Volume 38,Issue 11,2009 Table of Contents
2009, 38(11).
Abstract:
Nanocrystal blue luminescent material GdVO4 was synthesized by a citrate-gel (CG) method. Through fluorescence spectra, XRD and SEM, the author made a comprehensive analysis of the crystal structure, particle size, morphology and luminescence properties of Yb-doped GdVO4:Tm. The results show that the particle size of Yb-doped GdVO4:Tm is about 80 nm. Excited by 260~310 nm ultraviolet radiation, the Yb-doped GdVO4:Tm can emits bright blue fluorescence, and has the optimal properties when Yb3+ concentration at 1 mol%
Nanocrystal blue luminescent material GdVO4 was synthesized by a citrate-gel (CG) method. Through fluorescence spectra, XRD and SEM, the author made a comprehensive analysis of the crystal structure, particle size, morphology and luminescence properties of Yb-doped GdVO4:Tm. The results show that the particle size of Yb-doped GdVO4:Tm is about 80 nm. Excited by 260~310 nm ultraviolet radiation, the Yb-doped GdVO4:Tm can emits bright blue fluorescence, and has the optimal properties when Yb3+ concentration at 1 mol%
2009, 38(11):1881-1885.
Abstract:
Ag-MoS2 composite brushes were fabricated by means of powder metallurgy process. The composite was detected by the method of XRD after sintering, and the worn surface of the brush was analyzed by XPS after the wearing experiments with current. Results showed that the components of the composite didn’t change during sintering, but the surface components of it changed upon wearing and some matters such as MoO3 and MoO2 were produced. At the same time, Cu2O, CuO and Cu2S were detected due to the adhesion transfer of elemental Cu from the slipping ring to the brush surface and the reaction between the elemental Cu and the ambient air molecules. During electrical sliding wearing, the surface film can reduce the friction coefficient and be beneficial to the frictional performance of the material
Ag-MoS2 composite brushes were fabricated by means of powder metallurgy process. The composite was detected by the method of XRD after sintering, and the worn surface of the brush was analyzed by XPS after the wearing experiments with current. Results showed that the components of the composite didn’t change during sintering, but the surface components of it changed upon wearing and some matters such as MoO3 and MoO2 were produced. At the same time, Cu2O, CuO and Cu2S were detected due to the adhesion transfer of elemental Cu from the slipping ring to the brush surface and the reaction between the elemental Cu and the ambient air molecules. During electrical sliding wearing, the surface film can reduce the friction coefficient and be beneficial to the frictional performance of the material
3 Microstructure Selection Involving Nucleation in Directionally Solidified Nd-Fe-B Peritectic Alloys
2009, 38(11):1886-1889.
Abstract:
Directional solidification experiments were performed on Nd14Fe79B7 alloys to investigate microstructure formation related to nucleation. It was found that a small amount of α-Fe dendrites with equiaxed morphology existed in specimens grown at 200 and 500 μm/s. A banded structure showing alternate growth of α-Fe and Nd2Fe14B dendrites, was formed in the specimen at 500 μm/s. The formation of the equiaxed morphology microstructure or the banded structure is attributed to the phase nucleation ahead of the solidifying interface, since an undercooled zone corresponding to γ-Fe liquidus would appear ahead of the growing γ-Fe interface at the growth velocity of 200 and 500 μm/s. However, at growth velocity of 500 μm/s, only an undercooled zone corresponding to Nd2Fe14B liquidus would appear. These undercooled zones cause the nucleation of γ-Fe and Nd2Fe14B phases, resulting in the different microstructure patterns. The theoretical predictions are in good agreement with the experimental results.
Directional solidification experiments were performed on Nd14Fe79B7 alloys to investigate microstructure formation related to nucleation. It was found that a small amount of α-Fe dendrites with equiaxed morphology existed in specimens grown at 200 and 500 μm/s. A banded structure showing alternate growth of α-Fe and Nd2Fe14B dendrites, was formed in the specimen at 500 μm/s. The formation of the equiaxed morphology microstructure or the banded structure is attributed to the phase nucleation ahead of the solidifying interface, since an undercooled zone corresponding to γ-Fe liquidus would appear ahead of the growing γ-Fe interface at the growth velocity of 200 and 500 μm/s. However, at growth velocity of 500 μm/s, only an undercooled zone corresponding to Nd2Fe14B liquidus would appear. These undercooled zones cause the nucleation of γ-Fe and Nd2Fe14B phases, resulting in the different microstructure patterns. The theoretical predictions are in good agreement with the experimental results.
2009, 38(11):1890-1893.
Abstract:
The effect of Al concentration on the correlations of Ni3Al precipitates (γ′) in Ni-Al alloys was studied based on the microscopic phase-field kinetic model and the microelasticity theory. The simulation results show that γ′ precipitates are arranged along the [001] and [010] directions regarding alloys with all concentration, but there exists different correlations. For the alloy with lower Al concentration, γ′ precipitates are independent each other; for the alloy with medium Al concentration, there are mainly four types correlations among the γ′ precipitates: L-shaped pattern, doublet pattern, triplet pattern and quartet pattern; for the alloy with higher Al concentration, the correlation of γ′ precipitates is mainly doublet pattern
The effect of Al concentration on the correlations of Ni3Al precipitates (γ′) in Ni-Al alloys was studied based on the microscopic phase-field kinetic model and the microelasticity theory. The simulation results show that γ′ precipitates are arranged along the [001] and [010] directions regarding alloys with all concentration, but there exists different correlations. For the alloy with lower Al concentration, γ′ precipitates are independent each other; for the alloy with medium Al concentration, there are mainly four types correlations among the γ′ precipitates: L-shaped pattern, doublet pattern, triplet pattern and quartet pattern; for the alloy with higher Al concentration, the correlation of γ′ precipitates is mainly doublet pattern
2009, 38(11):1894-1898.
Abstract:
The 40%SiC/5%Gr/Al composites with various-sizes graphite addition were fabricated by squeeze casting technology, and their friction and wear properties were investigated. Results showed that after the addition of graphite the friction coefficient of composites decreased and the wear resistance increased by 170 to 340 times. In addition, wear resistance was improved with increasing of graphite particle size, which is attributed to the enhancement of integrity of lubrication tribo-layer composed of a complex mixture of iron oxides, graphite as well as fractured SiC particles and some fine particles containing aluminum.
The 40%SiC/5%Gr/Al composites with various-sizes graphite addition were fabricated by squeeze casting technology, and their friction and wear properties were investigated. Results showed that after the addition of graphite the friction coefficient of composites decreased and the wear resistance increased by 170 to 340 times. In addition, wear resistance was improved with increasing of graphite particle size, which is attributed to the enhancement of integrity of lubrication tribo-layer composed of a complex mixture of iron oxides, graphite as well as fractured SiC particles and some fine particles containing aluminum.
2009, 38(11):1899-1903.
Abstract:
By the plasma spraying technology, nitrogen silicon zirconium-hydroxyl apatite (ZrSiN-HA) compound coating was prepared on the surface of pure titanium substrate and implanted with the mandible of the experimental animal. The appearance morphology of the compound coating was observed and analyzed by the scanning electron microscope. The bone binding forces of four groups of samples, e.g. ZrSiN-HA, ZrSiN, HA and pure titanium were examined and compared by the electronic universal testing machine; the appearance morphologies of the fracture regions of each group were observed. The corrosion resistance of the four groups of coatings was compared and examined on the electrochemistry corrosion testing system. The results indicate that the implant surface sprayed with the ZrSiN-HA is more compact than that sprayed with the HA. The crystallization is obvious. Compared with the other coatings, the ZrSiN-HA coating has the highest bone binding force, and its anti-corrosive performance is the best. The ZrSiN-HA coating application is beneficial to the long-term retention of implant and can be applied in the human body
By the plasma spraying technology, nitrogen silicon zirconium-hydroxyl apatite (ZrSiN-HA) compound coating was prepared on the surface of pure titanium substrate and implanted with the mandible of the experimental animal. The appearance morphology of the compound coating was observed and analyzed by the scanning electron microscope. The bone binding forces of four groups of samples, e.g. ZrSiN-HA, ZrSiN, HA and pure titanium were examined and compared by the electronic universal testing machine; the appearance morphologies of the fracture regions of each group were observed. The corrosion resistance of the four groups of coatings was compared and examined on the electrochemistry corrosion testing system. The results indicate that the implant surface sprayed with the ZrSiN-HA is more compact than that sprayed with the HA. The crystallization is obvious. Compared with the other coatings, the ZrSiN-HA coating has the highest bone binding force, and its anti-corrosive performance is the best. The ZrSiN-HA coating application is beneficial to the long-term retention of implant and can be applied in the human body
2009, 38(11):1904-1909.
