Volume 38,Issue 3,2009 Table of Contents
Yang Zhaozhu
,
Xue Chengshan
,
Zhuang Huizhao
,
Wang Gongtang
,
Chen Jinhua
,
Li Hong
,
Qin Lixia
,
Wang Zouping
2009, 38(3):377-379.
Abstract:
Large-scale GaN nanowires were synthesized on Si(111) substrates through ammoniating Ga2O3/V films. The as-grown products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that the grown GaN nanowires have a smooth and clean surface with diameters ranging from 20 nm to 60 nm and lengths of about several tens of micrometers. The results of HRTEM and selected-area electron diffraction (SAED) show that the nanowires are pure hexagonal GaN single crystal. The photoluminescence (PL) spectrum indicates that the GaN nanowires have good emission property. The growth mechanism is discussed briefly.
Large-scale GaN nanowires were synthesized on Si(111) substrates through ammoniating Ga2O3/V films. The as-grown products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that the grown GaN nanowires have a smooth and clean surface with diameters ranging from 20 nm to 60 nm and lengths of about several tens of micrometers. The results of HRTEM and selected-area electron diffraction (SAED) show that the nanowires are pure hexagonal GaN single crystal. The photoluminescence (PL) spectrum indicates that the GaN nanowires have good emission property. The growth mechanism is discussed briefly.
2009, 38(3):380-383.
Abstract:
The effects of Ti addition on the microstructure and magnetic properties of Nd9.4Fe79.6-xTixB11(x=0, 1, 2, 4, 6)nanocrystalline alloys were investigated. The results show that Ti addition suppresses the formation of unfavorable soft Nd2Fe23B3 and Fe3B phases, and promotes the formation of Nd2Fe14B phases. When the Ti content reaches a certain amount, Ti may precipitate as TiB2 from the alloys. TiB2 may serve as inoculants and promotes uniform nucleation, and thus increases the exchange coupling between the hard and soft phases. As a result, excellent magnetic properties of Br=0.87 T, Hcj=931 kA/m and (BH)max=115.4 kJ/m3 are achieved in Nd9.4Fe75.6Ti4B11 alloy ribbons.
The effects of Ti addition on the microstructure and magnetic properties of Nd9.4Fe79.6-xTixB11(x=0, 1, 2, 4, 6)nanocrystalline alloys were investigated. The results show that Ti addition suppresses the formation of unfavorable soft Nd2Fe23B3 and Fe3B phases, and promotes the formation of Nd2Fe14B phases. When the Ti content reaches a certain amount, Ti may precipitate as TiB2 from the alloys. TiB2 may serve as inoculants and promotes uniform nucleation, and thus increases the exchange coupling between the hard and soft phases. As a result, excellent magnetic properties of Br=0.87 T, Hcj=931 kA/m and (BH)max=115.4 kJ/m3 are achieved in Nd9.4Fe75.6Ti4B11 alloy ribbons.
2009, 38(3):384-388.
Abstract:
A layer of TiO2 film was prepared by sol-gel method on the surface of TLM(Ti-3Zr-2Sn-3Mo-25Nb) alloy. Then the coated samples were treated by hydroxyl solution and amination solution in order to introduce the OH- and NH2- active groups, and the heparin was linked on the surface of TiO2 film through these active groups. The phase identification and the surface characteristics of the samples were successively undertaken using XRD, SEM and EDS. The in vitro blood compatibility of the TLM alloy specimens with and without heparinization treatments was evaluated by the contact angle test, the hemolysis test and investigation of their platelet adhesion behavior. The results showed that the haemocompatibility of the TLM alloy could be significantly improved by surface modification via heparinization.
A layer of TiO2 film was prepared by sol-gel method on the surface of TLM(Ti-3Zr-2Sn-3Mo-25Nb) alloy. Then the coated samples were treated by hydroxyl solution and amination solution in order to introduce the OH- and NH2- active groups, and the heparin was linked on the surface of TiO2 film through these active groups. The phase identification and the surface characteristics of the samples were successively undertaken using XRD, SEM and EDS. The in vitro blood compatibility of the TLM alloy specimens with and without heparinization treatments was evaluated by the contact angle test, the hemolysis test and investigation of their platelet adhesion behavior. The results showed that the haemocompatibility of the TLM alloy could be significantly improved by surface modification via heparinization.
2009, 38(3):389-392.
Abstract:
Using H3BO3 as a flux, LaMgAl11O19:Mn2+ and LaMgAl11O19:RE, Mn2+(RE=Eu2+, Gd3+) were synthesized by solid state reaction at 1150 ℃ for 4 h. The effect of Mn2+ on the luminescent properties excited by vacuum ultraviolet (VUV) was investigated. The strong emission spectrum excited by 147 nm is composed of peaks from Eu2+ and Mn2+ luminescence in LaMgAl11O19:(Eu2+, Mn2+ ) and only Mn2+ luminescence in LaMgAl11O19:Mn2+ and LaMgAl11O19:(Gd3+, Mn2+). The results show that the green emission of Mn2+ becomes stronger because of efficient energy transferring from Eu2+ and Gd3+ to Mn2+
Using H3BO3 as a flux, LaMgAl11O19:Mn2+ and LaMgAl11O19:RE, Mn2+(RE=Eu2+, Gd3+) were synthesized by solid state reaction at 1150 ℃ for 4 h. The effect of Mn2+ on the luminescent properties excited by vacuum ultraviolet (VUV) was investigated. The strong emission spectrum excited by 147 nm is composed of peaks from Eu2+ and Mn2+ luminescence in LaMgAl11O19:(Eu2+, Mn2+ ) and only Mn2+ luminescence in LaMgAl11O19:Mn2+ and LaMgAl11O19:(Gd3+, Mn2+). The results show that the green emission of Mn2+ becomes stronger because of efficient energy transferring from Eu2+ and Gd3+ to Mn2+
2009, 38(3):393-397.
Abstract:
In hot rolling of large rings of titanium alloy (LRTs), the ratio of roll radii R1/R2, i.e., the ratio of the radius of the driver roll R1 to that of the idle roll R2, has a significant effect on the geometric shape of the deformation zone (GSDZ) which plays a decisive role in achieving LRTs with high quality. In the study, an analytical description of the GSDZ is presented, and quantitative relationships between the GSDZ and R1/R2 are determined. Then a validated coupled thermo-mechanical 3D-FE model of the process is developed in the dynamic explicit code ABAQUS/Explicit. Finally, an investigation is conducted regarding the effects of R1/R2 on the quality of LRTs from the view point of GSDZ using FE simulation. The results show that there is an optimized range of R1/R2 for obtaining LRTs with better end-plane quality and more uniform strain and temperature distributions
In hot rolling of large rings of titanium alloy (LRTs), the ratio of roll radii R1/R2, i.e., the ratio of the radius of the driver roll R1 to that of the idle roll R2, has a significant effect on the geometric shape of the deformation zone (GSDZ) which plays a decisive role in achieving LRTs with high quality. In the study, an analytical description of the GSDZ is presented, and quantitative relationships between the GSDZ and R1/R2 are determined. Then a validated coupled thermo-mechanical 3D-FE model of the process is developed in the dynamic explicit code ABAQUS/Explicit. Finally, an investigation is conducted regarding the effects of R1/R2 on the quality of LRTs from the view point of GSDZ using FE simulation. The results show that there is an optimized range of R1/R2 for obtaining LRTs with better end-plane quality and more uniform strain and temperature distributions
2009, 38(3):398-403.
