning Chengyun
,
Tan Guoxin
,
Xiong Wenming
,
Li Dan
,
Huang Shanshan
,
Ge Yongmei
,
Zheng Huade
2012, 41(8):1447-1551.
Abstract:
Two calcium and phosphate (Ca-P) coatings with special topographies were prepared on the pure titanium substrates by air plasma spraying. The microstructures and composition of the two special crystals were analyzed by SEM and EPMA. The phase compositions and crystallinty of coatings were quantitatively investigated by XRD. The results show that a lot of square prismatic-like dicalcium phosphates (Ca2P2O7) crystals with 4.61% crystallinity were formed under 22 kW spraying power and 400 mm/s rate of gun movement; and a large number of petal-like tetracalcium phosphate (Ca4P2O9) crystals with 6.02% crystallinity were formed under 26 kW spraying power and 300 mm/s rate of gun movement. As a result of the small particle size of the spaying powder, the HA has a low degree of crystallinity in both two coatings. In addition, the study of biodegradation shows that the processes of degradation of the two coatings proceed from fiercely to gently, but the degradation rate of the former is lower than that of the latter.
Two calcium and phosphate (Ca-P) coatings with special topographies were prepared on the pure titanium substrates by air plasma spraying. The microstructures and composition of the two special crystals were analyzed by SEM and EPMA. The phase compositions and crystallinty of coatings were quantitatively investigated by XRD. The results show that a lot of square prismatic-like dicalcium phosphates (Ca2P2O7) crystals with 4.61% crystallinity were formed under 22 kW spraying power and 400 mm/s rate of gun movement; and a large number of petal-like tetracalcium phosphate (Ca4P2O9) crystals with 6.02% crystallinity were formed under 26 kW spraying power and 300 mm/s rate of gun movement. As a result of the small particle size of the spaying powder, the HA has a low degree of crystallinity in both two coatings. In addition, the study of biodegradation shows that the processes of degradation of the two coatings proceed from fiercely to gently, but the degradation rate of the former is lower than that of the latter.
2012, 41(8):1452-1456.
Abstract:
The phosphors of (La,Ce,Tb)BO3 were synthesized by high temperature solid state reaction. X-ray diffractometry (XRD) patterns indicate that the crystal structures of (La,Ce,Tb)BO3 and LaBO3 are the same. The crystal structure has not been changed by Ce3+ and Tb3+ doping. Emission scanning electron microscopy (SEM) images show that the particle sizes of phosphors are more uniform, the morphology is more regular, and the granularity is about 5 μm. The content of TbBO3 phase in (La,Ce,Tb)BO3 increases with increasing of Tb content in (La,Ce,Tb)BO3. When Tb concentration reaches 15% and above, the content of TbBO3 phase in (La,Ce,Tb)BO3 increases more rapidly. The luminescence properties of (La,Ce,Tb)BO3 and the sensitization of Ce3+ to Tb3+ were studied. In the excitation spectrum of Ce3+ there are three peaks at 244, 268 and 330 nm, respectively. And in the emission spectrum of Ce3+, there are two peaks at 365 and 380 nm, respectively. All of them have the large overlap. The Maximum emission wavelength of Tb3+ is 541 nm, and its excitation peaks is 230 nm. Both the Tb3+ characteristic emission and excitation peaks and the Ce3+ characteristic emission and excitation peaks were observed in the emission and excitation spectrum of (La,Ce,Tb)BO3. Comparing the excitation spectrum of (La,Ce)BO3 with the emission spectrum of (La,Tb)BO3, it is found that they have the large overlap. It is indicated that there is a remarkable energy transfer from Ce3+ to Tb3+ in (La,Ce,Tb)BO3. When the concentration of Ce or Tb in (La,Ce,Tb)BO3 is fixed, because of concentration self-quenching effect, the relative intensity of main emission peak (at 541 nm)increases firstly and then decreases with increasing of the concentration of Tb or Ce. At fixed ratio of Ce concentration to Tb concentration, the relative intensity of the main emission peak of (La,Ce,Tb)BO3 is the highest when La concentration in (La,Ce,Tb)BO3 reaches 70 mol%. The sample with better luminescence properties will be obtained in the wide range of the concentration ratio of Ce to Tb at fixed La concentration of 80 mol%. When La concentration is 80 mol% and above, the relative intensity of the main emission peak of (La,Ce,Tb)BO3 will be the highest at 3/1 concentration ratio of Ce to Tb
