Volume 40,Issue 11,2011 Table of Contents
2011, 40(11):1881-1886.
Abstract:
Solution precursor plasma spraying (SPPS) was employed to prepare porous La0.8Sr0.2MnO3 (LSM) cathode for solid oxide fuel cell (SOFC). The surface morphology and microstructure of the LSM deposits were characterized by SEM. The phase structure of LSM was analyzed by XRD. The electrochemical behavior was investigated through the impedance spectroscopy. The effect of spray distance and annealing treatment on SPPS LSM microstructure was examined. Annealing at 1050 oC for 2 h in air, the coherent porous films of the perovskite phase with a fine microstructure were presented. The results show that the microstructure of SPPS LSM cathode exhibits a significant influence on the cathode polarization. The lowest specific surface resistance of 0.3 Ω·cm2 is obtained at 1000 oC for SPPS LSM cathode deposited at a spray distance of 60 mm. SPPS is a promising process to fabricate SOFC cathode with tailoring of the desired phase and microstructure
Solution precursor plasma spraying (SPPS) was employed to prepare porous La0.8Sr0.2MnO3 (LSM) cathode for solid oxide fuel cell (SOFC). The surface morphology and microstructure of the LSM deposits were characterized by SEM. The phase structure of LSM was analyzed by XRD. The electrochemical behavior was investigated through the impedance spectroscopy. The effect of spray distance and annealing treatment on SPPS LSM microstructure was examined. Annealing at 1050 oC for 2 h in air, the coherent porous films of the perovskite phase with a fine microstructure were presented. The results show that the microstructure of SPPS LSM cathode exhibits a significant influence on the cathode polarization. The lowest specific surface resistance of 0.3 Ω·cm2 is obtained at 1000 oC for SPPS LSM cathode deposited at a spray distance of 60 mm. SPPS is a promising process to fabricate SOFC cathode with tailoring of the desired phase and microstructure
2011, 40(11):1887-1890.
Abstract:
The superplastic deformation mechanism of Mg-7.0Al-0.4Zn alloy was studied by EBSD technology. Results indicate that with increasing of strain amount, the texture of {0002}//ED is strengthened obviously, and intragranular sliding plays a main role during the accommodated deformation. Twins have started at the medium and the final deformation stages; when approaching to failure, intragranular sliding vanishes, and twins replace it to play a main role. But the contribution of twins to deformation is relatively small
The superplastic deformation mechanism of Mg-7.0Al-0.4Zn alloy was studied by EBSD technology. Results indicate that with increasing of strain amount, the texture of {0002}//ED is strengthened obviously, and intragranular sliding plays a main role during the accommodated deformation. Twins have started at the medium and the final deformation stages; when approaching to failure, intragranular sliding vanishes, and twins replace it to play a main role. But the contribution of twins to deformation is relatively small
2011, 40(11):1891-1896.
Abstract:
Double glow plasma alloying of niobium was applied on TiAl alloy in order to improve its oxidation and wear resistances. Microstructure as well as tribological properties at ambient temperature and 600 oC were studied. The results show that a Nb-alloyed layer, about 12 μm in thickness, is formed on the surface of TiAl alloy after plasma alloying treatment. The alloyed layer consisting of AlNb2, AlNb3, Ti2AlNb and pure niobium is compact and homogenous. Under dry sliding condition, the wear resistance at 600 oC is enhanced greatly for Nb-alloyed TiAl and both anti-friction and wear-resistance at ambient temperature are also better than those of untreated TiAl alloy
Double glow plasma alloying of niobium was applied on TiAl alloy in order to improve its oxidation and wear resistances. Microstructure as well as tribological properties at ambient temperature and 600 oC were studied. The results show that a Nb-alloyed layer, about 12 μm in thickness, is formed on the surface of TiAl alloy after plasma alloying treatment. The alloyed layer consisting of AlNb2, AlNb3, Ti2AlNb and pure niobium is compact and homogenous. Under dry sliding condition, the wear resistance at 600 oC is enhanced greatly for Nb-alloyed TiAl and both anti-friction and wear-resistance at ambient temperature are also better than those of untreated TiAl alloy
2011, 40(11):1897-1900.
Abstract:
Spin ladder compounds Sr14-xCaxCu24O41 (SCCO) single crystals have been grown under different oxygen pressures by an optical floating-zone technique. The effects of oxygen pressure on the crystal growth and properties of SCCO were studied. The SCCO single crystals with x≤8 can be grown in a flowing oxygen atmosphere. But the growth of the SCCO compounds with higher Ca content (x>8) needs higher pressure (0.9 MPa). The single crystals were characterized by means of XRD, EDX and resistivity measurement. High pressure is in favor of forming of higher Ca-doped SCCO single crystals. SCCO single crystals grown under different oxygen pressures have almost the same quality
Spin ladder compounds Sr14-xCaxCu24O41 (SCCO) single crystals have been grown under different oxygen pressures by an optical floating-zone technique. The effects of oxygen pressure on the crystal growth and properties of SCCO were studied. The SCCO single crystals with x≤8 can be grown in a flowing oxygen atmosphere. But the growth of the SCCO compounds with higher Ca content (x>8) needs higher pressure (0.9 MPa). The single crystals were characterized by means of XRD, EDX and resistivity measurement. High pressure is in favor of forming of higher Ca-doped SCCO single crystals. SCCO single crystals grown under different oxygen pressures have almost the same quality
5 Preparation, Characterization and Photocatalytic Activity of Pt-SiO2/TiO2 with Core-Shell Structure
2011, 40(11):1901-1905.
Abstract:
SiO2/TiO2 photocatalyst with core-shell structure were synthesized by sol-gel method, using SiO2 microsphere with a mean size of about 300 nm as template. And then Pt was deposited on SiO2/TiO2 by chemical reduction method. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectra (PL). The results show that Pt particles mainly in form of Pt(0) can be deposited on SiO2/TiO2 surface un-uniformly. The absorption in visible light region and the separation efficiency of electron-hole pairs are enhanced obviously via Pt-deposition. The adsorption and kinetic constants of Rhodamine B (RB) over the obtained samples were evaluated. The results indicate that core-shell structure is helpful to improve the adsorption property. The presence of Pt on SiO2/TiO2 surface is found to significantly enhance the photodegradation of RB, and the optimal deposition of Pt is 0.5 wt%
SiO2/TiO2 photocatalyst with core-shell structure were synthesized by sol-gel method, using SiO2 microsphere with a mean size of about 300 nm as template. And then Pt was deposited on SiO2/TiO2 by chemical reduction method. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectra (PL). The results show that Pt particles mainly in form of Pt(0) can be deposited on SiO2/TiO2 surface un-uniformly. The absorption in visible light region and the separation efficiency of electron-hole pairs are enhanced obviously via Pt-deposition. The adsorption and kinetic constants of Rhodamine B (RB) over the obtained samples were evaluated. The results indicate that core-shell structure is helpful to improve the adsorption property. The presence of Pt on SiO2/TiO2 surface is found to significantly enhance the photodegradation of RB, and the optimal deposition of Pt is 0.5 wt%
2011, 40(11):1906-1909.
Abstract:
NiP basic substrates of hard disks were polished by electrochemical-mechanical polishing (ECMP) method with home-made slurry and a modified polisher. The effects of voltage, table rotation speed, pressure and slurry flow rate on the removal rate were investigated. The electrochemical mechanical polishing mechanism was primarily analyzed. The results show that NiP substrate can be polished with ECMP method at low pressure (3.5 kPa) and the material removal rate (MRR) can be controlled by adjusting polishing voltage, rotation speed of polishing table and slurry flow rate.