Abstract:
The complexity and diversity of microstructural information involved in Ti alloys makes it rather difficult to quantitatively analyze properties or describe microstructural evolution behavior. Feasible and rigorous models capable of quantifying various microstructural data are rarely researched. Based on metallographical characteristics and mechanism of microstructure evolution, applying the stereology and quantitative Metallography rules, a preliminary system of models and methods for quantifying many important microstructural features of Ti alloys was developed. The work is an exploration for investigating the microstructure evolution and the relationship between microstructure and performance of Ti alloys. These microstructural features mainly include phase volume fraction, β grain size, thickness of Widmanst?tten α laths, colony size, and α phase information (size/orientation/aspect) in some microstructures. Six rules for manual-splitting α phase on image processing was presented. These models and methods are feasible, and explained with some examples
The complexity and diversity of microstructural information involved in Ti alloys makes it rather difficult to quantitatively analyze properties or describe microstructural evolution behavior. Feasible and rigorous models capable of quantifying various microstructural data are rarely researched. Based on metallographical characteristics and mechanism of microstructure evolution, applying the stereology and quantitative Metallography rules, a preliminary system of models and methods for quantifying many important microstructural features of Ti alloys was developed. The work is an exploration for investigating the microstructure evolution and the relationship between microstructure and performance of Ti alloys. These microstructural features mainly include phase volume fraction, β grain size, thickness of Widmanst?tten α laths, colony size, and α phase information (size/orientation/aspect) in some microstructures. Six rules for manual-splitting α phase on image processing was presented. These models and methods are feasible, and explained with some examples
2009, 38(3):404-408.
Abstract:
Dynamic compressive performances of hot rolled AZ31B which have different angles between the compressive direction and the normal direction of the rolled sheet were tested using SHPB and strain control techniques. The mechanism of the plastic deformation at different strain amount was studied. Results indicate that when the strain rate is 1200 s-1, the twin number of samples in different orientation increases with plastic strain increasing; when the strain rate increases to 2800 s-1, the σ-ε curves have no obvious charges as the angle is 0o and 45o, compared with that at 1200 s-1; however the σ-ε curves vary from concave to convex when the angle is 90o, because thermal softening has occurred with increasing plastic strain, which results in the number of twin decreasing, and smaller strain hardening
Dynamic compressive performances of hot rolled AZ31B which have different angles between the compressive direction and the normal direction of the rolled sheet were tested using SHPB and strain control techniques. The mechanism of the plastic deformation at different strain amount was studied. Results indicate that when the strain rate is 1200 s-1, the twin number of samples in different orientation increases with plastic strain increasing; when the strain rate increases to 2800 s-1, the σ-ε curves have no obvious charges as the angle is 0o and 45o, compared with that at 1200 s-1; however the σ-ε curves vary from concave to convex when the angle is 90o, because thermal softening has occurred with increasing plastic strain, which results in the number of twin decreasing, and smaller strain hardening
2009, 38(3):409-412.
Abstract:
Microstructure, martensitic transformation temperature and shape memory effect of Co-Fe alloys were investigated by optical observation, X-ray diffraction, DSC and bending tests. Results show that the shape memory effect of Co-Fe alloys is associated with the fcc/hcp martensitic transformation. When Fe content is higher than 5.65wt%, the microstructure exhibits single γ phase with fcc structure. When Fe content is lower than 5.6wt%, the microstructure consists of γ phase and ε martensitic phase with hcp structure. The martensitic transformation temperatures of Co-xFe alloys are almost linearly decreased with increasing Fe content, following the relationship: Ms (℃) = 417-69.97x(Fe%). The highest recoverable strain of Co-4Fe (wt%) alloy is 0.86%. It is believed that Co-Fe alloys will exhibit better shape memory effect after proper heat treatment and shape memory training
Microstructure, martensitic transformation temperature and shape memory effect of Co-Fe alloys were investigated by optical observation, X-ray diffraction, DSC and bending tests. Results show that the shape memory effect of Co-Fe alloys is associated with the fcc/hcp martensitic transformation. When Fe content is higher than 5.65wt%, the microstructure exhibits single γ phase with fcc structure. When Fe content is lower than 5.6wt%, the microstructure consists of γ phase and ε martensitic phase with hcp structure. The martensitic transformation temperatures of Co-xFe alloys are almost linearly decreased with increasing Fe content, following the relationship: Ms (℃) = 417-69.97x(Fe%). The highest recoverable strain of Co-4Fe (wt%) alloy is 0.86%. It is believed that Co-Fe alloys will exhibit better shape memory effect after proper heat treatment and shape memory training
9 Effects of B Element on Hydrogen Storage Performances of Mg76-xTi12Fe8Ni4Bx (x=0, 1, 2, 3, 4) Alloys
2009, 38(3):413-415.
Abstract:
Mg76-xTi12Fe8Ni4Bx (x=0, 1, 2, 3, 4) alloys were prepared and the effects of substitution of B for Mg on hydrogen storage performances of the alloys were investigated. In the alloys, Mg2Ni and NiTi are main phases and the amorphous degree increases gradually with amount of B content increasing. Partial substitution of B for Mg can decrease the temperature of hydrogen absorption reaction and hysteresis effectively. On the other hand, substitution of B for Mg increases the hydrogen absorption/desorption plateau pressure and decreases hydrogen absorption capacity and absorption/desorption rate
Mg76-xTi12Fe8Ni4Bx (x=0, 1, 2, 3, 4) alloys were prepared and the effects of substitution of B for Mg on hydrogen storage performances of the alloys were investigated. In the alloys, Mg2Ni and NiTi are main phases and the amorphous degree increases gradually with amount of B content increasing. Partial substitution of B for Mg can decrease the temperature of hydrogen absorption reaction and hysteresis effectively. On the other hand, substitution of B for Mg increases the hydrogen absorption/desorption plateau pressure and decreases hydrogen absorption capacity and absorption/desorption rate
10 Microscopic Phase-Field Study of Antisite Defect of Ni3Al in High Al Concentration Ni75AlxV25-xAlloy
2009, 38(3):416-420.
Abstract:
The microscopic phase-field method was employed to study the antisite defect of Ni3Al which precipitated from high Al concentration Ni75AlxV25-x alloy. Result shows that the main antisite defect type of this alloy are VAl, NiAl; with the increasing of Al concentration, the AlNi antisite defect also increases; while changes of the other three types antisite defect NiAl, VAl, and VNi are slightly complex for its dependence on the precipitation or not of Ni3V phase; at comparatively lower Al concentration, when there is Ni3V phase, NiAl decrease with elevated Al concentration, while VNi increase and VAl keeps unconverted; at comparatively higher Al concentration, when there is no Ni3V phase precipitated from the matrix, NiAl slightly decreases with elevated Al concentration while VNi and VAl decrease sharply
The microscopic phase-field method was employed to study the antisite defect of Ni3Al which precipitated from high Al concentration Ni75AlxV25-x alloy. Result shows that the main antisite defect type of this alloy are VAl, NiAl; with the increasing of Al concentration, the AlNi antisite defect also increases; while changes of the other three types antisite defect NiAl, VAl, and VNi are slightly complex for its dependence on the precipitation or not of Ni3V phase; at comparatively lower Al concentration, when there is Ni3V phase, NiAl decrease with elevated Al concentration, while VNi increase and VAl keeps unconverted; at comparatively higher Al concentration, when there is no Ni3V phase precipitated from the matrix, NiAl slightly decreases with elevated Al concentration while VNi and VAl decrease sharply
11 Globularization Mechanisms during Hot Deformation Processes of TC11 Alloy with Lamellar Structure
2009, 38(3):421-425.
Abstract:
Microstructure and grain boundary character during hot deformation globularization processes of TC11 alloy with annealed-lamellar structure were investigated by TEM, SEM and EBSD techniques. The results indicate that globularization processes include: 1) forming of sub-structures with low-angle boundaries by deformation and recovery in α plates; 2) disintegrating of α plates by diffusion and slipping along grain boundaries; 3) globularizing of α grains and homogenizing of structure by diffusing and slipping along grain boundaries. EBSD testing results indicate that globularization mechanisms during hot deformation processes of the alloy with lamellar structure are continuous dynamic recrystallization occurring in α plates and dynamic recovery or discontinuous dynamic recrystallization occurring in β phase
Microstructure and grain boundary character during hot deformation globularization processes of TC11 alloy with annealed-lamellar structure were investigated by TEM, SEM and EBSD techniques. The results indicate that globularization processes include: 1) forming of sub-structures with low-angle boundaries by deformation and recovery in α plates; 2) disintegrating of α plates by diffusion and slipping along grain boundaries; 3) globularizing of α grains and homogenizing of structure by diffusing and slipping along grain boundaries. EBSD testing results indicate that globularization mechanisms during hot deformation processes of the alloy with lamellar structure are continuous dynamic recrystallization occurring in α plates and dynamic recovery or discontinuous dynamic recrystallization occurring in β phase
2009, 38(3):426-430.
