Volume 41,Issue 3,2012 Table of Contents
2012, 41(3):377-382.
Abstract:
Au/α-Fe2O3 catalysts for CO oxidation were prepared by chemical coprecipitation at different pH values, and the as-prepared samples were calcined or UV (λ=254 nm) irradiated, respectively. The structure was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption and desorption analysis (BET) and temperature programmed reduction (H2-TPR), and the active Au species on the catalysts was investigated. The results show that Au3+, Auδ+（0≤δ≤1）and Au0 coexist on the surface of Au/α-Fe2O3 catalysts treated at 110 °C, and their activity order is Au3+> Auδ+> Au0. The sample prepared at pH=8 shows the best catalytic performance since it has more Au3+ species and high specific surface area. High temperature calcination can cause serious deactivation due to the reduction of Au3+ and Auδ+ species, together with the decrease of the specific surface area of α-Fe2O3. UV irradiation can also cause the reduction of oxidative Au species and the growth of Au particle.
Au/α-Fe2O3 catalysts for CO oxidation were prepared by chemical coprecipitation at different pH values, and the as-prepared samples were calcined or UV (λ=254 nm) irradiated, respectively. The structure was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption and desorption analysis (BET) and temperature programmed reduction (H2-TPR), and the active Au species on the catalysts was investigated. The results show that Au3+, Auδ+（0≤δ≤1）and Au0 coexist on the surface of Au/α-Fe2O3 catalysts treated at 110 °C, and their activity order is Au3+> Auδ+> Au0. The sample prepared at pH=8 shows the best catalytic performance since it has more Au3+ species and high specific surface area. High temperature calcination can cause serious deactivation due to the reduction of Au3+ and Auδ+ species, together with the decrease of the specific surface area of α-Fe2O3. UV irradiation can also cause the reduction of oxidative Au species and the growth of Au particle.
2012, 41(3):383-386.
Abstract:
The near-infrared (NIR) and infrared (IR) transmissions of Indium (In) doped Cd1-xMnxTe (CMT) crystals were measured, and both the results show that the transmittances decline dramatically after doping. The reason is that the lattice absorption and free carriers absorption together determine the IR absorption of the crystals. The photoluminescence (PL) spectra measurements show that the donor-acceptor pair (D, A) peak is increased after doping, but the acceptor-bound exciton (A0, X) peak is reduced. With increasing of In concentrations the (A0, X) peak disappears and the (D, A) peak stands out completely. This series of changes result from that the substitutional In atoms act as donors and compensate the point defects VCd. The Raman scattering (RS) measurements exhibit that In doping makes the RS spectra of the longitudinal-optic (LO1) phonon peak a slight reduction, where LO1 is relative to the phonon peak of “CdTe-like”. Magnetization measurements show that the effects of In-doping on the magnetization of CMT are insignificant.
The near-infrared (NIR) and infrared (IR) transmissions of Indium (In) doped Cd1-xMnxTe (CMT) crystals were measured, and both the results show that the transmittances decline dramatically after doping. The reason is that the lattice absorption and free carriers absorption together determine the IR absorption of the crystals. The photoluminescence (PL) spectra measurements show that the donor-acceptor pair (D, A) peak is increased after doping, but the acceptor-bound exciton (A0, X) peak is reduced. With increasing of In concentrations the (A0, X) peak disappears and the (D, A) peak stands out completely. This series of changes result from that the substitutional In atoms act as donors and compensate the point defects VCd. The Raman scattering (RS) measurements exhibit that In doping makes the RS spectra of the longitudinal-optic (LO1) phonon peak a slight reduction, where LO1 is relative to the phonon peak of “CdTe-like”. Magnetization measurements show that the effects of In-doping on the magnetization of CMT are insignificant.
2012, 41(3):387-392.
Abstract:
Aiming at the special material equipment, a multi-layer database structure was studied. The data characteristics, the intrinsic relationship of each layer, and the multi-layer database structure related to the material trademark and its performance were defined. The logical organization and the physical structure of the material series database and the material performance database were designed, as well as the software system was developed based on the Oracle and the J2EE technology. The data exchange between the two databases of the material trademark and the performance can be seamlessly connected, which shows that the system can effectively manage and intuitionisticly display the?material series framework and detail information with text, picture, forms and so on.
Aiming at the special material equipment, a multi-layer database structure was studied. The data characteristics, the intrinsic relationship of each layer, and the multi-layer database structure related to the material trademark and its performance were defined. The logical organization and the physical structure of the material series database and the material performance database were designed, as well as the software system was developed based on the Oracle and the J2EE technology. The data exchange between the two databases of the material trademark and the performance can be seamlessly connected, which shows that the system can effectively manage and intuitionisticly display the?material series framework and detail information with text, picture, forms and so on.
2012, 41(3):393-396.
Abstract:
By means of the rapid heating followed by water quenching, thermal shock experiments were conducted for CuW70 alloys to study the variations of mechanical behaviour. On the other hand, the simulation with finite element method was implemented to analyze the variations and the distributions of the temperature and the thermal stresses of CuW70 specimens during thermal shock process. The results show that the strength of CuW70 alloys degenerates and the ductility is improved after repeated thermal shock, and the maximum thermal stress appears at the beginning of heating and quenching period. The alternated thermal stresses which vary between tensile and compression stress will be applied on the internal and the external of CuW70 alloys during repeated thermal shock.
By means of the rapid heating followed by water quenching, thermal shock experiments were conducted for CuW70 alloys to study the variations of mechanical behaviour. On the other hand, the simulation with finite element method was implemented to analyze the variations and the distributions of the temperature and the thermal stresses of CuW70 specimens during thermal shock process. The results show that the strength of CuW70 alloys degenerates and the ductility is improved after repeated thermal shock, and the maximum thermal stress appears at the beginning of heating and quenching period. The alternated thermal stresses which vary between tensile and compression stress will be applied on the internal and the external of CuW70 alloys during repeated thermal shock.
2012, 41(3):397-401.
Abstract:
For TC11 alloy, this paper presented a more accurate constitutive model based on Arrhenius-type hyperbolic sine method by the cubic piecewise function of strain. During this modeling, compression tests of thermal simulation were carried out firstly. The effect of the flow factors on material flow stress was analyzed secondly. On analysis of the test data, the cubic piecewise functions of strain were proposed to ensure the Arrhenius-type hyperbolic sine model of high precision. Comparison with test results shows that the model presented is with high precision and simulation testing proposed show that this model is reliable.
For TC11 alloy, this paper presented a more accurate constitutive model based on Arrhenius-type hyperbolic sine method by the cubic piecewise function of strain. During this modeling, compression tests of thermal simulation were carried out firstly. The effect of the flow factors on material flow stress was analyzed secondly. On analysis of the test data, the cubic piecewise functions of strain were proposed to ensure the Arrhenius-type hyperbolic sine model of high precision. Comparison with test results shows that the model presented is with high precision and simulation testing proposed show that this model is reliable.
2012, 41(3):402-405.
Abstract:
ZrO2 dispersion-strengthened Pt-3Rh alloy was prepared by powder metallurgy-internal oxidation-sintering. The high temperature properties were tested and analyzed. After Pt-3Rh are dispersion strengthened, its coefficient of expansion is bigger than that of Pt-3Rh below 800 °C and smaller than that of Pt-3Rh above 800 °C. The thermal tensile strength and elongation are increased. The stability of crystal structure is strengthened. The service life of strengthened Pt-3Rh drawing bushings is equal to that of Pt-10Rh.
ZrO2 dispersion-strengthened Pt-3Rh alloy was prepared by powder metallurgy-internal oxidation-sintering. The high temperature properties were tested and analyzed. After Pt-3Rh are dispersion strengthened, its coefficient of expansion is bigger than that of Pt-3Rh below 800 °C and smaller than that of Pt-3Rh above 800 °C. The thermal tensile strength and elongation are increased. The stability of crystal structure is strengthened. The service life of strengthened Pt-3Rh drawing bushings is equal to that of Pt-10Rh.