NiP basic substrates of hard disks were polished by electrochemical-mechanical polishing (ECMP) method with home-made slurry and a modified polisher. The effects of voltage, table rotation speed, pressure and slurry flow rate on the removal rate were investigated. The electrochemical mechanical polishing mechanism was primarily analyzed. The results show that NiP substrate can be polished with ECMP method at low pressure (3.5 kPa) and the material removal rate (MRR) can be controlled by adjusting polishing voltage, rotation speed of polishing table and slurry flow rate.
2011, 40(11):1916-1920.
Abstract:
The super-cell system of Ti-doped VH2 was optimized by means of plane-wave pseudopotential, employing the first-principle of density functional theory (DFT). The results show that the cell parameters of V1-xTixH2 and total energy of the system increase gradually with the increment of Ti, so the stability of the system decreases and the capability of releasing hydrogen is improved. The density of states, net charge, bond order and electronic density of V1-xTixH2 (x = 0, 0.13, 0.30, 0.48, 0.65, 1) were also computed and analyzed. The calculation results show that the net charge of V increases whereas that of H decreases gradually with the increment of Ti; the ionic interaction between V-H is reinforced and at the same time the valent interaction is weakened; the bond order of V-H increases, the interaction between V and H becomes stronger, and thus the capability of absorbing hydrogen is improved by adding a certain amount of Ti to VH2. However, when the content of Ti in VH2 exceeds 0.48 (x>0.48), the bond order of V-H decreases, and the capability of absorbing hydrogen is decreased.
The super-cell system of Ti-doped VH2 was optimized by means of plane-wave pseudopotential, employing the first-principle of density functional theory (DFT). The results show that the cell parameters of V1-xTixH2 and total energy of the system increase gradually with the increment of Ti, so the stability of the system decreases and the capability of releasing hydrogen is improved. The density of states, net charge, bond order and electronic density of V1-xTixH2 (x = 0, 0.13, 0.30, 0.48, 0.65, 1) were also computed and analyzed. The calculation results show that the net charge of V increases whereas that of H decreases gradually with the increment of Ti; the ionic interaction between V-H is reinforced and at the same time the valent interaction is weakened; the bond order of V-H increases, the interaction between V and H becomes stronger, and thus the capability of absorbing hydrogen is improved by adding a certain amount of Ti to VH2. However, when the content of Ti in VH2 exceeds 0.48 (x>0.48), the bond order of V-H decreases, and the capability of absorbing hydrogen is decreased.
2011, 40(11):1921-1925.
Abstract:
LaNi5-xAlx (x=0, 0.25, 0.75, 1.2) alloys were prepared by vacuum induction melting. The microstructure, mechanical property, cyclic stability of hydrogen absorption/desorption and pulverization resistance of the alloys were investigated. The results demonstrate that the addition of Al element can markedly improve the stability of crystal structure and hydrogen storage capacity of the alloys; with increase of the Al content, the pulverization resistance of the alloys becomes worse at first, and then is improved; mechanical property, which is the main factor, and hydrogen storage capacity jointly influence pulverization resistance property of the alloys; in the atmosphere of ordinary high-purity hydrogen, the main reason for the capacity attenuation of the LaNi5-xAlx (x=0-1.2) alloys should be their intrinsic properties, mostly maybe the disproportionation reaction
LaNi5-xAlx (x=0, 0.25, 0.75, 1.2) alloys were prepared by vacuum induction melting. The microstructure, mechanical property, cyclic stability of hydrogen absorption/desorption and pulverization resistance of the alloys were investigated. The results demonstrate that the addition of Al element can markedly improve the stability of crystal structure and hydrogen storage capacity of the alloys; with increase of the Al content, the pulverization resistance of the alloys becomes worse at first, and then is improved; mechanical property, which is the main factor, and hydrogen storage capacity jointly influence pulverization resistance property of the alloys; in the atmosphere of ordinary high-purity hydrogen, the main reason for the capacity attenuation of the LaNi5-xAlx (x=0-1.2) alloys should be their intrinsic properties, mostly maybe the disproportionation reaction
2011, 40(11):1926-1930.
Abstract:
The initiation and propagation characteristics of the fatigue cracks were studied for 2197-T851 alloy. The results indicate that fatigue crack initiation is related to stress. Under smaller stress, fatigue cracks mainly initiate from the second phase particles and the interface between the second phase particles and matrix as well as from the surface defect. While with larger stress, fatigue cracks easily initiate from the grain boundary and the slip band. Fatigue cracks grow along the favorable slip plane with priority. When the favorable slip planes in the adjacent grains have an angle, the crack deflects. The coherent δ′ particles that can be sheared by dislocation result in the crack path meandering in the grain. The cracks grow mainly in transgranular mode along the (111) plane, and also along the small-angle grain boundaries.
The initiation and propagation characteristics of the fatigue cracks were studied for 2197-T851 alloy. The results indicate that fatigue crack initiation is related to stress. Under smaller stress, fatigue cracks mainly initiate from the second phase particles and the interface between the second phase particles and matrix as well as from the surface defect. While with larger stress, fatigue cracks easily initiate from the grain boundary and the slip band. Fatigue cracks grow along the favorable slip plane with priority. When the favorable slip planes in the adjacent grains have an angle, the crack deflects. The coherent δ′ particles that can be sheared by dislocation result in the crack path meandering in the grain. The cracks grow mainly in transgranular mode along the (111) plane, and also along the small-angle grain boundaries.
2011, 40(11):1931-1935.
Abstract:
Cu-7Cr and Cu-7Cr-0.07Ag in-situ composites were prepared by the cast and thermo-mechanical treatment process. The microstructure, mechanical properties and conductivity of the in-situ composites were investigated by optical microscope, scanning electronic microscope, tensile-testing machine and microhmmeter. Results indicate that the trace addition of Ag can refine primary Cr dendrites and deformed Cr fibre, which leads to a significant increase in strength and slight improvement in conductivity. At the same time, the Cu-7Cr-0.07Ag in-situ composite shows a little higher plasticity
Cu-7Cr and Cu-7Cr-0.07Ag in-situ composites were prepared by the cast and thermo-mechanical treatment process. The microstructure, mechanical properties and conductivity of the in-situ composites were investigated by optical microscope, scanning electronic microscope, tensile-testing machine and microhmmeter. Results indicate that the trace addition of Ag can refine primary Cr dendrites and deformed Cr fibre, which leads to a significant increase in strength and slight improvement in conductivity. At the same time, the Cu-7Cr-0.07Ag in-situ composite shows a little higher plasticity
2011, 40(11):1936-1940.
Abstract:
Li and Fe atom sites of LiFePO4 were doped by rare earth ions (Er3+, Y3+, Nd3+), respectively. The change of structure and performance of LiFePO4 was investigated by XRD, galvanostatic charge and discharge experiments and electrochemical impedance tests. The results show that the microstructure and performance of doped samples are interrelated with radii of doping ions and doping site. LiFe0.99Y0.01PO4 displays the excellent electrochemical performance. Its initial discharge capacity is 149.8 mAh·g-1 under the current density of 15 mA·g-1. When 300 mA·g-1 current is applied, its discharge capacity is 134.3 mAh·g-1. Its capacity retention is 99.1% after 50 cycles.
Li and Fe atom sites of LiFePO4 were doped by rare earth ions (Er3+, Y3+, Nd3+), respectively. The change of structure and performance of LiFePO4 was investigated by XRD, galvanostatic charge and discharge experiments and electrochemical impedance tests. The results show that the microstructure and performance of doped samples are interrelated with radii of doping ions and doping site. LiFe0.99Y0.01PO4 displays the excellent electrochemical performance. Its initial discharge capacity is 149.8 mAh·g-1 under the current density of 15 mA·g-1. When 300 mA·g-1 current is applied, its discharge capacity is 134.3 mAh·g-1. Its capacity retention is 99.1% after 50 cycles.
