Volume 40,Issue 7,2011 Table of Contents
2011, 40(7):1129-1132.
Abstract:
A novel DS superalloy DZ142 was developed in order to maximize the longitudinal rupture strength while retaining acceptable ductility with good environmental properties. The microstructure, the creep rupture, the hot corrosion and the oxidation resistance of DZ142 alloy were studied by scanning electron microscopy，optical microscopy and X-ray diffraction. The results indicate that the microstructure of the alloy after heat treatment are composed of γ, γ￠,(γ+γ￠) eutectic and carbides. After long term aged, DZ142 alloy exhibits good microstructure stability without deleterious TCP phases and the carbide is still of MC type. The creep rupture, the hot corrosion and the oxidation resistance of DZ142 alloy is better than those of DZ125L alloy
A novel DS superalloy DZ142 was developed in order to maximize the longitudinal rupture strength while retaining acceptable ductility with good environmental properties. The microstructure, the creep rupture, the hot corrosion and the oxidation resistance of DZ142 alloy were studied by scanning electron microscopy，optical microscopy and X-ray diffraction. The results indicate that the microstructure of the alloy after heat treatment are composed of γ, γ￠,(γ+γ￠) eutectic and carbides. After long term aged, DZ142 alloy exhibits good microstructure stability without deleterious TCP phases and the carbide is still of MC type. The creep rupture, the hot corrosion and the oxidation resistance of DZ142 alloy is better than those of DZ125L alloy
2011, 40(7):1133-1137.
Abstract:
The influence of heat treatment process on the microstructure and property of Mg-Nd-Gd-Zn-Zr magnesium alloy was studied. The results show that, with the increase of the solid solution temperature, the grains of the alloy grow obviously and its elongation rate is decreased, but the residual second phase in grain boundary reduces, and the fracture mode of the alloy changes from a combination of second-phase fracture and trans-grain fracture to the trans-grain cleavage fracture; with the increase of solution time, the change of the tensile strength is not evident and the elongation rate is increased, but oxidation extent tends to increasing; the double-stage ageing process can improve the elongation rate, but the tensile strength is lowered to some extent
The influence of heat treatment process on the microstructure and property of Mg-Nd-Gd-Zn-Zr magnesium alloy was studied. The results show that, with the increase of the solid solution temperature, the grains of the alloy grow obviously and its elongation rate is decreased, but the residual second phase in grain boundary reduces, and the fracture mode of the alloy changes from a combination of second-phase fracture and trans-grain fracture to the trans-grain cleavage fracture; with the increase of solution time, the change of the tensile strength is not evident and the elongation rate is increased, but oxidation extent tends to increasing; the double-stage ageing process can improve the elongation rate, but the tensile strength is lowered to some extent
2011, 40(7):1138-1140.
Abstract:
The high pure W (HPW) was deposited on the surface of purity Cu tubes through WF6 reduction by H2 adopting cold-wall atmospheric pressure CVD system. Results show that the compressive strength of the tungsten tube with the mixture phase deposited at 440 °C is much lower than that with only α phase deposited at 540 °C. The existence of β phase has a significant negative influence on the compressive property. After annealing treatment at 400 °C for 1 h, the β phase in the mixture will disappear, and its compressive strength reaches the level of the as-deposited α-W.
The high pure W (HPW) was deposited on the surface of purity Cu tubes through WF6 reduction by H2 adopting cold-wall atmospheric pressure CVD system. Results show that the compressive strength of the tungsten tube with the mixture phase deposited at 440 °C is much lower than that with only α phase deposited at 540 °C. The existence of β phase has a significant negative influence on the compressive property. After annealing treatment at 400 °C for 1 h, the β phase in the mixture will disappear, and its compressive strength reaches the level of the as-deposited α-W.
2011, 40(7):1141-1145.
Abstract:
A two-step anodization method was adopted to prepare the porous anode alumina (PAA) template through the oxalic acid solution. By adjusting the parameters (such as current density, oxidation time, electrolyte concentration and other factors), the PAA template was obtained, which has the evenly distributed pores with similar diameters and hexagonal-shaped mouth. Meanwhile, by removing the barrier layer without peeling off the film, the residual aluminum becomes the base and acts as electrode. In the non-aqueous system, the nanowire of RE simple-substance (SS) Nd has been prepared with the template DC electrodeposition. The aperture diameter of PAA template is approximately 60 nm, and there is little change before and after the barrier layer is removed. The Nd nanowire given is orderly and in similar size. EDS shows that the nanowires contain simple-substance (SS) Nd and a tiny of Nd2O3, while the content of SS Nd is 92.73 wt%. Both the SS Nd and Nd2O3 nanowire are possessed of hexagonal structure
A two-step anodization method was adopted to prepare the porous anode alumina (PAA) template through the oxalic acid solution. By adjusting the parameters (such as current density, oxidation time, electrolyte concentration and other factors), the PAA template was obtained, which has the evenly distributed pores with similar diameters and hexagonal-shaped mouth. Meanwhile, by removing the barrier layer without peeling off the film, the residual aluminum becomes the base and acts as electrode. In the non-aqueous system, the nanowire of RE simple-substance (SS) Nd has been prepared with the template DC electrodeposition. The aperture diameter of PAA template is approximately 60 nm, and there is little change before and after the barrier layer is removed. The Nd nanowire given is orderly and in similar size. EDS shows that the nanowires contain simple-substance (SS) Nd and a tiny of Nd2O3, while the content of SS Nd is 92.73 wt%. Both the SS Nd and Nd2O3 nanowire are possessed of hexagonal structure
2011, 40(7):1146-1151.
Abstract:
In order to improve the electrochemical hydrogen storage performances of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by element Co. The nanocrystalline and amorphous Mg20Ni10-xCox (x=0, 1, 2, 3, 4) alloys were prepared by melt-spinning technology. The structures of the as-cast and spun alloys were studied by XRD, SEM and HRTEM. The electrochemical hydrogen storage characteristics of the alloys were measured. The results show that the substitution of Co for Ni leads to the formation of secondary phase MgCo2 without altering the major phase of Mg2Ni. No amorphous phase is detected in the as-spun alloy (x=0), whereas the as-spun alloy (x=4) holds a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni significantly increases the glass forming ability of the Mg2Ni-type alloy. The substitution of Co for Ni significantly improves the electrochemical hydrogen storage performances of the alloys, including the discharge capacity and the cycle stability, for which the increased glass forming ability by Co substitution is mainly responsible
In order to improve the electrochemical hydrogen storage performances of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by element Co. The nanocrystalline and amorphous Mg20Ni10-xCox (x=0, 1, 2, 3, 4) alloys were prepared by melt-spinning technology. The structures of the as-cast and spun alloys were studied by XRD, SEM and HRTEM. The electrochemical hydrogen storage characteristics of the alloys were measured. The results show that the substitution of Co for Ni leads to the formation of secondary phase MgCo2 without altering the major phase of Mg2Ni. No amorphous phase is detected in the as-spun alloy (x=0), whereas the as-spun alloy (x=4) holds a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni significantly increases the glass forming ability of the Mg2Ni-type alloy. The substitution of Co for Ni significantly improves the electrochemical hydrogen storage performances of the alloys, including the discharge capacity and the cycle stability, for which the increased glass forming ability by Co substitution is mainly responsible
2011, 40(7):1152-1156.