The phosphors of (La,Ce,Tb)BO3 were synthesized by high temperature solid state reaction. X-ray diffractometry (XRD) patterns indicate that the crystal structures of (La,Ce,Tb)BO3 and LaBO3 are the same. The crystal structure has not been changed by Ce3+ and Tb3+ doping. Emission scanning electron microscopy (SEM) images show that the particle sizes of phosphors are more uniform, the morphology is more regular, and the granularity is about 5 μm. The content of TbBO3 phase in (La,Ce,Tb)BO3 increases with increasing of Tb content in (La,Ce,Tb)BO3. When Tb concentration reaches 15% and above, the content of TbBO3 phase in (La,Ce,Tb)BO3 increases more rapidly. The luminescence properties of (La,Ce,Tb)BO3 and the sensitization of Ce3+ to Tb3+ were studied. In the excitation spectrum of Ce3+ there are three peaks at 244, 268 and 330 nm, respectively. And in the emission spectrum of Ce3+, there are two peaks at 365 and 380 nm, respectively. All of them have the large overlap. The Maximum emission wavelength of Tb3+ is 541 nm, and its excitation peaks is 230 nm. Both the Tb3+ characteristic emission and excitation peaks and the Ce3+ characteristic emission and excitation peaks were observed in the emission and excitation spectrum of (La,Ce,Tb)BO3. Comparing the excitation spectrum of (La,Ce)BO3 with the emission spectrum of (La,Tb)BO3, it is found that they have the large overlap. It is indicated that there is a remarkable energy transfer from Ce3+ to Tb3+ in (La,Ce,Tb)BO3. When the concentration of Ce or Tb in (La,Ce,Tb)BO3 is fixed, because of concentration self-quenching effect, the relative intensity of main emission peak (at 541 nm)increases firstly and then decreases with increasing of the concentration of Tb or Ce. At fixed ratio of Ce concentration to Tb concentration, the relative intensity of the main emission peak of (La,Ce,Tb)BO3 is the highest when La concentration in (La,Ce,Tb)BO3 reaches 70 mol%. The sample with better luminescence properties will be obtained in the wide range of the concentration ratio of Ce to Tb at fixed La concentration of 80 mol%. When La concentration is 80 mol% and above, the relative intensity of the main emission peak of (La,Ce,Tb)BO3 will be the highest at 3/1 concentration ratio of Ce to Tb
2012, 41(8):1457-1462.
Abstract:
The solidification process of cast Ni-base superalloy IN792 was comparatively investigated by differential scanning calorimeter (DSC) and isothermal solidification quenching (ISQ) experiment. The distribution characteristics of elements in solidified solid and residual liquid at different temperatures were also concerned. The isothermal solidification microstructure, the phase precipitation diagram, the solidification characteristic curve and the segregation behavior of elements at different temperatures in liquidus and solidus range were obtained. The results of ISQ indicate that the IN792 alloy possesses a liquidus temperature of 1328 ℃. The onset of MC carbides and eutectic (γ+γ’) formation take place at 1310 and 1225 ℃, respectively. The secondary γ’ is precipitated at 1190 ℃. The macro-solidus temperature determined by DSC was 1250 ℃. The volume fraction of residual liquid at this temperature can reach about 5%. The end of the solidification happened at 1180℃, designated as micro-solidus temperature. No liquid remained at this temperature. There is a 70 ℃ gap between macro and micro-solidus temperature. The hot tearing tends to occur in this temperature range. About 85 vol% solid phase was formed within a range of 30 ℃ below the liquidus temperature. In 1300~1270 ℃ range, the residual liquid in the interdendritic region changed from connected channels to the isolated micro-liquid pools, which is related to the formation of micro-porosity defect. The distribution coefficient of element W and Co are more than 1, indicating that they tend to distribute in solid phase in dendritic region, which are negative segregation elements. The distribution coefficients of element Zr, Mo, Ti, Ta and Cr are less than 1, indicating that they tend to distribute in liquid phase in interdendritic region, which are positive segregation elements. The element Al tends to distribute to liquid phase at the beginning of the solidification, and then be prone to concentrate in the solid phase in the dendritic region and transform to a negative segregation element followed by the solidification temperature decreased. The distribution coefficient of element Al and Ni increases but Mo and Cr decreases followed by the solidification temperature decreasing in 1325~1210 ℃ range. On the contrary, The distribution of element Al and Ni decreases but Mo and Cr increases followed by the solidification temperature decreasing in 1210~1180 ℃ range