Abstract:
Based on the DEFORM-3D software, a finite element model considering macro-micro forming of rib-web component isothermal local loading has been established. The forming process of H-shaped component and the effects of loading mode and sequence, position of die partition, and process parameters on the filling of ribs and primary a-phase grain size have been investigated. The results show that the position of die partition has a significant effect on the filling of rib, the rib will be filled better and the distribution of primary a-phase grain size is more uniform when the die is partitioned along the rib. Comparing with only by local loading forming mode and through local loading combining with sizing forming, the deformation is more uniform and the difference of filling depths between ribs is smaller with better distribution of streamline. Enlarging the fillet radius between rib and web, the rib is filled well and the filling depth difference between transverse and longitudinal ribs increases. With the increase of loading speed, the filling depth of rib decreases, and the primary a-phase grain size decreases, but the distribution of primary a-phase grain size is more non-uniform. But the loading sequence has little effect on primary a-phase grain size
Based on the DEFORM-3D software, a finite element model considering macro-micro forming of rib-web component isothermal local loading has been established. The forming process of H-shaped component and the effects of loading mode and sequence, position of die partition, and process parameters on the filling of ribs and primary a-phase grain size have been investigated. The results show that the position of die partition has a significant effect on the filling of rib, the rib will be filled better and the distribution of primary a-phase grain size is more uniform when the die is partitioned along the rib. Comparing with only by local loading forming mode and through local loading combining with sizing forming, the deformation is more uniform and the difference of filling depths between ribs is smaller with better distribution of streamline. Enlarging the fillet radius between rib and web, the rib is filled well and the filling depth difference between transverse and longitudinal ribs increases. With the increase of loading speed, the filling depth of rib decreases, and the primary a-phase grain size decreases, but the distribution of primary a-phase grain size is more non-uniform. But the loading sequence has little effect on primary a-phase grain size
2009, 38(11):1910-1915.
Abstract:
The influence of equal channel angular pressing (ECAP) routes on the microstructure and properties of hcp commercial-purity titanium (CP-Ti) was investigated. Samples were successfully deformed at room temperature via three different processing routes: A, B, and C, using a die with an internal angle Φ of 120° and an outer curvature angle Ψ of 20°. After two passes, the microstructure and mechanical properties of as-pressed CP-Ti were studied. The results show that the ultimate strength and microhardness of CP-Ti billet were sharply enhanced after two ECAP passes by three ECAP routes at room temperature. But the ECAP route does not have significant effect on the strength and the microhardness of as-pressed CP-Ti. The microstructure developments occurred during the first pass, such as gain shape and deformed mechanism, vary with different routes during the second ECAP pass.
The influence of equal channel angular pressing (ECAP) routes on the microstructure and properties of hcp commercial-purity titanium (CP-Ti) was investigated. Samples were successfully deformed at room temperature via three different processing routes: A, B, and C, using a die with an internal angle Φ of 120° and an outer curvature angle Ψ of 20°. After two passes, the microstructure and mechanical properties of as-pressed CP-Ti were studied. The results show that the ultimate strength and microhardness of CP-Ti billet were sharply enhanced after two ECAP passes by three ECAP routes at room temperature. But the ECAP route does not have significant effect on the strength and the microhardness of as-pressed CP-Ti. The microstructure developments occurred during the first pass, such as gain shape and deformed mechanism, vary with different routes during the second ECAP pass.
2009, 38(11):1916-1919.
Abstract:
Differential scanning calorimetry (DSC) method and metallographic observation method have been adapted for the measurement of α＋β/β transformation temperatures of α titanium alloy TA7, α＋β titanium alloy TC4 and near β titanium alloy Ti-1023, and the coincidence has been discussed in the present paper. For the TA7 alloy, an obvious endothermic peak which covers a temperature range of about 60 ℃ occurred during α＋β/β transformation. The transformation temperature defined by the peak of first order derivative of the DSC curve was much near the temperature determined by the metallographic observation method. For the alloys TC4 and Ti-1023, on the other hand, only little baseline shifts which cover a temperature range of about 10~15 ℃ was observed during transformation. A better coincidence with the metallographic observation method was achieved for the alloys TC4 and Ti-1023 owing to the much narrow transformation temperature range.
Differential scanning calorimetry (DSC) method and metallographic observation method have been adapted for the measurement of α＋β/β transformation temperatures of α titanium alloy TA7, α＋β titanium alloy TC4 and near β titanium alloy Ti-1023, and the coincidence has been discussed in the present paper. For the TA7 alloy, an obvious endothermic peak which covers a temperature range of about 60 ℃ occurred during α＋β/β transformation. The transformation temperature defined by the peak of first order derivative of the DSC curve was much near the temperature determined by the metallographic observation method. For the alloys TC4 and Ti-1023, on the other hand, only little baseline shifts which cover a temperature range of about 10~15 ℃ was observed during transformation. A better coincidence with the metallographic observation method was achieved for the alloys TC4 and Ti-1023 owing to the much narrow transformation temperature range.
2009, 38(11):1920-1923.
Abstract:
The superplastic deformation behavior of titanium alloy TC11 has been investigated in the temperature range of 810~1050 ℃ at the strain rate of 0.001 s-1 by tensile tests at high temperature, and the microstructures of samples deformed have been observed and analysed by metallographic microscope and transmission electron microscope. The results showed that the titanium alloy TC11 would not exhibit superplasicity in the b phase field, but exhibit in the temperature range of 810~980 ℃ in the a+b phase field with an optimal deformation temperature of near 900 ℃ and maximum elongation of 595%. The intracrystalline deformation, interface sliding, dynamic recrystallization or diffusion creep take part in the superplastic deformation at 900 ℃, and the interface sliding appears at a/b phase interface. The relative content of a and b phases has a heavy effect on the superplasicity and the titanium alloy TC11 exhibits an optimal superplasicity when the content of primary a phase is about 70%.
The superplastic deformation behavior of titanium alloy TC11 has been investigated in the temperature range of 810~1050 ℃ at the strain rate of 0.001 s-1 by tensile tests at high temperature, and the microstructures of samples deformed have been observed and analysed by metallographic microscope and transmission electron microscope. The results showed that the titanium alloy TC11 would not exhibit superplasicity in the b phase field, but exhibit in the temperature range of 810~980 ℃ in the a+b phase field with an optimal deformation temperature of near 900 ℃ and maximum elongation of 595%. The intracrystalline deformation, interface sliding, dynamic recrystallization or diffusion creep take part in the superplastic deformation at 900 ℃, and the interface sliding appears at a/b phase interface. The relative content of a and b phases has a heavy effect on the superplasicity and the titanium alloy TC11 exhibits an optimal superplasicity when the content of primary a phase is about 70%.
2009, 38(11):1924-1928.
Abstract:
The effect of hydrogenation on the microstructure and properties of TC21 alloy by die forming and sintering using hydrogenated powder to produce titanium alloy was researched by means of the room-temperature die forming and sintering in a protection atmosphere. The results show that the TC21 titanium sintered body using hydrogenated powder with hydrogen content of 0.39 wt% by die forming and sintering has a thinner microstructure and higher density, compression strength and compressive yield strength than the others. With hydrogen content increasing, the sheet microstructure gets thinner and finer and the grain size becomes smaller and homogeneous with safe hydrogen content. As a conclusion, the hydrogen content of 0.39wt% is the best for the TC21 titanium alloy sintered body according to the density and mechanical property.