2011, 40(11):1941-1945.
Abstract:
Multi-porous titanium dioxide films were prepared on pure titanium plates by micro-arc oxidation and the films were characterized. Micro-arc oxidation tests were carried out at room temperature and 0.5 mol/L H3PO4 used as electrolyte. Voltage was controlled as potentiostatic mode (200-350 V). Porous titanium dioxide layers are formed under all voltages but the morphological difference is obvious. The distribution of micro-pore size increases with increasing of the voltage. XRD and XPS analysis indicate that the micro-arc oxidized films are mainly composed of TiO2 and TiP2O7. With increasing of the applied voltage, both the TiO2 crystalline phase and the P content increase. The incubation results of the samples in simulated body fluid (SBF) show that HA (hydroxyapatite) formation is mainly due to the TiP2O7 resolved into . The ions are adsorbed in the sample surface as nuclear sites. The P content of about 4at% in the sample surface can hasten the apatite formation
Multi-porous titanium dioxide films were prepared on pure titanium plates by micro-arc oxidation and the films were characterized. Micro-arc oxidation tests were carried out at room temperature and 0.5 mol/L H3PO4 used as electrolyte. Voltage was controlled as potentiostatic mode (200-350 V). Porous titanium dioxide layers are formed under all voltages but the morphological difference is obvious. The distribution of micro-pore size increases with increasing of the voltage. XRD and XPS analysis indicate that the micro-arc oxidized films are mainly composed of TiO2 and TiP2O7. With increasing of the applied voltage, both the TiO2 crystalline phase and the P content increase. The incubation results of the samples in simulated body fluid (SBF) show that HA (hydroxyapatite) formation is mainly due to the TiP2O7 resolved into . The ions are adsorbed in the sample surface as nuclear sites. The P content of about 4at% in the sample surface can hasten the apatite formation
Xin Xin
,
Sun Wenru
,
Duan Zhongyuan
,
Qi Feng
,
Zhang Weihong
,
Liu Fang
,
Yang Hongcai
,
Hu Zhuangqi
2011, 40(11):1946-1950.
Abstract:
The effects of increasing Al and decreasing Nb on microstructure and mechanical properties of GH706 alloy were studied. With increasing Al from 0.35% to 1.26% and decreasing Nb from 2.88% to 1.98%, the precipitation of γ″-Ni3Nb phase is constrained, while the formation of γ′-Ni3Al phase is promoted. As a result, the tensile strength at room temperature is decreased, but the impact energy is improved. However, such a modification of Al and Nb constrains the precipitation of intergranular η-Ni3(Ti,Nb) phase, and enhances the precipitation of Laves phase rich in Nb and Cr2Nb phase rich in Nb and Cr, which decreases the grain boundary cohesion and deteriorates the stress rupture properties at 650 oC and 690 MPa
The effects of increasing Al and decreasing Nb on microstructure and mechanical properties of GH706 alloy were studied. With increasing Al from 0.35% to 1.26% and decreasing Nb from 2.88% to 1.98%, the precipitation of γ″-Ni3Nb phase is constrained, while the formation of γ′-Ni3Al phase is promoted. As a result, the tensile strength at room temperature is decreased, but the impact energy is improved. However, such a modification of Al and Nb constrains the precipitation of intergranular η-Ni3(Ti,Nb) phase, and enhances the precipitation of Laves phase rich in Nb and Cr2Nb phase rich in Nb and Cr, which decreases the grain boundary cohesion and deteriorates the stress rupture properties at 650 oC and 690 MPa
2011, 40(11):1951-1955.
Abstract:
The relationship between processing and property of materials is complex. In the present investigation, based on a lot of experimental data, the technique of artificial neural network was employed to develop the prediction model of processing and property for TC11 titanium alloy. The inputs of the neural network were different forging process parameters such as forging temperature, forging style and cooling style. The outputs of the model were the tensile properties, including ultimate tensile strength, yield strength, elongation and reduction of area. The mechanical properties of TC11 titanium alloy were predicted by the established model, and the accuracy of the prediction was compared with the experimental data. Besides, the model was used to study the influence of the processing on the properties of TC11 titanium alloy. Results show that the model can predict the properties of this alloy with high accuracy and reliability, and the complex relationship between processing and properties can be well presented by the trained neural network, which is consistent with the metallurgical trends
The relationship between processing and property of materials is complex. In the present investigation, based on a lot of experimental data, the technique of artificial neural network was employed to develop the prediction model of processing and property for TC11 titanium alloy. The inputs of the neural network were different forging process parameters such as forging temperature, forging style and cooling style. The outputs of the model were the tensile properties, including ultimate tensile strength, yield strength, elongation and reduction of area. The mechanical properties of TC11 titanium alloy were predicted by the established model, and the accuracy of the prediction was compared with the experimental data. Besides, the model was used to study the influence of the processing on the properties of TC11 titanium alloy. Results show that the model can predict the properties of this alloy with high accuracy and reliability, and the complex relationship between processing and properties can be well presented by the trained neural network, which is consistent with the metallurgical trends
2011, 40(11):1956-1960.
Abstract:
Microstructure and compressive stress in thermal growth oxide (TGO) of Pt-modified aluminide coating on nickel base superalloy CSMX4 for thermal barrier coating (TBC) application after discontinuous oxidation at high temperature in air have been studied. Using a micro Raman instrument technology, photo-stimulated-luminescence-spectra (PSLS) of θ- and α-Al2O3 formation are obtained for Pt-modified aluminide coating after 20 h oxidation exposure at 900 °C in air; however, a compact and protective α-Al2O3 layer is formed over the coating at 1100 °C in air. Thermal growth stress in α-Al2O3 was calculated according to the spectra shift compared with stress-free alumina spectra, a little higher than 3.0 GPa for TGO in TBC system after oxidation exposure. The stress within “ridges” of alumina surface over the coating is lower due to cracks’ formation during high temperature oxidation. Alumina rumpling is obvious for Pt-modified aluminide coating due to absence of ceramic layer. At the same time, Al element’s quick diffusion along substrate grain boundary results in more γ′-Ni3Al phase formed along boundary during oxidation. Coefficient of thermal expansion for the coating is changed with phase transformation from β-NiAl to γ′-Ni3Al, and finally affects the stress in TGO and coating lifetime during high temperature oxidation.
Microstructure and compressive stress in thermal growth oxide (TGO) of Pt-modified aluminide coating on nickel base superalloy CSMX4 for thermal barrier coating (TBC) application after discontinuous oxidation at high temperature in air have been studied. Using a micro Raman instrument technology, photo-stimulated-luminescence-spectra (PSLS) of θ- and α-Al2O3 formation are obtained for Pt-modified aluminide coating after 20 h oxidation exposure at 900 °C in air; however, a compact and protective α-Al2O3 layer is formed over the coating at 1100 °C in air. Thermal growth stress in α-Al2O3 was calculated according to the spectra shift compared with stress-free alumina spectra, a little higher than 3.0 GPa for TGO in TBC system after oxidation exposure. The stress within “ridges” of alumina surface over the coating is lower due to cracks’ formation during high temperature oxidation. Alumina rumpling is obvious for Pt-modified aluminide coating due to absence of ceramic layer. At the same time, Al element’s quick diffusion along substrate grain boundary results in more γ′-Ni3Al phase formed along boundary during oxidation. Coefficient of thermal expansion for the coating is changed with phase transformation from β-NiAl to γ′-Ni3Al, and finally affects the stress in TGO and coating lifetime during high temperature oxidation.