The solidification process of cast Ni-base superalloy IN792 was comparatively investigated by differential scanning calorimeter (DSC) and isothermal solidification quenching (ISQ) experiment. The distribution characteristics of elements in solidified solid and residual liquid at different temperatures were also concerned. The isothermal solidification microstructure, the phase precipitation diagram, the solidification characteristic curve and the segregation behavior of elements at different temperatures in liquidus and solidus range were obtained. The results of ISQ indicate that the IN792 alloy possesses a liquidus temperature of 1328 ℃. The onset of MC carbides and eutectic (γ+γ’) formation take place at 1310 and 1225 ℃, respectively. The secondary γ’ is precipitated at 1190 ℃. The macro-solidus temperature determined by DSC was 1250 ℃. The volume fraction of residual liquid at this temperature can reach about 5%. The end of the solidification happened at 1180℃, designated as micro-solidus temperature. No liquid remained at this temperature. There is a 70 ℃ gap between macro and micro-solidus temperature. The hot tearing tends to occur in this temperature range. About 85 vol% solid phase was formed within a range of 30 ℃ below the liquidus temperature. In 1300~1270 ℃ range, the residual liquid in the interdendritic region changed from connected channels to the isolated micro-liquid pools, which is related to the formation of micro-porosity defect. The distribution coefficient of element W and Co are more than 1, indicating that they tend to distribute in solid phase in dendritic region, which are negative segregation elements. The distribution coefficients of element Zr, Mo, Ti, Ta and Cr are less than 1, indicating that they tend to distribute in liquid phase in interdendritic region, which are positive segregation elements. The element Al tends to distribute to liquid phase at the beginning of the solidification, and then be prone to concentrate in the solid phase in the dendritic region and transform to a negative segregation element followed by the solidification temperature decreased. The distribution coefficient of element Al and Ni increases but Mo and Cr decreases followed by the solidification temperature decreasing in 1325~1210 ℃ range. On the contrary, The distribution of element Al and Ni decreases but Mo and Cr increases followed by the solidification temperature decreasing in 1210~1180 ℃ range
2012, 41(8):1463-1466.
Abstract:
The wear resistance of titanium alloy is comparatively low, which becomes the technical bottleneck to use titanium alloy as high strength and corrosion resistance tubing materials in petroleum industrials. In this work, wear properties of TC4 alloy were studied. The relationship between temperature and weight loss rate of wear or wear coefficient or topography of wear mark, wear mechanism of TC4 alloy was discussed. The results show that the wear degree of TC4 alloy deceases with the rise of temperature, TC4 alloy wear has two stages that is wear stage and stable wear stage, The wear mark of TC4 alloy presents furrow morphology, the wear mechanism of TC4 alloy are delamination abrasion and adhesive abrasion and fatigue abrasion at lower temperature and are delamination abrasion and adhesive abrasion and oxidation abrasion at higher temperature
The wear resistance of titanium alloy is comparatively low, which becomes the technical bottleneck to use titanium alloy as high strength and corrosion resistance tubing materials in petroleum industrials. In this work, wear properties of TC4 alloy were studied. The relationship between temperature and weight loss rate of wear or wear coefficient or topography of wear mark, wear mechanism of TC4 alloy was discussed. The results show that the wear degree of TC4 alloy deceases with the rise of temperature, TC4 alloy wear has two stages that is wear stage and stable wear stage, The wear mark of TC4 alloy presents furrow morphology, the wear mechanism of TC4 alloy are delamination abrasion and adhesive abrasion and fatigue abrasion at lower temperature and are delamination abrasion and adhesive abrasion and oxidation abrasion at higher temperature
Wang Jie
,
Xu Youlong
,
Ma Jianhua
,
Zhang Xuanhong
,
Meng Linbin
,
Shi Hongfu
,
Jiang Chunqiang
,
Peng Dan
2012, 41(8):1467-1471.