The effect of hydrogenation on the microstructure and properties of TC21 alloy by die forming and sintering using hydrogenated powder to produce titanium alloy was researched by means of the room-temperature die forming and sintering in a protection atmosphere. The results show that the TC21 titanium sintered body using hydrogenated powder with hydrogen content of 0.39 wt% by die forming and sintering has a thinner microstructure and higher density, compression strength and compressive yield strength than the others. With hydrogen content increasing, the sheet microstructure gets thinner and finer and the grain size becomes smaller and homogeneous with safe hydrogen content. As a conclusion, the hydrogen content of 0.39wt% is the best for the TC21 titanium alloy sintered body according to the density and mechanical property.
2009, 38(11):1929-1934.
Abstract:
A finite element modeling based on the actual microstructure is established to analyse the thermal cycling behavior of metal Al matrix composites (MMC). The distribution of Von Mises effective stress and principle stress is presented, and the results show that during the heating, the thermal stress is negative in matrix, but positive in particles; during the cooling, the thermal stress is positive in matrix, but negative in particles. Simultaneously, the principle stress s22 after three thermal cycles is calculated to be steady after the two cycles. The effect of volume fraction on the thermal cycles is analysed in the cell model, finding that the distribution of von Mises stress is more uniform than the previous model. Through comparison, it is shown that the composites with high volume particle fraction possess a higher dimensional stability
A finite element modeling based on the actual microstructure is established to analyse the thermal cycling behavior of metal Al matrix composites (MMC). The distribution of Von Mises effective stress and principle stress is presented, and the results show that during the heating, the thermal stress is negative in matrix, but positive in particles; during the cooling, the thermal stress is positive in matrix, but negative in particles. Simultaneously, the principle stress s22 after three thermal cycles is calculated to be steady after the two cycles. The effect of volume fraction on the thermal cycles is analysed in the cell model, finding that the distribution of von Mises stress is more uniform than the previous model. Through comparison, it is shown that the composites with high volume particle fraction possess a higher dimensional stability
2009, 38(11):1935-1939.
Abstract:
基于微观相场动力学模型，研究原子间相互作用能对Ni75AlxV25-x合金孕育期的影响。根据Khachaturyan所给的占位几率公式进一步得到了长程序参数的求值公式。结果表明，先析出相为DO22时，Ni-Al最近邻原子间作用能VNi-Al增大，L12相的孕育期缩短，DO22相的孕育期变化不明显；Ni-V最近邻原子间作用能VNi-V增大，L12相和DO22相的孕育期均缩短。先析出相为L12相时，VNi-Al增大，L12相和DO22相孕育期均缩短；VNi-V增大，L12相孕育期变化不明显，DO22相的孕育期缩短
基于微观相场动力学模型，研究原子间相互作用能对Ni75AlxV25-x合金孕育期的影响。根据Khachaturyan所给的占位几率公式进一步得到了长程序参数的求值公式。结果表明，先析出相为DO22时，Ni-Al最近邻原子间作用能VNi-Al增大，L12相的孕育期缩短，DO22相的孕育期变化不明显；Ni-V最近邻原子间作用能VNi-V增大，L12相和DO22相的孕育期均缩短。先析出相为L12相时，VNi-Al增大，L12相和DO22相孕育期均缩短；VNi-V增大，L12相孕育期变化不明显，DO22相的孕育期缩短
14 Thermodynamic Calculation of the Precipitation Reaction of MgZn Phase in Mg-6Zn-1Mn Magnesium Alloy
2009, 38(11):1940-1944.
Abstract:
Based on the Miedema model and the Toop model, the activities of Mg and Zn in the Mg-6Zn-1Mn alloy were calculated by a thermodynamic calculation model for predicting the precipitation behaviors of the intermetallic compounds in ternary metallic alloys. The relationship between the temperatures and the Gibbs free energy change during the precipitation reaction of the primary strengthening phase MgZn was deduced. According to the calculation, the precipitating temperature of MgZn phase is 580 K, in good agreement with the homogenizing temperature of this alloy and approved by our thermal analysis experimental results
Based on the Miedema model and the Toop model, the activities of Mg and Zn in the Mg-6Zn-1Mn alloy were calculated by a thermodynamic calculation model for predicting the precipitation behaviors of the intermetallic compounds in ternary metallic alloys. The relationship between the temperatures and the Gibbs free energy change during the precipitation reaction of the primary strengthening phase MgZn was deduced. According to the calculation, the precipitating temperature of MgZn phase is 580 K, in good agreement with the homogenizing temperature of this alloy and approved by our thermal analysis experimental results
2009, 38(11):1945-1949.
Abstract:
Microstructure and recrystallization behaviour were studied for a sort of Al-Zn-Mg-Cu-Sc alloy in different conditions by means of OM and SEM with EDS and TEM, as well as using topology for grain and boundary. The results show that the recrystallization temperature can be obviously increased with addition of 0.15%Sc to base alloy. The course of recrystallization is speeded up with increasing the velocity of strain at a constant total distortion. Under the condition of dissymmetrical deformation, there are some shear bands or cracks in the region, which can be looked as an “empty zone” without any solute or solvent. It is found that the deformation boundary bending leads to recrystallization nucleation, and the subgrain rotation coalescence leads to growth. The “secondary crystal”is accomplished by the assembly of solute or solvent atoms entering the “empty zone” by diffusing, with a lot of vacancies and solute atoms segregating in the vacancies
Microstructure and recrystallization behaviour were studied for a sort of Al-Zn-Mg-Cu-Sc alloy in different conditions by means of OM and SEM with EDS and TEM, as well as using topology for grain and boundary. The results show that the recrystallization temperature can be obviously increased with addition of 0.15%Sc to base alloy. The course of recrystallization is speeded up with increasing the velocity of strain at a constant total distortion. Under the condition of dissymmetrical deformation, there are some shear bands or cracks in the region, which can be looked as an “empty zone” without any solute or solvent. It is found that the deformation boundary bending leads to recrystallization nucleation, and the subgrain rotation coalescence leads to growth. The “secondary crystal”is accomplished by the assembly of solute or solvent atoms entering the “empty zone” by diffusing, with a lot of vacancies and solute atoms segregating in the vacancies
2009, 38(11):1950-1954.
Abstract:
AZ31 magnesium alloy is used as a research object to explore whether the solid-solution, large strain deformation and post heat treatment can be used to prepare a high strength magnesium alloy. It is found that a yield strength of about 330 MPa can be got by the solid-solution and large strain deformation, and a yield strength of about 370 MPa can be got by the post appropriate aging due to aging strengthening. The plasticity can be enhanced by post recrystallization, keeping the strength of solid-solution state at the same time. Many twins and dislocations are found in the large strain deformation sample with a mean grain size of 1~3 μm. It can be concluded that the solid-solution, large strain deformation and post heat treatment technology is an a effective method to enhance the strength and ductility for aluminum alloys and magnesium alloys
AZ31 magnesium alloy is used as a research object to explore whether the solid-solution, large strain deformation and post heat treatment can be used to prepare a high strength magnesium alloy. It is found that a yield strength of about 330 MPa can be got by the solid-solution and large strain deformation, and a yield strength of about 370 MPa can be got by the post appropriate aging due to aging strengthening. The plasticity can be enhanced by post recrystallization, keeping the strength of solid-solution state at the same time. Many twins and dislocations are found in the large strain deformation sample with a mean grain size of 1~3 μm. It can be concluded that the solid-solution, large strain deformation and post heat treatment technology is an a effective method to enhance the strength and ductility for aluminum alloys and magnesium alloys
2009, 38(11):1955-1959.
Abstract:
The structure, morphology, hardness, breaking toughness, strengthening and toughening mechanism of MoSi2-Si3N4(p)/SiC(w) composites were investigated by means of XRD, SEM, Vichers hardness tester and electrical omnipotence material tester in this paper. It is shown that the SiC whiskers and Si3N4 particles have the coordinated strengthening and toughening effect on MoSi2, the bending strength and room temperature fracture toughness of MoSi2-20 vol% Si3N4(p)-20 vol%SiC(w) composite are 427 MPa and 10.4 MPa·m1/2, respectively, which is higher than that of MoSi2 strengthened and toughened by SiC whiskers or Si3N4 particles. The strengthening mechanism of MoSi2-Si3N4(p)/SiC(w) composites are the fine grains and dispersion strengthening, and the toughening mechanism are the fine grain toughening and the crack deflection and the micro bridge join toughening.