Abstract:
Transverse mechanical properties of TMCs reinforced by two types of SiC fibers with and without C coating were determined by use of cross-shaped specimens. The initial nonlinear stress of the stress-strain curve under the applied transverse tensile load was adopted to calculate the interface strength. The interface strength with C coating was 53 MPa which was lower than 196 MPa of the one without C coating. The debonding position of two interface were different, i.e. the former was between the fiber and C coating, but the latter was between the matrix and reaction products. The initial nonlinearity stress of TMCs reinforced by multiple fibers with 30% volume fraction was lower than that of single fiber reinforced TMCs, which was caused by the decrease of residual stress on the surface of fiber, and the interface strength was not influenced by the more additional fibers
Transverse mechanical properties of TMCs reinforced by two types of SiC fibers with and without C coating were determined by use of cross-shaped specimens. The initial nonlinear stress of the stress-strain curve under the applied transverse tensile load was adopted to calculate the interface strength. The interface strength with C coating was 53 MPa which was lower than 196 MPa of the one without C coating. The debonding position of two interface were different, i.e. the former was between the fiber and C coating, but the latter was between the matrix and reaction products. The initial nonlinearity stress of TMCs reinforced by multiple fibers with 30% volume fraction was lower than that of single fiber reinforced TMCs, which was caused by the decrease of residual stress on the surface of fiber, and the interface strength was not influenced by the more additional fibers
2009, 38(3):431-433.
Abstract:
Bulk metallic glassy (BMG) alloys Gd60Co26Al14 were prepared by a copper-mold casting method. Their structure and thermomagnetic properties were studied by DSC, XRD and SQUID. XRD analysis shows that the as-cast Gd60Co26Al14 cylinder was fully amorphous structure in 3 mm diameter. The DSC reveals that Gd60Co26Al14 BMG had a distinct glass transition temperature at 571 K and two crystallization temperatures at 602 K and 642 K, respectively. SQUID measurements indicate that the Gd60Co26Al14 BMG had two Curie temperatures occurring at 82 K and 128 K, respectively. The entropy change was 7 J·(kg·K)-1 at 82 K in 5 T magnetic field
Bulk metallic glassy (BMG) alloys Gd60Co26Al14 were prepared by a copper-mold casting method. Their structure and thermomagnetic properties were studied by DSC, XRD and SQUID. XRD analysis shows that the as-cast Gd60Co26Al14 cylinder was fully amorphous structure in 3 mm diameter. The DSC reveals that Gd60Co26Al14 BMG had a distinct glass transition temperature at 571 K and two crystallization temperatures at 602 K and 642 K, respectively. SQUID measurements indicate that the Gd60Co26Al14 BMG had two Curie temperatures occurring at 82 K and 128 K, respectively. The entropy change was 7 J·(kg·K)-1 at 82 K in 5 T magnetic field
2009, 38(3):434-438.
Abstract:
By means of calculating the elements diffusion mobility and γ￠-phase directional coarsening rate of Ni-Cr-Co-W-Mo-Al-Ta single crystal superalloys with different compositions, the effect of element reaction on the rate of element diffusion and γ￠-phase directional coarsening was studied. Results show that during the γ￠-phase directional coarsening period, the rafted rate of γ￠-phase changes with composition and stress, and the rafted time is decreased with the stress increasing. The driving force of the elements diffusion and γ￠-phase directional coarsening during tensile creep are related to the applied stress and elastic modulus. Element reaction has effect on the diffusion rate of Al. As the total content of Ta+Mo and the ratio of Ta/W increased, the diffusion activation energy of Al is increased and diffusion rate decreased, and the rafted time of γ￠-phase is elongated. In the diffusion field of γ￠-phase directional coarsening, the formation of γ￠-order phase is attributed to the concentration of the atoms Al and Ta, which is a spontaneous process of the decreased free energy. The Al, Ta atoms with bigger radius are diffused to {100} planes to form the stable arranging order and the linking bond of the atoms with different kinds, which is a main reason of γ￠-order phase formation with Ll2 structure
By means of calculating the elements diffusion mobility and γ￠-phase directional coarsening rate of Ni-Cr-Co-W-Mo-Al-Ta single crystal superalloys with different compositions, the effect of element reaction on the rate of element diffusion and γ￠-phase directional coarsening was studied. Results show that during the γ￠-phase directional coarsening period, the rafted rate of γ￠-phase changes with composition and stress, and the rafted time is decreased with the stress increasing. The driving force of the elements diffusion and γ￠-phase directional coarsening during tensile creep are related to the applied stress and elastic modulus. Element reaction has effect on the diffusion rate of Al. As the total content of Ta+Mo and the ratio of Ta/W increased, the diffusion activation energy of Al is increased and diffusion rate decreased, and the rafted time of γ￠-phase is elongated. In the diffusion field of γ￠-phase directional coarsening, the formation of γ￠-order phase is attributed to the concentration of the atoms Al and Ta, which is a spontaneous process of the decreased free energy. The Al, Ta atoms with bigger radius are diffused to {100} planes to form the stable arranging order and the linking bond of the atoms with different kinds, which is a main reason of γ￠-order phase formation with Ll2 structure
2009, 38(3):439-442.
Abstract:
By analyzing the phase diagram, four kinds of alloys with different component, Au-24Ag-3.25Si, Au-24Ag-3.25Si-1.5Cu, Au-24Ag-3.25Si-2.0Cu, Au-24Ag-3.25Si-2.5Cu(wt%) were prepared by the vacuum melting method in a medium-frequency induction furnace. The welding experiment was done in a tube type resistance furnace with flow H2 as protective gas, the welding temperature was 550 ℃ and the base plate is pure Ni sheet. The melting temperature was measured by a microscale DTA analyzer and the microstructure and welding performance of the brazing alloy were studied by metallographic and SEM analysis together with X-ray energy spectrum analysis. The results show that the addition of proper Cu can reduce the melting temperature and the interval between solidus and liquidus of the Au-24Ag-3.25Si brazing alloy. The microstructure of the alloy was also changed greatly because of the addition of Cu. There is a new type of solid solution formed, which makes the microhardness of the alloy increased accordingly. The spreading pattern is fine and the wetting angle is small after the Au-24Ag-3.25Si-1.5Cu brazing alloy welding with Ni, whose welding interface structure is almost the same as that without Cu. There is also IMC layer in the interface and the X-ray energy spectrum analysis show that the IMC layer is Ni-Si intermetallic. The addition of Cu will not improve the welding performance of the Au-24Ag-3.25Si brazing alloy with Ni obviously
By analyzing the phase diagram, four kinds of alloys with different component, Au-24Ag-3.25Si, Au-24Ag-3.25Si-1.5Cu, Au-24Ag-3.25Si-2.0Cu, Au-24Ag-3.25Si-2.5Cu(wt%) were prepared by the vacuum melting method in a medium-frequency induction furnace. The welding experiment was done in a tube type resistance furnace with flow H2 as protective gas, the welding temperature was 550 ℃ and the base plate is pure Ni sheet. The melting temperature was measured by a microscale DTA analyzer and the microstructure and welding performance of the brazing alloy were studied by metallographic and SEM analysis together with X-ray energy spectrum analysis. The results show that the addition of proper Cu can reduce the melting temperature and the interval between solidus and liquidus of the Au-24Ag-3.25Si brazing alloy. The microstructure of the alloy was also changed greatly because of the addition of Cu. There is a new type of solid solution formed, which makes the microhardness of the alloy increased accordingly. The spreading pattern is fine and the wetting angle is small after the Au-24Ag-3.25Si-1.5Cu brazing alloy welding with Ni, whose welding interface structure is almost the same as that without Cu. There is also IMC layer in the interface and the X-ray energy spectrum analysis show that the IMC layer is Ni-Si intermetallic. The addition of Cu will not improve the welding performance of the Au-24Ag-3.25Si brazing alloy with Ni obviously
2009, 38(3):443-446.