Abstract:
Nanostructured hydrous ruthenium oxide (RuO2·xH2O) was directly deposited on tantalum (Ta) substrates by cyclic voltammetry (CV) technology in RuCl3·xH2O aqueous solutions. The growth mechanism, revealed by energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) techniques, is that Ru3+ ions are reduced to nanostructured ruthenium (Ru) particles during negative potential scanning, then are oxidized to RuO2·xH2O granules (also in nanometers) during the following positive scanning. The unique nanometer structure of RuO2·xH2O, rather than the conventional “mud-cracked” structure, enable itself a high specific capacitance of 730 F·g-1 at a scanning rate of 50 mV·s-1 and a very fast charging/discharging ability. The speci?c capacitance is still up to 700 F·g-1 when the oxide loading is up to 1.2 mg·cm?2. In addition, the capacitance retains about 100% after 100,000 charging/discharging cycles. All of these indicate that the nanosized RuO2·xH2O is an excellent electrode material for energy storage and conversion devices, such as supercapacitors
Nanostructured hydrous ruthenium oxide (RuO2·xH2O) was directly deposited on tantalum (Ta) substrates by cyclic voltammetry (CV) technology in RuCl3·xH2O aqueous solutions. The growth mechanism, revealed by energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) techniques, is that Ru3+ ions are reduced to nanostructured ruthenium (Ru) particles during negative potential scanning, then are oxidized to RuO2·xH2O granules (also in nanometers) during the following positive scanning. The unique nanometer structure of RuO2·xH2O, rather than the conventional “mud-cracked” structure, enable itself a high specific capacitance of 730 F·g-1 at a scanning rate of 50 mV·s-1 and a very fast charging/discharging ability. The speci?c capacitance is still up to 700 F·g-1 when the oxide loading is up to 1.2 mg·cm?2. In addition, the capacitance retains about 100% after 100,000 charging/discharging cycles. All of these indicate that the nanosized RuO2·xH2O is an excellent electrode material for energy storage and conversion devices, such as supercapacitors
34 Effect of Substituting B for Al on Structure and Spectral Properties of Phosphors CaAl2Si2O8: Eu2+
2012, 41(8):1472-1476.
Abstract:
A series of luminescence phosphors Ca0.955Al2-xBxSi2O8: Eu2+ (x=0～0.7) were prepared by solid-state reaction in weak reductive atmosphere. The lattice positions and the luminescent mechanism of Eu2+ in the host were discussed. The effects of BⅢ-substitution on the host lattices and spectral properties were also investigated. It is found that when BⅢ enters CaAl2Si2O8 lattice and substitutes AlⅢ, complete solid solutions are formed in the whole range of x = 0～0.7. The lattice parameters (a, b, c, γ) and unit cell volumes of phosphors Ca0.955Al2-xGaxSi2O8:Eu2+ (x=0～1.0) decrease linearly and the lattice parameters(α，β) increase linearly as BⅢ content increases. A broad excitation spectrum consists of four excitation bands, which are located between 225 nm and 420 nm，the maximum excitation wavelength of which is at 352 nm，and FWHM decreases from 112 nm to 95 nm with the increase of the substitution amount of BⅢ. The emission spectrum, which is also a broad band between 370 nm and 600 nm，can be fitted by two peaks at 423 nm and 460 nm and its apparent peak is at 425 nm. Two fitted peaks are blue shifted, and the intensity ratio of the fitted peaks decreases linearly with increasing of the amount of BⅢ-substitution
A series of luminescence phosphors Ca0.955Al2-xBxSi2O8: Eu2+ (x=0～0.7) were prepared by solid-state reaction in weak reductive atmosphere. The lattice positions and the luminescent mechanism of Eu2+ in the host were discussed. The effects of BⅢ-substitution on the host lattices and spectral properties were also investigated. It is found that when BⅢ enters CaAl2Si2O8 lattice and substitutes AlⅢ, complete solid solutions are formed in the whole range of x = 0～0.7. The lattice parameters (a, b, c, γ) and unit cell volumes of phosphors Ca0.955Al2-xGaxSi2O8:Eu2+ (x=0～1.0) decrease linearly and the lattice parameters(α，β) increase linearly as BⅢ content increases. A broad excitation spectrum consists of four excitation bands, which are located between 225 nm and 420 nm，the maximum excitation wavelength of which is at 352 nm，and FWHM decreases from 112 nm to 95 nm with the increase of the substitution amount of BⅢ. The emission spectrum, which is also a broad band between 370 nm and 600 nm，can be fitted by two peaks at 423 nm and 460 nm and its apparent peak is at 425 nm. Two fitted peaks are blue shifted, and the intensity ratio of the fitted peaks decreases linearly with increasing of the amount of BⅢ-substitution
2012, 41(8):1477-1482.