Abstract:
The relation between the effective hydrogen storage capacity CH of Ti-V-Cr alloys and out-layer electrons, atomic diameter difference, electronegativity difference has been studied. It is shown that their relation can be expressed as TlnCH = 0.45922T＋5044.8 (DX)2＋1250.6δ2－285.80 n2/3. The factor of out-layer electrons has the largest effect on the CH of Ti-V-Cr alloys, while the factor of electronegativity difference has the smallest effect among the three bond parameters. The effective hydrogen storage capacity of Ti-V-Cr alloys is greater than 2.0wt% when n2/3 values of Ti-V-Cr alloys are between 1.98 and 2.14, d2 values are between 0.255 and 0.288 and (DX) 2 values are between 0.0638 and 0.0765
The relation between the effective hydrogen storage capacity CH of Ti-V-Cr alloys and out-layer electrons, atomic diameter difference, electronegativity difference has been studied. It is shown that their relation can be expressed as TlnCH = 0.45922T＋5044.8 (DX)2＋1250.6δ2－285.80 n2/3. The factor of out-layer electrons has the largest effect on the CH of Ti-V-Cr alloys, while the factor of electronegativity difference has the smallest effect among the three bond parameters. The effective hydrogen storage capacity of Ti-V-Cr alloys is greater than 2.0wt% when n2/3 values of Ti-V-Cr alloys are between 1.98 and 2.14, d2 values are between 0.255 and 0.288 and (DX) 2 values are between 0.0638 and 0.0765
2011, 40(7):1157-1162.
Abstract:
The hot extrusion process of G3 nickel-base alloy was modeled and analyzed by the finite-element method (FEM) to obtain the wear depth of nodes on the die surface based on the modified Archard wear theory. BP neutral network was applied to identify the relationship between the die profile and wear depth of the extrusion die. A genetic algorithm (GA) was used to optimize the die profile which yields more uniform wear distribution on die surface. Thus, the FEM, neutral network, and genetic algorithm were combined to develop a method for the design of the optimal shape of a hot extrusion die. The result shows that the maximum wear depth of the extrusion die is decreased by about 30%, and the wear distribution along the die profile surface is more uniform, indicating that the above approach can improve the wear resistance and the life of extrusion die in hot extrusion of G3 alloy
The hot extrusion process of G3 nickel-base alloy was modeled and analyzed by the finite-element method (FEM) to obtain the wear depth of nodes on the die surface based on the modified Archard wear theory. BP neutral network was applied to identify the relationship between the die profile and wear depth of the extrusion die. A genetic algorithm (GA) was used to optimize the die profile which yields more uniform wear distribution on die surface. Thus, the FEM, neutral network, and genetic algorithm were combined to develop a method for the design of the optimal shape of a hot extrusion die. The result shows that the maximum wear depth of the extrusion die is decreased by about 30%, and the wear distribution along the die profile surface is more uniform, indicating that the above approach can improve the wear resistance and the life of extrusion die in hot extrusion of G3 alloy
8 Study of Amorphous Alloy Nano-crystallization and Giant Magnetic Impedance by Pulsing Magnetic Field
2011, 40(7):1163-1167.
Abstract:
Amorphous Co68.15Fe4.35Si12.5B15 alloy ribbons were treated by low-frequency pulsing magnetic field. M?ssbauer spectroscopy and TEM observation show that initial nano-crystallization of the amorphous samples occurs, and the volume fraction of crystallized phase has a relation with pulsing magnetic field intensity. The giant magnetic impedance (GMI ) of the samples were tested by a GMI instrument; the results show a non-monotonic change between GMI and pulsing magnetic field intensity HP, and the GMI reaches the greatest value of 263.5% under the magnetic field intensity HP=350 kA·m-1. The transverse anisotropy induced by pulsing magnetic field in specimens affects the GMI effect. When the external dc current magnetic filed Hex is equal to Hk, GMI reaches the peak value
Amorphous Co68.15Fe4.35Si12.5B15 alloy ribbons were treated by low-frequency pulsing magnetic field. M?ssbauer spectroscopy and TEM observation show that initial nano-crystallization of the amorphous samples occurs, and the volume fraction of crystallized phase has a relation with pulsing magnetic field intensity. The giant magnetic impedance (GMI ) of the samples were tested by a GMI instrument; the results show a non-monotonic change between GMI and pulsing magnetic field intensity HP, and the GMI reaches the greatest value of 263.5% under the magnetic field intensity HP=350 kA·m-1. The transverse anisotropy induced by pulsing magnetic field in specimens affects the GMI effect. When the external dc current magnetic filed Hex is equal to Hk, GMI reaches the peak value
2011, 40(7):1168-1172.
Abstract:
The effects of Ca addition on microstructure and mechanical properties of ZA104 permanent moulding magnesium alloy were investigated. The results indicate that micro-alloying element Ca is involved in the formation of strengthening phases in ZA104 tested alloy. With increase of Ca content, discontinuous or semi-continuous lamellar and fine lattice microstructures evolve into coarse, continuous and bone-like network gradually. Strengthening phases change from τ and φ phases into τ1 and τ2 phases by degrees. Brinell hardness of the alloy is increased linearly. And it increases sharply when Ca content is lower than 0.3%, while increases slightly with further increase of Ca addition. Ca addition effectively improves high-temperature tensile strength by solid solution and participation in formation of high-temperature strengthening phase. When 0.3%Ca is added, both the room temperature and elevated temperature tensile strengths of the tested alloy reach the peak, which are 203 and 190 MPa, respectively. Meanwhile, the maximum of elongation –17.3% is obtained.
The effects of Ca addition on microstructure and mechanical properties of ZA104 permanent moulding magnesium alloy were investigated. The results indicate that micro-alloying element Ca is involved in the formation of strengthening phases in ZA104 tested alloy. With increase of Ca content, discontinuous or semi-continuous lamellar and fine lattice microstructures evolve into coarse, continuous and bone-like network gradually. Strengthening phases change from τ and φ phases into τ1 and τ2 phases by degrees. Brinell hardness of the alloy is increased linearly. And it increases sharply when Ca content is lower than 0.3%, while increases slightly with further increase of Ca addition. Ca addition effectively improves high-temperature tensile strength by solid solution and participation in formation of high-temperature strengthening phase. When 0.3%Ca is added, both the room temperature and elevated temperature tensile strengths of the tested alloy reach the peak, which are 203 and 190 MPa, respectively. Meanwhile, the maximum of elongation –17.3% is obtained.
2011, 40(7):1173-1177.
Abstract:
The effect of trace vanadium addition on the microstructure of AZ91D magnesium alloy was investigated. Vanadium was introduced by adding AlV55 master alloy. The microstructure variations before and after vanadium addition and the existence form of vanadium in the alloy were analyzed by OM, SEM, EDS and XRD. The results show that the discontinuously reticulated β-Mg17Al12 phase in magnesium alloy become gradually discrete due to vanadium addition. Vanadium added in AZ91D alloy presents in the form of Al3V phase dissolving or dispersing in the β-Mg17Al12 and α-Mg phase. The mechanism of the microstructure refinement is that Al3V phase, which has a higher melting point, has formed prior to the other phases, gathering on the solid-liquid interface and inhibiting the growth of the grain during the solidification of AZ91D alloy. The increase of the grain boundary area reduces the melt volume of eutectic reaction, resulting in the refinement of β-Mg17Al12 phase. Due to the grain refinement and strengthening of Al3V phase, the brinell hardness of AZ91D alloy increases with the V content increasing
The effect of trace vanadium addition on the microstructure of AZ91D magnesium alloy was investigated. Vanadium was introduced by adding AlV55 master alloy. The microstructure variations before and after vanadium addition and the existence form of vanadium in the alloy were analyzed by OM, SEM, EDS and XRD. The results show that the discontinuously reticulated β-Mg17Al12 phase in magnesium alloy become gradually discrete due to vanadium addition. Vanadium added in AZ91D alloy presents in the form of Al3V phase dissolving or dispersing in the β-Mg17Al12 and α-Mg phase. The mechanism of the microstructure refinement is that Al3V phase, which has a higher melting point, has formed prior to the other phases, gathering on the solid-liquid interface and inhibiting the growth of the grain during the solidification of AZ91D alloy. The increase of the grain boundary area reduces the melt volume of eutectic reaction, resulting in the refinement of β-Mg17Al12 phase. Due to the grain refinement and strengthening of Al3V phase, the brinell hardness of AZ91D alloy increases with the V content increasing
2011, 40(7):1178-1183.