The structure, morphology, hardness, breaking toughness, strengthening and toughening mechanism of MoSi2-Si3N4(p)/SiC(w) composites were investigated by means of XRD, SEM, Vichers hardness tester and electrical omnipotence material tester in this paper. It is shown that the SiC whiskers and Si3N4 particles have the coordinated strengthening and toughening effect on MoSi2, the bending strength and room temperature fracture toughness of MoSi2-20 vol% Si3N4(p)-20 vol%SiC(w) composite are 427 MPa and 10.4 MPa·m1/2, respectively, which is higher than that of MoSi2 strengthened and toughened by SiC whiskers or Si3N4 particles. The strengthening mechanism of MoSi2-Si3N4(p)/SiC(w) composites are the fine grains and dispersion strengthening, and the toughening mechanism are the fine grain toughening and the crack deflection and the micro bridge join toughening.
2009, 38(11):1960-1964.
Abstract:
The influence of complex Cr, Yb and Zr alloying on the microstructures and fracture characteristics of Al-Zn-Mg-Cu alloy has been investigated and the mechanism of toughening by adding Cr, Yb and Zr was analyzed. The results show that the Al-Zn-Mg-Cu alloy containing Cr, Yb and Zr may form the spherical dispersoids containing the Cr, Yb and Zr homogeneously distributed in the Al matrix, which can strongly pin the dislocation and subgrain boundaries, retain the deformation-recovery Al matrix with low angle boundary in the alloy and inhibit the recrystallization of Al matrix. By complex Cr, Yb and Zr alloying to Al-Zn-Mg-Cu alloy tempered as T6, the fractographs consist of dimple-type transgranular cracking with minor intergranular cracking. Compared with the Al-Zn-Mg-Cu-Zr alloy, the intergranular fracture resistance increases obviously, the precipitates free zone is wider with discontinuous distribution on the grain boundaries for the precipitates
The influence of complex Cr, Yb and Zr alloying on the microstructures and fracture characteristics of Al-Zn-Mg-Cu alloy has been investigated and the mechanism of toughening by adding Cr, Yb and Zr was analyzed. The results show that the Al-Zn-Mg-Cu alloy containing Cr, Yb and Zr may form the spherical dispersoids containing the Cr, Yb and Zr homogeneously distributed in the Al matrix, which can strongly pin the dislocation and subgrain boundaries, retain the deformation-recovery Al matrix with low angle boundary in the alloy and inhibit the recrystallization of Al matrix. By complex Cr, Yb and Zr alloying to Al-Zn-Mg-Cu alloy tempered as T6, the fractographs consist of dimple-type transgranular cracking with minor intergranular cracking. Compared with the Al-Zn-Mg-Cu-Zr alloy, the intergranular fracture resistance increases obviously, the precipitates free zone is wider with discontinuous distribution on the grain boundaries for the precipitates
2009, 38(11):1965-1968.
Abstract:
In this paper, the magnetic properties and crystal structure of the PtCo alloys around the equiatomic composition have been studied. The PtxCo1-x (x=0.48,0.49,0.50,0.51) bulk samples are prepared by arc melting and heat treatment. The magnetic measurement results indicate that the increase of platinum content causes the decrease of remanence and the increase of coercivity. The XRD result indicates that the axial ratio c/a of the tetragonal structure decreases with increasing the content of platinum, which leads to an increase of the deviation from unity of the tetragonal structure. So that, the anisotropy field of the ordered phase is improved and the coercivity is increased.
In this paper, the magnetic properties and crystal structure of the PtCo alloys around the equiatomic composition have been studied. The PtxCo1-x (x=0.48,0.49,0.50,0.51) bulk samples are prepared by arc melting and heat treatment. The magnetic measurement results indicate that the increase of platinum content causes the decrease of remanence and the increase of coercivity. The XRD result indicates that the axial ratio c/a of the tetragonal structure decreases with increasing the content of platinum, which leads to an increase of the deviation from unity of the tetragonal structure. So that, the anisotropy field of the ordered phase is improved and the coercivity is increased.
2009, 38(11):1969-1973.
Abstract:
In the present paper, 3-D numerical simulations of electromagnetic stirring during vacuum arc remelting (VAR) were conducted by using the ANSYS software to study the distribution of remelting current, magnetic field and Lorentz force. The effects of coil on magnetic and Lorensz force were also discussed. The results show that the current flows during VAR from crucible wall to the electrode via the surface of the ingot melt pool，and the currents in the crucible base and the ingot base are almost zero. The magnetic field inducted by remelting current is axisymmetric and rounding, and the magnetic flux density along radial direction increases to a maximum value near the edge of the electrode and then decreases. The magnetic field in ingot inducted by coil is parallel to the symmetry axis and the magnetic flux density is nearly uniform. The Lorentz force of coil could circumrotate the ingot melt pool
In the present paper, 3-D numerical simulations of electromagnetic stirring during vacuum arc remelting (VAR) were conducted by using the ANSYS software to study the distribution of remelting current, magnetic field and Lorentz force. The effects of coil on magnetic and Lorensz force were also discussed. The results show that the current flows during VAR from crucible wall to the electrode via the surface of the ingot melt pool，and the currents in the crucible base and the ingot base are almost zero. The magnetic field inducted by remelting current is axisymmetric and rounding, and the magnetic flux density along radial direction increases to a maximum value near the edge of the electrode and then decreases. The magnetic field in ingot inducted by coil is parallel to the symmetry axis and the magnetic flux density is nearly uniform. The Lorentz force of coil could circumrotate the ingot melt pool
2009, 38(11):1974-1977.
Abstract:
A three-dimension finite element model (FEM) was used to analyze the effect of particles with different shapes, volume fractions and particle sizes on the mechanical properties of SiC particle reinforced aluminum-matrix composites. The results show that the particle shape has greater effect on the stress of particle, the strain of matrix and the ductility of composites than that of the particle size and volume fraction. There are serious stress concentration round the particle corner and strain concentration in the matrix adjacent to the particle corners along the load. The stress increases quickly, the ductility decreases and the elastic modulus increases with decreasing the particle corner degree. The stress decreases and the elastic modulus increases with increasing the volume fraction of SiC particles. The particle size has little effect on the stress and strain of the composites with small particle size
A three-dimension finite element model (FEM) was used to analyze the effect of particles with different shapes, volume fractions and particle sizes on the mechanical properties of SiC particle reinforced aluminum-matrix composites. The results show that the particle shape has greater effect on the stress of particle, the strain of matrix and the ductility of composites than that of the particle size and volume fraction. There are serious stress concentration round the particle corner and strain concentration in the matrix adjacent to the particle corners along the load. The stress increases quickly, the ductility decreases and the elastic modulus increases with decreasing the particle corner degree. The stress decreases and the elastic modulus increases with increasing the volume fraction of SiC particles. The particle size has little effect on the stress and strain of the composites with small particle size
2009, 38(11):1978-1982.
Abstract:
In order to use titanium in frictional pair with relative motion, titanium surfaces were modified by self-assembled method and the prepared samples were irradiated by ultraviolet radiation/ozone photochemical process. The characterization and tribological properties of samples were conducted by contact angle measuring meter, atomic force microscopy and microtribometer, and the hydroxylation of titanium surfaces by different methods was explored. The effects of load, sliding velocity and ultraviolet radiation on the tribological properties of samples were analyzed. The results show that the combining Piranha solution with ultraviolet radiation/ozone photochemical process can prove the effect of titanium surfaces hydroxylation. The titanium surface modified by FOTS SAMs is uniform and exhibits good hydrophobic and tribological properties. The friction coefficient between Si3N4 balls and sample surfaces modified by FOTS SAMs increases with load and sliding velocity increasing. The effect of modification treated by FOTS SAMs can be improved by an ultraviolet radiation/ozone photochemical process for 5 min. The durability of friction pairs is retained in the case of reduction of coefficient of friction for the modified titanium surfaces
In order to use titanium in frictional pair with relative motion, titanium surfaces were modified by self-assembled method and the prepared samples were irradiated by ultraviolet radiation/ozone photochemical process. The characterization and tribological properties of samples were conducted by contact angle measuring meter, atomic force microscopy and microtribometer, and the hydroxylation of titanium surfaces by different methods was explored. The effects of load, sliding velocity and ultraviolet radiation on the tribological properties of samples were analyzed. The results show that the combining Piranha solution with ultraviolet radiation/ozone photochemical process can prove the effect of titanium surfaces hydroxylation. The titanium surface modified by FOTS SAMs is uniform and exhibits good hydrophobic and tribological properties. The friction coefficient between Si3N4 balls and sample surfaces modified by FOTS SAMs increases with load and sliding velocity increasing. The effect of modification treated by FOTS SAMs can be improved by an ultraviolet radiation/ozone photochemical process for 5 min. The durability of friction pairs is retained in the case of reduction of coefficient of friction for the modified titanium surfaces
2009, 38(11):1983-1986.