2011, 40(11):1961-1965.
Abstract:
High pure ultrafine AgO powder was synthesized by ozone oxidation of AgNO3. Silver valence change of AgO at different temperatures was determined by differential thermal analysis. AgO powder were also characterized by XRD, SEM and XPS to analyze the phase and morphology and the silver valence change of the powder heated at different temperatures. The results show that the crystal structure of the prepared ultrafine AgO powder belongs to monoclinic system and AgO particles are of virgulate shapes. The colour of ultrafine AgO powder changes obviously after heating. In the heating process, with increasing of the temperature, the content of AgO decreases gradually, the content of Ag2O increases firstly and then decreases and the content of Ag increases gradually. When the temperature exceeds 350 oC, AgO decompose completely, 46.49 % of which transforms into Ag2O and 53.51% transforms into Ag. And complete decomposition to Ag occurs at 400 oC. The XPS spectra of O1s on different powder surfaces are quite distinct, reflecting the lattice structure change of powder
High pure ultrafine AgO powder was synthesized by ozone oxidation of AgNO3. Silver valence change of AgO at different temperatures was determined by differential thermal analysis. AgO powder were also characterized by XRD, SEM and XPS to analyze the phase and morphology and the silver valence change of the powder heated at different temperatures. The results show that the crystal structure of the prepared ultrafine AgO powder belongs to monoclinic system and AgO particles are of virgulate shapes. The colour of ultrafine AgO powder changes obviously after heating. In the heating process, with increasing of the temperature, the content of AgO decreases gradually, the content of Ag2O increases firstly and then decreases and the content of Ag increases gradually. When the temperature exceeds 350 oC, AgO decompose completely, 46.49 % of which transforms into Ag2O and 53.51% transforms into Ag. And complete decomposition to Ag occurs at 400 oC. The XPS spectra of O1s on different powder surfaces are quite distinct, reflecting the lattice structure change of powder
2011, 40(11):1966-1970.
Abstract:
The microstructure and precipitates of a novel nickel-based powder metallurgy (P/M) superalloy FGH98 I in subsolvus and supersolvus heat treatment condition was studied by means of thermodynamic calculation, OM, FESEM and chemical phase analysis. The relationship between microstructure and mechanical properties was also analyzed. The results show that the precipitates of the alloy FGH98 I heat treated at 1130 oC and 1190 oC are γ′, MC, M23C6 and M3B2, without the observation of TCP phases. The grains of subsolvus heat treated FGH98 I grow slightly, and there are primary, secondary and tertiary γ′ phases with different sizes. The grains of supersolvus heat treated FGH98 I grow significantly, and the alloy has monomodal γ′ precipitate distribution. The former has higher strength because of finer grains, while the latter has improved high temperature ductility and stress rupture properties due to the reduced size of secondary γ′ phases and the elimination of primary γ′ phases, PPB (prior particle boundary) and residual dendrite structure. It reveals that the different grain sizes and γ′ characteristics are the key factors for dual-property FGH98 I disk
The microstructure and precipitates of a novel nickel-based powder metallurgy (P/M) superalloy FGH98 I in subsolvus and supersolvus heat treatment condition was studied by means of thermodynamic calculation, OM, FESEM and chemical phase analysis. The relationship between microstructure and mechanical properties was also analyzed. The results show that the precipitates of the alloy FGH98 I heat treated at 1130 oC and 1190 oC are γ′, MC, M23C6 and M3B2, without the observation of TCP phases. The grains of subsolvus heat treated FGH98 I grow slightly, and there are primary, secondary and tertiary γ′ phases with different sizes. The grains of supersolvus heat treated FGH98 I grow significantly, and the alloy has monomodal γ′ precipitate distribution. The former has higher strength because of finer grains, while the latter has improved high temperature ductility and stress rupture properties due to the reduced size of secondary γ′ phases and the elimination of primary γ′ phases, PPB (prior particle boundary) and residual dendrite structure. It reveals that the different grain sizes and γ′ characteristics are the key factors for dual-property FGH98 I disk
2011, 40(11):1972-1975.
Abstract:
A kind of low-density niobium-based alloy NbTiAlVZr with density of 5.9 g/cm3, the lowest density for refractory alloys, was prepared by arc-melting and processing method. The microstructure and mechanical properties were characterized by optical microscopy (OM), transmission electron microscope (TEM) and tensile test. Results show that the average ultimate tensile strength (UTS) and elongation of the samples are 990 MPa, 16% at room temperature, respectively and 80 MPa, 44% at 1100 oC, respectively. This new alloy combines TiC nano-particle dispersion strengthening with solution strengthening to increase the UTS, and retains enough plasticity for hot and cold processing
A kind of low-density niobium-based alloy NbTiAlVZr with density of 5.9 g/cm3, the lowest density for refractory alloys, was prepared by arc-melting and processing method. The microstructure and mechanical properties were characterized by optical microscopy (OM), transmission electron microscope (TEM) and tensile test. Results show that the average ultimate tensile strength (UTS) and elongation of the samples are 990 MPa, 16% at room temperature, respectively and 80 MPa, 44% at 1100 oC, respectively. This new alloy combines TiC nano-particle dispersion strengthening with solution strengthening to increase the UTS, and retains enough plasticity for hot and cold processing
2011, 40(11):1976-1980.
Abstract:
The effects of Y and Nb on the microstructure and mechanical properties of rapidly solidified TiAl alloys were investigated. Results show that the rapidly solidified TiAl alloys with various Y contents are of equiaxed microstructure, and composed mainly of α2 and a few amount of γ phase. With Y content increasing, the volume fraction of γ phase is increased and the microstructure of the TiAl alloys is gradually refined. The alloys with various Nb contents show lamellar structure with reduced interlamellar spacings of 15-17 nm and massive structure. γ and α2 are also the two main phases for rapidly solidified TiAl alloys with various Nb addition. The hardness of rapidly solidified TiAl alloys is higher than that of the conventionally cast TiAl alloys
The effects of Y and Nb on the microstructure and mechanical properties of rapidly solidified TiAl alloys were investigated. Results show that the rapidly solidified TiAl alloys with various Y contents are of equiaxed microstructure, and composed mainly of α2 and a few amount of γ phase. With Y content increasing, the volume fraction of γ phase is increased and the microstructure of the TiAl alloys is gradually refined. The alloys with various Nb contents show lamellar structure with reduced interlamellar spacings of 15-17 nm and massive structure. γ and α2 are also the two main phases for rapidly solidified TiAl alloys with various Nb addition. The hardness of rapidly solidified TiAl alloys is higher than that of the conventionally cast TiAl alloys
2011, 40(11):1982-1985.
Abstract:
2LiBH4/MgH2 hydrogen storage composite was prepared by ball-milling technology, and its microstructures and hydrogen storage properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and hydrogen storage measurements. The effects of Ce-based catalysts on the hydrogen storage properties of the composite were studied. The results show that hydrogen release of 2LiBH4/MgH2 composite is a two-step process, i.e., the first is the decomposition of MgH2 and the second is the reaction between LiBH4 and Mg just produced. Ce or CeF3 addition can improve the dehydrogenation of 2LiBH4/MgH2 composite. Ce mainly improves the behavior of the second step reaction while CeF3 influences the behavior of the two steps greatly. For the 2LiBH4/MgH2 composite with addition of 5 mol% CeF3, the total hydrogen capacity reaches 10.6 wt% at 450 oC and the initial hydrogen release temperature is decreased by around 100 oC. LiBH1-xFx is formed by partial substitution of F- for H-, which decreases the decomposition temperature of LiBH4.