Abstract:
The flow stress behaviors and the microstructure characteristics of 690 alloy with different grain sizes were investigated by isothermal compression tests in the temperature range of 1100~1200 °C and strain rate range of 0.1~10 s-1 on thermo-simulation machine. The flow stress constitutive relationship with initial grain size parameter of 690 alloy was established. The results show that increasing of initial grain size produces higher values of flow stress and the critical strain for the onset of dynamic recrystallization. Dynamic recrystallization volume decreases with increasing of grain size. The flow stress of 690 alloy predicted by the proposed models well agrees with experimental results. Therefore, the constitutive equation of 690 alloy during hot deformation process is improved
The flow stress behaviors and the microstructure characteristics of 690 alloy with different grain sizes were investigated by isothermal compression tests in the temperature range of 1100~1200 °C and strain rate range of 0.1~10 s-1 on thermo-simulation machine. The flow stress constitutive relationship with initial grain size parameter of 690 alloy was established. The results show that increasing of initial grain size produces higher values of flow stress and the critical strain for the onset of dynamic recrystallization. Dynamic recrystallization volume decreases with increasing of grain size. The flow stress of 690 alloy predicted by the proposed models well agrees with experimental results. Therefore, the constitutive equation of 690 alloy during hot deformation process is improved
2012, 41(8):1483-1486.
Abstract:
Transparent beryllium hydride (BeH2) films were prepared by the pyrolysis of di-t-butylberyllium etherate (t-Bu2Be·Et2O) under low pressure using metalorganic chemical vapor deposition (MOCVD) apparatus. The films were heated to 300 ℃ for dehydrogenation, and the released H2 was detected by gas chromatography. The XPS analysis shows that the surface layer of BeH2 film is BeO. The IR spectrum indicates that there exists Be-H-Be bend vibration
Transparent beryllium hydride (BeH2) films were prepared by the pyrolysis of di-t-butylberyllium etherate (t-Bu2Be·Et2O) under low pressure using metalorganic chemical vapor deposition (MOCVD) apparatus. The films were heated to 300 ℃ for dehydrogenation, and the released H2 was detected by gas chromatography. The XPS analysis shows that the surface layer of BeH2 film is BeO. The IR spectrum indicates that there exists Be-H-Be bend vibration
2012, 41(8):1487-1490.
Abstract:
A high speed steel composite roll billet which has not only favorable interface quality of outer shell and core material and regular outer shape, but also shallow oscillation marks and compact microstructure was manufactured by electromagnetism continuous casting for cladding method. When the relations of the technique parameters are proper. The results indicate that the microstructure of the roll billet is composed of chilled solidified layer, dendrite zone, interfacial zone of bimetal and core material zone. The microstructures of the outer shell material include martensite, bainite, residual austenite and some small labyrinth-shape, small-short lath-shape, or dollop-shape eutectic carbides. The microstructure of the core material is slice-shape pearlite and a little ferrite along boundary of cells. The interface region microstructure of bimetallic composite roll consists of diffusion region, chilled solidified layer and columnar grain region
A high speed steel composite roll billet which has not only favorable interface quality of outer shell and core material and regular outer shape, but also shallow oscillation marks and compact microstructure was manufactured by electromagnetism continuous casting for cladding method. When the relations of the technique parameters are proper. The results indicate that the microstructure of the roll billet is composed of chilled solidified layer, dendrite zone, interfacial zone of bimetal and core material zone. The microstructures of the outer shell material include martensite, bainite, residual austenite and some small labyrinth-shape, small-short lath-shape, or dollop-shape eutectic carbides. The microstructure of the core material is slice-shape pearlite and a little ferrite along boundary of cells. The interface region microstructure of bimetallic composite roll consists of diffusion region, chilled solidified layer and columnar grain region
2012, 41(8):1491-1494.