Abstract:
High quality GaAs/GaAsSb superlattices were grown by molecular beam epitaxy (MBE) and the Sb/As exchange action was characterized by high resolution X-ray diffraction (HRXRD). The Sb desorption from the GaAs surface increases with the increase of substrate temperature, causing a net decrease in Sb composition. The Sb flux and the Sb soak time have no obvious effects on the Sb/As exchange. It is shown that the exchange action was restrained on the surface and the Sb diffusion in GaAs was limited
High quality GaAs/GaAsSb superlattices were grown by molecular beam epitaxy (MBE) and the Sb/As exchange action was characterized by high resolution X-ray diffraction (HRXRD). The Sb desorption from the GaAs surface increases with the increase of substrate temperature, causing a net decrease in Sb composition. The Sb flux and the Sb soak time have no obvious effects on the Sb/As exchange. It is shown that the exchange action was restrained on the surface and the Sb diffusion in GaAs was limited
2009, 38(11):1987-1991.
Abstract:
Cerium (Ce)-doped barium strontium titanate (Ba0.6Sr0.4TiO3, BST) films and undoped BST films have been prepared by an improved Sol-gel method. The surface structures have been studied by X-ray photoelectron spectroscopy (XPS). The result reveals that the surface structures are composed of perovskited structure and non-perovskited structure, and the Ce doping significantly reduces the non-perovskited structure. It is by scanning electron microscope and atomic force microscope shown that the Ce-doped BST films are smooth and compact without crack or shrinkage cavity, which are associated with the formation of the non-perovskited structure. The voltage-capacitance curves demonstrate that the Ce-doped BST films have significant improvement in dielectric properties with a tunability of more than 60.8% at 40 voltage, and a dielectric loss (tand) of 0.0265 at zero bias. The improved mechanism of Ce doping is discussed
Cerium (Ce)-doped barium strontium titanate (Ba0.6Sr0.4TiO3, BST) films and undoped BST films have been prepared by an improved Sol-gel method. The surface structures have been studied by X-ray photoelectron spectroscopy (XPS). The result reveals that the surface structures are composed of perovskited structure and non-perovskited structure, and the Ce doping significantly reduces the non-perovskited structure. It is by scanning electron microscope and atomic force microscope shown that the Ce-doped BST films are smooth and compact without crack or shrinkage cavity, which are associated with the formation of the non-perovskited structure. The voltage-capacitance curves demonstrate that the Ce-doped BST films have significant improvement in dielectric properties with a tunability of more than 60.8% at 40 voltage, and a dielectric loss (tand) of 0.0265 at zero bias. The improved mechanism of Ce doping is discussed
2009, 38(11):1992-1996.
Abstract:
Corrosion behaviors of bulk amorphous Fe41Co7Cr15Mo14C15B6Y2 alloy in 0.5, 1, 2, 4 mol/L HCl solutions were studied by potentiodynamic polarization experiments and electrochemical impedance spectroscopy (EIS). Moreover, the corrosion behaviors of amorphous alloy and stainless steel were compared in 1 mol/L HCl solution. The results of potentiodynamic polarization experiment show that the amorphous Fe41Co7Cr15Mo14C15B6Y2 alloy has excellent corrosion resistance in different concentration of HCl solutions and its anodic reaction has a passive character. With the concentration of the HCl solutions increasing, the corrosion resistance of the amorphous alloy decreases. The results of potentiodynamic polarization experiments in 1 mol/L HCl solution show that the corrosion potential of the amorphous alloy is higher and the corrosion current density is lower than those of stainless steel. EIS experimental results show that the Nyquist figures of amorphous alloy and stainless steel are both composed of one single semi-circle in the state of open circuit potential. But the amorphous alloy has a higher charge transfer reaction resistance than the stainless steel. This result is accord with that of potentiodynamic polarization. The present results demonstrate that the corrosion resistance of bulk amorphous Fe41Co7Cr15Mo14C15B6Y2 alloy is much better than stainless steel.
Corrosion behaviors of bulk amorphous Fe41Co7Cr15Mo14C15B6Y2 alloy in 0.5, 1, 2, 4 mol/L HCl solutions were studied by potentiodynamic polarization experiments and electrochemical impedance spectroscopy (EIS). Moreover, the corrosion behaviors of amorphous alloy and stainless steel were compared in 1 mol/L HCl solution. The results of potentiodynamic polarization experiment show that the amorphous Fe41Co7Cr15Mo14C15B6Y2 alloy has excellent corrosion resistance in different concentration of HCl solutions and its anodic reaction has a passive character. With the concentration of the HCl solutions increasing, the corrosion resistance of the amorphous alloy decreases. The results of potentiodynamic polarization experiments in 1 mol/L HCl solution show that the corrosion potential of the amorphous alloy is higher and the corrosion current density is lower than those of stainless steel. EIS experimental results show that the Nyquist figures of amorphous alloy and stainless steel are both composed of one single semi-circle in the state of open circuit potential. But the amorphous alloy has a higher charge transfer reaction resistance than the stainless steel. This result is accord with that of potentiodynamic polarization. The present results demonstrate that the corrosion resistance of bulk amorphous Fe41Co7Cr15Mo14C15B6Y2 alloy is much better than stainless steel.
2009, 38(11):1997-2000.
Abstract:
The microstructures of both as-cast and heat treated Mg-2.54Nd-0.26Zn-0.32Zr alloy were investigated by means of XRD, DTA, OM and TEM in this study. The results show that the massive Mg-RE phase Mg12Nd is mainly distributed on the grain boundary of as-cast Mg-2.54Nd-0.26Zn-0.32Zr. Only a small amount of flaky and grainy Mg12Nd distribute in the intracrystalline and grain boundary. The Mg12Nd phase is uniformly distributed on the matrix as crossed plate gathered by spotted state phase after solution and aging treatment.
The microstructures of both as-cast and heat treated Mg-2.54Nd-0.26Zn-0.32Zr alloy were investigated by means of XRD, DTA, OM and TEM in this study. The results show that the massive Mg-RE phase Mg12Nd is mainly distributed on the grain boundary of as-cast Mg-2.54Nd-0.26Zn-0.32Zr. Only a small amount of flaky and grainy Mg12Nd distribute in the intracrystalline and grain boundary. The Mg12Nd phase is uniformly distributed on the matrix as crossed plate gathered by spotted state phase after solution and aging treatment.
2009, 38(11):2001-2004.
Abstract:
The hydrogen absorption kinetics of the magnetic refrigeration material LaFe11.6Si1.4 alloy at different temperatures was investigated by the P-C-T testing. It is found that increasing temperature conduces to form the hydride of LaFe11.6Si1.4 at 30~80 ℃. The hydrogen desorption P-C-T curves of LaFe11.6Si1.4 hydrides at different temperatures show that no hydrogen-desorption platform appears at a pressure of 0~0.4 MPa, and the hydrogen in the alloy gradually decreases with the decreasing of pressure. A thermal analysis is used to study the thermal stability of temperature for the hydride. The TG curve shows that the hydrogen in the alloy gradually releases with the increase of temperature up to a relatively little value at 60 ℃, then increases above 60 ℃. An effective method to regulate the hydrogen content in the alloy by increasing temperature or decreasing pressure then to controll the Curie temperature of alloy is presented in this article
The hydrogen absorption kinetics of the magnetic refrigeration material LaFe11.6Si1.4 alloy at different temperatures was investigated by the P-C-T testing. It is found that increasing temperature conduces to form the hydride of LaFe11.6Si1.4 at 30~80 ℃. The hydrogen desorption P-C-T curves of LaFe11.6Si1.4 hydrides at different temperatures show that no hydrogen-desorption platform appears at a pressure of 0~0.4 MPa, and the hydrogen in the alloy gradually decreases with the decreasing of pressure. A thermal analysis is used to study the thermal stability of temperature for the hydride. The TG curve shows that the hydrogen in the alloy gradually releases with the increase of temperature up to a relatively little value at 60 ℃, then increases above 60 ℃. An effective method to regulate the hydrogen content in the alloy by increasing temperature or decreasing pressure then to controll the Curie temperature of alloy is presented in this article
2009, 38(11):2004-2007.