Abstract:
The as-heat-treated microstructure characteristics of GH80A superalloy were analyzed qualitatively and quantitatively by HRTEM, XRD and physical-chemical phase analysis. Results show that M7C3 and M23C6 carbides distribute at the grain boundaries to strengthen the grain boundaries and γ' phase distribute dispersively in the grains to increase the high-temperature strength. Besides, the equilibrium precipitates and non-equilibrium solidification process were simulated and calculated by Thermo-Calc software and Ni-base database. The effect of Al and Ti on the precipitated temperature and mass fraction of γ' phase and the effect of carbon on the carbide precipitation rules of MC, M7C3 and M23C6 were also studied
The as-heat-treated microstructure characteristics of GH80A superalloy were analyzed qualitatively and quantitatively by HRTEM, XRD and physical-chemical phase analysis. Results show that M7C3 and M23C6 carbides distribute at the grain boundaries to strengthen the grain boundaries and γ' phase distribute dispersively in the grains to increase the high-temperature strength. Besides, the equilibrium precipitates and non-equilibrium solidification process were simulated and calculated by Thermo-Calc software and Ni-base database. The effect of Al and Ti on the precipitated temperature and mass fraction of γ' phase and the effect of carbon on the carbide precipitation rules of MC, M7C3 and M23C6 were also studied
2011, 40(7):1184-1187.
Abstract:
Dynamic testing of Ti-5Mo-5V-2Cr-3Al (TB10) alloy was carried out in hat-shaped specimens by a split Hopkinson pressure bar (SHPB) technique. The microstructure of adiabatic shear band (ASB) in TB10 alloy was investigated by means of OM and TEM. The results show that the transition zone between the shear band and the matrix is composed of grains of 20-50 nm in width with high dislocation density, and the grains are elongated along the shear direction. The center of the shear band consists of a number of recrystallized grains with diameters of 50-100 nm and low dislocation density, exhibiting typical recrystallization characteristics. The average value of temperature rising in the ASB during the adiabatic shearing deformation is about 784 oC. Dynamic recrystallization occurs in ASB and the grain sizes are about 50-100 nm
Dynamic testing of Ti-5Mo-5V-2Cr-3Al (TB10) alloy was carried out in hat-shaped specimens by a split Hopkinson pressure bar (SHPB) technique. The microstructure of adiabatic shear band (ASB) in TB10 alloy was investigated by means of OM and TEM. The results show that the transition zone between the shear band and the matrix is composed of grains of 20-50 nm in width with high dislocation density, and the grains are elongated along the shear direction. The center of the shear band consists of a number of recrystallized grains with diameters of 50-100 nm and low dislocation density, exhibiting typical recrystallization characteristics. The average value of temperature rising in the ASB during the adiabatic shearing deformation is about 784 oC. Dynamic recrystallization occurs in ASB and the grain sizes are about 50-100 nm
2011, 40(7):1188-1191.
Abstract:
It is one of the basic processes that the oxide film form and rupture in the tip of stress corrosion cracking (SCC) of nickel-base alloys in high temperature water environment of the nuclear pressure vessel. Because of the particularity of the propagating mode and morphology of the tip of SCC, the stress and strain in the tip of SCC constituted of the tip oxide film and base metal was simulated and analyzed under the micro scale based on the sub-model technology in ABAQUS software. The results show that the groove-type crack significantly affects the stress and the plastic strain in the oxide film at the SCC crack tip, and the longer the groove-type crack is, the more obvious the effect is. On the other hand, compared with stress, the plastic strain is more sensitive to the morphology of the tip of SCC; therefore, the plastic strain should be an appropriate mechanical parameter to investigate the oxide film character in the SCC crack tip
It is one of the basic processes that the oxide film form and rupture in the tip of stress corrosion cracking (SCC) of nickel-base alloys in high temperature water environment of the nuclear pressure vessel. Because of the particularity of the propagating mode and morphology of the tip of SCC, the stress and strain in the tip of SCC constituted of the tip oxide film and base metal was simulated and analyzed under the micro scale based on the sub-model technology in ABAQUS software. The results show that the groove-type crack significantly affects the stress and the plastic strain in the oxide film at the SCC crack tip, and the longer the groove-type crack is, the more obvious the effect is. On the other hand, compared with stress, the plastic strain is more sensitive to the morphology of the tip of SCC; therefore, the plastic strain should be an appropriate mechanical parameter to investigate the oxide film character in the SCC crack tip
2011, 40(7):1192-1197.
Abstract:
A series of Au/CuMn catalysts was prepared via a deposition-precipitation method and characterized by X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) techniques. The influences of Au loadings and the calcination temperature on the catalytic activity of Au/CuMn catalyst were investigated. The results demonstrate that the catalyst with 3% Au loading obtained at the calcination temperature of 60 oC exhibits the highest activity, i.e. 72.4% NO conversion at the reaction temperature as low as 50 oC, but the deactivation soon occurs. XPS analysis reveals that Au3+ and Oads. presenting on the catalyst surface are active centers and play an important role. The deactivation during reaction process is related with the partial reduction of both oxidized gold species and Oads. species on the surface of the catalysts. Furthermore, the covering of catalyst surface by carbonate, nitrates and formate formed during catalytic operation is another reason of deactivation
A series of Au/CuMn catalysts was prepared via a deposition-precipitation method and characterized by X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) techniques. The influences of Au loadings and the calcination temperature on the catalytic activity of Au/CuMn catalyst were investigated. The results demonstrate that the catalyst with 3% Au loading obtained at the calcination temperature of 60 oC exhibits the highest activity, i.e. 72.4% NO conversion at the reaction temperature as low as 50 oC, but the deactivation soon occurs. XPS analysis reveals that Au3+ and Oads. presenting on the catalyst surface are active centers and play an important role. The deactivation during reaction process is related with the partial reduction of both oxidized gold species and Oads. species on the surface of the catalysts. Furthermore, the covering of catalyst surface by carbonate, nitrates and formate formed during catalytic operation is another reason of deactivation
2011, 40(7):1198-1201.
Abstract:
In order to improve the leaching efficiency of vanadium pentoxide from BOF slag containing low-vanadium oxide and provide theoretical foundations, the whole leaching process was analyzed from the kinetic aspect. The effects of reaction temperature, the liquid-solid ratio, sulphuric acid concentration and stirring speed on the leaching efficiency were investigated. The results show that the leaching rate of vanadium pentoxide can reach 95.3% under the condition of temperature 90 oC, liquid-solid ratio 10: 1, sulfuric acid concentration 6 mol/L, and leaching time 9 h. By means of the orthogonal experiment and kinetic deduction, an empirical equation for the leaching process is established, and the apparent activation energy is 12.794 kJ/mol. The leaching process of BOF slag containing low-vanadium oxide could be simulated with a shrinking core model, which indicates that the control factor of the leaching process is the diffusion rate of reacting reagents in a porous solid layer. The leaching efficiency and speed can be increased by enhancing the temperature, liquid-solid ratio and sulfuric acid concentration
In order to improve the leaching efficiency of vanadium pentoxide from BOF slag containing low-vanadium oxide and provide theoretical foundations, the whole leaching process was analyzed from the kinetic aspect. The effects of reaction temperature, the liquid-solid ratio, sulphuric acid concentration and stirring speed on the leaching efficiency were investigated. The results show that the leaching rate of vanadium pentoxide can reach 95.3% under the condition of temperature 90 oC, liquid-solid ratio 10: 1, sulfuric acid concentration 6 mol/L, and leaching time 9 h. By means of the orthogonal experiment and kinetic deduction, an empirical equation for the leaching process is established, and the apparent activation energy is 12.794 kJ/mol. The leaching process of BOF slag containing low-vanadium oxide could be simulated with a shrinking core model, which indicates that the control factor of the leaching process is the diffusion rate of reacting reagents in a porous solid layer. The leaching efficiency and speed can be increased by enhancing the temperature, liquid-solid ratio and sulfuric acid concentration
2011, 40(7):1202-1205.