Abstract:
The flexible ITO films were fabricated on PET substrate by Ion Beam Assisted Deposition(IBAD), and the effects of SiO2 buffer layer on the properties of ITO films were researched. The properties of ITO films were studied using X-ray diffraction (XRD), UV-VIS spectrometer, four-point probe and optical profiler. The results show that the SiO2 interlayer between ITO films and PET results in an increase of X-ray peak intensity of ITO film and a decrease of resistivity to 1.21×10-3 Ω·cm; in addition, the transmittance decreases to 85% and the surface is relatively smooth. The resistivity of the ITO films bent to some extent keeps some stability
The flexible ITO films were fabricated on PET substrate by Ion Beam Assisted Deposition(IBAD), and the effects of SiO2 buffer layer on the properties of ITO films were researched. The properties of ITO films were studied using X-ray diffraction (XRD), UV-VIS spectrometer, four-point probe and optical profiler. The results show that the SiO2 interlayer between ITO films and PET results in an increase of X-ray peak intensity of ITO film and a decrease of resistivity to 1.21×10-3 Ω·cm; in addition, the transmittance decreases to 85% and the surface is relatively smooth. The resistivity of the ITO films bent to some extent keeps some stability
2009, 38(3):447-450.
Abstract:
A fixed laser spot heat source, which can heat and cool amorphous alloys at a high rate, was used to re-melt the amorphous alloy Zr48Cu45Al17. The analysis of crystallization characteristics indicates that the heated-affected zone (HAZ) is liable to crystallize more easily than the molten zone (MZ), and at the boundary between the HAZ and the parent alloy there is a critical state between crystalline and amorphous state. Crystallization start diagram should be tangent with the thermal cycle of the critical location. Accordingly, the crystallization start diagram for amorphous alloy Zr48Cu45Al17 at high heating and cooling rate was determined with tangential points of the numerical simulated thermal cycles at the boundaries under different re-melting conditions
A fixed laser spot heat source, which can heat and cool amorphous alloys at a high rate, was used to re-melt the amorphous alloy Zr48Cu45Al17. The analysis of crystallization characteristics indicates that the heated-affected zone (HAZ) is liable to crystallize more easily than the molten zone (MZ), and at the boundary between the HAZ and the parent alloy there is a critical state between crystalline and amorphous state. Crystallization start diagram should be tangent with the thermal cycle of the critical location. Accordingly, the crystallization start diagram for amorphous alloy Zr48Cu45Al17 at high heating and cooling rate was determined with tangential points of the numerical simulated thermal cycles at the boundaries under different re-melting conditions
Cheng Lifang
,
Wang Runbo
,
Pu Chaohui
,
Wang Baoguo
,
Li Zhilin
,
Lou Yuwan
,
He Dannong
,
Yang Chuanzheng
2009, 38(3):451-455.
Abstract:
Hydrogen storage alloy La0.6Pr0.2Mg0.2(Ni0.85-xCo0.15Alx)3.5(x=0, 0.01, 0.02, 0.03, and 0.04) were prepared by induced melting method followed by annealing treatment at 900 ℃. The effects of partial substitution Al for Ni on the structure, electrochemical properties of the alloys were investigated systematically. X-ray diffraction (XRD) results indicate that the alloys were composed of La2Ni7 and LaNi5 phase with the Ce2Ni7-type and CaCu5-type structure. The value of c/a increases with the increase of Al content. The electrochemical analysis shows that the increase of Al leads to some decrease in both the discharge capacity and the HRD (high-rate dischargeability), but leads to a significant improvement in cycling stability of alloys. The discharge capacity decreases from 394.6 mAh/g (x=0.01) to 380.6 mAh/g (x=0.04), and the HRD decreases from 61% (x=0.01) to 35% (x=0.04) as the electrodes were discharged at 1200 mA/g. However, the rate of attenuation decreases from –0.32 mAh/(g·cycle) (x=0.01) to –0.20 mAh/(g·cycle) (x=0.04). This research reveals higher discharge capacity was remained, and cycling stability was improved remarkably when x≤0.02
Hydrogen storage alloy La0.6Pr0.2Mg0.2(Ni0.85-xCo0.15Alx)3.5(x=0, 0.01, 0.02, 0.03, and 0.04) were prepared by induced melting method followed by annealing treatment at 900 ℃. The effects of partial substitution Al for Ni on the structure, electrochemical properties of the alloys were investigated systematically. X-ray diffraction (XRD) results indicate that the alloys were composed of La2Ni7 and LaNi5 phase with the Ce2Ni7-type and CaCu5-type structure. The value of c/a increases with the increase of Al content. The electrochemical analysis shows that the increase of Al leads to some decrease in both the discharge capacity and the HRD (high-rate dischargeability), but leads to a significant improvement in cycling stability of alloys. The discharge capacity decreases from 394.6 mAh/g (x=0.01) to 380.6 mAh/g (x=0.04), and the HRD decreases from 61% (x=0.01) to 35% (x=0.04) as the electrodes were discharged at 1200 mA/g. However, the rate of attenuation decreases from –0.32 mAh/(g·cycle) (x=0.01) to –0.20 mAh/(g·cycle) (x=0.04). This research reveals higher discharge capacity was remained, and cycling stability was improved remarkably when x≤0.02
2009, 38(3):456-459.
Abstract:
The electrochemical reduction process of Zr(Ⅳ) was studied at molybdenum electrodes in K2ZrF6-LiCl-KCl molten salt at 923 K by transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry and chronoamperometry. The experimental results show that Zr(Ⅳ) was reduced to Zr metal by a two-step mechanism corresponding to the Zr(Ⅳ)/Zr(Ⅱ) and Zr(Ⅱ)/Zr transition. The intermediate product was identified as ZrCl2 by X-ray diffraction. The chronoamperometric studies indicate that nucleation polarization existed during the electrodeposition process of zirconium at molybdenum electrode. This polarization is an instantaneous nucleation process
The electrochemical reduction process of Zr(Ⅳ) was studied at molybdenum electrodes in K2ZrF6-LiCl-KCl molten salt at 923 K by transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry and chronoamperometry. The experimental results show that Zr(Ⅳ) was reduced to Zr metal by a two-step mechanism corresponding to the Zr(Ⅳ)/Zr(Ⅱ) and Zr(Ⅱ)/Zr transition. The intermediate product was identified as ZrCl2 by X-ray diffraction. The chronoamperometric studies indicate that nucleation polarization existed during the electrodeposition process of zirconium at molybdenum electrode. This polarization is an instantaneous nucleation process
2009, 38(3):460-464.
Abstract:
Based on engineering vibration control, an experimental study is completed on the mechanical property of TiNi shape memory alloy bar at room temperature. Phase transformation stress, deformation module, residual strain, dissipated energy and so on, are considered as mechanical characteristic parameters of these specimens. The changes of these parameters with loading rate, strain amplitude and cyclic loading are analyzed. The results indicate that superelastic TiNi shape memory alloy bars have the characteristics of high energy dissipation and damping property, so they are suitable for engineering vibration control. Even so, in order to apply this alloy bars to practice, the influence of loading rate, strain amplitude and cyclic loading on mechanical behavior of TiNi shape memory alloy bars should be considered, and the appropriate design should be proposed according to practical condition
Based on engineering vibration control, an experimental study is completed on the mechanical property of TiNi shape memory alloy bar at room temperature. Phase transformation stress, deformation module, residual strain, dissipated energy and so on, are considered as mechanical characteristic parameters of these specimens. The changes of these parameters with loading rate, strain amplitude and cyclic loading are analyzed. The results indicate that superelastic TiNi shape memory alloy bars have the characteristics of high energy dissipation and damping property, so they are suitable for engineering vibration control. Even so, in order to apply this alloy bars to practice, the influence of loading rate, strain amplitude and cyclic loading on mechanical behavior of TiNi shape memory alloy bars should be considered, and the appropriate design should be proposed according to practical condition
2009, 38(3):465-467.