Abstract:
The mechanics properties of U-2.5%Nb alloy from –100 to 700 ℃ were studied. The results show that alloy tensile strength decreases with the temperature increasing, The plasticity isn’t monotone change below 600 ℃, and the elongation ratio and the area reduction ratio obtain the minimums value near 500 ℃. The tensile fracture morphology along grain boundary rupture presents obviously contrast room temperature, and the plasticity increases obviously beyond 600 ℃. Upon heating up to 500 ℃, for 1 h and then cooling to room temperature(20 ℃)，the impact toughness of the alloy decreases in contrast to no heating up. In the range of –100 ℃～room temperature, the impact toughness of the alloy decreases with the temperature decreasing, the ductile-brittle transition temperatures of U-2.5%Nb alloy is in the range of –30～–10 ℃, the trend mentioned above becomes weak below –30 ℃. The fracture plane is irregular after the impact test, which has a rupture characteristic of quasi-cleavage.
The mechanics properties of U-2.5%Nb alloy from –100 to 700 ℃ were studied. The results show that alloy tensile strength decreases with the temperature increasing, The plasticity isn’t monotone change below 600 ℃, and the elongation ratio and the area reduction ratio obtain the minimums value near 500 ℃. The tensile fracture morphology along grain boundary rupture presents obviously contrast room temperature, and the plasticity increases obviously beyond 600 ℃. Upon heating up to 500 ℃, for 1 h and then cooling to room temperature(20 ℃)，the impact toughness of the alloy decreases in contrast to no heating up. In the range of –100 ℃～room temperature, the impact toughness of the alloy decreases with the temperature decreasing, the ductile-brittle transition temperatures of U-2.5%Nb alloy is in the range of –30～–10 ℃, the trend mentioned above becomes weak below –30 ℃. The fracture plane is irregular after the impact test, which has a rupture characteristic of quasi-cleavage.
2012, 41(8):1495-1499.
Abstract:
Adopting a novel technology for plasticizing powder extrusion molding (PEM), some types of novel binder for PEM of tungsten heavy alloy has been developed, and the compatibility, extruding and debinding characteristics of the binders have been studied. The thermodynamic calculation and thermal analysis, and the observation of SEM and polarization microscope were used to certify binder ingredient compatibility. The large aspect ratio tungsten alloy bars with diameters up to 24 mm have used manufactured at 60 ℃ and 75 ℃ respectively by optimizing the preparation technology of feedstock and extrusion process. By adopting the solvent-thermal debinding method the fast extruded bars with 24 mm in diameter and without defect debinding have been obtained
Adopting a novel technology for plasticizing powder extrusion molding (PEM), some types of novel binder for PEM of tungsten heavy alloy has been developed, and the compatibility, extruding and debinding characteristics of the binders have been studied. The thermodynamic calculation and thermal analysis, and the observation of SEM and polarization microscope were used to certify binder ingredient compatibility. The large aspect ratio tungsten alloy bars with diameters up to 24 mm have used manufactured at 60 ℃ and 75 ℃ respectively by optimizing the preparation technology of feedstock and extrusion process. By adopting the solvent-thermal debinding method the fast extruded bars with 24 mm in diameter and without defect debinding have been obtained
2012, 41(8):1500-1504.
Abstract:
A review was given on the development of the high-capacity RE-Mg-Ni-base A2B7-type superlattice hydrogen storage alloys, which can be divided into three stages: 1997~2004, 2005~2007, 2008~now currently, the maximum discharge capacity and cyclic life of A2B7-type alloys are more than 380 mAh/g and 500 cycles, respectively. During the industrialization process of A2B7-type alloys in China, there will be some problems needed to be solved as fellows: the quantitative determination of PuNi3-type, Ce2Ni7-type, and Pr5Co19-type superlattice structures, the breakthrough of key industrial technology, and the application in encapsulated high-capacity Ni/MH rechargeable battery
A review was given on the development of the high-capacity RE-Mg-Ni-base A2B7-type superlattice hydrogen storage alloys, which can be divided into three stages: 1997~2004, 2005~2007, 2008~now currently, the maximum discharge capacity and cyclic life of A2B7-type alloys are more than 380 mAh/g and 500 cycles, respectively. During the industrialization process of A2B7-type alloys in China, there will be some problems needed to be solved as fellows: the quantitative determination of PuNi3-type, Ce2Ni7-type, and Pr5Co19-type superlattice structures, the breakthrough of key industrial technology, and the application in encapsulated high-capacity Ni/MH rechargeable battery