Abstract:
Based on a high power CO2 laser, the bioceramic coating included bioactive phases was fabricated on the surface of Ti-6Al-4V alloy. The morphology, 他the phase composition and the elemental distribution of the composite and interface were analyzed by SEM, XRD and EPMA. The results show that the bioceramic coating contains such bioactive phases as hydroxyapatite and tricalcium phosphate during laser cladoping. And the interlaced flake structure and micropores of about 0.5~2 μm in size exist on the surface of accidented gradient bioceramic coating, suitable to grow new bone along with the surface and micropore. A solid metallurgically bond to the titanium alloy substrate with the bioceramic coating is set up by the diffusion between the elements of coating (Ca, P) and substrate (Ti, Al, V). The residual stress gradually decreases from coating to substrate, is 221 MPa at the interface between bioceramic coating and transition layer, and 108 MPa between coating and substrate
Based on a high power CO2 laser, the bioceramic coating included bioactive phases was fabricated on the surface of Ti-6Al-4V alloy. The morphology, 他the phase composition and the elemental distribution of the composite and interface were analyzed by SEM, XRD and EPMA. The results show that the bioceramic coating contains such bioactive phases as hydroxyapatite and tricalcium phosphate during laser cladoping. And the interlaced flake structure and micropores of about 0.5~2 μm in size exist on the surface of accidented gradient bioceramic coating, suitable to grow new bone along with the surface and micropore. A solid metallurgically bond to the titanium alloy substrate with the bioceramic coating is set up by the diffusion between the elements of coating (Ca, P) and substrate (Ti, Al, V). The residual stress gradually decreases from coating to substrate, is 221 MPa at the interface between bioceramic coating and transition layer, and 108 MPa between coating and substrate
2009, 38(11):2008-2011.
Abstract:
The oxidation kinetics curves of both AlN and AlN/BN laminated composite ceramics at 1000 and 1300 ℃ were studied using a cycle-oxidation method. The result shows that the weight increase of AlN/h-BN laminated ceramic composites is lower than AlN ceramic at 1000 ℃, and the oxidation dynamics curve of AlN/BN laminated composite ceramics could be divided into three courses at 1300 ℃: a slowly weight increase, a rapid weight increase and a parabola shape weight increase. The XRD analysis and SEM observations show that there was no BN inside the AlN/BN laminated composite ceramics after 1300 ℃ oxidation and the micropores remain due to the vaporizing of B2O3 oxidized by BN
The oxidation kinetics curves of both AlN and AlN/BN laminated composite ceramics at 1000 and 1300 ℃ were studied using a cycle-oxidation method. The result shows that the weight increase of AlN/h-BN laminated ceramic composites is lower than AlN ceramic at 1000 ℃, and the oxidation dynamics curve of AlN/BN laminated composite ceramics could be divided into three courses at 1300 ℃: a slowly weight increase, a rapid weight increase and a parabola shape weight increase. The XRD analysis and SEM observations show that there was no BN inside the AlN/BN laminated composite ceramics after 1300 ℃ oxidation and the micropores remain due to the vaporizing of B2O3 oxidized by BN
2009, 38(11):2012-2016.
Abstract:
Ag nanoparticles were deposited photocatalytically on the TiO2 nanotube surface prepared by anodizing in an electrolyte of AgNO3 and characterized by XRD, SEM and X-ray Photoelectron Spectroscopy (XPS). The results show that the Ag particles (from 10 ~120 nm in size) are deposited on the TiO2 nanotube surface un-uniformly as Ag0 and Ag particles, showing a good chemical stability. The photo-degradation rate of mathylene blue solution increases as the content of Ag loaded on nanotube surface increase. If the content is greater then the most optimally content, the photo-degradation rate will decrease. It is shown that the photo-degradation rate is the highest when the content of Ag is about 1.15%. The Ag loaded nanotubes have much higher photo-degradation rate of about 22.98% than un-loaded nanotubes. The degradation rate is about 100% after UV irradiation of mathylene blue solution of 10×10-6mol/L for 3 h
Ag nanoparticles were deposited photocatalytically on the TiO2 nanotube surface prepared by anodizing in an electrolyte of AgNO3 and characterized by XRD, SEM and X-ray Photoelectron Spectroscopy (XPS). The results show that the Ag particles (from 10 ~120 nm in size) are deposited on the TiO2 nanotube surface un-uniformly as Ag0 and Ag particles, showing a good chemical stability. The photo-degradation rate of mathylene blue solution increases as the content of Ag loaded on nanotube surface increase. If the content is greater then the most optimally content, the photo-degradation rate will decrease. It is shown that the photo-degradation rate is the highest when the content of Ag is about 1.15%. The Ag loaded nanotubes have much higher photo-degradation rate of about 22.98% than un-loaded nanotubes. The degradation rate is about 100% after UV irradiation of mathylene blue solution of 10×10-6mol/L for 3 h
2009, 38(11):2020-2022.
Abstract:
Three-layer Ti-Cu-Zr filler metal was developed by explosive cladding and rolling, and the brazing foil of 0.2 mm thickness can be got. The properties of Ti-25Cu-25Zr brazing titanium were studied. The diffusion and contact reaction between the filler metal and titanium base metal was analyzed according to the TLP (Transient Liquid Phase Diffusion Bonding) principle, and the relationship between the holding time and the strength of brazed joint has been got. The results show that when the holding time is less than 1.0 s, the rupture load will below 600 N due to the un-completely diffusion and reaction between the filler metal and the titanium base metal, and a rupture occurs on the brazed joint; comparatively, if the holding time is more than 1.0 s, the rupture load reaches to 700 N, the joint strength can be improved because of the obviously diffusion and reaction happened between the filler metal and the titanium base metal, and the rupture occurs on the heat-affected zone of the titanium. The joint strength would be getting the unity, when the holding time is within the range of 1.0 ~ 4.0 s
Three-layer Ti-Cu-Zr filler metal was developed by explosive cladding and rolling, and the brazing foil of 0.2 mm thickness can be got. The properties of Ti-25Cu-25Zr brazing titanium were studied. The diffusion and contact reaction between the filler metal and titanium base metal was analyzed according to the TLP (Transient Liquid Phase Diffusion Bonding) principle, and the relationship between the holding time and the strength of brazed joint has been got. The results show that when the holding time is less than 1.0 s, the rupture load will below 600 N due to the un-completely diffusion and reaction between the filler metal and the titanium base metal, and a rupture occurs on the brazed joint; comparatively, if the holding time is more than 1.0 s, the rupture load reaches to 700 N, the joint strength can be improved because of the obviously diffusion and reaction happened between the filler metal and the titanium base metal, and the rupture occurs on the heat-affected zone of the titanium. The joint strength would be getting the unity, when the holding time is within the range of 1.0 ~ 4.0 s
2009, 38(11):2023-2026.
Abstract:
The nanocomposite Ag-SnO2 and La-doped Ag-SnO2 electrical contact alloys are prepared by chemical co-precipitation method and hot pressing and sintering technique. The main physics performances were measured in this paper. The breakdown field strength of contacts alloys were investigated in vacuum and the microstructures are observed by field emission scanning electron microscopy. The results show that the nanosized SnO2 of the same morphology and grain size as the prepared powders，disperses evenly in the Ag based. Especially for the La-doped nanocomposite Ag-SnO2 contact alloys, the oxide grain size is less, and disperses more evenly. With the oxide grain size decreasing, the hardness and electrical resistivity increase, and the breakdown field strength and the arc erosion rate decrease.