2012, 41(3):406-412.
Abstract:
High temperature quasi-static compression test and RT dynamic compression tests on TC6 titanium alloy samples with 4 kinds of original microstructures were carried out using the gleeble-1500-type thermal simulation testing machine and Hopkinson bar. Effects of different original microstructures on their microstructure evolution in high temperature deformation, thermal distortion behavior and mechanical properties of TC6 alloy were studied, by combining the corresponding transmission electron microscope (TEM) analysis and the stress-strain curves. Results show that there exist two types of microstructure evolution for the 4 kinds of microstructures of TC6 alloy in the hot deformation. One type is equiaxed-type microstructure evolution, whose process is elongation of equiaxed α phase—dynamic recrystallization—growth of dynamic recrystallized grain—phase transformation of α/β. The other is lamellar-type microstructure evolution, whose process involves bending of lath-shaped α phase—breakdown of the lath-shaped α phase—dynamic recrystallization—growth of dynamic recrystallized grain—phase transformation of α/β and lath-shaped α phase becoming short-bar α phase. Dislocation movement and dynamic recrystallization are important factors that control microstructure evolution and mechanical properties of TC6 alloy during high temperature deformation. Lamellar structure shows the highest flow stress among the 4 kinds of microstructures due to its large quantity of grain boundaries which obstruct the dislocation movement. The equiaxed structure displays the lowest flow stress in the 4 kinds of microstructures owing to its larger grain size which involve lesser obstacles to movement of dislocation. The flow stresses of the binary and the solution and aging structure are between that of lamellar structure and that of the equiaxed structure because of their mixed construction of equiaxed grains and acerose grains. The room temperature dynamic mechanical properties of the TC6 alloy with 4 kinds of microstructures are sensitive to strain-rate. According to sort in descending, the plasticity of the 4 types of microstructures of TC6 alloy is equiaxed, binary, solution and aging, lamellar in turn and the flow stress of them is solution and aging, binary, lamellar, and equiaxed in turn, respectively, under the condition of dynamic compression with strain-rate from 2500 s-1 to 4000 s-1.
High temperature quasi-static compression test and RT dynamic compression tests on TC6 titanium alloy samples with 4 kinds of original microstructures were carried out using the gleeble-1500-type thermal simulation testing machine and Hopkinson bar. Effects of different original microstructures on their microstructure evolution in high temperature deformation, thermal distortion behavior and mechanical properties of TC6 alloy were studied, by combining the corresponding transmission electron microscope (TEM) analysis and the stress-strain curves. Results show that there exist two types of microstructure evolution for the 4 kinds of microstructures of TC6 alloy in the hot deformation. One type is equiaxed-type microstructure evolution, whose process is elongation of equiaxed α phase—dynamic recrystallization—growth of dynamic recrystallized grain—phase transformation of α/β. The other is lamellar-type microstructure evolution, whose process involves bending of lath-shaped α phase—breakdown of the lath-shaped α phase—dynamic recrystallization—growth of dynamic recrystallized grain—phase transformation of α/β and lath-shaped α phase becoming short-bar α phase. Dislocation movement and dynamic recrystallization are important factors that control microstructure evolution and mechanical properties of TC6 alloy during high temperature deformation. Lamellar structure shows the highest flow stress among the 4 kinds of microstructures due to its large quantity of grain boundaries which obstruct the dislocation movement. The equiaxed structure displays the lowest flow stress in the 4 kinds of microstructures owing to its larger grain size which involve lesser obstacles to movement of dislocation. The flow stresses of the binary and the solution and aging structure are between that of lamellar structure and that of the equiaxed structure because of their mixed construction of equiaxed grains and acerose grains. The room temperature dynamic mechanical properties of the TC6 alloy with 4 kinds of microstructures are sensitive to strain-rate. According to sort in descending, the plasticity of the 4 types of microstructures of TC6 alloy is equiaxed, binary, solution and aging, lamellar in turn and the flow stress of them is solution and aging, binary, lamellar, and equiaxed in turn, respectively, under the condition of dynamic compression with strain-rate from 2500 s-1 to 4000 s-1.
2012, 41(3):413-419.
Abstract:
A finite element (FE) model was established to investigate the preforming process of TA15 titanium alloy complex component based on DEFORM-3D platform, and the influence law of forming parameters on the microstructure evolution and the equiaxed α grain size during performing was simulated and analyzed. Results show that the equiaxed α-phases are refined as deformation proceeds. With the increase of temperature, the primary α-phase grain size increases when deformed between 950 oC and 980 oC. The grain size distribution is inhomogeneous when deformed at 980 oC. With the increasing of the deformation rate, the primary α-phase grain size decreases. Forming at deformation rates of 0.5 and 1.0 mm/s, the effect of temperature on the grain size is small. The primary α-phase grain size increases more rapidly with the increase of temperature at the deformation rate of 0.1 mm/s. The average grain size of α-phase decreases with the increase of the friction factor, and the inhomogeneity of grain size distribution increases.
A finite element (FE) model was established to investigate the preforming process of TA15 titanium alloy complex component based on DEFORM-3D platform, and the influence law of forming parameters on the microstructure evolution and the equiaxed α grain size during performing was simulated and analyzed. Results show that the equiaxed α-phases are refined as deformation proceeds. With the increase of temperature, the primary α-phase grain size increases when deformed between 950 oC and 980 oC. The grain size distribution is inhomogeneous when deformed at 980 oC. With the increasing of the deformation rate, the primary α-phase grain size decreases. Forming at deformation rates of 0.5 and 1.0 mm/s, the effect of temperature on the grain size is small. The primary α-phase grain size increases more rapidly with the increase of temperature at the deformation rate of 0.1 mm/s. The average grain size of α-phase decreases with the increase of the friction factor, and the inhomogeneity of grain size distribution increases.
2012, 41(3):420-425.
Abstract:
The vacuum reduction refining was used to prepare the high titanium ferroalloy with low oxygen, using the high titanium ferroalloy prepared by an aluminum thermal method as raw materials, and Al as the reducing agent. Effects of the refining temperature and time on the refining result were studied, and the high titanium ferroalloy was characterized by XRD, SEM and chemical elemental analysis. The results show that the refined high titanium ferroalloy consists mainly of TiFe2, Fe2TiO5, TiO, Al2O3, TiAl and Fe0.942O phases. The microstructure of the refined alloy is uniform and compact, the inclusions in the alloy are effectively removed and the oxygen content decreases dramatically. However, too high refining temperature and too long refining time will worsen refining effect. The titanium content in the refined alloy is within (69.00-71.00)%, Al content is lower than 2.50%, silicon content is lower than 2.63%, and the oxygen content is lower than 3.52%, which is fully consistent with the technical indicators of the high quality high titanium ferroalloy.
The vacuum reduction refining was used to prepare the high titanium ferroalloy with low oxygen, using the high titanium ferroalloy prepared by an aluminum thermal method as raw materials, and Al as the reducing agent. Effects of the refining temperature and time on the refining result were studied, and the high titanium ferroalloy was characterized by XRD, SEM and chemical elemental analysis. The results show that the refined high titanium ferroalloy consists mainly of TiFe2, Fe2TiO5, TiO, Al2O3, TiAl and Fe0.942O phases. The microstructure of the refined alloy is uniform and compact, the inclusions in the alloy are effectively removed and the oxygen content decreases dramatically. However, too high refining temperature and too long refining time will worsen refining effect. The titanium content in the refined alloy is within (69.00-71.00)%, Al content is lower than 2.50%, silicon content is lower than 2.63%, and the oxygen content is lower than 3.52%, which is fully consistent with the technical indicators of the high quality high titanium ferroalloy.