Abstract:
High cycle fatigue (HCF) of Ti-600 alloy was tested at a frequency of 120-130 Hz and load ratio R of 0.1. The results show that the HCF strength for the alloy at ambient temperature is 475 MPa, comparable with that of IMI834 alloy. The observed high tensile strength and high HCF strength is attributed to its overlapping fine and thin-plate-like α+β phase microstructure. The propagating region of the fatigue crack for the as-annealed composite is regular and wide, which contribute to its improved HCF strength and prolonged fatigue crack propagation life. The distance between two fatigue stripes for the sample fractured at 8.61′105 cycles is wider than that of the sample failed at 1.78′106 cycles, indicating that their propagation resistance for fatigue cracks is smaller. The average grain size of rare earth phases ranges from several micrometers to 0.2 mm, and no cracks corresponding to rare earth particles are initiated
High cycle fatigue (HCF) of Ti-600 alloy was tested at a frequency of 120-130 Hz and load ratio R of 0.1. The results show that the HCF strength for the alloy at ambient temperature is 475 MPa, comparable with that of IMI834 alloy. The observed high tensile strength and high HCF strength is attributed to its overlapping fine and thin-plate-like α+β phase microstructure. The propagating region of the fatigue crack for the as-annealed composite is regular and wide, which contribute to its improved HCF strength and prolonged fatigue crack propagation life. The distance between two fatigue stripes for the sample fractured at 8.61′105 cycles is wider than that of the sample failed at 1.78′106 cycles, indicating that their propagation resistance for fatigue cracks is smaller. The average grain size of rare earth phases ranges from several micrometers to 0.2 mm, and no cracks corresponding to rare earth particles are initiated
2011, 40(7):1206-1210.
Abstract:
The effect of trace addition of Zn on the stress corrosion cracking (SCC) resistance and microstructure of Al-4.2Cu-1.4Mg alloy was studied by means of the slow strain rate technique (SSRT), potentiodynamic polarization test, transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD). The results show that the stress corrosion cracking resistance is improved at the beginning and then decreased with the increase of Zn content. The optimum amount of Zn addition is 0.29% to improve SCC resistance. EBSD results show that there are much more low-angle grain boundaries with low energy in the 0.29% Zn contained alloy, which is probably the main reason why Zn can significantly influence SCC resistance of the alloy
The effect of trace addition of Zn on the stress corrosion cracking (SCC) resistance and microstructure of Al-4.2Cu-1.4Mg alloy was studied by means of the slow strain rate technique (SSRT), potentiodynamic polarization test, transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD). The results show that the stress corrosion cracking resistance is improved at the beginning and then decreased with the increase of Zn content. The optimum amount of Zn addition is 0.29% to improve SCC resistance. EBSD results show that there are much more low-angle grain boundaries with low energy in the 0.29% Zn contained alloy, which is probably the main reason why Zn can significantly influence SCC resistance of the alloy
2011, 40(7):1211-1215.
Abstract:
K2Ti6O13 whisker (PTW) reinforced AZ91D magnesium matrix composites were fabricated by a stirring casting method. The corrosion behavior of the composites was examined by potentiodynamic polarization and static corrosion tests. The surface morphology of the composites were investigated by SEM before and after corrosion tests. The results show that α-Mg grains are refined and the distribution of β phase become more uniform for the AZ91D magnesium matrix with the addition of PTW. Meanwhile, the morphologies of β phase in composites with different contents of PTW are obviously different, namely the skeletal structure of β phase is gradually transformed into partially detached honeycomb structure, and lamellar structure disappears. It can be deduced that fine α Mg grains and the decrease of β phase volume fraction lead to the inhibition of galvanic corrosion, thus increasing the corrosion resistance of the AZ91D magnesium composites.
K2Ti6O13 whisker (PTW) reinforced AZ91D magnesium matrix composites were fabricated by a stirring casting method. The corrosion behavior of the composites was examined by potentiodynamic polarization and static corrosion tests. The surface morphology of the composites were investigated by SEM before and after corrosion tests. The results show that α-Mg grains are refined and the distribution of β phase become more uniform for the AZ91D magnesium matrix with the addition of PTW. Meanwhile, the morphologies of β phase in composites with different contents of PTW are obviously different, namely the skeletal structure of β phase is gradually transformed into partially detached honeycomb structure, and lamellar structure disappears. It can be deduced that fine α Mg grains and the decrease of β phase volume fraction lead to the inhibition of galvanic corrosion, thus increasing the corrosion resistance of the AZ91D magnesium composites.
2011, 40(7):1216-1219.
Abstract:
Zirconium-based alloys with different Nb and Fe addition ratios were treated by β-quenching at 1050 oC for 0.5 h and the followed annealing at 560 oC for 10 h; then their microstructure and second phase particles (SPPs) were examined by high-resolution transmission electron microscopy (HR-TEM) equipped with an energy dispersive X-ray spectroscopy (EDS). Results show that with the increasing of Nb addition and the Nb/Fe ratios, SPPs Zr(Fe,Cr)2 with a hexagonal close packed (HCP) structure in Zircaly-4 transform to SPPs Zr(Nb,Fe,Cr)2 with a hexagonal close packed structure; meanwhile the Nb/Fe ratio of Zr(Nb,Fe,Cr)2 is increased too. SPPs βNb with a body center cubic structure could be observed besides HCP-Zr(Nb,Fe,Cr)2 precipitates when Nb contents and Nb/Fe ratios are high enough
Zirconium-based alloys with different Nb and Fe addition ratios were treated by β-quenching at 1050 oC for 0.5 h and the followed annealing at 560 oC for 10 h; then their microstructure and second phase particles (SPPs) were examined by high-resolution transmission electron microscopy (HR-TEM) equipped with an energy dispersive X-ray spectroscopy (EDS). Results show that with the increasing of Nb addition and the Nb/Fe ratios, SPPs Zr(Fe,Cr)2 with a hexagonal close packed (HCP) structure in Zircaly-4 transform to SPPs Zr(Nb,Fe,Cr)2 with a hexagonal close packed structure; meanwhile the Nb/Fe ratio of Zr(Nb,Fe,Cr)2 is increased too. SPPs βNb with a body center cubic structure could be observed besides HCP-Zr(Nb,Fe,Cr)2 precipitates when Nb contents and Nb/Fe ratios are high enough
2011, 40(7):1220-1224.