The nanocomposite Ag-SnO2 and La-doped Ag-SnO2 electrical contact alloys are prepared by chemical co-precipitation method and hot pressing and sintering technique. The main physics performances were measured in this paper. The breakdown field strength of contacts alloys were investigated in vacuum and the microstructures are observed by field emission scanning electron microscopy. The results show that the nanosized SnO2 of the same morphology and grain size as the prepared powders，disperses evenly in the Ag based. Especially for the La-doped nanocomposite Ag-SnO2 contact alloys, the oxide grain size is less, and disperses more evenly. With the oxide grain size decreasing, the hardness and electrical resistivity increase, and the breakdown field strength and the arc erosion rate decrease.
2009, 38(11):2027-2031.
Abstract:
(Nd,Pr)13Fe80Nb1B6 ribbons were melt-spun at 10~35 m/s and subsequently crystallized, the effect of wheel velocity and crystallization conditions on the microstructures and coercivities were studied. The XRD results indicate that the ribbons spun at 10~20 m/s consist of (Nd, Pr)2Fe14B nano-crystalline phase, while the ribbons spun at 25 and 35 m/s are partly and fully amorphous, respectively. In addition, the (004), (006) and (008) peaks of (Nd, Pr)2Fe14B are obvious on the ribbons spun at 18 m/s, suggesting the c-axis anisotropy. The coercivity of the ribbons prepared at 10~25 m/s increases with the increase of wheel velocity, with the maximum of 1216 kA/m at 25 m/s. After the ribbons spun at 25 m/s and 35 m/s are crystallized, the (Nd, Pr)2Fe14B phase and rich-rare earth phase are co-existed. And the coercivities of the ribbons spun at 35 m/s are much higher and with more homogeneous microstructures than those at 25 m/s. The maximum coercivity, 1616 kA/m, is obtained in the ribbons spun at 35 m/s after crystallizing at 973 K for 19 min due to the Pr and Nb addition. Because the Pr2Fe14B has a higher anisotropic coercive field than that of Nd2Fe14B, and the Nb element can inhibit the formation of α-Fe phase and refine the sizes of grains
(Nd,Pr)13Fe80Nb1B6 ribbons were melt-spun at 10~35 m/s and subsequently crystallized, the effect of wheel velocity and crystallization conditions on the microstructures and coercivities were studied. The XRD results indicate that the ribbons spun at 10~20 m/s consist of (Nd, Pr)2Fe14B nano-crystalline phase, while the ribbons spun at 25 and 35 m/s are partly and fully amorphous, respectively. In addition, the (004), (006) and (008) peaks of (Nd, Pr)2Fe14B are obvious on the ribbons spun at 18 m/s, suggesting the c-axis anisotropy. The coercivity of the ribbons prepared at 10~25 m/s increases with the increase of wheel velocity, with the maximum of 1216 kA/m at 25 m/s. After the ribbons spun at 25 m/s and 35 m/s are crystallized, the (Nd, Pr)2Fe14B phase and rich-rare earth phase are co-existed. And the coercivities of the ribbons spun at 35 m/s are much higher and with more homogeneous microstructures than those at 25 m/s. The maximum coercivity, 1616 kA/m, is obtained in the ribbons spun at 35 m/s after crystallizing at 973 K for 19 min due to the Pr and Nb addition. Because the Pr2Fe14B has a higher anisotropic coercive field than that of Nd2Fe14B, and the Nb element can inhibit the formation of α-Fe phase and refine the sizes of grains
2009, 38(11):2027-2019.
Abstract:
The titanium plates modified by NaOH alkali solution were immered into silane solution to prepare compact silane films on titanium substrate. The characteristics of the silane films were investigated by SEM, FTIR, EDS and surface contact angle analyzer. The results show that the different concentrations of silane solutions have greater effects on the surface morphology, the surface contact angle and the composition of surface groups of the silane film. The integrated silane film with lots of small close packing pieces is made as the samples dipped into silane solution with a concentration of 33% and surface contact angle of 71.8 °
The titanium plates modified by NaOH alkali solution were immered into silane solution to prepare compact silane films on titanium substrate. The characteristics of the silane films were investigated by SEM, FTIR, EDS and surface contact angle analyzer. The results show that the different concentrations of silane solutions have greater effects on the surface morphology, the surface contact angle and the composition of surface groups of the silane film. The integrated silane film with lots of small close packing pieces is made as the samples dipped into silane solution with a concentration of 33% and surface contact angle of 71.8 °
2009, 38(11):2032-2035.
Abstract:
In this study, a series of Y3Al5O12:Sm3+ luminescent materials with different Sm doping were successfully synthesized by the sol-gel combustion method, and characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectrum to investigate the relationships among structure, luminescent properties and Sm3+ concentration, and the mechanism of self concentration quenching of Sm3+. It is found that the Sm3+ concentration has no effect on the crystal structure with the strongest excitation peak of 405 nm, corresponding to the 6H5/2→4F7/2 transition of Sm3+. At 405 nm excitation, the Y3Al5O12:Sm3+ gives a red luminescence centered at about 617 nm (4G5/2→6H7/2). The suitable doping-concentration of Sm3+ in Y3Al5O12 is 3 mol%, and the quenching mechanism is the cross relaxation (4G5/2+6H5/2→6F9/2+6F9/2) caused by the interaction of electric quadrupoles between Sm3+ ions
In this study, a series of Y3Al5O12:Sm3+ luminescent materials with different Sm doping were successfully synthesized by the sol-gel combustion method, and characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectrum to investigate the relationships among structure, luminescent properties and Sm3+ concentration, and the mechanism of self concentration quenching of Sm3+. It is found that the Sm3+ concentration has no effect on the crystal structure with the strongest excitation peak of 405 nm, corresponding to the 6H5/2→4F7/2 transition of Sm3+. At 405 nm excitation, the Y3Al5O12:Sm3+ gives a red luminescence centered at about 617 nm (4G5/2→6H7/2). The suitable doping-concentration of Sm3+ in Y3Al5O12 is 3 mol%, and the quenching mechanism is the cross relaxation (4G5/2+6H5/2→6F9/2+6F9/2) caused by the interaction of electric quadrupoles between Sm3+ ions
2009, 38(11):2036-2038.
Abstract:
Ta-N/Zr diffusion barrier was grown on the Si (100) substrates under various substrate temperatures in a RF magnetron sputtering system. Investigated the effect of thin Zr layer insertion on the Ta-N diffusion barrier performance of Ta-N film in Cu metallization has been investigated. The results reveal that the microstructure of Ta-N films is amorphous phase at different substrate temperatures with a higher barrier breakdown temperature of about 100 ℃ than Ta-N film, which can effectively prevent the diffusion of Cu after annealing at 800 ℃ due to the production of Zr-Si layer after annealing at high temperatures
Ta-N/Zr diffusion barrier was grown on the Si (100) substrates under various substrate temperatures in a RF magnetron sputtering system. Investigated the effect of thin Zr layer insertion on the Ta-N diffusion barrier performance of Ta-N film in Cu metallization has been investigated. The results reveal that the microstructure of Ta-N films is amorphous phase at different substrate temperatures with a higher barrier breakdown temperature of about 100 ℃ than Ta-N film, which can effectively prevent the diffusion of Cu after annealing at 800 ℃ due to the production of Zr-Si layer after annealing at high temperatures
2009, 38(11):2039-2042.