2012, 41(3):426-431.
Abstract:
The effects of adding Cr on the transformation and the low temperature deformation characteristics in the deformed plus annealed Ti-Ni shape memory alloy (SMA) were investigated by differential scanning calorimetry and tensile test. The results show that after adding trace Cr, the R and martensite (M) transformation temperatures θR and θM decrease a lot, the M transformation temperature hysteresis ΔθM increases, the platform-stress σM in the stress-strain curves increases significantly, and the superelasticity (SE) improves, and the ductility deteriorates in Ti-Ni SMA. After adding trace Cr, the low-temperature SE of Ti-Ni SMA also improves greatly. At room temperature, the Ti-50.8Ni SMA shows shape memory effect (SME) + SE, while the Ti-50.8Ni-0.3Cr SMA shows SE. The annealing temperature affects low temperature deformation characteristics of Ti-Ni SMA. When deformed at 10 oC, the 400-500 oC annealed Ti-50.8Ni SMA shows SME, the 550-650 oC annealed Ti-50.8Ni SMA shows SME + SE, while the 400-650 oC annealed Ti-50.8Ni-0.3Cr SMA shows SE continuously.
The effects of adding Cr on the transformation and the low temperature deformation characteristics in the deformed plus annealed Ti-Ni shape memory alloy (SMA) were investigated by differential scanning calorimetry and tensile test. The results show that after adding trace Cr, the R and martensite (M) transformation temperatures θR and θM decrease a lot, the M transformation temperature hysteresis ΔθM increases, the platform-stress σM in the stress-strain curves increases significantly, and the superelasticity (SE) improves, and the ductility deteriorates in Ti-Ni SMA. After adding trace Cr, the low-temperature SE of Ti-Ni SMA also improves greatly. At room temperature, the Ti-50.8Ni SMA shows shape memory effect (SME) + SE, while the Ti-50.8Ni-0.3Cr SMA shows SE. The annealing temperature affects low temperature deformation characteristics of Ti-Ni SMA. When deformed at 10 oC, the 400-500 oC annealed Ti-50.8Ni SMA shows SME, the 550-650 oC annealed Ti-50.8Ni SMA shows SME + SE, while the 400-650 oC annealed Ti-50.8Ni-0.3Cr SMA shows SE continuously.
2012, 41(3):432-436.
Abstract:
The deformation behavior of GH690 alloy from 298 K to 623 K was investigated by tensile tests. The deformation microstructure was observed by OM, SEM, and TEM. The results show that the twinning is the main deformation mechanism for GH690 alloy at 298 K. Under this condition, both high tensile strength and elongation can be obtained because the deformation twins formed in plastic deformation can act as obstacles to dislocations, resulting in obvious work hardening effect. However, as the number of the deformation twins decreases with increasing of the testing temperature, the deformation mechanism of the alloy translates from twinning to dislocation slipping. As the work hardening effect of dislocation slip mechanism is less than that of twinning mechanism, the tensile strength and plasticity of the alloy are decreased with increasing of the testing temperature.
The deformation behavior of GH690 alloy from 298 K to 623 K was investigated by tensile tests. The deformation microstructure was observed by OM, SEM, and TEM. The results show that the twinning is the main deformation mechanism for GH690 alloy at 298 K. Under this condition, both high tensile strength and elongation can be obtained because the deformation twins formed in plastic deformation can act as obstacles to dislocations, resulting in obvious work hardening effect. However, as the number of the deformation twins decreases with increasing of the testing temperature, the deformation mechanism of the alloy translates from twinning to dislocation slipping. As the work hardening effect of dislocation slip mechanism is less than that of twinning mechanism, the tensile strength and plasticity of the alloy are decreased with increasing of the testing temperature.
2012, 41(3):437-441.
Abstract:
The electronic structures of Ti-Al alloys with Cr, V addition were studied using the first-principle pseudopotential plane-wave method. The total energy, cohesive energy, mechanical property, the charge density and density of states of the alloys were calculated, and the reason that the mechanical property was improved after Cr, V infiltration in Ti-Al alloys in terms of theory was explained. The results show that with the alloying elements Cr (0-25at%), V (0-25at%) content increasing, the absolute value of cohesive energy of the alloys becomes larger and the structure is more stable; the values of shear modulus G and Young’s modulus E increase, but the increment gradually decrease. The main reason is that the addition of Cr in the alloys enhances reciprocal hybridization of Cr 3d, Al 3p and Ti 3d, while V in the alloys enhances reciprocal hybridization of V 3d, Ti 3d and Al 3p, and the alloys’ binding capacity is increased.
The electronic structures of Ti-Al alloys with Cr, V addition were studied using the first-principle pseudopotential plane-wave method. The total energy, cohesive energy, mechanical property, the charge density and density of states of the alloys were calculated, and the reason that the mechanical property was improved after Cr, V infiltration in Ti-Al alloys in terms of theory was explained. The results show that with the alloying elements Cr (0-25at%), V (0-25at%) content increasing, the absolute value of cohesive energy of the alloys becomes larger and the structure is more stable; the values of shear modulus G and Young’s modulus E increase, but the increment gradually decrease. The main reason is that the addition of Cr in the alloys enhances reciprocal hybridization of Cr 3d, Al 3p and Ti 3d, while V in the alloys enhances reciprocal hybridization of V 3d, Ti 3d and Al 3p, and the alloys’ binding capacity is increased.
13 Microstructure and Welding Properties of Single-Roller Melt Spinned Au-19.25Ag-12.80Ge Solder Ribbon
2012, 41(3):442-446.
Abstract:
Au-19.25Ag-12.80Ge solder ribbons were prepared by single-roller melt spinning technology. The melting behavior and microstructure of the solder ribbons were analyzed by means of differential thermal analyzers, SEM and TEM, and the welding property with Ni was also studied. The results show that liquidus temperature of the solder ribbons prepared by the single-roller melt spinning method is some lower than that of the mother alloy, and the melting temperature interval is decreased by 4 oC. Uniformly distributed and greatly refined microstructure has been obtained because of the melt spinning process, and nanocrystalline with a size of 40-50 nm has formed close to the roller surface side; there exists a structure mutation in the direction of ribbon thickness, and the mutation is possibly caused by the critical cooling rate. The solder ribbon has good wettability with Ni and reliable metallurgical bonding interface has formed. Under the same condition, the shear strength of the welding joint with Ni has increased by 60% compared with that of the welding joint of the mother alloy solder.
Au-19.25Ag-12.80Ge solder ribbons were prepared by single-roller melt spinning technology. The melting behavior and microstructure of the solder ribbons were analyzed by means of differential thermal analyzers, SEM and TEM, and the welding property with Ni was also studied. The results show that liquidus temperature of the solder ribbons prepared by the single-roller melt spinning method is some lower than that of the mother alloy, and the melting temperature interval is decreased by 4 oC. Uniformly distributed and greatly refined microstructure has been obtained because of the melt spinning process, and nanocrystalline with a size of 40-50 nm has formed close to the roller surface side; there exists a structure mutation in the direction of ribbon thickness, and the mutation is possibly caused by the critical cooling rate. The solder ribbon has good wettability with Ni and reliable metallurgical bonding interface has formed. Under the same condition, the shear strength of the welding joint with Ni has increased by 60% compared with that of the welding joint of the mother alloy solder.
2012, 41(3):447-451.