Abstract:
Producing on scale for sintered NdFeB magnets demands consistency of magnets. The effect of element Zr and Nb on consistency of magnets was investigated. It was found that as Zr content increased from 0 to 0.07at%, the sinter temperature of magnet could reach to 1110 ℃ with no abnormal grain growth, and coercivity increased to 1021 kA/m. And Nb addition was benefit for squareness improvement. Combined addition of Nb 0.07at% and Zr 0.07at%, the magnets showed much better properties consistency even at different positions in same furnace and the energy densities reached 403.8±4.7 kJ/m3. It was attributed that the sensitization of sinter temperature of magnets was greatly removed by Zr and Nb addition
Producing on scale for sintered NdFeB magnets demands consistency of magnets. The effect of element Zr and Nb on consistency of magnets was investigated. It was found that as Zr content increased from 0 to 0.07at%, the sinter temperature of magnet could reach to 1110 ℃ with no abnormal grain growth, and coercivity increased to 1021 kA/m. And Nb addition was benefit for squareness improvement. Combined addition of Nb 0.07at% and Zr 0.07at%, the magnets showed much better properties consistency even at different positions in same furnace and the energy densities reached 403.8±4.7 kJ/m3. It was attributed that the sensitization of sinter temperature of magnets was greatly removed by Zr and Nb addition
2009, 38(3):468-472.
Abstract:
In this paper, soldered lap joint specimens were fabricated by a solder reflow process using a Sn-3.8Ag-0.7Cu-xRE (x=0, 0.1wt%, 0.25wt%, 0.5wt%) BGA solder ball on FR4 substrate parts. The effects of rare earth(RE) content and strain rate on the shear properties of soldered lap joint were investigated. The Results show that the addition of minute RE (<0.25wt%) can improve the shear strength and elongation of the lap joint. However, further increasing of RE content would degrade the shear properties of the lap joint. The shear strength and elongation of the lap joint increase with the increase of strain rate. The analysis of the microstructure and fractograph indicated that through the addition of minute RE, the microstructure of the lap joint was refined, especially the growth of intermetallic compound was inhibited, and thus the shear properties of the lap joint were improved. In addition, the observation of fractographs confirmed that the elongation of the lap joint increase with the increase of strain rate
In this paper, soldered lap joint specimens were fabricated by a solder reflow process using a Sn-3.8Ag-0.7Cu-xRE (x=0, 0.1wt%, 0.25wt%, 0.5wt%) BGA solder ball on FR4 substrate parts. The effects of rare earth(RE) content and strain rate on the shear properties of soldered lap joint were investigated. The Results show that the addition of minute RE (<0.25wt%) can improve the shear strength and elongation of the lap joint. However, further increasing of RE content would degrade the shear properties of the lap joint. The shear strength and elongation of the lap joint increase with the increase of strain rate. The analysis of the microstructure and fractograph indicated that through the addition of minute RE, the microstructure of the lap joint was refined, especially the growth of intermetallic compound was inhibited, and thus the shear properties of the lap joint were improved. In addition, the observation of fractographs confirmed that the elongation of the lap joint increase with the increase of strain rate
2009, 38(3):473-476.
Abstract:
TiN coatings were successfully prepared by magnetron sputtering technology on biomedical Ti6Al7Nb alloy in order to improve its wear resistance. SEM and XRD were applied to observe the morphologies and analyze the structures of the coating, respectively. Pin-on-disc wear tests were carried out to compare the wear properties of specimen with and without coating. The results show that the coating has a good adhesion to the substrate. The composition and structure of the coating vary with sputtering time. When sputtered for 3 h, the coating is composed of TiN，TiN+Ti2N, Ti2N from the outer surface to the inner layer in sequence. The micro-hardness of TiN layer is increased to 3 times that of substrate. The wear resistance of the surface modified specimens is greatly improved under 10~40 N load, and wear mechanism changes from original oxidative and adhesive to abrasive-dominant
TiN coatings were successfully prepared by magnetron sputtering technology on biomedical Ti6Al7Nb alloy in order to improve its wear resistance. SEM and XRD were applied to observe the morphologies and analyze the structures of the coating, respectively. Pin-on-disc wear tests were carried out to compare the wear properties of specimen with and without coating. The results show that the coating has a good adhesion to the substrate. The composition and structure of the coating vary with sputtering time. When sputtered for 3 h, the coating is composed of TiN，TiN+Ti2N, Ti2N from the outer surface to the inner layer in sequence. The micro-hardness of TiN layer is increased to 3 times that of substrate. The wear resistance of the surface modified specimens is greatly improved under 10~40 N load, and wear mechanism changes from original oxidative and adhesive to abrasive-dominant
2009, 38(3):477-480.
Abstract:
The content and distributing of P in Electroless Nickel/Immersion Gold (ENIG) surface finishes effect the reliability of interface between solder joint and surface finishes. 289 I/Os lead-free Sn-3.0Ag-0.5Cu BGAs was assembled on the ENIG print circuit board by reflow soldering technology. The print circuit board was tested by random vibration. After random vibration test, the failure and not failure samples were studied by X-ray, SEM, and EDX et al. The failure mechanism was confirmed and the relation of failure and content and distributing of P in ENIG finishes was discussed. The failure and not failure samples after vibration test show similar microstructure at the interface of solder joint and surface finishes. The cross-sectioning of the affected area shows a “tooth decay” effect of corrosion of the nickel layer, and “mud cracks” in the topography on the surface. The enrichment of P on the surface accelerated the oxidation of Ni, and also reduced the mechanical intensity of interface. The oxidation of Ni and the enrichment of P on the surface result in the crack of solder/finish interface
The content and distributing of P in Electroless Nickel/Immersion Gold (ENIG) surface finishes effect the reliability of interface between solder joint and surface finishes. 289 I/Os lead-free Sn-3.0Ag-0.5Cu BGAs was assembled on the ENIG print circuit board by reflow soldering technology. The print circuit board was tested by random vibration. After random vibration test, the failure and not failure samples were studied by X-ray, SEM, and EDX et al. The failure mechanism was confirmed and the relation of failure and content and distributing of P in ENIG finishes was discussed. The failure and not failure samples after vibration test show similar microstructure at the interface of solder joint and surface finishes. The cross-sectioning of the affected area shows a “tooth decay” effect of corrosion of the nickel layer, and “mud cracks” in the topography on the surface. The enrichment of P on the surface accelerated the oxidation of Ni, and also reduced the mechanical intensity of interface. The oxidation of Ni and the enrichment of P on the surface result in the crack of solder/finish interface
2009, 38(3):481-484.
Abstract:
Amorphous ribbon and rods of Fe75-xMxHf3Y2B20(M=Co, Nb; x=0, 4) alloys were prepared by the melt-spun and copper mold casting method, respectively. The thermal stability, crystallization, melting behavior and soft magnetic properties were investigated by differential scanning calorimetry (DSC), differential thermal analysis (DTA), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The results indicate that the thermal stability and glass-forming ability of Fe75Hf3Y2B20 can be obviously increased via the replacement of Fe by 4 at% Nb or Co element, and the amorphous alloys of Fe71Nb4Hf3Y2B20 exhibits wide supercooled liquid region of 75 K, high glass forming ability of 4 mm and high saturation magnetization of 0.97~1.08 T. The amorphous alloy has the high thermal stability, the better glass-forming ability and soft magnetic properties
Amorphous ribbon and rods of Fe75-xMxHf3Y2B20(M=Co, Nb; x=0, 4) alloys were prepared by the melt-spun and copper mold casting method, respectively. The thermal stability, crystallization, melting behavior and soft magnetic properties were investigated by differential scanning calorimetry (DSC), differential thermal analysis (DTA), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The results indicate that the thermal stability and glass-forming ability of Fe75Hf3Y2B20 can be obviously increased via the replacement of Fe by 4 at% Nb or Co element, and the amorphous alloys of Fe71Nb4Hf3Y2B20 exhibits wide supercooled liquid region of 75 K, high glass forming ability of 4 mm and high saturation magnetization of 0.97~1.08 T. The amorphous alloy has the high thermal stability, the better glass-forming ability and soft magnetic properties
2009, 38(3):485-487.