2LiBH4/MgH2 hydrogen storage composite was prepared by ball-milling technology, and its microstructures and hydrogen storage properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and hydrogen storage measurements. The effects of Ce-based catalysts on the hydrogen storage properties of the composite were studied. The results show that hydrogen release of 2LiBH4/MgH2 composite is a two-step process, i.e., the first is the decomposition of MgH2 and the second is the reaction between LiBH4 and Mg just produced. Ce or CeF3 addition can improve the dehydrogenation of 2LiBH4/MgH2 composite. Ce mainly improves the behavior of the second step reaction while CeF3 influences the behavior of the two steps greatly. For the 2LiBH4/MgH2 composite with addition of 5 mol% CeF3, the total hydrogen capacity reaches 10.6 wt% at 450 oC and the initial hydrogen release temperature is decreased by around 100 oC. LiBH1-xFx is formed by partial substitution of F- for H-, which decreases the decomposition temperature of LiBH4.
2011, 40(11):1986-1989.
Abstract:
The poison of Pd membrane in CO2 at different temperatures and the hydrogenization of the poisoned membrane were carried out in a silica tubular furnace and the hydrogen isotope permeation capacity was tested. The variation of Pd membrane phase and morphology was analyzed and observed by XPS and SEM. The cause and the mechanism of the variation were discussed. The results show that the molecule CO2 will dissociate to C=O, C–O and O on Pd membrane surface. The adsorptive capacity of C–O and O increases and that of C=O decreases with increasing of the temperature. PdO and micropores can be detected apparently when the poison temperature reaches 500 oC, and C–O will be adsorbed on Pd membrane surface firmly. After hydrogenization, the PdO, C–O and free O on the Pd surface vanish while C=O reappear. After the Pd membrane is poisoned by CO2, the hydrogen isotope permeation capacity of Pd membrane decreases because the atom O and C–O occupy H site and react with atom H easily
The poison of Pd membrane in CO2 at different temperatures and the hydrogenization of the poisoned membrane were carried out in a silica tubular furnace and the hydrogen isotope permeation capacity was tested. The variation of Pd membrane phase and morphology was analyzed and observed by XPS and SEM. The cause and the mechanism of the variation were discussed. The results show that the molecule CO2 will dissociate to C=O, C–O and O on Pd membrane surface. The adsorptive capacity of C–O and O increases and that of C=O decreases with increasing of the temperature. PdO and micropores can be detected apparently when the poison temperature reaches 500 oC, and C–O will be adsorbed on Pd membrane surface firmly. After hydrogenization, the PdO, C–O and free O on the Pd surface vanish while C=O reappear. After the Pd membrane is poisoned by CO2, the hydrogen isotope permeation capacity of Pd membrane decreases because the atom O and C–O occupy H site and react with atom H easily
2011, 40(11):1990-1993.
Abstract:
Nano TiC particles dispersion strengthened ultra fine grained (UFG) W-TiC composites were fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). The microstructure and the room temperature mechanical properties of the W-TiC composites were studied. The results show that the well-combined and highly-densified (nearly 98.6%) UFG W-TiC composites can be obtained by SPS at 1700 oC for 1 min. The addition of the nano TiC can refine the grains of W, and accelerate its densification. The grain size, relative density, bending strength and the Vicker hardness HV0.2 of the UFG W-TiC composites are 0.5 μm, 98.6%, 1262 MPa and 6.45 GPa, respectively when the content of TiC is 0.7wt%.
Nano TiC particles dispersion strengthened ultra fine grained (UFG) W-TiC composites were fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). The microstructure and the room temperature mechanical properties of the W-TiC composites were studied. The results show that the well-combined and highly-densified (nearly 98.6%) UFG W-TiC composites can be obtained by SPS at 1700 oC for 1 min. The addition of the nano TiC can refine the grains of W, and accelerate its densification. The grain size, relative density, bending strength and the Vicker hardness HV0.2 of the UFG W-TiC composites are 0.5 μm, 98.6%, 1262 MPa and 6.45 GPa, respectively when the content of TiC is 0.7wt%.
2011, 40(11):1994-1997.
Abstract:
Thermomechanical treatments including hot extrusion, heat treatment and cold drawing were used to prepare Ag-15Cu in situ filamentary composites. The obtained composites can achieve a strength of 996 MPa and keep a conductivity of 62%IACS. Homogenization treatment and low temperature aging can effectively improve the strengthening potential of the material, while low temperature heat treatment of several times during drawing can greatly improve the conductivity and there is no loss of strength even at high strain. The influencing mechanism of heat treatments on the microstructure and properties were discussed
Thermomechanical treatments including hot extrusion, heat treatment and cold drawing were used to prepare Ag-15Cu in situ filamentary composites. The obtained composites can achieve a strength of 996 MPa and keep a conductivity of 62%IACS. Homogenization treatment and low temperature aging can effectively improve the strengthening potential of the material, while low temperature heat treatment of several times during drawing can greatly improve the conductivity and there is no loss of strength even at high strain. The influencing mechanism of heat treatments on the microstructure and properties were discussed
2011, 40(11):1998-2001.
Abstract:
effects of annealing temperatures (Ta) on microstructure and tensile behavior of Ti-50.8Ni-0.3Cr (at%) low-temperature superelastic alloy were investigated by optical microscopy and tensile tests. The results show that, the microstructure of the as-received alloy is fibriform, and the recovery and the recrystallization occur in the alloy during annealing. When Ta =350-500 oC, the alloy is at the recovery stage, and the microstructure is fibriform. When Ta =550-590 oC, the alloy is at the recrystallization stage, the microstructure turns to the unstrained equiaxed grains, and the recrystallization temperature of the alloy is about 570 oC. when Ta =600-800 oC, the alloy is at the grain growth stage, the microstructure shows larger and asymmetrical grains. Ta also strongly influences the tensile behavior of the alloy at low temperature (8 oC). With increasing of Ta, the critical stress of the stress-induced martensitic transformation declines at first and then rises; the work hardening ability and the tensile strength of the alloy annealed at 350-500 oC are higher than those of the alloy annealed at 550-700 oC, but the elongation of the latter is significantly larger than that of the former. When Ta >650 oC, the elongation of the alloy decreases due to the grain growth.
effects of annealing temperatures (Ta) on microstructure and tensile behavior of Ti-50.8Ni-0.3Cr (at%) low-temperature superelastic alloy were investigated by optical microscopy and tensile tests. The results show that, the microstructure of the as-received alloy is fibriform, and the recovery and the recrystallization occur in the alloy during annealing. When Ta =350-500 oC, the alloy is at the recovery stage, and the microstructure is fibriform. When Ta =550-590 oC, the alloy is at the recrystallization stage, the microstructure turns to the unstrained equiaxed grains, and the recrystallization temperature of the alloy is about 570 oC. when Ta =600-800 oC, the alloy is at the grain growth stage, the microstructure shows larger and asymmetrical grains. Ta also strongly influences the tensile behavior of the alloy at low temperature (8 oC). With increasing of Ta, the critical stress of the stress-induced martensitic transformation declines at first and then rises; the work hardening ability and the tensile strength of the alloy annealed at 350-500 oC are higher than those of the alloy annealed at 550-700 oC, but the elongation of the latter is significantly larger than that of the former. When Ta >650 oC, the elongation of the alloy decreases due to the grain growth.
2011, 40(11):2002-2005.