Abstract:
By means of the enduring properties measurement and microstructure observation, the influence of the microstructure on the enduring properties and fracture mechanism for FGH95 nickel-base superalloy was investigated. The results show that after solution treated at 1150 oC, the thicker g ￠ phase is distributed discontinuously in the wider boundary regions in which exists the poor-zone of the finer g ￠ phase. When the solution temperature rises to 1160 oC, the thicker g ￠ phase in the alloy is fully dissolved, and the fine g ￠ phase with high volume fraction is dispersively distributed within the grains, and thereinto the particles of (Nb, Ti)C carbide phase are discontinuously precipitated along the boundaries. After solution treated at 1165 oC, the grain sizes are obviously grown up, and the films of the carbide is continuously precipitated along the boundary. The particle carbides which are discontinuously precipitated along the boundary can effectively pin the grain boundaries and restrain boundaries sliding, resulting in the alloy possessing better enduring properties under the applied stress of 1034 MPa at 650 oC. In the later stage of creep, the deformed characteristic of the alloy is single and double orientation slipping, and the slipping trace on the sample surface increases to bring out the stress concentration as the creep goes on, which results in the initiating and propagating of the micro-cracks along the boundaries up to rupture.
By means of the enduring properties measurement and microstructure observation, the influence of the microstructure on the enduring properties and fracture mechanism for FGH95 nickel-base superalloy was investigated. The results show that after solution treated at 1150 oC, the thicker g ￠ phase is distributed discontinuously in the wider boundary regions in which exists the poor-zone of the finer g ￠ phase. When the solution temperature rises to 1160 oC, the thicker g ￠ phase in the alloy is fully dissolved, and the fine g ￠ phase with high volume fraction is dispersively distributed within the grains, and thereinto the particles of (Nb, Ti)C carbide phase are discontinuously precipitated along the boundaries. After solution treated at 1165 oC, the grain sizes are obviously grown up, and the films of the carbide is continuously precipitated along the boundary. The particle carbides which are discontinuously precipitated along the boundary can effectively pin the grain boundaries and restrain boundaries sliding, resulting in the alloy possessing better enduring properties under the applied stress of 1034 MPa at 650 oC. In the later stage of creep, the deformed characteristic of the alloy is single and double orientation slipping, and the slipping trace on the sample surface increases to bring out the stress concentration as the creep goes on, which results in the initiating and propagating of the micro-cracks along the boundaries up to rupture.
2012, 41(3):452-456.
Abstract:
(La0.6Ce0.4)65Al10Cu25 bulk metallic glasses (BMGs) were prepared by copper-mold casting. The crystallization behavior and thermal stability of (La0.6Ce0.4)65Al10Cu25 were investigated by X-ray diffraction and differential scanning caloricity (DSC) after being annealed at its supercooled liquid region under the pressure ranging from ambient pressure to 1015 MPa. Results show that pressure promotes crystallization of (La0.6Ce0.4)65Al10Cu25 BMGs. The onset crystallization temperature Tx decreases with increasing of preannealing pressure at a slope of –5.17 K/GPa, and the apparent activation energy of the crystallization Ep determined by Kissinger equation increases with increasing of preannealing pressure. The influencing mechanism of preannealing under pressure on the crystallization of (La0.6Ce0.4)65Al10Cu25 BMGs were discussed in the view of Gibbs free energy and chemical short range order.
(La0.6Ce0.4)65Al10Cu25 bulk metallic glasses (BMGs) were prepared by copper-mold casting. The crystallization behavior and thermal stability of (La0.6Ce0.4)65Al10Cu25 were investigated by X-ray diffraction and differential scanning caloricity (DSC) after being annealed at its supercooled liquid region under the pressure ranging from ambient pressure to 1015 MPa. Results show that pressure promotes crystallization of (La0.6Ce0.4)65Al10Cu25 BMGs. The onset crystallization temperature Tx decreases with increasing of preannealing pressure at a slope of –5.17 K/GPa, and the apparent activation energy of the crystallization Ep determined by Kissinger equation increases with increasing of preannealing pressure. The influencing mechanism of preannealing under pressure on the crystallization of (La0.6Ce0.4)65Al10Cu25 BMGs were discussed in the view of Gibbs free energy and chemical short range order.
2012, 41(3):457-461.
Abstract:
At first, the Ni-Zn coating was electroplated, then, the coating was immersed in concentrated alkali solution to remove zinc and the porous nickel was obtained. Finally, the Ni/LaNi5 porous composite electrode was prepared on this porous nickel surface by means of the composite electro-deposition. The electro-catalytic properties for hydrogen evolution reaction of the electrode were evaluated by electrochemical steady-state polarization curve and electrochemical impendence spectroscopy (EIS). And the stability of the electrode was studied by open circuit potential and constant potential electrolysis technology for long time and discontinuity electrolysis. Results show that the apparent exchange current density of the porous composite electrode is 172 and 26 times as much as that of the nickel electrode and the porous nickel electrode, respectively. Because LaNi5 possesses the effect of electrode protection, the stability of the porous composite electrode is better than that of the porous nickel.
At first, the Ni-Zn coating was electroplated, then, the coating was immersed in concentrated alkali solution to remove zinc and the porous nickel was obtained. Finally, the Ni/LaNi5 porous composite electrode was prepared on this porous nickel surface by means of the composite electro-deposition. The electro-catalytic properties for hydrogen evolution reaction of the electrode were evaluated by electrochemical steady-state polarization curve and electrochemical impendence spectroscopy (EIS). And the stability of the electrode was studied by open circuit potential and constant potential electrolysis technology for long time and discontinuity electrolysis. Results show that the apparent exchange current density of the porous composite electrode is 172 and 26 times as much as that of the nickel electrode and the porous nickel electrode, respectively. Because LaNi5 possesses the effect of electrode protection, the stability of the porous composite electrode is better than that of the porous nickel.
2012, 41(3):462-466.
Abstract:
By means of thermal decomposition, Pb3O4 layer was introduced into the Ti/SnO2-Sb electrode to increase the electrode service life through increasing the cohesive force between PbO2 and Ti. The results show that the introduction of the Pb3O4 layer greatly enhances the accelerated test life of the PbO2 electrode from 100.5 h to 970 h. The enhancement causes of the accelerated life for the PbO2 electrode due to the introduction of the Pb3O4 layer were analyzed based on the results of XRF, XRD and SEM.
By means of thermal decomposition, Pb3O4 layer was introduced into the Ti/SnO2-Sb electrode to increase the electrode service life through increasing the cohesive force between PbO2 and Ti. The results show that the introduction of the Pb3O4 layer greatly enhances the accelerated test life of the PbO2 electrode from 100.5 h to 970 h. The enhancement causes of the accelerated life for the PbO2 electrode due to the introduction of the Pb3O4 layer were analyzed based on the results of XRF, XRD and SEM.
Xie Qinglian
,
Ji Lu
,
Pan Yinsong
,
Zhang Yuting
,
Huang Guohua
,
Zhao Xinjie
,
Fang Lan
,
Yan Shaolin
2012, 41(3):467-471.
Abstract:
Tl-2212 high temperature superconducting (HTS) films were prepared on r-cut sapphire substrates buffered with CeO2 by dc magnetron sputtering technique and post-annealing process. The effects of various thicknesses of Tl-2212 films on their surface morphologies and superconducting properties were investigated. The results show that with increasing of the superconducting film thickness, the dense surface morphology evolves into flake-like crystal structure, the critical temperature Tc and critical current density Jc increase and then decrease, and the microwave surface resistance Rs decreases and then increases. The maximum thickness limitation of the crack-free Tl-2212 films, with CeO2 buffer layers annealed, reaches to 600 nm. The films possess excellent superconducting properties.
Tl-2212 high temperature superconducting (HTS) films were prepared on r-cut sapphire substrates buffered with CeO2 by dc magnetron sputtering technique and post-annealing process. The effects of various thicknesses of Tl-2212 films on their surface morphologies and superconducting properties were investigated. The results show that with increasing of the superconducting film thickness, the dense surface morphology evolves into flake-like crystal structure, the critical temperature Tc and critical current density Jc increase and then decrease, and the microwave surface resistance Rs decreases and then increases. The maximum thickness limitation of the crack-free Tl-2212 films, with CeO2 buffer layers annealed, reaches to 600 nm. The films possess excellent superconducting properties.