Abstract:
Rare earth doped phosphate luminescent nanoparticles were prepared in a Microreactor system in the ethylene glycol solution, using Ln(NO3)3·6H2O (Ln=Ce, Tb) and NaH2PO4·2H2O as raw materials. The crystal property, the shape and size of the particles of the LaPO4:Ce3+,Tb3+ nanoparticles were characterized by X-ray diffraction instrument(XRD), transmission electron microscopy(TEM). And the fluorescence property was detected by fluorescence spectrum instrument. The results indicated that the nanoparticles had hexagonal crystalline form, uniform particle size distribution and intensive fluorescence property
Rare earth doped phosphate luminescent nanoparticles were prepared in a Microreactor system in the ethylene glycol solution, using Ln(NO3)3·6H2O (Ln=Ce, Tb) and NaH2PO4·2H2O as raw materials. The crystal property, the shape and size of the particles of the LaPO4:Ce3+,Tb3+ nanoparticles were characterized by X-ray diffraction instrument(XRD), transmission electron microscopy(TEM). And the fluorescence property was detected by fluorescence spectrum instrument. The results indicated that the nanoparticles had hexagonal crystalline form, uniform particle size distribution and intensive fluorescence property
2009, 38(3):488-491.
Abstract:
In the paper, the cathode spot movements and chopping current of pure graphite and copper-impregnated metallized graphite (Cu-C) in vacuum were investigated. It can be found that cathode spot movements produce an arc erosion pattern composed of a large number of craters with varying distances between them. The size of the craters is less than 3 μm in diameter. This pattern indicates that the cathode spot walk randomly on the surface. Whereas, cathode spots initiated selectively on the Cu phases in Cu-C materials. The diameter of the cathode spots depends on the dimension of the Cu phases and the displacement of a cathode spot moving is equal to the distance between the Cu phases. Meanwhile, the chopping current of Cu-C is 1.18 A, far larger than that of pure graphite. The phenomenon can be explained by the different characteristics of the cathode spot movement
In the paper, the cathode spot movements and chopping current of pure graphite and copper-impregnated metallized graphite (Cu-C) in vacuum were investigated. It can be found that cathode spot movements produce an arc erosion pattern composed of a large number of craters with varying distances between them. The size of the craters is less than 3 μm in diameter. This pattern indicates that the cathode spot walk randomly on the surface. Whereas, cathode spots initiated selectively on the Cu phases in Cu-C materials. The diameter of the cathode spots depends on the dimension of the Cu phases and the displacement of a cathode spot moving is equal to the distance between the Cu phases. Meanwhile, the chopping current of Cu-C is 1.18 A, far larger than that of pure graphite. The phenomenon can be explained by the different characteristics of the cathode spot movement
2009, 38(3):492-495.
Abstract:
The pitting behavior of 316L before and after explosive welding was studied with X-ray diffraction(XRD), scanning electron microcopy(SEM), optical microscope(OM), potentiodynamic polarization and immersion corrosion technology. XRD analysis indicates that the second phase and δ ferrite phase emerged on the side weld and fusion area of 316L relative to the sample of 316L base; The result of potentiodynamic polarization and immersion corrosion test indicates that 316L base and welded metal had passivity, but welded 316L pitting resistance was decreased and welded seam and fusion area were corroded firstly
The pitting behavior of 316L before and after explosive welding was studied with X-ray diffraction(XRD), scanning electron microcopy(SEM), optical microscope(OM), potentiodynamic polarization and immersion corrosion technology. XRD analysis indicates that the second phase and δ ferrite phase emerged on the side weld and fusion area of 316L relative to the sample of 316L base; The result of potentiodynamic polarization and immersion corrosion test indicates that 316L base and welded metal had passivity, but welded 316L pitting resistance was decreased and welded seam and fusion area were corroded firstly
2009, 38(3):496-499.
Abstract:
A new technology for preparation of TaC coating on Carbon/carbon composites is reported. TaC was turned from TaO2F·rH2O·TaF5, which was characterized by FITR, XRD and SEM. The morphologies of TaC coating at different temperatures were observed by SEM. At 1200 ℃, the TaC coating shows the particular form. When the heat treatment temperature increased to 1800 ℃, the TaC coating was mainly columnar. The formation mechanism of TaC is that Carbon atom diffuse into Ta2O5 deposit, which is coming from TaO2F·rH2O·TaF5 and reacted into TaC at high temperature. The morphology of TaC coating can be interpreted by the theory of Ta2O5 deposited nucleation
A new technology for preparation of TaC coating on Carbon/carbon composites is reported. TaC was turned from TaO2F·rH2O·TaF5, which was characterized by FITR, XRD and SEM. The morphologies of TaC coating at different temperatures were observed by SEM. At 1200 ℃, the TaC coating shows the particular form. When the heat treatment temperature increased to 1800 ℃, the TaC coating was mainly columnar. The formation mechanism of TaC is that Carbon atom diffuse into Ta2O5 deposit, which is coming from TaO2F·rH2O·TaF5 and reacted into TaC at high temperature. The morphology of TaC coating can be interpreted by the theory of Ta2O5 deposited nucleation
2009, 38(3):500-505.
Abstract:
High valency spherical Ni1/3Co1/3Mn1/3OOH and low valency spherical Ni1/3Co1/3Mn1/3(OH)2 precursor powders were synthesized respectively by co-precipitation method and oxidation method at different conditions. And then spherical Li(Ni1/3Co1/3Mn1/3)O2 powders were prepared at different temperature by their precursors, which were sintered with LiOH·H2O. XPS studies indicated that the predominant oxidation states of Ni, Co and Mn in spherical precursor Ni1/3Co1/3Mn1/3OOH were 2+, 3+ and 4+, furthermore, the spherical Li(Ni1/3Co1/3Mn1/3)O2 powders with a well-ordered layered α-NaFeO2 structure and small amount of cation mixing can be synthesized at low temperature by Ni1/3Co1/3Mn1/3OOH, which indicated that the activity of spherical Ni1/3Co1/3Mn1/3OOH is higher than that of spherical Ni1/3Co1/3Mn1/3(OH)2. Charge and discharge capacity showed that the synthesized spherical cathodes by Ni1/3Co1/3Mn1/3OOH delivered higher discharge capacity and better cycling properties
High valency spherical Ni1/3Co1/3Mn1/3OOH and low valency spherical Ni1/3Co1/3Mn1/3(OH)2 precursor powders were synthesized respectively by co-precipitation method and oxidation method at different conditions. And then spherical Li(Ni1/3Co1/3Mn1/3)O2 powders were prepared at different temperature by their precursors, which were sintered with LiOH·H2O. XPS studies indicated that the predominant oxidation states of Ni, Co and Mn in spherical precursor Ni1/3Co1/3Mn1/3OOH were 2+, 3+ and 4+, furthermore, the spherical Li(Ni1/3Co1/3Mn1/3)O2 powders with a well-ordered layered α-NaFeO2 structure and small amount of cation mixing can be synthesized at low temperature by Ni1/3Co1/3Mn1/3OOH, which indicated that the activity of spherical Ni1/3Co1/3Mn1/3OOH is higher than that of spherical Ni1/3Co1/3Mn1/3(OH)2. Charge and discharge capacity showed that the synthesized spherical cathodes by Ni1/3Co1/3Mn1/3OOH delivered higher discharge capacity and better cycling properties
2009, 38(3):506-509.
Abstract:
A nanocrystalline surface layer was fabricated on a pure zircaloy-4 plate by using the high-speed shot peening (HSSP) technique. The microstructural evolution of the zircaloy-4 was characterized by using X-ray diffraction, and transmission electron microscopy(TEM). After the high-speed shot peening treatment, obvious grain refinement was observed and a nanocrystalline surface layer was found. The grain size increased along with the distance far from nanocrystalline surface. The nanocrystallization mechanism was analyzed in terms of the deformation behavior and TEM observations of the microstructural evolution of the treated samples
A nanocrystalline surface layer was fabricated on a pure zircaloy-4 plate by using the high-speed shot peening (HSSP) technique. The microstructural evolution of the zircaloy-4 was characterized by using X-ray diffraction, and transmission electron microscopy(TEM). After the high-speed shot peening treatment, obvious grain refinement was observed and a nanocrystalline surface layer was found. The grain size increased along with the distance far from nanocrystalline surface. The nanocrystallization mechanism was analyzed in terms of the deformation behavior and TEM observations of the microstructural evolution of the treated samples
2009, 38(3):510-513.