Abstract:
By means of split Hopkinson bar, the dynamic compression and dynamic shear tests on TC6 titanium alloy with different microstructures were carried out under the condition of high strain-rate loading; the specimens are cylindrical and hat-shaped, respectively. The adiabatic shearing sensitivities of the three kinds of typical microstructures of TC6 titanium alloy at different stress states were studied by mechanical response and micro-analysis. Results show that at the stress state of uniaxial compression, the descending order for the adiabatic shearing sensitivities of these typical microstructures are basketwave, equiaxed and duplex. And at the stress state of compression-shearing combination, their descending order is equiaxed, duplex and basketwave. The difference in the adiabatic shearing sensitivity is substantively the embodiment of plastic deforming ability of different microstructures at different stress states and spreading ability of adiabatic shear band in different microstructures.
By means of split Hopkinson bar, the dynamic compression and dynamic shear tests on TC6 titanium alloy with different microstructures were carried out under the condition of high strain-rate loading; the specimens are cylindrical and hat-shaped, respectively. The adiabatic shearing sensitivities of the three kinds of typical microstructures of TC6 titanium alloy at different stress states were studied by mechanical response and micro-analysis. Results show that at the stress state of uniaxial compression, the descending order for the adiabatic shearing sensitivities of these typical microstructures are basketwave, equiaxed and duplex. And at the stress state of compression-shearing combination, their descending order is equiaxed, duplex and basketwave. The difference in the adiabatic shearing sensitivity is substantively the embodiment of plastic deforming ability of different microstructures at different stress states and spreading ability of adiabatic shear band in different microstructures.
2011, 40(11):2006-2009.
Abstract:
A method combining optical metallograph with rotating orientation X-ray diffraction was applied for the measurement and evaluation of orientation for molybdenum-niobium alloy single crystal quickly and accurately. The diffraction angle of (111) orientation plane measured by this method almost accords with the calculated value. The disorientation angles of the samples are 0.73 o and 0.91o, respectively, which are consistent with the results measured by EBSD. The degree of scatter in the preferred orientation is about 1o
A method combining optical metallograph with rotating orientation X-ray diffraction was applied for the measurement and evaluation of orientation for molybdenum-niobium alloy single crystal quickly and accurately. The diffraction angle of (111) orientation plane measured by this method almost accords with the calculated value. The disorientation angles of the samples are 0.73 o and 0.91o, respectively, which are consistent with the results measured by EBSD. The degree of scatter in the preferred orientation is about 1o
2011, 40(11):2010-2013.
Abstract:
The p-t curves of deuterium and tritium absorption by uranium were investigated at 150-300 oC by the reaction rate analysis in a constant volume system. The results show that the rate of tritium absorption is equivalent to the rate of deuterium absorption at the same temperature. However, the rate of tritium (deuterium) absorption is decreased when the tritium (deuterium) absorption temperature is increased due to the effect of contrary reaction namely desorption of uranium tritide (deuteride). The rate constants of deuterium and tritium absorption at different temperatures are determined and the activation energy value obtained by this analysis is (–42.8±0.3) and (–43.2±1.2) kJ·mol-1, respectively. Therefore, there are not remarkable kinetic isotope effects for deuterium and tritium absorption by uranium.
The p-t curves of deuterium and tritium absorption by uranium were investigated at 150-300 oC by the reaction rate analysis in a constant volume system. The results show that the rate of tritium absorption is equivalent to the rate of deuterium absorption at the same temperature. However, the rate of tritium (deuterium) absorption is decreased when the tritium (deuterium) absorption temperature is increased due to the effect of contrary reaction namely desorption of uranium tritide (deuteride). The rate constants of deuterium and tritium absorption at different temperatures are determined and the activation energy value obtained by this analysis is (–42.8±0.3) and (–43.2±1.2) kJ·mol-1, respectively. Therefore, there are not remarkable kinetic isotope effects for deuterium and tritium absorption by uranium.
2011, 40(11):2014-2017.
Abstract:
The direct electro-deoxidation process of solid titanium dioxide was investigated in molten calcium chloride. This study focused on cathodic reactions of the electrolytic process. Products of low-voltage electrolysis were characterized by XRD. The results indicate that titanium dioxide cathode is reduced, although calcium does not exist in molten salt. The current-time plots of the constant voltage electrolysis using different cathodes demonstrate that direct electrochemical reduction of titanium dioxide is the primary reaction in cathodes; at the same time, faint calcium thermal reduction also exists.
The direct electro-deoxidation process of solid titanium dioxide was investigated in molten calcium chloride. This study focused on cathodic reactions of the electrolytic process. Products of low-voltage electrolysis were characterized by XRD. The results indicate that titanium dioxide cathode is reduced, although calcium does not exist in molten salt. The current-time plots of the constant voltage electrolysis using different cathodes demonstrate that direct electrochemical reduction of titanium dioxide is the primary reaction in cathodes; at the same time, faint calcium thermal reduction also exists.
2011, 40(11):2018-2021.
Abstract:
Potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS) techniques were employed to investigate the corrosion electrochemical behavior of the different faces of AZ61 magnesium alloy rolled sheets in simulated sea water. The surface morphology of the level, the side and the cross section of the corroded rolled sheet was observed using scanning electron microscopy (SEM). Results show that the major corrosion form of the different faces is pitting for the rolled sheet in simulated sea water. The corrosion tendency of the three faces of the rolled sheet is level
Potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS) techniques were employed to investigate the corrosion electrochemical behavior of the different faces of AZ61 magnesium alloy rolled sheets in simulated sea water. The surface morphology of the level, the side and the cross section of the corroded rolled sheet was observed using scanning electron microscopy (SEM). Results show that the major corrosion form of the different faces is pitting for the rolled sheet in simulated sea water. The corrosion tendency of the three faces of the rolled sheet is level
2011, 40(11):2022-2025.
Abstract:
Based on the macro characterization of micro-damage, macro damage variables of ductile metal in deformation process were characterized by various test methods. Six samples under different true strains were prepared by pre-tension deformation. And based on the result of compression test of different pre-deformed samples with micro compression tester (MCT-W501), ductile damage of metal was characterized by normalization indices, such as hardness, elastic modulus, toughness indicator and resistivity. The changing rules and physical meaning of the above damage variables were discussed. The research shows that the integration of the above damage variables and equivalent damage curve should be applied in order to reflect and to explain the real process of damage of ductile metal
Based on the macro characterization of micro-damage, macro damage variables of ductile metal in deformation process were characterized by various test methods. Six samples under different true strains were prepared by pre-tension deformation. And based on the result of compression test of different pre-deformed samples with micro compression tester (MCT-W501), ductile damage of metal was characterized by normalization indices, such as hardness, elastic modulus, toughness indicator and resistivity. The changing rules and physical meaning of the above damage variables were discussed. The research shows that the integration of the above damage variables and equivalent damage curve should be applied in order to reflect and to explain the real process of damage of ductile metal
2011, 40(11):2026-2029.