2012, 41(3):472-476.
Abstract:
The microstructure evolution, crystallographic texture and dislocation configuration during recrystallization of the cold-drawn Ti6Al4V alloy were investigated by optical microscope (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Recrystallization treatment in the 60% cold worked samples was carried out at various temperatures between 700 oC and 880 oC and holding time from 1 min to 240 min. The results demonstrate that recrystallization of the 60% cold-drawn alloy and subsequent grain growth have led α phase to fine equiaxed grains, while β phase distribute along grain boundaries of the α-phase in strip shape or small grains. The value of recrystallization activation energy of the alloy after 60% cold deformation is 107 kJ/mol, which is about 50% higher than that of the deformed pure titanium experienced the equal deformation. The microstructure evolution at different grain stages can be classified as recoveration, nucleation and grain growth stages. It is shown that the recovery involves rearrangement of dislocation cells into subgrains, formation of nuclei through growth or coalescence of subgrains, and growth of nuclei by high angle boundary migration during the annealing of the Ti6Al4V alloy. The as-cold drawn wires present strong <10
The microstructure evolution, crystallographic texture and dislocation configuration during recrystallization of the cold-drawn Ti6Al4V alloy were investigated by optical microscope (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Recrystallization treatment in the 60% cold worked samples was carried out at various temperatures between 700 oC and 880 oC and holding time from 1 min to 240 min. The results demonstrate that recrystallization of the 60% cold-drawn alloy and subsequent grain growth have led α phase to fine equiaxed grains, while β phase distribute along grain boundaries of the α-phase in strip shape or small grains. The value of recrystallization activation energy of the alloy after 60% cold deformation is 107 kJ/mol, which is about 50% higher than that of the deformed pure titanium experienced the equal deformation. The microstructure evolution at different grain stages can be classified as recoveration, nucleation and grain growth stages. It is shown that the recovery involves rearrangement of dislocation cells into subgrains, formation of nuclei through growth or coalescence of subgrains, and growth of nuclei by high angle boundary migration during the annealing of the Ti6Al4V alloy. The as-cold drawn wires present strong <10
2012, 41(3):477-481.
Abstract:
Hot compression tests of as-cast titanium alloy TB6 were conducted using the Thermecmaster-Z hot simulation test machine in the β process, and its dynamic recrystallization (DRX) behavior was investigated. The results indicate that there are two kinds of typical nucleation sites, namely, grain interiors and near grain boundaries. Accordingly, there are two kinds of dynamic recrystallization mechanism: discontinuous and continuous dynamic recrystallization. The operation of discontinuous dynamic recrystallization (DDRX) as predominant mechanisms is anticipated in case of strain rate higher than 0.01 s-1, which leads to a low degree of DRX and thus does not to marked grains refinement. And the operation of continuous dynamic recrystallization (CDRX) by mechanism of subgrain rotation, leading to grains refinement, is observed in case of strain rate no more than 0.001 s-1 and temperature higher than 950 oC.
Hot compression tests of as-cast titanium alloy TB6 were conducted using the Thermecmaster-Z hot simulation test machine in the β process, and its dynamic recrystallization (DRX) behavior was investigated. The results indicate that there are two kinds of typical nucleation sites, namely, grain interiors and near grain boundaries. Accordingly, there are two kinds of dynamic recrystallization mechanism: discontinuous and continuous dynamic recrystallization. The operation of discontinuous dynamic recrystallization (DDRX) as predominant mechanisms is anticipated in case of strain rate higher than 0.01 s-1, which leads to a low degree of DRX and thus does not to marked grains refinement. And the operation of continuous dynamic recrystallization (CDRX) by mechanism of subgrain rotation, leading to grains refinement, is observed in case of strain rate no more than 0.001 s-1 and temperature higher than 950 oC.
2012, 41(3):506-509.
Abstract:
Fourth order Runge-Kutta method is commonly used to solve the differential equations in engineering due to its high precision and easy convergence. In this paper, based on the Feynman et al.’s calculated method, the classical fourth order Runge-Kutta method was applied to solve the Thomas-Fermi-Dirac (TFD) equation and more accurate results have been obtained. Using this method, the numerical solution of the TFD equation for the element Cu was solved, and the electron density values of some common elements at the Wigner-Seitz radius were calculated.
Fourth order Runge-Kutta method is commonly used to solve the differential equations in engineering due to its high precision and easy convergence. In this paper, based on the Feynman et al.’s calculated method, the classical fourth order Runge-Kutta method was applied to solve the Thomas-Fermi-Dirac (TFD) equation and more accurate results have been obtained. Using this method, the numerical solution of the TFD equation for the element Cu was solved, and the electron density values of some common elements at the Wigner-Seitz radius were calculated.
2012, 41(3):510-513.
Abstract:
The phase structure and magnetic properties of nanocrystalline Fe73.5Cu1Nb3-xTixSi13.5B9 (x=0, 1, 2, 3) powders were investigated. The samples were obtained from melt-spun ribbons by high energy ball milling and subsequent annealing at 550 oC for 1 h. The result shows that the lattice constant of the precipitated phase in the annealed and Ti-free Fe73.5Cu1Nb3Si13.5B9 powders increases with the elongation of milling time. With the doping of Ti, the annealed Fe73.5Cu1Nb3-xTixSi13.5B9 (x=0, 1, 2, 3) powders after milling for 60 h keep single α-Fe(Si) phase. In addition, with the increase of Ti content, the lattice constant of the precipitated phase decreases, the saturation magnetization increases and the coercivity decreases.
The phase structure and magnetic properties of nanocrystalline Fe73.5Cu1Nb3-xTixSi13.5B9 (x=0, 1, 2, 3) powders were investigated. The samples were obtained from melt-spun ribbons by high energy ball milling and subsequent annealing at 550 oC for 1 h. The result shows that the lattice constant of the precipitated phase in the annealed and Ti-free Fe73.5Cu1Nb3Si13.5B9 powders increases with the elongation of milling time. With the doping of Ti, the annealed Fe73.5Cu1Nb3-xTixSi13.5B9 (x=0, 1, 2, 3) powders after milling for 60 h keep single α-Fe(Si) phase. In addition, with the increase of Ti content, the lattice constant of the precipitated phase decreases, the saturation magnetization increases and the coercivity decreases.
2012, 41(3):514-517.
Abstract:
The static and dynamic mechanical responses of Mg-Li alloy prepared by vacuum induction melting were investigated by split Hopkinson pressure bar (SHPB) under the strain rates of 1.7×10-3-1026 s-1, and the stress-strain curves under different strain rates were obtained. Based on the SHPB experimental results, the constitutive relation of this alloy under one-dimensional stress high strain rates impact was fitted. Besides, the metallurgical structure of the Mg-Li alloy after impact under different strain rates was also analyzed. Results show that the dynamic impact properties of the Mg-Li alloy are not sensitive to the strain rate. The constitutive relation of the Mg-Li alloy under one-dimensional stress high strain rates impact is σ=1.5ε (σ<0.12 GPa), and σ=0.12+2.7ε1.2 (σ≥0.12 GPa). With increase of the strain rate, the grains become smaller at first and then tend to be irregular shapes. The short-strip compounds are concentrated distributing in the boundaries.