Abstract:
A series of three-way catalysts was prepared by different cell density substrates with different precious metal contents and washcoat loading. Light-off characteristics of the catalysts were studied by analog computation and tested on engine bench. The results indicate that high cell density of the substrate can improve the catalyst light-off characteristics and air-fuel ratio characteristics markedly, decrease precious metals content in the catalyst and enhance the capability of purifying HCs. The light-off temperature is dependent on the synergic relationship between the substrate cell density and precious metals content. The influence of substrate cell density on air-fuel ratio characteristics is stronger than that of precious metals content. For the aged catalyst, the precious metals content is still an important factor for maintaining catalytic conversion
A series of three-way catalysts was prepared by different cell density substrates with different precious metal contents and washcoat loading. Light-off characteristics of the catalysts were studied by analog computation and tested on engine bench. The results indicate that high cell density of the substrate can improve the catalyst light-off characteristics and air-fuel ratio characteristics markedly, decrease precious metals content in the catalyst and enhance the capability of purifying HCs. The light-off temperature is dependent on the synergic relationship between the substrate cell density and precious metals content. The influence of substrate cell density on air-fuel ratio characteristics is stronger than that of precious metals content. For the aged catalyst, the precious metals content is still an important factor for maintaining catalytic conversion
2011, 40(7):1225-1229.
Abstract:
Surface-repaired samples of TC4 forgings were prepared by Laser Forming Repair (LFR), and the microstructure, tensile property and low cycle fatigue property of the repaired samples were investigated. Microstructure of laser-repaired zone (LRZ) is typical Widmanstaten structure consisting of initial coarse columnar β grains, within which are fine acicular α and α+β basket weave structure, and there is a good metallurgical bonding between LRZ and the forging substrate. The heat affected zone (HAZ) presents a continuous change from the forging substrate microstructure to the repaired zone microstructure. The repaired samples were divided into two groups, and then they were treated by relief annealing (RA) and RA + shot peening (SP) respectively and their low cycle fatigue curves were obtained. It can be found that the fatigue life of the two groups is higher than that of the die forging in the area of low strain, but lower than that in the area of high strain. This is because the strength of the repaired sample is higher than that of forging, while the plasticity is poorer than the forging’s. The strength play a major role in fatigue life when samples are suffering a low strain, and the plasticity decides the fatigue life at high strain. It is shown that the fatigue life is improved by SP both at low strain and high strain. Moreover, the fatigue life of the LFRed samples with SP is close to the level of the forging at high strain, and longer than that of the forging at low strain by 1 order of magnitude
Surface-repaired samples of TC4 forgings were prepared by Laser Forming Repair (LFR), and the microstructure, tensile property and low cycle fatigue property of the repaired samples were investigated. Microstructure of laser-repaired zone (LRZ) is typical Widmanstaten structure consisting of initial coarse columnar β grains, within which are fine acicular α and α+β basket weave structure, and there is a good metallurgical bonding between LRZ and the forging substrate. The heat affected zone (HAZ) presents a continuous change from the forging substrate microstructure to the repaired zone microstructure. The repaired samples were divided into two groups, and then they were treated by relief annealing (RA) and RA + shot peening (SP) respectively and their low cycle fatigue curves were obtained. It can be found that the fatigue life of the two groups is higher than that of the die forging in the area of low strain, but lower than that in the area of high strain. This is because the strength of the repaired sample is higher than that of forging, while the plasticity is poorer than the forging’s. The strength play a major role in fatigue life when samples are suffering a low strain, and the plasticity decides the fatigue life at high strain. It is shown that the fatigue life is improved by SP both at low strain and high strain. Moreover, the fatigue life of the LFRed samples with SP is close to the level of the forging at high strain, and longer than that of the forging at low strain by 1 order of magnitude
2011, 40(7):1230-1233.
Abstract:
The evolution mechanism of the weld zone microstructure and the room temperature tensile strength of the weldment for Ti2AlNb/TC11 dissimilar alloy were investigated through changing the isothermal deformation parameters. Results show that at lower strain rate with higher deformation, the grain refinement of the welded interface is related to dislocation cutting across grain boundary and intragranlar strip O/α2-phase and elongated O/α2-phase necking down. With low deformation, the grain refinement is only related to dislocation cutting across the grain-boundaries and transgranular strip O/α2-phases. Appearance of course and fine strip O/α2-phases is related to response of dynamic recrystallization at low strain rate (10-4 s-1) and high strain rate (10-2 s-1). After hot deformation at 980 °C, at strain rate of 10-2-10-4 s-1 and deformation of 30%-50%, the room-temperature strength of the Ti2AlNb/TC11 dual-alloy joint is better than that of TC11 alloy
The evolution mechanism of the weld zone microstructure and the room temperature tensile strength of the weldment for Ti2AlNb/TC11 dissimilar alloy were investigated through changing the isothermal deformation parameters. Results show that at lower strain rate with higher deformation, the grain refinement of the welded interface is related to dislocation cutting across grain boundary and intragranlar strip O/α2-phase and elongated O/α2-phase necking down. With low deformation, the grain refinement is only related to dislocation cutting across the grain-boundaries and transgranular strip O/α2-phases. Appearance of course and fine strip O/α2-phases is related to response of dynamic recrystallization at low strain rate (10-4 s-1) and high strain rate (10-2 s-1). After hot deformation at 980 °C, at strain rate of 10-2-10-4 s-1 and deformation of 30%-50%, the room-temperature strength of the Ti2AlNb/TC11 dual-alloy joint is better than that of TC11 alloy
2011, 40(7):1239-1242.
Abstract:
Surface nanocrystallization treatment of pure titanium TA2 was conducted by Supersonic Fine Particles Bombarding (SFPB) followed by heat treatment at different temperatures. The nanocrystallization mechanism and the thermal stability of TA2 sample after SFPB treatment were investigated by optical microscope (OM), X-ray diffraction (XRD), microhardness testing and transmission electron microscope (TEM). The results show that equiaxed nanocrystallites with random crystallographic orientations are obtained in the surface layer with SFPB, and the grain size is about 20 nm. During SFPB processing, deformation twinning is the main deformation mode in industrial pure titanium, and with the increase in the layer depth, twin deformation gradually changes from a multi-line system to a single one. In addition, when the annealing temperature is 450 oC, the grain size is below 100 nm and the sample has good thermal stability; when the annealing temperature is higher than 450 oC, the grains grow significantly (> 100 nm)
Surface nanocrystallization treatment of pure titanium TA2 was conducted by Supersonic Fine Particles Bombarding (SFPB) followed by heat treatment at different temperatures. The nanocrystallization mechanism and the thermal stability of TA2 sample after SFPB treatment were investigated by optical microscope (OM), X-ray diffraction (XRD), microhardness testing and transmission electron microscope (TEM). The results show that equiaxed nanocrystallites with random crystallographic orientations are obtained in the surface layer with SFPB, and the grain size is about 20 nm. During SFPB processing, deformation twinning is the main deformation mode in industrial pure titanium, and with the increase in the layer depth, twin deformation gradually changes from a multi-line system to a single one. In addition, when the annealing temperature is 450 oC, the grain size is below 100 nm and the sample has good thermal stability; when the annealing temperature is higher than 450 oC, the grains grow significantly (> 100 nm)
2011, 40(7):1243-1246.
Abstract:
Effects of Gd purity on glass-forming ability (GFA) and magnetocaloric effect (MCE) of Gd52.5Co18.5Al29 amorphous alloy were investigated. It is shown that the impurities have an influence on the GFA of Gd52.5Co18.5Al29 glassy alloy rods and the maximum diameters decrease from 4 mm to 3 mm when the purity of Gd decreases from 99.94% to 99.2%. However, no decline of magnetocaloric effect is observed for different-purity alloys and the maximum magnetic entropy changes and relative cooling power of high-purity and low-purity Gd52.5Co18.5Al29 alloys are 9.4 J·kg-1·K-1, 8.1×102 J·kg-1 and 9.5 J·kg-1·K-1, 8.4×102 J·kg-1, respectively. Therefore, it indicates that lower cost Gd52.5Co18.5Al29 alloy prepared by commercial Gd is promising for further application as magnetic refrigerant
Effects of Gd purity on glass-forming ability (GFA) and magnetocaloric effect (MCE) of Gd52.5Co18.5Al29 amorphous alloy were investigated. It is shown that the impurities have an influence on the GFA of Gd52.5Co18.5Al29 glassy alloy rods and the maximum diameters decrease from 4 mm to 3 mm when the purity of Gd decreases from 99.94% to 99.2%. However, no decline of magnetocaloric effect is observed for different-purity alloys and the maximum magnetic entropy changes and relative cooling power of high-purity and low-purity Gd52.5Co18.5Al29 alloys are 9.4 J·kg-1·K-1, 8.1×102 J·kg-1 and 9.5 J·kg-1·K-1, 8.4×102 J·kg-1, respectively. Therefore, it indicates that lower cost Gd52.5Co18.5Al29 alloy prepared by commercial Gd is promising for further application as magnetic refrigerant
2011, 40(7):1247-1250.