Abstract:
The microstructural evolution of GH864 superalloy during the hot working process of gas turbine blades was systematically studied by observation of grain size, SEM micrographs and X-ray analysis of samples extracted from rolled bars and forged blades with or without standard heat treatment. The results show that the original rolled bar had uniform equiaxed grains, while necklace structure was found in some locations of blades. This kind of non-uniform grain size was caused mainly by different dynamic recrystallization behavior due to unequal strain in different locations of the blade during forging. Static recrystallization and grain growth happened during heat treatment, which led to more uniform and bigger grain structure. M23C6 and partial secondary MC dissolved after forging. Only a small amount of TiC existed in alloy, which mostly distributed in the grain boundaries, and heat treatment resulted in sufficient precipitation of block-shaped M23C6 discontinuously precipitated along the grain boundaries
The microstructural evolution of GH864 superalloy during the hot working process of gas turbine blades was systematically studied by observation of grain size, SEM micrographs and X-ray analysis of samples extracted from rolled bars and forged blades with or without standard heat treatment. The results show that the original rolled bar had uniform equiaxed grains, while necklace structure was found in some locations of blades. This kind of non-uniform grain size was caused mainly by different dynamic recrystallization behavior due to unequal strain in different locations of the blade during forging. Static recrystallization and grain growth happened during heat treatment, which led to more uniform and bigger grain structure. M23C6 and partial secondary MC dissolved after forging. Only a small amount of TiC existed in alloy, which mostly distributed in the grain boundaries, and heat treatment resulted in sufficient precipitation of block-shaped M23C6 discontinuously precipitated along the grain boundaries
2009, 38(3):515-518.
Abstract:
Au colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The effects of reductant amounts, mixing procedures, reaction time and stirring speed on the concentration, size, shape and monodispersity of Au colloid were investigated. UV-vis and TEM were used to characterize the size, shape, structure and optical properties of the samples. It's found that the optimal conditions for preparing Au colloid of small size are Na3C6H5O7(aq):HAuCl4(aq)=3:1(V:V), mixing Na3C6H5O7 firstly, reacting for 6 min and 650 r/min stirring speed. The colloid was prepared successfully which has superiority in shape, monodispersity and stability. The size of nanoparticles is only about 6~7 nm
Au colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The effects of reductant amounts, mixing procedures, reaction time and stirring speed on the concentration, size, shape and monodispersity of Au colloid were investigated. UV-vis and TEM were used to characterize the size, shape, structure and optical properties of the samples. It's found that the optimal conditions for preparing Au colloid of small size are Na3C6H5O7(aq):HAuCl4(aq)=3:1(V:V), mixing Na3C6H5O7 firstly, reacting for 6 min and 650 r/min stirring speed. The colloid was prepared successfully which has superiority in shape, monodispersity and stability. The size of nanoparticles is only about 6~7 nm
2009, 38(3):519-522.
Abstract:
The effect of the frequency of the pulsed magnetic field on Mg-Gd-Y-Zr alloy during solidification was investigated. When the pulsed magnetic field is applied to Mg-Gd-Y-Zr alloy during the solidification process, the grain refinement is achieved. The average grain size of the as-cast Mg-Gd-Y-Zr alloy is from 65 mm without the pulsed magnetic filed to 37 mm with the pulsed magnetic field of 5 Hz. Grain refinement of Mg-Gd-Y-Zr alloy is due to the electromagnetic undercooling and reduction of temperature gradient by the vibration of melt resulted from the pulsed magnetic field. Compared those casting method with traditional one, the tensile strength and elongation are increased by 4.8% and 78.5%, respectively
The effect of the frequency of the pulsed magnetic field on Mg-Gd-Y-Zr alloy during solidification was investigated. When the pulsed magnetic field is applied to Mg-Gd-Y-Zr alloy during the solidification process, the grain refinement is achieved. The average grain size of the as-cast Mg-Gd-Y-Zr alloy is from 65 mm without the pulsed magnetic filed to 37 mm with the pulsed magnetic field of 5 Hz. Grain refinement of Mg-Gd-Y-Zr alloy is due to the electromagnetic undercooling and reduction of temperature gradient by the vibration of melt resulted from the pulsed magnetic field. Compared those casting method with traditional one, the tensile strength and elongation are increased by 4.8% and 78.5%, respectively
2009, 38(3):523-526.
Abstract:
A novel polymer-assisted chemical solution deposition (PACSD) has been proposed to deposit an over-160nm-thick Eu0.3Ce0.7O1.85-x (ECO) single buffer layer on biaxially textured NiW (200) substrate. As-grown ECO buffer layer displayed excellent bi-axial texture as well as smooth, crack-free microstructure. It is observed that Eu-doping can augment the critical thickness of CeO2 as single buffer layer. YBCO deposited on ECO buffered NiW yielded a zero transition temperature at Tc0 = 86 K and a critical current of Jc (0 T, 77 K) = 0.4 MA/cm2. These results offer a simple and cost-effective approach for the preparation of single buffer layer on coated conductors
A novel polymer-assisted chemical solution deposition (PACSD) has been proposed to deposit an over-160nm-thick Eu0.3Ce0.7O1.85-x (ECO) single buffer layer on biaxially textured NiW (200) substrate. As-grown ECO buffer layer displayed excellent bi-axial texture as well as smooth, crack-free microstructure. It is observed that Eu-doping can augment the critical thickness of CeO2 as single buffer layer. YBCO deposited on ECO buffered NiW yielded a zero transition temperature at Tc0 = 86 K and a critical current of Jc (0 T, 77 K) = 0.4 MA/cm2. These results offer a simple and cost-effective approach for the preparation of single buffer layer on coated conductors
2009, 38(3):527-531.
Abstract:
The preparation and formability of 30W-Cu EFP(explosively formed projectile) liner were studied. At first the two different 30W-Cu materials were prepared by tungsten powder, copper powder and ultrafine tungsten-copper composite powder, and then the two materials’ formability were tested. Finally the material which had good formability was used to prepare EFP liner. It was found that the 30W-Cu material prepared by common tungsten powder and copper powder had a good formability. 98.2% of the theoretical density of the density of the 30W-Cu EFP liner material was obtained. After annealing, the tensile strength of the material reached 315 MPa and elongation reached 15.3%
The preparation and formability of 30W-Cu EFP(explosively formed projectile) liner were studied. At first the two different 30W-Cu materials were prepared by tungsten powder, copper powder and ultrafine tungsten-copper composite powder, and then the two materials’ formability were tested. Finally the material which had good formability was used to prepare EFP liner. It was found that the 30W-Cu material prepared by common tungsten powder and copper powder had a good formability. 98.2% of the theoretical density of the density of the 30W-Cu EFP liner material was obtained. After annealing, the tensile strength of the material reached 315 MPa and elongation reached 15.3%
2009, 38(3):532-535.
Abstract:
Using simple and efficient template method, sphere assembled structure; shuttle-like structure and flake assembled structure of calcium carbonate were obtained. The morphologies of products were researched, and the sphere assembled calcium carbonate with large surface was modified and combined with silver nanoparticles to obtain the silver nanoparticle/calcium carbonate composite for the first time. The composite has extensive applications in sterilization and medicine areas etc. The composite can not only reduce the silver quantity, but also provide a good route for applications of calcium carbonate nanomaterials
Using simple and efficient template method, sphere assembled structure; shuttle-like structure and flake assembled structure of calcium carbonate were obtained. The morphologies of products were researched, and the sphere assembled calcium carbonate with large surface was modified and combined with silver nanoparticles to obtain the silver nanoparticle/calcium carbonate composite for the first time. The composite has extensive applications in sterilization and medicine areas etc. The composite can not only reduce the silver quantity, but also provide a good route for applications of calcium carbonate nanomaterials
2009, 38(3):536-540.