The static and dynamic mechanical responses of Mg-Li alloy prepared by vacuum induction melting were investigated by split Hopkinson pressure bar (SHPB) under the strain rates of 1.7×10-3-1026 s-1, and the stress-strain curves under different strain rates were obtained. Based on the SHPB experimental results, the constitutive relation of this alloy under one-dimensional stress high strain rates impact was fitted. Besides, the metallurgical structure of the Mg-Li alloy after impact under different strain rates was also analyzed. Results show that the dynamic impact properties of the Mg-Li alloy are not sensitive to the strain rate. The constitutive relation of the Mg-Li alloy under one-dimensional stress high strain rates impact is σ=1.5ε (σ<0.12 GPa), and σ=0.12+2.7ε1.2 (σ≥0.12 GPa). With increase of the strain rate, the grains become smaller at first and then tend to be irregular shapes. The short-strip compounds are concentrated distributing in the boundaries.
2012, 41(3):518-521.
Abstract:
Plasma nitriding combined with pulsed bias arc ion plating was employed to treat cast pure titanium (PT) used as a kind of medical and dental materials in order to improve the surface properties and to obtain better the color stability. The morphology and phase structure of the modified layer were analyzed using XRD and SEM. The contact angle and color of the samples were studied after ion nitriding/TiN-coated compound treatment (compound nitriding, CN) by Easy Drop Standard and spectraphotometer, respectively. The results show that a composite gradient TiN coating, which is uniform, stable and dense, is formed after CN. The contact angle of the artificial saliva on samples treated by CN (60.29±2.00)° is obviously lower than that of the untreated PT samples (73.12±3.29)°. And the color of CN samples with L*: 61.22±0.455, a*: 1.84±0.055, b*: 25.66±0.219 in CIE-1976- L*, a*, b* colorrange system is bright and golden. The main phases on the specimen surface are TiN and Ti2N with good wear resistance.
Plasma nitriding combined with pulsed bias arc ion plating was employed to treat cast pure titanium (PT) used as a kind of medical and dental materials in order to improve the surface properties and to obtain better the color stability. The morphology and phase structure of the modified layer were analyzed using XRD and SEM. The contact angle and color of the samples were studied after ion nitriding/TiN-coated compound treatment (compound nitriding, CN) by Easy Drop Standard and spectraphotometer, respectively. The results show that a composite gradient TiN coating, which is uniform, stable and dense, is formed after CN. The contact angle of the artificial saliva on samples treated by CN (60.29±2.00)° is obviously lower than that of the untreated PT samples (73.12±3.29)°. And the color of CN samples with L*: 61.22±0.455, a*: 1.84±0.055, b*: 25.66±0.219 in CIE-1976- L*, a*, b* colorrange system is bright and golden. The main phases on the specimen surface are TiN and Ti2N with good wear resistance.
2012, 41(3):522-526.
Abstract:
Tantalum was prepared by solid oxygen-ion membrane (SOM) process from Ta2O5 directly in molten flux CaCl2 system. The micro-structural features and the porosities of the Ta2O5 pellets prepared at different pressures and sintered at different temperatures were investigated, and then the effect laws of the cathode microstructure on product morphology and oxygen contents were obtained. The results show that the particle size of cathode pellets and porosities are importance factors for the electrochemical reduction process. The porosities of the Ta2O5 pellets decrease remarkably as the pressure and sintering temperature increase. High porosity can enhance the rate of deoxidization and obtain bigger particle products; contrarily, a compact outer layer of metal tantalum is formed. When the Ta2O5 pellets are pressed at 4 MPa and sintered at 1150 oC for 2 h (or pressed at 6 MPa and sintered at 1100 oC for 2 h), electrolysis reaction activity is good and electrolytic products have low oxygen content.
Tantalum was prepared by solid oxygen-ion membrane (SOM) process from Ta2O5 directly in molten flux CaCl2 system. The micro-structural features and the porosities of the Ta2O5 pellets prepared at different pressures and sintered at different temperatures were investigated, and then the effect laws of the cathode microstructure on product morphology and oxygen contents were obtained. The results show that the particle size of cathode pellets and porosities are importance factors for the electrochemical reduction process. The porosities of the Ta2O5 pellets decrease remarkably as the pressure and sintering temperature increase. High porosity can enhance the rate of deoxidization and obtain bigger particle products; contrarily, a compact outer layer of metal tantalum is formed. When the Ta2O5 pellets are pressed at 4 MPa and sintered at 1150 oC for 2 h (or pressed at 6 MPa and sintered at 1100 oC for 2 h), electrolysis reaction activity is good and electrolytic products have low oxygen content.
2012, 41(3):527-530.
Abstract:
A novel concept of stepped superplasticity deformation (Stepped-SPD) was proposed for exploring a way from superplasticity deformation process to enhance the metal plasticity. In that Stepped-SPD process, the constant speed deformation and the maximum m superplasticity deformation ( Max m SPD) were adopted superlatively to finish the tension of samples through two steps. The strain of the first step and clearance time between two steps in Stepped-SPD were controlled in order to facilitate the grain refinement and structure improvement which induced plasticity enhancement. In these experiments, stepped tension deformation was compared with single-step tensile deformation and the influences of pre-strain of the first step in Stepped-SPD on elongation and microstructure were analyzed. The results for TC6 alloy without grain refinement treating show that the Stepped-SPD tensile method obtains the best SPD capability, with an elongation of 2053% corresponding to the pre-strain of 2.0, whereas the Max m SPD and constant speed tensile method produces the biggest elongations of 1347% and 753.9%, respectively. The elongation for TC4 titanium alloy using stepped tensile test is 2147% corresponding to the pre-strain of 1.5 in the first deformation step. Thus, it is indicated that the Stepped-SPD induces the plastic enhancement in comparison with the single-step deformation. Moreover, the pre-strain determines the grain size of the tensile sample in Stepped-SPD.
A novel concept of stepped superplasticity deformation (Stepped-SPD) was proposed for exploring a way from superplasticity deformation process to enhance the metal plasticity. In that Stepped-SPD process, the constant speed deformation and the maximum m superplasticity deformation ( Max m SPD) were adopted superlatively to finish the tension of samples through two steps. The strain of the first step and clearance time between two steps in Stepped-SPD were controlled in order to facilitate the grain refinement and structure improvement which induced plasticity enhancement. In these experiments, stepped tension deformation was compared with single-step tensile deformation and the influences of pre-strain of the first step in Stepped-SPD on elongation and microstructure were analyzed. The results for TC6 alloy without grain refinement treating show that the Stepped-SPD tensile method obtains the best SPD capability, with an elongation of 2053% corresponding to the pre-strain of 2.0, whereas the Max m SPD and constant speed tensile method produces the biggest elongations of 1347% and 753.9%, respectively. The elongation for TC4 titanium alloy using stepped tensile test is 2147% corresponding to the pre-strain of 1.5 in the first deformation step. Thus, it is indicated that the Stepped-SPD induces the plastic enhancement in comparison with the single-step deformation. Moreover, the pre-strain determines the grain size of the tensile sample in Stepped-SPD.
2012, 41(3):531-534.
Abstract:
The Ag+ were reduced to elemental silver by free-electron from microwave radiation [Ag(NH3)2]OH complex aqueous solution without any reducing agent, and the nano-silver sol was formed under the protection of PVP. UV-Vis absorption spectra show that the absorbance of the colloidal silver nanoparticles increases with the radiation time, but the maximal absorption wavelength does not change. The absorbance keeps stable when the microwave radiation time is up to 5 min at the mass ratio of Ag+/PVP=1:8. TEM observation and image analysis results show that the morphology of nano-silver particles are spherical and monodisperse, with an average diameter of 1.36 nm and the standard deviation of 0.54 nm.
The Ag+ were reduced to elemental silver by free-electron from microwave radiation [Ag(NH3)2]OH complex aqueous solution without any reducing agent, and the nano-silver sol was formed under the protection of PVP. UV-Vis absorption spectra show that the absorbance of the colloidal silver nanoparticles increases with the radiation time, but the maximal absorption wavelength does not change. The absorbance keeps stable when the microwave radiation time is up to 5 min at the mass ratio of Ag+/PVP=1:8. TEM observation and image analysis results show that the morphology of nano-silver particles are spherical and monodisperse, with an average diameter of 1.36 nm and the standard deviation of 0.54 nm.