Abstract:
Dissimilar materials of TiNi shape memory alloy (SMA) and stainless steel of 0.2 mm thickness were butt welded by micro impulse laser and the microstructure characteristics of the weld joint were studied. The results show that good joining between TiNi SMA and stainless steel can be realized with pure Ni wire as filler material and micro impulse laser as welding heat source. The microstructures of weld center are fine equiaxed crystals and the main elements in weld seam are Ti, Ni and Fe. In weld seam, the content of Ti is similar to that of stainless steel base metal, while Ni is a little more than that of TiNi SMA base metal and much more than that of stainless steel base metal. There is little Fe element in TiNi SMA base metal. There is an obvious interfacial zone of about 10-20 μm width between TiNi SMA base metal and the weld, and there are Fe and Cr elements in the interfacial zone, which diffuse from stainless steel base metal. The width of the interfacial zone between stainless steel base metal and the weld is small and the interface is a line
Dissimilar materials of TiNi shape memory alloy (SMA) and stainless steel of 0.2 mm thickness were butt welded by micro impulse laser and the microstructure characteristics of the weld joint were studied. The results show that good joining between TiNi SMA and stainless steel can be realized with pure Ni wire as filler material and micro impulse laser as welding heat source. The microstructures of weld center are fine equiaxed crystals and the main elements in weld seam are Ti, Ni and Fe. In weld seam, the content of Ti is similar to that of stainless steel base metal, while Ni is a little more than that of TiNi SMA base metal and much more than that of stainless steel base metal. There is little Fe element in TiNi SMA base metal. There is an obvious interfacial zone of about 10-20 μm width between TiNi SMA base metal and the weld, and there are Fe and Cr elements in the interfacial zone, which diffuse from stainless steel base metal. The width of the interfacial zone between stainless steel base metal and the weld is small and the interface is a line
2011, 40(11):2030-2032.
Abstract:
InGaN quantum dots were grown on sapphire substrate by radio-frequency plasma-excited molecular beam epitaxy (RF-MBE). The effects of InN nuclear layer on the structural and optical characteristics of InGaN quantum dots were studied. In-situ reflection high energy electron diffraction (RHEED) was used to analyze the growth of the InGaN dots structures. Atomic force microscope (AFM) and photoluminescence (PL) were used to characterize the structure and optical properties of the InGaN quantum dots. The results show that the InGaN quantum dots grown on the InN nuclear layer can get higher density and better quality compared with that grown directly on GaN layer. The sizes of InGaN quantum dots grown on the InN nuclear layer are more uniform, about 35-45 nm and the density can reach 3.2 × 1010/cm2. The PL intensity of the InGaN quantum dots grown on the InN nuclear layer is twice as high as that of the InGaN quantum dots grown directly on GaN layer. The FWHM of the quantum dots PL peak is about 10 nm
InGaN quantum dots were grown on sapphire substrate by radio-frequency plasma-excited molecular beam epitaxy (RF-MBE). The effects of InN nuclear layer on the structural and optical characteristics of InGaN quantum dots were studied. In-situ reflection high energy electron diffraction (RHEED) was used to analyze the growth of the InGaN dots structures. Atomic force microscope (AFM) and photoluminescence (PL) were used to characterize the structure and optical properties of the InGaN quantum dots. The results show that the InGaN quantum dots grown on the InN nuclear layer can get higher density and better quality compared with that grown directly on GaN layer. The sizes of InGaN quantum dots grown on the InN nuclear layer are more uniform, about 35-45 nm and the density can reach 3.2 × 1010/cm2. The PL intensity of the InGaN quantum dots grown on the InN nuclear layer is twice as high as that of the InGaN quantum dots grown directly on GaN layer. The FWHM of the quantum dots PL peak is about 10 nm
2011, 40(11):2033-2037.
Abstract:
Spherical tungsten powder was prepared by radio frequency (RF) plasma with irregular tungsten powder as starting material. The effect of feeding rate and particle size on the spheroidization efficiency was studied. The phase composition, morphologies and particle size distributions of the powder before and after spheroidization were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser micron sizer (LMS). The results show that the spherical tungsten powder can be obtained from irregular powder with particle size of 5.5-26.5 μm after RF plasma spheroidization. The powder presents smooth surface and good dispersity, and the spheroidization efficiency is almost 100%. The particle size of tungsten powder is increased slightly after plasma treatment. The spheroidization efficiency of the sample decreases gradually with increasing of the feeding rate. The loose density and powder flowability of tungsten powder are enhanced greatly after RF plasma processing. The loose density is raised from 6.80 g/cm3 to 11.5 g/cm3 and the powder flowability is improved from 14.12 s/50 g to 6.95 s/50 g
Spherical tungsten powder was prepared by radio frequency (RF) plasma with irregular tungsten powder as starting material. The effect of feeding rate and particle size on the spheroidization efficiency was studied. The phase composition, morphologies and particle size distributions of the powder before and after spheroidization were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser micron sizer (LMS). The results show that the spherical tungsten powder can be obtained from irregular powder with particle size of 5.5-26.5 μm after RF plasma spheroidization. The powder presents smooth surface and good dispersity, and the spheroidization efficiency is almost 100%. The particle size of tungsten powder is increased slightly after plasma treatment. The spheroidization efficiency of the sample decreases gradually with increasing of the feeding rate. The loose density and powder flowability of tungsten powder are enhanced greatly after RF plasma processing. The loose density is raised from 6.80 g/cm3 to 11.5 g/cm3 and the powder flowability is improved from 14.12 s/50 g to 6.95 s/50 g
2011, 40(11):2038-2041.
Abstract:
The effect of the micro-alloying elements (C, B, Zr), casting system and aging treatment on microstructure and mechanical properties of Ni based superalloy GMR235 was studied. The equilibrium phase diagram of the alloy was calculated by Thermo-Calc software. The results show that equilibrium phases contain γ, γ’, M6C, MC, M23C6 carbides and M3B2. Proper carbon addition can improve the rupture life of the alloy, keep its plasticity and increase the high temperature tensile properties. The addition of micro-alloying elements B and Zr can improve the high temperature stress rupture properties and plastic properties of the alloy, restraining the precipitation of the carbide and refining carbide particles. The optimum properties can be obtained when the mould temperature is 800 oC and tapping temperature is 1420 oC. Rupture life is significantly increased after 5 h aging with good plastic properties like as-cast alloys. g￠ coarsens as the aging time gets longer, decreasing the strength of the alloy at high temperature
The effect of the micro-alloying elements (C, B, Zr), casting system and aging treatment on microstructure and mechanical properties of Ni based superalloy GMR235 was studied. The equilibrium phase diagram of the alloy was calculated by Thermo-Calc software. The results show that equilibrium phases contain γ, γ’, M6C, MC, M23C6 carbides and M3B2. Proper carbon addition can improve the rupture life of the alloy, keep its plasticity and increase the high temperature tensile properties. The addition of micro-alloying elements B and Zr can improve the high temperature stress rupture properties and plastic properties of the alloy, restraining the precipitation of the carbide and refining carbide particles. The optimum properties can be obtained when the mould temperature is 800 oC and tapping temperature is 1420 oC. Rupture life is significantly increased after 5 h aging with good plastic properties like as-cast alloys. g￠ coarsens as the aging time gets longer, decreasing the strength of the alloy at high temperature
2011, 40(11):2043-2046.
Abstract:
In the CaCl2 molten salt, TiFe alloy was prepared by electroanalysis using titanium concentrate as the cathode. XRD and SEM analyses of products were performed. The electrolytic products at different temperatures were compared. Results show that the temperature has significant effects on diffused alloying process, and the phases and structures of electrolytic products are different. At 850 oC, the final electrolytic product is the TiFe2 and Ti discrete ball-type structure with the particle size of 1 μm, while at 900 oC the final product is the TiFe space net structure with the particle size of 3 μm
In the CaCl2 molten salt, TiFe alloy was prepared by electroanalysis using titanium concentrate as the cathode. XRD and SEM analyses of products were performed. The electrolytic products at different temperatures were compared. Results show that the temperature has significant effects on diffused alloying process, and the phases and structures of electrolytic products are different. At 850 oC, the final electrolytic product is the TiFe2 and Ti discrete ball-type structure with the particle size of 1 μm, while at 900 oC the final product is the TiFe space net structure with the particle size of 3 μm
2011, 40(11):2047-2050.