Abstract:
HfSixOy thin film has been prepared by using radiation frequency (RF) magnetron sputtering. The influence of process parameters on the deposition rate of HfSixOy film was studied systematically. The structures of as-deposited HfO2 and HfSixOy films have been investigated, and analyzed for the films after annealing. The results show that the deposition rate of HfSixOy film increases with the increase of RF power, Ar gas flow and area of Si, while decreases with the increase of sputtering pressure. The results of structure analysis show that the as-deposited HfO2 and HfSixOy films deposited at room temperature are amorphous. With the substrate temperature increasing, the HfO2 film crystallizes but HfSixOy film is still amorphous. The HfSixOy film remains amorphous after annealing at 800 ℃ but HfO2 thin film crystallizes obviously after annealing at 400 ℃. It indicates that the thermal stability of HfSixOy thin film is better than that of HfO2 film
HfSixOy thin film has been prepared by using radiation frequency (RF) magnetron sputtering. The influence of process parameters on the deposition rate of HfSixOy film was studied systematically. The structures of as-deposited HfO2 and HfSixOy films have been investigated, and analyzed for the films after annealing. The results show that the deposition rate of HfSixOy film increases with the increase of RF power, Ar gas flow and area of Si, while decreases with the increase of sputtering pressure. The results of structure analysis show that the as-deposited HfO2 and HfSixOy films deposited at room temperature are amorphous. With the substrate temperature increasing, the HfO2 film crystallizes but HfSixOy film is still amorphous. The HfSixOy film remains amorphous after annealing at 800 ℃ but HfO2 thin film crystallizes obviously after annealing at 400 ℃. It indicates that the thermal stability of HfSixOy thin film is better than that of HfO2 film
2009, 38(11):2043-2047.
Abstract:
The effect of near isothermal forging and gradient heat treatment on the micro-hardness distribution, the trend of elements diffusion, the microstructure and tensile property have been investigated for the welding Ti-24Al-15Nb-1.5Mo/TC11 dual alloys joint. The results show that the joint can be strengthened through near isothermal forging and gradient heat treatment. During heat working, the martensite a’ phase and a2 phase in fusion zone of joint are breaken up into a balance microstructure consisting of a (a2) phase + b phase. The Widmanstatten structure changes into the basket weave structure in the alloy TC11 heat-affected zone of joint. In addition, the joint has excellent high temperature properties after near isothermal deformation and gradient heat treatment (sb is 840 MPa, d is 18.5%, and y is 65%)
The effect of near isothermal forging and gradient heat treatment on the micro-hardness distribution, the trend of elements diffusion, the microstructure and tensile property have been investigated for the welding Ti-24Al-15Nb-1.5Mo/TC11 dual alloys joint. The results show that the joint can be strengthened through near isothermal forging and gradient heat treatment. During heat working, the martensite a’ phase and a2 phase in fusion zone of joint are breaken up into a balance microstructure consisting of a (a2) phase + b phase. The Widmanstatten structure changes into the basket weave structure in the alloy TC11 heat-affected zone of joint. In addition, the joint has excellent high temperature properties after near isothermal deformation and gradient heat treatment (sb is 840 MPa, d is 18.5%, and y is 65%)
2009, 38(11):2048-2052.
Abstract:
The effect of pulsed high-energy electron beam on the surface modification of AZ91 magnesium alloy has been studied. The results show that the re-melted coatings (20~60 mm in thickness) on the surface of AZ91 magnesium alloy has been obtained under different treatment conditions. It was found that the thickness of the melted surface layer varies with the electron beam current and numbers of pulses, but the voltage has a minimal effect. The intensity of the diffraction peak assigned to Mg17Al12 increases with the increase of the electron beam energy, and a metastable AlMg phase has also been found from the XRD patterns of the treated AZ91 alloy. The treated surface layer exhibits a higher hardness than the AZ91 alloy, and the hardness of the topmost layer is two times as higher as the substrate. The friction coefficient and the wear volume of AZ91 alloy after electron beam treatment decrease obviously. The wear resistance of treated samples increases obviously, may be due to the high hardness from the grain refinement
The effect of pulsed high-energy electron beam on the surface modification of AZ91 magnesium alloy has been studied. The results show that the re-melted coatings (20~60 mm in thickness) on the surface of AZ91 magnesium alloy has been obtained under different treatment conditions. It was found that the thickness of the melted surface layer varies with the electron beam current and numbers of pulses, but the voltage has a minimal effect. The intensity of the diffraction peak assigned to Mg17Al12 increases with the increase of the electron beam energy, and a metastable AlMg phase has also been found from the XRD patterns of the treated AZ91 alloy. The treated surface layer exhibits a higher hardness than the AZ91 alloy, and the hardness of the topmost layer is two times as higher as the substrate. The friction coefficient and the wear volume of AZ91 alloy after electron beam treatment decrease obviously. The wear resistance of treated samples increases obviously, may be due to the high hardness from the grain refinement
2009, 38(11):2053-2056.
Abstract:
The Ba-hexaferrite powders, BaCo2Fe16O27(Co2W), were synthesized by the molten salt method using NaCl+KCl mixture. The effects of sintering temperature, holding time and the ratio (R) of molten salt to reactant weight on the product phase were discussed. At the same time, the microwave absorption properties and static magnetic properties of Co2W were investigated. The results showed that the Co2W single phase was successfully fabricated in the condition of R=3, at a calcinations temperature of 1250 ℃ in air for 4 h. The saturation magnetization (Ms), the remanent magnetization (Mr) and the coercitivity (Hc) of the Co2W ferrite are 60.76, 3.78 (A·m2)/kg and 70.7×79.6 A/m, respectively. Compared to sol-gel method, an excellent microwave absorption properties with majorbiggish improvement was obtained for the Co2W ferrite using the molten salt method, which could be a potential way to enhance the properties of the composites filled with hexagonal ferrite powders for electromagnetic applications.
The Ba-hexaferrite powders, BaCo2Fe16O27(Co2W), were synthesized by the molten salt method using NaCl+KCl mixture. The effects of sintering temperature, holding time and the ratio (R) of molten salt to reactant weight on the product phase were discussed. At the same time, the microwave absorption properties and static magnetic properties of Co2W were investigated. The results showed that the Co2W single phase was successfully fabricated in the condition of R=3, at a calcinations temperature of 1250 ℃ in air for 4 h. The saturation magnetization (Ms), the remanent magnetization (Mr) and the coercitivity (Hc) of the Co2W ferrite are 60.76, 3.78 (A·m2)/kg and 70.7×79.6 A/m, respectively. Compared to sol-gel method, an excellent microwave absorption properties with majorbiggish improvement was obtained for the Co2W ferrite using the molten salt method, which could be a potential way to enhance the properties of the composites filled with hexagonal ferrite powders for electromagnetic applications.
2009, 38(11):2060-2064.
Abstract:
As a new type of cathode materials for lithium-ion battery, the olivine LiFePO4 has many advantages, such as abundant resources, low cost, environmental friend, higher energy density and theoretical capacity, steady discharge voltage, good thermal stability and excellent cycling performance, to be a strong competitor for the next generation cathode materials for lithium-ion battery. In this paper, the structure, properties and existing problems are briefly introduced and various synthetic methods for preparation state-of-the-art are summarized for LiFePO4, such as solid-state reaction methods and liquid-state synthetic methods. The advantages and drawbacks of each methods are compared and analyzed at the same time. The research progresses on improving electrochemical property of LiFePO4 at home and abroad in recent years are discussed, and the developing trend of LiFePO4 is also prospected
As a new type of cathode materials for lithium-ion battery, the olivine LiFePO4 has many advantages, such as abundant resources, low cost, environmental friend, higher energy density and theoretical capacity, steady discharge voltage, good thermal stability and excellent cycling performance, to be a strong competitor for the next generation cathode materials for lithium-ion battery. In this paper, the structure, properties and existing problems are briefly introduced and various synthetic methods for preparation state-of-the-art are summarized for LiFePO4, such as solid-state reaction methods and liquid-state synthetic methods. The advantages and drawbacks of each methods are compared and analyzed at the same time. The research progresses on improving electrochemical property of LiFePO4 at home and abroad in recent years are discussed, and the developing trend of LiFePO4 is also prospected
2009, 38(11):2065-2068.
Abstract:
Molybdate as a promising red phosphor used for white LED is introduced and its latest progress on the preparation and synthesis as major contents is emphasized in this paper. In the last part of the paper, the development prospect of molybdate as red phosphors used for white LED is exhibited.
Molybdate as a promising red phosphor used for white LED is introduced and its latest progress on the preparation and synthesis as major contents is emphasized in this paper. In the last part of the paper, the development prospect of molybdate as red phosphors used for white LED is exhibited.