2012, 41(3):535-538.
Abstract:
The silver-coated copper powders were prepared by a reduction method, using glucose as the reductant. The different adding processes of silver-ammonia solution varied the micro-morphology and appearance color of the powders. The coated powders were characterized by SEM and EDS. The silver contents of different adding processes were calculated by titration. Thus the optimal adding process was determined. Meanwhile, the silver coating deposit process was analyzed by observation of the powders taken out from the solution at different stages during silver plating.
The silver-coated copper powders were prepared by a reduction method, using glucose as the reductant. The different adding processes of silver-ammonia solution varied the micro-morphology and appearance color of the powders. The coated powders were characterized by SEM and EDS. The silver contents of different adding processes were calculated by titration. Thus the optimal adding process was determined. Meanwhile, the silver coating deposit process was analyzed by observation of the powders taken out from the solution at different stages during silver plating.
2012, 41(3):539-541.
Abstract:
A measurement method of Ta contents in U-Ta alloy by energy dispersive X-ray fluorescence (EDXRF) was introduced. Dissolved by acid, coated on filter paper and prepared the filter paper samples, the Ta contents in U-Ta alloy samples were determined by EDXRF. The method is simple, rapid, accurate, and applicable to the determination of Ta content in 1%-6% U-Ta alloy samples. The relative standard deviation (RSD) of this method for the U-Ta alloy sample of 1.5% tantalum content is less than 0.6%, while for the U-Ta alloy sample of 5% tantalum content is less than 0.3%.
A measurement method of Ta contents in U-Ta alloy by energy dispersive X-ray fluorescence (EDXRF) was introduced. Dissolved by acid, coated on filter paper and prepared the filter paper samples, the Ta contents in U-Ta alloy samples were determined by EDXRF. The method is simple, rapid, accurate, and applicable to the determination of Ta content in 1%-6% U-Ta alloy samples. The relative standard deviation (RSD) of this method for the U-Ta alloy sample of 1.5% tantalum content is less than 0.6%, while for the U-Ta alloy sample of 5% tantalum content is less than 0.3%.
2012, 41(3):542-547.
Abstract:
Rare earth-Magnesium-Nickel-based hydrogen storage alloys with superstructure have attracted intensive interests as the next-generation negative electrode materials of nickel/metal hydride (Ni/MH) batteries due to their high hydrogen storage capacity and high rate dischargeability. From the point of view of the correlation between phase structure, hydrogen storage characteristics and electrochemical properties, the state-of-arts of the R-Mg-Ni-based AB3, A2B7 and A5B19-type hydrogen storage electrode alloys were reviewed. It is expected to be helpful for exploring novel rare earth-based hydrogen storage electrode alloys with high discharge capacity and long cycling life.
Rare earth-Magnesium-Nickel-based hydrogen storage alloys with superstructure have attracted intensive interests as the next-generation negative electrode materials of nickel/metal hydride (Ni/MH) batteries due to their high hydrogen storage capacity and high rate dischargeability. From the point of view of the correlation between phase structure, hydrogen storage characteristics and electrochemical properties, the state-of-arts of the R-Mg-Ni-based AB3, A2B7 and A5B19-type hydrogen storage electrode alloys were reviewed. It is expected to be helpful for exploring novel rare earth-based hydrogen storage electrode alloys with high discharge capacity and long cycling life.
2012, 41(3):548-553.
Abstract:
Various types of magnetic fields in solidification and their application are introduced, and their main pros ans cons for solidification process are discussed. There are two main kinds of magnetic fields used in solidification: steady magnetic fields and non-steady magnetic fields. The steady magnetic field includes cusp magnetic field (CMF), vertical magnetic field (VMF) and horizontal magnetic field (HMF), while the non-steady magnetic field includes rotating magnetic field (RMF), traveling magnetic field (TMF), alternating (pulsating) magnetic field (AMF, PMF) and eletromagnetic field (EMF). The prosperous future of the magnetic field process is expected.
Various types of magnetic fields in solidification and their application are introduced, and their main pros ans cons for solidification process are discussed. There are two main kinds of magnetic fields used in solidification: steady magnetic fields and non-steady magnetic fields. The steady magnetic field includes cusp magnetic field (CMF), vertical magnetic field (VMF) and horizontal magnetic field (HMF), while the non-steady magnetic field includes rotating magnetic field (RMF), traveling magnetic field (TMF), alternating (pulsating) magnetic field (AMF, PMF) and eletromagnetic field (EMF). The prosperous future of the magnetic field process is expected.
2012, 41(3):554-558.
Abstract:
Some experimental methods used to characterize the interfacial reaction between titanium alloys and mold materials are presented. The effects of mold materials, processing parameters and alloying elements on the interfacial reaction are reviewed. Furthermore, the theoretical research status on interfacial reaction is introduced, and some results of the interfacial reaction research are collected systematically.
Some experimental methods used to characterize the interfacial reaction between titanium alloys and mold materials are presented. The effects of mold materials, processing parameters and alloying elements on the interfacial reaction are reviewed. Furthermore, the theoretical research status on interfacial reaction is introduced, and some results of the interfacial reaction research are collected systematically.
33 Research Progress in Precise Shape-controlling Technology of Single Crystal Hollow Turbine Blades
2012, 41(3):559-564.
Abstract:
According to the precise shape-controlling technique of single crystal hollow turbine blade in aero-engine, the research achievements on the precise shape-controlling technology of single crystal hollow turbine blade were generalized and analyzed from several aspects, which include the precise forming technology of complex ceramic core, the near net-shape investment casting technology and the controlling means of dimensional accuracy combining with the research situation at home and abroad. The researching results of the precise shape-controlling technique for single crystal hollow turbine blade were mainly introduced. Meanwhile, the future researching scope of the precise shape-controlling technique of single crystal hollow turbine blade was discussed.
According to the precise shape-controlling technique of single crystal hollow turbine blade in aero-engine, the research achievements on the precise shape-controlling technology of single crystal hollow turbine blade were generalized and analyzed from several aspects, which include the precise forming technology of complex ceramic core, the near net-shape investment casting technology and the controlling means of dimensional accuracy combining with the research situation at home and abroad. The researching results of the precise shape-controlling technique for single crystal hollow turbine blade were mainly introduced. Meanwhile, the future researching scope of the precise shape-controlling technique of single crystal hollow turbine blade was discussed.
2012, 41(3):851-856.
Abstract:
Nanocrystalline Co-Ni-Fe alloys were synthesized by pulsed electrodeposition. The composition, microstructure and surface morphologies were studied by EDS、XRD, TEM and SEM. The effect of Co content and grain sizes on the electrochemical corrosion behaviour of nanocrystalline Co-Ni-Fe deposits in 3.5wt% NaCl solution were investigated using Tafel polarization curves. The results reveal that the grain sizes of the nanocrystalline fcc Co-Ni-Fe alloys descrease with increasing of the content of Co in the coating. The grain sizes of nanocrystalline Co-Ni-Fe alloys increase with increasing of the annealing temperature，showing a strong （111）texture. The corrosion rates of Co-Ni-Fe alloys decrease first and then increase with increasing of the Co content in the coating. The corrosion rates decline gradually with increasing of the annealing temperature. Comparing to the nanocrystalline deposits, the coarse grain deposit exhibits a quite a different corrosion morphologies.