Abstract:
Mg58Al42 hydrogen storage alloy was prepared by mechanical alloying (MA) method and its microstructural characteristics and electrochemical properties such as discharge capacities and corrosion mechanisms were investigated by XRD, PARM273A and M5210 electrochemical apparatus. The results show that the X-ray diffraction peaks have a deviation and broadening with increment of ball milling time because of fine grain size and internal stress. The discharge capacities of the present alloy increase at the beginning of ball milling and afterwards decrease with increment of ball milling, discharge capacity of which is biggest when it is milled for 20 h. There are passivation phenomena in potentiodynamic polarization curves. The corrosion current densities of the present alloy increase with time at the beginning of ball milling and afterwards decrease. The electrochemical impedance spectroscopies(EIS) of the present alloy are composed of single capacitive loop and electrode reaction is controlled by charge transfer at alloy/electrolyte interface. The CPE-T of alloy increases. It showed that the specific surface areas of the alloy increase with ball milling time
Mg58Al42 hydrogen storage alloy was prepared by mechanical alloying (MA) method and its microstructural characteristics and electrochemical properties such as discharge capacities and corrosion mechanisms were investigated by XRD, PARM273A and M5210 electrochemical apparatus. The results show that the X-ray diffraction peaks have a deviation and broadening with increment of ball milling time because of fine grain size and internal stress. The discharge capacities of the present alloy increase at the beginning of ball milling and afterwards decrease with increment of ball milling, discharge capacity of which is biggest when it is milled for 20 h. There are passivation phenomena in potentiodynamic polarization curves. The corrosion current densities of the present alloy increase with time at the beginning of ball milling and afterwards decrease. The electrochemical impedance spectroscopies(EIS) of the present alloy are composed of single capacitive loop and electrode reaction is controlled by charge transfer at alloy/electrolyte interface. The CPE-T of alloy increases. It showed that the specific surface areas of the alloy increase with ball milling time
2009, 38(3):541-544.
Abstract:
At 300 K and between 0~13.3 kPa, adsorption isotherms for O2, CO, CH4 on porous palladium were measured by using PVT method in low-vacuum system. The results indicate that Adsorption isotherms for CO on Pd is identical with the type adsorption isotherms that the amount adsorbed of CO increases with increasing pressure(<2.6 kPa), but little additional CO adsorbs with pressure increasing(<13.3 kPa). Isotherm for adsorption of O2 or CH4 has a different effect in contrast to CO, i.e. significant adsorption of O2 even at low pressure (<100 Pa), and the isotherms doesn’t saturate at higher pressure(<13.3 kPa), and the amount adsorbed of CH4 is little and increases slightly with equilibrium pressure rising sharply (<13.3 kPa). And isotherm for adsorption of CO or CH4 can been classified Longmuir adsorption type, and that of O2 can been described by Longmuir adsorption model only when equilibrium pressure is less than 1.33 kPa
At 300 K and between 0~13.3 kPa, adsorption isotherms for O2, CO, CH4 on porous palladium were measured by using PVT method in low-vacuum system. The results indicate that Adsorption isotherms for CO on Pd is identical with the type adsorption isotherms that the amount adsorbed of CO increases with increasing pressure(<2.6 kPa), but little additional CO adsorbs with pressure increasing(<13.3 kPa). Isotherm for adsorption of O2 or CH4 has a different effect in contrast to CO, i.e. significant adsorption of O2 even at low pressure (<100 Pa), and the isotherms doesn’t saturate at higher pressure(<13.3 kPa), and the amount adsorbed of CH4 is little and increases slightly with equilibrium pressure rising sharply (<13.3 kPa). And isotherm for adsorption of CO or CH4 can been classified Longmuir adsorption type, and that of O2 can been described by Longmuir adsorption model only when equilibrium pressure is less than 1.33 kPa
2009, 38(3):545-549.
Abstract:
The NiCoCrAlYTa coating was prepared on Ni-based single crystal super-alloys by low pressure plasma spraying (LPPS). The influences of heat treatment and pre-peening on the interface recrystallization of NiCoCrAlYTa coating and nickel-based super-alloy substrate were investigated by X-ray, SEM, BES and EPXMA. It was found that cellular recrystallization occurred at the diffusion area of samples adopting the vacuum heat treatment at the temperature of 1080 ℃, while no recrystallization appeared at the temperatures of 1000 ℃ and 850 ℃. Recrystallization was also observed in the sample subjected by pre-peening with more than 0.2 MPa, followed by 1080 ℃, 6 h heat treatment and 850 ℃, 24 h aging treatment, while no recrystallization was observed in the sample subjected by no pre-peening followed by above mentioned heat treatment. The results revealed that element Ta aggregated within cellular grains and that inter-diffusion took place and Ta-rich phases (Ni2Ta, Cr2Ta) were formed at the interface through heat treatment
The NiCoCrAlYTa coating was prepared on Ni-based single crystal super-alloys by low pressure plasma spraying (LPPS). The influences of heat treatment and pre-peening on the interface recrystallization of NiCoCrAlYTa coating and nickel-based super-alloy substrate were investigated by X-ray, SEM, BES and EPXMA. It was found that cellular recrystallization occurred at the diffusion area of samples adopting the vacuum heat treatment at the temperature of 1080 ℃, while no recrystallization appeared at the temperatures of 1000 ℃ and 850 ℃. Recrystallization was also observed in the sample subjected by pre-peening with more than 0.2 MPa, followed by 1080 ℃, 6 h heat treatment and 850 ℃, 24 h aging treatment, while no recrystallization was observed in the sample subjected by no pre-peening followed by above mentioned heat treatment. The results revealed that element Ta aggregated within cellular grains and that inter-diffusion took place and Ta-rich phases (Ni2Ta, Cr2Ta) were formed at the interface through heat treatment
2009, 38(3):550-553.
Abstract:
With Gleeble-1500 heat simulator performing heat compressive deformation on Ti-1300 near β alloy, its heat deformation behavior is researched with the temperature range of 800~1010 ℃, strain rate of 0.01~10 s-1 and maximum deformation of 60%. The structure analysis after heat deformation indicates that re-crystallization primarily occurs under the condition of low rate of strain, but dynamic recovery under the condition of high rate of strain. According to the test data, the manufacturing drawing of this alloy is obtained. The result indicates that for Ti-1300 alloy, rheological phenomenon easily occurs under the condition of high rate of strain which leads its unstableness. Therefore, its forging procedure should be performed under relative low rate of strain, thus relative fine structure of equal axial dynamic re-crystal could be obtained
With Gleeble-1500 heat simulator performing heat compressive deformation on Ti-1300 near β alloy, its heat deformation behavior is researched with the temperature range of 800~1010 ℃, strain rate of 0.01~10 s-1 and maximum deformation of 60%. The structure analysis after heat deformation indicates that re-crystallization primarily occurs under the condition of low rate of strain, but dynamic recovery under the condition of high rate of strain. According to the test data, the manufacturing drawing of this alloy is obtained. The result indicates that for Ti-1300 alloy, rheological phenomenon easily occurs under the condition of high rate of strain which leads its unstableness. Therefore, its forging procedure should be performed under relative low rate of strain, thus relative fine structure of equal axial dynamic re-crystal could be obtained
2009, 38(3):554-558.
Abstract:
TiAl-based alloys are emerging as potential light-weight, high-temperature structural materials and possess wide capacities of engineering applications in aeronautics, space and automobile industries because of their low density, high specific strength and specific modulus, good oxidation-resistance and creep-resistance, and excellent fatigue properties. The paper will focus on the melting and investment casting technology of TiAl-based alloys. Some applications of TiAl components are summarized and some shortcomings and challenges for the investment casting of TiAl-based alloys are also proposed
TiAl-based alloys are emerging as potential light-weight, high-temperature structural materials and possess wide capacities of engineering applications in aeronautics, space and automobile industries because of their low density, high specific strength and specific modulus, good oxidation-resistance and creep-resistance, and excellent fatigue properties. The paper will focus on the melting and investment casting technology of TiAl-based alloys. Some applications of TiAl components are summarized and some shortcomings and challenges for the investment casting of TiAl-based alloys are also proposed
2009, 38(3):559-564.
Abstract:
In this paper, the fabrication methods of magnesium matrix composites were introduced and the new fabrication process was emphasized. The effects of the fabrication processes on the composition, structure and properties of the composites were analyzed. Developing new reinforcements and novel in-situ reaction synthesis, optimizing the fabrication process and preparing high performance composites on larger scale are main research keys to the magnesium matrix composites
In this paper, the fabrication methods of magnesium matrix composites were introduced and the new fabrication process was emphasized. The effects of the fabrication processes on the composition, structure and properties of the composites were analyzed. Developing new reinforcements and novel in-situ reaction synthesis, optimizing the fabrication process and preparing high performance composites on larger scale are main research keys to the magnesium matrix composites