Abstract:
U-5.7Nb alloy specimens were artificially aged by isothermal treatments at 190 °C for 1 to 16 h. X-ray diffraction data were collected and discussed. Aging-induced changes in the structure, including lattice parameters, lattice strains and residual niobium in solution, were given. The results show that spinodal decomposition takes place in the U-5.7Nb alloy after aging at 190 °C for 2 h, and further aging causes formation of γ0 phase
U-5.7Nb alloy specimens were artificially aged by isothermal treatments at 190 °C for 1 to 16 h. X-ray diffraction data were collected and discussed. Aging-induced changes in the structure, including lattice parameters, lattice strains and residual niobium in solution, were given. The results show that spinodal decomposition takes place in the U-5.7Nb alloy after aging at 190 °C for 2 h, and further aging causes formation of γ0 phase
2011, 40(7):1251-1255.
Abstract:
A series of copper-silver bimetallic powder was prepared by a chemical replacement method. In this process, ionic masking agent was added to eliminate copper ammonia complex ions adsorption on copper powder surface, which realizes silver continuous coating on the copper powder surfaces. The masking mechanism and the main influencing factors were analyzed. Besides that, TEM, TGA and XRD were used to characterize the Cu-Ag bimetallic powder. Results show that the copper-silver bimetallic powder with the ionic masking agent is of a continuous coating type structure, which has good dispersity, effectively improving antioxidation properties of the copper powder.
A series of copper-silver bimetallic powder was prepared by a chemical replacement method. In this process, ionic masking agent was added to eliminate copper ammonia complex ions adsorption on copper powder surface, which realizes silver continuous coating on the copper powder surfaces. The masking mechanism and the main influencing factors were analyzed. Besides that, TEM, TGA and XRD were used to characterize the Cu-Ag bimetallic powder. Results show that the copper-silver bimetallic powder with the ionic masking agent is of a continuous coating type structure, which has good dispersity, effectively improving antioxidation properties of the copper powder.
2011, 40(7):1256-1259.
Abstract:
Changes of the relative mass and heat absorption-heat evolution of palladium were measured by TG and DSC in a temperature rising process from room temperature to 1200 oC. The surface chemical species of palladium samples with different treatment systems were determined by XPS. For sponge palladium, a series of thermal effects, such as the formation, decomposition and evaporation of PdO at 260, 720 and 877 oC, respectively were observed on the heat absorption-heat evolution curves. The oxidation of palladium is a mass-gain process below 750 oC, and the decomposition and evaporation of PdO lead to mass loss at temperatures above 750 oC. When heated or quenched above 850 oC, Pd presents Pdo state and keep a bright metallic surface; while heated or quenched below 850 oC, Pd is coated by PdO and thus exhibits a dull color
Changes of the relative mass and heat absorption-heat evolution of palladium were measured by TG and DSC in a temperature rising process from room temperature to 1200 oC. The surface chemical species of palladium samples with different treatment systems were determined by XPS. For sponge palladium, a series of thermal effects, such as the formation, decomposition and evaporation of PdO at 260, 720 and 877 oC, respectively were observed on the heat absorption-heat evolution curves. The oxidation of palladium is a mass-gain process below 750 oC, and the decomposition and evaporation of PdO lead to mass loss at temperatures above 750 oC. When heated or quenched above 850 oC, Pd presents Pdo state and keep a bright metallic surface; while heated or quenched below 850 oC, Pd is coated by PdO and thus exhibits a dull color
2011, 40(7):1260-1263.
Abstract:
Due to the high oxygen content of the superalloy powder produced by a novel Spark Plasma Discharge Process, the reduction process of superalloy powder was studied exploringly. Results show that under the protection of argon by atmospheric pressure at 550 oC and with CaH2 as its deoxidizer, the oxygen content of the Ni-based superalloy powder prepared by the novel method is decreased from 9.26% to 1.52%, and the final oxygen content depends mainly on the content of CaO left
Due to the high oxygen content of the superalloy powder produced by a novel Spark Plasma Discharge Process, the reduction process of superalloy powder was studied exploringly. Results show that under the protection of argon by atmospheric pressure at 550 oC and with CaH2 as its deoxidizer, the oxygen content of the Ni-based superalloy powder prepared by the novel method is decreased from 9.26% to 1.52%, and the final oxygen content depends mainly on the content of CaO left
2011, 40(7):1264-1267.
Abstract:
The polarization switching property of antiferroelectric materials La-doped Pb(Zr,Sn,Ti)O3 stimulated by monopulse rectangle voltage was investigated. The electronic hysteresis loop characteristics of the ceramic samples excited by 1 Hz-sine alternating voltage and monopulse rectangle voltage with different pulse widths were measured and analyzed. And the phase transition time of the ceramic samples was discussed. Compared with 1 Hz-sine alternating voltage, forward electric switching field increases and backward switching electric field decreases when monopulse voltage is applied. Under monopulse voltage, forward switching time is 394 ns. The minimum pulse width which results in the beginning of polarization switching is in the range of 50-100 ns.
The polarization switching property of antiferroelectric materials La-doped Pb(Zr,Sn,Ti)O3 stimulated by monopulse rectangle voltage was investigated. The electronic hysteresis loop characteristics of the ceramic samples excited by 1 Hz-sine alternating voltage and monopulse rectangle voltage with different pulse widths were measured and analyzed. And the phase transition time of the ceramic samples was discussed. Compared with 1 Hz-sine alternating voltage, forward electric switching field increases and backward switching electric field decreases when monopulse voltage is applied. Under monopulse voltage, forward switching time is 394 ns. The minimum pulse width which results in the beginning of polarization switching is in the range of 50-100 ns.
2011, 40(7):1268-1270.
Abstract:
The synthesis and spectral properties of YAG:Tb phosphor were investigated. The results show that the single pure YAG:Tb phosphor powder can be synthesized at 1400 oC by solid state reaction. The Tb concentration has no influence on the excited spectra of the phosphor, while it changes the emission spectra and the relative brightness of the phosphor obviously. The relative brightness of the phosphor increases gradually with the growing Tb concentration. There is no obvious concentration quenching phenomenon in the experiment. The relative brightness of the phosphor increases first and then decreases with Ga doping. The excited spectra and emission spectra of the phosphor doped with Ga changes independently
The synthesis and spectral properties of YAG:Tb phosphor were investigated. The results show that the single pure YAG:Tb phosphor powder can be synthesized at 1400 oC by solid state reaction. The Tb concentration has no influence on the excited spectra of the phosphor, while it changes the emission spectra and the relative brightness of the phosphor obviously. The relative brightness of the phosphor increases gradually with the growing Tb concentration. There is no obvious concentration quenching phenomenon in the experiment. The relative brightness of the phosphor increases first and then decreases with Ga doping. The excited spectra and emission spectra of the phosphor doped with Ga changes independently
2011, 40(7):1271-1276.