Abstract:
By using monotonic tension and fully-reversed tension-compression loading with strain control (R = emin/emax= –1), the tensile properties and low cycle fatigue (LCF) behavior of NZ2 alloy plate were studied with different hot-rolling temperatures (650, 700 and 800 oC), different orientation (rectangular and transverse) and different testing temperatures (room temperature and 375 oC). Results indicate that NZ2 alloy plates with lower hot-rolling temperature (650 oC) have better comprehensive mechanical properties by analyzing the microstructure, mechanical properties and the low cycle fatigue lifetime curves
By using monotonic tension and fully-reversed tension-compression loading with strain control (R = emin/emax= –1), the tensile properties and low cycle fatigue (LCF) behavior of NZ2 alloy plate were studied with different hot-rolling temperatures (650, 700 and 800 oC), different orientation (rectangular and transverse) and different testing temperatures (room temperature and 375 oC). Results indicate that NZ2 alloy plates with lower hot-rolling temperature (650 oC) have better comprehensive mechanical properties by analyzing the microstructure, mechanical properties and the low cycle fatigue lifetime curves
2011, 40(11):2051-2054.
Abstract:
Hexagonal WO3 nanorods and orthorhombic WO3 nanoparticles were prepared by a simple hydrothermal method with Na2WO4·2H2O and hydrochloric acid as raw materials, and then WO3 was prepared into gas sensor by a screen printing method. The gas sensitivity of the sensor was investigated in the H2 concentration range from 5 to 100 μL/L at 200, 250, 300 and 350 oC. The results show that the sensitivity, stability and response-restoring characteristics of the H2 gas sensors are all excellent. When n(Na2WO4·2H2O):n(HCl) = 1:2, the sensitivity and stability of the product are the highest. And the sensitivity of the H2 gas sensor gradually ascends as the temperature and the H2 concentration are increased.
Hexagonal WO3 nanorods and orthorhombic WO3 nanoparticles were prepared by a simple hydrothermal method with Na2WO4·2H2O and hydrochloric acid as raw materials, and then WO3 was prepared into gas sensor by a screen printing method. The gas sensitivity of the sensor was investigated in the H2 concentration range from 5 to 100 μL/L at 200, 250, 300 and 350 oC. The results show that the sensitivity, stability and response-restoring characteristics of the H2 gas sensors are all excellent. When n(Na2WO4·2H2O):n(HCl) = 1:2, the sensitivity and stability of the product are the highest. And the sensitivity of the H2 gas sensor gradually ascends as the temperature and the H2 concentration are increased.
2011, 40(11):2055-2059.
Abstract:
Gold nanoparticles were prepared in W/O microemulsions of AOT/heptane/HAuCl4·3H2O system using N2H4·H2O as the reducing regent. These particles were characterized by UV-vis spectrum, TEM and FT-IR. The influences of the molar ratio of water to surfactant (ω=nH2O/nAOT) and the concentration of tetrachloroauric acid on the particle size were investigated. The results show that the average particle size of the prepared gold nanoparticles is from 4 nm to 12 nm, and their distribution is narrow. The relation between ω and average particles size is linearity. On the other hand, the influence of tetrachloroauric acid concentration is complex. As the concentration increases, the particle size decreases firstly and increases subsequently. FT-IR spectra indicate that the surfactant molecules are strongly absorbed on the surface of gold nanoparticles through a coordination bond between the gold atom and the sulfonic group of AOT molecules, so the surfactant AOT has a good protection effect.
Gold nanoparticles were prepared in W/O microemulsions of AOT/heptane/HAuCl4·3H2O system using N2H4·H2O as the reducing regent. These particles were characterized by UV-vis spectrum, TEM and FT-IR. The influences of the molar ratio of water to surfactant (ω=nH2O/nAOT) and the concentration of tetrachloroauric acid on the particle size were investigated. The results show that the average particle size of the prepared gold nanoparticles is from 4 nm to 12 nm, and their distribution is narrow. The relation between ω and average particles size is linearity. On the other hand, the influence of tetrachloroauric acid concentration is complex. As the concentration increases, the particle size decreases firstly and increases subsequently. FT-IR spectra indicate that the surfactant molecules are strongly absorbed on the surface of gold nanoparticles through a coordination bond between the gold atom and the sulfonic group of AOT molecules, so the surfactant AOT has a good protection effect.
2011, 40(11):2060-2064.
Abstract:
The research states of TiAl based composites at home and abroad were reviewed. The fabrication processes and mechanical properties of TiB2, Al2O3 etc. particulate reinforced TiAl matrix composites were discussed, as well as the selection of both the TiAl matrixes and the reinforcements. Furthermore, the advantages and disadvantages of the fabrication processes and the development direction were introduced.
The research states of TiAl based composites at home and abroad were reviewed. The fabrication processes and mechanical properties of TiB2, Al2O3 etc. particulate reinforced TiAl matrix composites were discussed, as well as the selection of both the TiAl matrixes and the reinforcements. Furthermore, the advantages and disadvantages of the fabrication processes and the development direction were introduced.
2011, 40(11):2065-2069.
Abstract:
The acid decomposition-extraction-spectrophotometric method of determining the rhenium concentration in molybdenum ores and flue dust was introduced. The conditions such as dissolution methods, extraction, absorption curve and determination were investigated systematically. The optimal condition of rhenium measurement was obtained based on a series of tests. The concentration of rhenium in different molybdenum ores and flue dust was determined by the proposed method; the relative standard deviation (RSD) of the method is below 3.5 %. Compared with ICP-AES standard addition method and alkaline fusion-extraction spectrophotometric method, the method gets satisfying results
The acid decomposition-extraction-spectrophotometric method of determining the rhenium concentration in molybdenum ores and flue dust was introduced. The conditions such as dissolution methods, extraction, absorption curve and determination were investigated systematically. The optimal condition of rhenium measurement was obtained based on a series of tests. The concentration of rhenium in different molybdenum ores and flue dust was determined by the proposed method; the relative standard deviation (RSD) of the method is below 3.5 %. Compared with ICP-AES standard addition method and alkaline fusion-extraction spectrophotometric method, the method gets satisfying results
2011, 40(11):19101915.
Abstract:
TiV1.1Mn0.9Ni0.5-ZrCr2 composite electrode alloy was prepared by two-step re-melting. Results of XRD, EDS, ICP and EIS analyses show that the composite alloy is of two-phase structure which is the same as that of the matrix alloy, whereas the characteristic parameters of the two phases in the composite alloy and the thermodynamic characteristics of the alloy electrode change a lot. Synergetic effect appears distinctly during the composite process of the compositive alloys. The maximum discharge capacity of the composite alloy electrode reaches to 457.2 mAh/g. The dynamic characteristics such as the cyclic durability, the charge retention and high-rate discharging are notably improved. The high-rate dischargeability is controlled by both the charge-transfer reaction of hydrogen at the electrode/electrolyte interface and the hydrogen diffusion in the bulk of the alloy at discharge current density of 1000 mA/g
TiV1.1Mn0.9Ni0.5-ZrCr2 composite electrode alloy was prepared by two-step re-melting. Results of XRD, EDS, ICP and EIS analyses show that the composite alloy is of two-phase structure which is the same as that of the matrix alloy, whereas the characteristic parameters of the two phases in the composite alloy and the thermodynamic characteristics of the alloy electrode change a lot. Synergetic effect appears distinctly during the composite process of the compositive alloys. The maximum discharge capacity of the composite alloy electrode reaches to 457.2 mAh/g. The dynamic characteristics such as the cyclic durability, the charge retention and high-rate discharging are notably improved. The high-rate dischargeability is controlled by both the charge-transfer reaction of hydrogen at the electrode/electrolyte interface and the hydrogen diffusion in the bulk of the alloy at discharge current density of 1000 mA/g