Nanocrystalline Co-Ni-Fe alloys were synthesized by pulsed electrodeposition. The composition, microstructure and surface morphologies were studied by EDS、XRD, TEM and SEM. The effect of Co content and grain sizes on the electrochemical corrosion behaviour of nanocrystalline Co-Ni-Fe deposits in 3.5wt% NaCl solution were investigated using Tafel polarization curves. The results reveal that the grain sizes of the nanocrystalline fcc Co-Ni-Fe alloys descrease with increasing of the content of Co in the coating. The grain sizes of nanocrystalline Co-Ni-Fe alloys increase with increasing of the annealing temperature，showing a strong （111）texture. The corrosion rates of Co-Ni-Fe alloys decrease first and then increase with increasing of the Co content in the coating. The corrosion rates decline gradually with increasing of the annealing temperature. Comparing to the nanocrystalline deposits, the coarse grain deposit exhibits a quite a different corrosion morphologies.
2012, 41(3):857-861.
Abstract:
Based on the fundamental thermodynamic principles, the ordering behavior of the ThMn12-type intermetallics NdFe10-xCoxMo2 were studied using a general four-sublattice model supported with first-principles calculations. The results show that the 2a sublattices are occupied by the rare earth elements Nd exclusively, while the 50% of 8i sublattices are occupied by Mo atoms, 8f, 8j and the rest 50% of 8i sublattices are shared by Fe and Co atoms, which agreed well with the reported experimental results. Site occupancy fractions of Fe and Co atoms vary with temperature in the quaternary alloys due to the partial solid solution of Fe and Co atoms in sublattice 8f and 8j, while they keep constant in ternary alloys upon varying temperature. Co and Fe atoms can substitute each other without affecting the ordering behavior of the intermetallics. In the alloy NdFe5Co5Mo2, with an equal the content of Fe and Co, Fe atoms favor the occupancy of sublattice 8f, while Co atoms prefer the occupancy of sublattice 8j.
Based on the fundamental thermodynamic principles, the ordering behavior of the ThMn12-type intermetallics NdFe10-xCoxMo2 were studied using a general four-sublattice model supported with first-principles calculations. The results show that the 2a sublattices are occupied by the rare earth elements Nd exclusively, while the 50% of 8i sublattices are occupied by Mo atoms, 8f, 8j and the rest 50% of 8i sublattices are shared by Fe and Co atoms, which agreed well with the reported experimental results. Site occupancy fractions of Fe and Co atoms vary with temperature in the quaternary alloys due to the partial solid solution of Fe and Co atoms in sublattice 8f and 8j, while they keep constant in ternary alloys upon varying temperature. Co and Fe atoms can substitute each other without affecting the ordering behavior of the intermetallics. In the alloy NdFe5Co5Mo2, with an equal the content of Fe and Co, Fe atoms favor the occupancy of sublattice 8f, while Co atoms prefer the occupancy of sublattice 8j.
2012, 41(3):862-866.
Abstract:
The microstructures, hardness and electrochemical properties of AlCoCrFeNiTi0.5 high-entropy alloys fabricated by cold crucible levitation melting (CCLM) with as-cast structure and tempering treated structures were investigated. The results show that in contrast to suction casting using copper molds, CCLM causes the growth of dendrite phase and separation of ω phase. As the increase of temperature, the dendrite grains grow up, the amount of eutectic structures increases, and the intensity of BCC peak shows a rising trend after the first drop. At the temperature of 800 ℃, the dendrite grains become refined. And then, as the temperature increases, the element segregation of interdendrite is weakened. The alloy exhibits a superior resistance to tempering and softening property. Furthermore, pitting corrosions are mainly concentrated in the place between dendrite phase and eutectic α phase. The tempering treatment improves corrosion properties in a 3.5% NaCl solution, and the alloy tempered at 700 exhibits the best corrosion property among the experimental alloys.
The microstructures, hardness and electrochemical properties of AlCoCrFeNiTi0.5 high-entropy alloys fabricated by cold crucible levitation melting (CCLM) with as-cast structure and tempering treated structures were investigated. The results show that in contrast to suction casting using copper molds, CCLM causes the growth of dendrite phase and separation of ω phase. As the increase of temperature, the dendrite grains grow up, the amount of eutectic structures increases, and the intensity of BCC peak shows a rising trend after the first drop. At the temperature of 800 ℃, the dendrite grains become refined. And then, as the temperature increases, the element segregation of interdendrite is weakened. The alloy exhibits a superior resistance to tempering and softening property. Furthermore, pitting corrosions are mainly concentrated in the place between dendrite phase and eutectic α phase. The tempering treatment improves corrosion properties in a 3.5% NaCl solution, and the alloy tempered at 700 exhibits the best corrosion property among the experimental alloys.
2012, 41(3):867-871.
Abstract:
The microstructures and the creep behavior of ZK31+4Si magnesium alloy processed by Equal channel angular pressing (ECAP) were investigated. The experimental results show that the coarse Chinese script-like Mg2Si precipitates are refined to fine polygonal shape particles and redistributed dispersedly after ECAP. The creep resistance is greatly enhanced after ECAP. The ctable creep rate of the 8-pass ECAPed specimen is nearly 1/15 of that of the as-cast one, and its creep life is increased by about 8 times. The curves of the minimum strain rate versus the stress show that the alloy ECAPed either through 8 passes or through 4 passes exhibit a same stress exponent n?4. Furthermore, the theoretical calculation results according to the dislocation creep model with n=4 are well in agreement with the experimental values, indicating that the creep under the present test condition is controlled by the movement of dislocations.
The microstructures and the creep behavior of ZK31+4Si magnesium alloy processed by Equal channel angular pressing (ECAP) were investigated. The experimental results show that the coarse Chinese script-like Mg2Si precipitates are refined to fine polygonal shape particles and redistributed dispersedly after ECAP. The creep resistance is greatly enhanced after ECAP. The ctable creep rate of the 8-pass ECAPed specimen is nearly 1/15 of that of the as-cast one, and its creep life is increased by about 8 times. The curves of the minimum strain rate versus the stress show that the alloy ECAPed either through 8 passes or through 4 passes exhibit a same stress exponent n?4. Furthermore, the theoretical calculation results according to the dislocation creep model with n=4 are well in agreement with the experimental values, indicating that the creep under the present test condition is controlled by the movement of dislocations.
2012, 41(3):872-876.
Abstract:
Al-Ni-Y-Co and Al-Ni-Mm-Fe amorphous and nanocrystalline composite coatings were prepared on the surface of AZ91 magnesium alloy by automatic high velocity arc spraying system. The microstructures of the composite coatings were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that the composite coatings compose of amorphous phases and crystalline phases. The composite coatings have a compact structure with low porosity. The Vickers microhardness HV of Al-Ni-Y-Co and Al-Ni-Mm-Fe coatings is 3117.6 MPa and 3407.2 MPa, respectively, which is about four times higher than that of the traditional Al-RE coatings and five times higher than that of the AZ91 magnesium alloy. The electrochemistry experimental results show that the corrosion resistances of the Al-Ni-Y-Co and Al-Ni-Mm-Fe amorphous and nanocrystalline composite coatings are superior to those of the traditional Al-RE coatings and AZ91 magnesium alloy.
Al-Ni-Y-Co and Al-Ni-Mm-Fe amorphous and nanocrystalline composite coatings were prepared on the surface of AZ91 magnesium alloy by automatic high velocity arc spraying system. The microstructures of the composite coatings were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that the composite coatings compose of amorphous phases and crystalline phases. The composite coatings have a compact structure with low porosity. The Vickers microhardness HV of Al-Ni-Y-Co and Al-Ni-Mm-Fe coatings is 3117.6 MPa and 3407.2 MPa, respectively, which is about four times higher than that of the traditional Al-RE coatings and five times higher than that of the AZ91 magnesium alloy. The electrochemistry experimental results show that the corrosion resistances of the Al-Ni-Y-Co and Al-Ni-Mm-Fe amorphous and nanocrystalline composite coatings are superior to those of the traditional Al-RE coatings and AZ91 magnesium alloy.