Abstract:
A new technology for surface self-nanocrystallization of Mg-15Gd-3Y magnesium alloy induced by HVOF (high velocity oxygen-fuel flame) microparticles impact at low temperature was investigated, and the influencing rule of the surface layer deformation and nanocrystallization with different processing parameters were analyzed. It is found that diameter size of the impacting steel shots, bombardment distance and treating time have an important influence on the microstructure of deformed layer and microhardness distribution with depth. The deformation characteristics and nanocrystallization effect of the top surface layer of magnesium alloy specimen with the surface self-nanocrystallization were investigated by optical microscopy (OM) and transmission electron microscopy (TEM), respectively. Meanwhile, the microhardness distribution from the topmost surface to the matrix of the specimen was tested by a microhardness tester. The phase of surface layer in the specimen before and after treatment was analyzed using X-ray diffractometer (XRD). Results show that surface self-nanocrystallization of the magnesium alloy is realized by the new technology, verified by the TEM testing results, and grain size of the top surface layer is refined to about 20 nm. The microhardness of the most top surface layer is increased up to above twice as that of the substrate. No oxide of the magnesium alloy is found in top surface layer of the treated specimen.
A new technology for surface self-nanocrystallization of Mg-15Gd-3Y magnesium alloy induced by HVOF (high velocity oxygen-fuel flame) microparticles impact at low temperature was investigated, and the influencing rule of the surface layer deformation and nanocrystallization with different processing parameters were analyzed. It is found that diameter size of the impacting steel shots, bombardment distance and treating time have an important influence on the microstructure of deformed layer and microhardness distribution with depth. The deformation characteristics and nanocrystallization effect of the top surface layer of magnesium alloy specimen with the surface self-nanocrystallization were investigated by optical microscopy (OM) and transmission electron microscopy (TEM), respectively. Meanwhile, the microhardness distribution from the topmost surface to the matrix of the specimen was tested by a microhardness tester. The phase of surface layer in the specimen before and after treatment was analyzed using X-ray diffractometer (XRD). Results show that surface self-nanocrystallization of the magnesium alloy is realized by the new technology, verified by the TEM testing results, and grain size of the top surface layer is refined to about 20 nm. The microhardness of the most top surface layer is increased up to above twice as that of the substrate. No oxide of the magnesium alloy is found in top surface layer of the treated specimen.
2011, 40(7):1277-1281.
Abstract:
The effects of friction stir processing on the structures and performances of Zr41Ti14Cu12.5Ni10Be22.5 bulk amorphous alloy were investigated. The results show that the microstructure of the stir zone exhibits amorphous state after friction stir processing. The strength of base metal, heat affecting zone (HAZ) and stir zone are almost similar under room temperature quasi static state compressing. However, the elastic modulus of the stir zone and the HAZ is increased markedly and the serration flow phenomena are found in the compressing curve of HAZ and stir zone before fracture. The fracture surface of stir zone and HAZ exhibit obvious multiple shear characters. It is considered that friction stir processing changes the concentration and distribution of freedom volume in stir zone and HAZ
The effects of friction stir processing on the structures and performances of Zr41Ti14Cu12.5Ni10Be22.5 bulk amorphous alloy were investigated. The results show that the microstructure of the stir zone exhibits amorphous state after friction stir processing. The strength of base metal, heat affecting zone (HAZ) and stir zone are almost similar under room temperature quasi static state compressing. However, the elastic modulus of the stir zone and the HAZ is increased markedly and the serration flow phenomena are found in the compressing curve of HAZ and stir zone before fracture. The fracture surface of stir zone and HAZ exhibit obvious multiple shear characters. It is considered that friction stir processing changes the concentration and distribution of freedom volume in stir zone and HAZ
2011, 40(7):1282-1286.
Abstract:
The Mo-Ru-Se nano-clusters doped with Pt were synthesized by a low temperature method and characterized by XRD, EDS and XPS. The electro-catalytic performance to oxygen reduction was studied for the Pt-W-Ru-Se catalysts in acid electrolytes with or without methanol by a linear sweep voltammetry (LSV) method. The results show that the activity of W-Ru-Se doped with Pt on oxygen reduction is markedly increased compared with that of platinum-free W-Ru-Se under the same reaction condition. The optimum Pt loading is about 5 %. In 0.5 mol?L-1 H2SO4, the initial potential of oxygen reduction of Pt-W-Ru-Se (5% Pt) is 0.25 V, the peak current density is 310 mA·mg-1, approaching 2.2 times that of W-Ru-Se and the activity is close to that of Pt/C. In addition, the activity and methanol-resistance of Pt-W-Ru-Se (5% Pt) is better than that of Pt/C in 0.5 mol?L-1 H2SO4 with methanol
The Mo-Ru-Se nano-clusters doped with Pt were synthesized by a low temperature method and characterized by XRD, EDS and XPS. The electro-catalytic performance to oxygen reduction was studied for the Pt-W-Ru-Se catalysts in acid electrolytes with or without methanol by a linear sweep voltammetry (LSV) method. The results show that the activity of W-Ru-Se doped with Pt on oxygen reduction is markedly increased compared with that of platinum-free W-Ru-Se under the same reaction condition. The optimum Pt loading is about 5 %. In 0.5 mol?L-1 H2SO4, the initial potential of oxygen reduction of Pt-W-Ru-Se (5% Pt) is 0.25 V, the peak current density is 310 mA·mg-1, approaching 2.2 times that of W-Ru-Se and the activity is close to that of Pt/C. In addition, the activity and methanol-resistance of Pt-W-Ru-Se (5% Pt) is better than that of Pt/C in 0.5 mol?L-1 H2SO4 with methanol
Zhou Zhuojun
,
Zhu Yanjuan
,
Zhang Zhongju
,
Ye Xiancong
,
Wu Shanggai
,
Zheng Hanzhong
,
Lin Xiaoran
,
Bao Jie
2011, 40(7):1287-1291.
Abstract:
Nickel hydroxides doped with different yttrium contents were prepared by a supersonic co-precipitation method. Their particle size distribution, crystal structures and electrochemical performance were characterized. The XRD results show the co-existence of α and β phase in the nickel hydroxides. The laser particle size measurement indicates that all the samples are of nanoparticles, which are distributed uniformly with average size of 50-80 nm. Complex electrodes were prepared by mixing 8wt% nickel hydroxides with commercial micro-sized spherical nickel. The cyclic voltammetry results show that the reversibility and charge efficiency of the electrodes are increased initially and then decreased with the increase of Y content. The best reversibility and charge efficiency is observed in the electrodes with 1.17wt% Y. The discharge capacity reaches 370 mAh/g at 0.1 C and 358 mAh/g at 0.5 C for the 1.17wt% Y-doped electrodes, higher than the theoretical value of pure β-Ni(OH)2. The data is 48%-60% higher than the capacity of market Ni(OH)2 battery (230-250 mAh/g). F Furthermore, low charge potential and high discharge plateau are also observed. inally, the samples prepared under supersonic were compared with that without supersonic
Nickel hydroxides doped with different yttrium contents were prepared by a supersonic co-precipitation method. Their particle size distribution, crystal structures and electrochemical performance were characterized. The XRD results show the co-existence of α and β phase in the nickel hydroxides. The laser particle size measurement indicates that all the samples are of nanoparticles, which are distributed uniformly with average size of 50-80 nm. Complex electrodes were prepared by mixing 8wt% nickel hydroxides with commercial micro-sized spherical nickel. The cyclic voltammetry results show that the reversibility and charge efficiency of the electrodes are increased initially and then decreased with the increase of Y content. The best reversibility and charge efficiency is observed in the electrodes with 1.17wt% Y. The discharge capacity reaches 370 mAh/g at 0.1 C and 358 mAh/g at 0.5 C for the 1.17wt% Y-doped electrodes, higher than the theoretical value of pure β-Ni(OH)2. The data is 48%-60% higher than the capacity of market Ni(OH)2 battery (230-250 mAh/g). F Furthermore, low charge potential and high discharge plateau are also observed. inally, the samples prepared under supersonic were compared with that without supersonic
2011, 40(7):1292-1294.
Abstract:
The electrodeposition of molybdenum in the binary alkali metal salts of bis[(tri-fluoromethyl)sulfony]amide LiTFSI-CsTFSI (eutectic point, 0.07: 0.93 in mole fraction; m.p., 112 oC) was investigated. Results show that MoCl3 was selected as the molybdenum ion source and electroreduced into metallic molybdenum on nickel plate in the eutectic LiTFSI-CsTFSI melt at 200 oC and 150 oC. Cyclic voltammetry measurement combined with SEM and XPS were employed. The results confirm that the electrodeposits obtained potentiostatically at 1.4 V (vs. Li+/Li) on nickel electrode are amorphous molybdenum
The electrodeposition of molybdenum in the binary alkali metal salts of bis[(tri-fluoromethyl)sulfony]amide LiTFSI-CsTFSI (eutectic point, 0.07: 0.93 in mole fraction; m.p., 112 oC) was investigated. Results show that MoCl3 was selected as the molybdenum ion source and electroreduced into metallic molybdenum on nickel plate in the eutectic LiTFSI-CsTFSI melt at 200 oC and 150 oC. Cyclic voltammetry measurement combined with SEM and XPS were employed. The results confirm that the electrodeposits obtained potentiostatically at 1.4 V (vs. Li+/Li) on nickel electrode are amorphous molybdenum
2011, 40(7):1295-1299.
Abstract:
The effects of the retrogression heating rates (340, 57, 4.3 oC·min-1) on the microstructure evolution of aluminum alloy 7050 during retrogression heating up were investigated by means of differential scanning calorimetry (DSC), high temperature X-ray diffraction (HTXRD), transmission electron microscopy (TEM), hardness measurement and electrical conductivity testing. The results show that during the process of retrogression heating up, the pre-aged microstructures suffer the process of GP zone and η′ phase re-solution, or the phase transformation from GP zone and η′ phase into η′ phase and followed η phase, respectively. And the heating rate affects evidently the temperature of re-solution and phase transformation. With the heating rates increasing, the temperature of re-solution and phase transformation rises, too. When the retrogression temperature is affirmatory, the microstructures formed during heating up process are different due to the various heating rates. And this kind of microstructure will affect the phase transformation at the retrogression stage. This work thinks that at the medium heating rate, the microstructures formed during heating up process are more propitious to the microstructure transformation at the retrogression stage.
The effects of the retrogression heating rates (340, 57, 4.3 oC·min-1) on the microstructure evolution of aluminum alloy 7050 during retrogression heating up were investigated by means of differential scanning calorimetry (DSC), high temperature X-ray diffraction (HTXRD), transmission electron microscopy (TEM), hardness measurement and electrical conductivity testing. The results show that during the process of retrogression heating up, the pre-aged microstructures suffer the process of GP zone and η′ phase re-solution, or the phase transformation from GP zone and η′ phase into η′ phase and followed η phase, respectively. And the heating rate affects evidently the temperature of re-solution and phase transformation. With the heating rates increasing, the temperature of re-solution and phase transformation rises, too. When the retrogression temperature is affirmatory, the microstructures formed during heating up process are different due to the various heating rates. And this kind of microstructure will affect the phase transformation at the retrogression stage. This work thinks that at the medium heating rate, the microstructures formed during heating up process are more propitious to the microstructure transformation at the retrogression stage.
2011, 40(7):1300-1304.
Abstract:
The microstructure and the tensile deformation behavior between 200 °C and 900 °C of solution strengthened Ni-Cr-W base superalloy were studied by OM, SEM, TEM and a high temperature tensile testing machine. The results show that there are only two phases of γ and M6C in the matrix. Lots of stacking faults are formed in the superalloy microstructure. With the increasing temperature, ultimate tensile strength and yield strength decrease slowly when the temperature is below 650 °C. When the temperature is above 650 °C, ultimate tensile strength decrease rapidly and yield strength almost keep invariable. The elongation and reduction in cross-section of the superalloy change little below 650 °C, but both of them increase rapidly when the temperature is higher than 650 °C. Serration stress-strain curves are induced by mechanical twins mechanism in the temperature range of 400~700 °C. The fracture is of ductile dimple fracture mode. The cracks are initiated mainly in the interface between γ and M6C
The microstructure and the tensile deformation behavior between 200 °C and 900 °C of solution strengthened Ni-Cr-W base superalloy were studied by OM, SEM, TEM and a high temperature tensile testing machine. The results show that there are only two phases of γ and M6C in the matrix. Lots of stacking faults are formed in the superalloy microstructure. With the increasing temperature, ultimate tensile strength and yield strength decrease slowly when the temperature is below 650 °C. When the temperature is above 650 °C, ultimate tensile strength decrease rapidly and yield strength almost keep invariable. The elongation and reduction in cross-section of the superalloy change little below 650 °C, but both of them increase rapidly when the temperature is higher than 650 °C. Serration stress-strain curves are induced by mechanical twins mechanism in the temperature range of 400~700 °C. The fracture is of ductile dimple fracture mode. The cracks are initiated mainly in the interface between γ and M6C
38 Correlation between Microscopically Structural Inhomogeneity and the Plasticity in Amorphous Alloy
2011, 40(7):1305-1310.
Abstract:
The application of bulk amorphous alloys as structural materials is favored by their high strength and high elastic strain, but limited by their lack of plasticity. However, recent research advances show that the introduction of microscopically structural inhomogeneities results in excellent room-temperature plasticity of amorphous alloys. Various microstructural inhomogeneities in bulk amorphous alloys are reviewed in the present paper, with emphasis on their forming conditions, characterization techniques and correlations between shear banding behavior and plasticity. Influences of preparing conditions and chemical compositions on microstructure and plasticity of amorphous alloys are discussed. Finally, some unresolved fundamental issues in the amorphous field are highlighted
The application of bulk amorphous alloys as structural materials is favored by their high strength and high elastic strain, but limited by their lack of plasticity. However, recent research advances show that the introduction of microscopically structural inhomogeneities results in excellent room-temperature plasticity of amorphous alloys. Various microstructural inhomogeneities in bulk amorphous alloys are reviewed in the present paper, with emphasis on their forming conditions, characterization techniques and correlations between shear banding behavior and plasticity. Influences of preparing conditions and chemical compositions on microstructure and plasticity of amorphous alloys are discussed. Finally, some unresolved fundamental issues in the amorphous field are highlighted
2011, 40(7):1311-1316.
Abstract:
According to the nanoparticles’ dimension, the preparation methods and research status of nano silver with various morphologies are introduced. The shortages in the fabrication process of silver nanoparticles are analyzed. The possible developing trends of the controlled preparation of nano silver with various morphologies are also prospected. The questions existing in industrialization progress of nanostructured silver are also discussed. Nano silver with various morphologies is considered as a kind of significant material for nanodevices with different functions.
According to the nanoparticles’ dimension, the preparation methods and research status of nano silver with various morphologies are introduced. The shortages in the fabrication process of silver nanoparticles are analyzed. The possible developing trends of the controlled preparation of nano silver with various morphologies are also prospected. The questions existing in industrialization progress of nanostructured silver are also discussed. Nano silver with various morphologies is considered as a kind of significant material for nanodevices with different functions.
