Titanium plates with a Ti−O solid solution surface-hardened layer were cold roll-bonded with 304 stainless steel plates with high work hardening rates.The evolution and mechanisms affecting the interfacial bonding str...Titanium plates with a Ti−O solid solution surface-hardened layer were cold roll-bonded with 304 stainless steel plates with high work hardening rates.The evolution and mechanisms affecting the interfacial bonding strength in titanium/stainless steel laminated composites were investigated.Results indicate that the hardened layer reduces the interfacial bonding strength from over 261 MPa to less than 204 MPa.During the cold roll-bonding process,the hardened layer fractures,leading to the formation of multi-scale cracks that are difficult for the stainless steel to fill.This not only hinders the development of an interlocking interface but also leads to the presence of numerous microcracks and hardened blocks along the nearly straight interface,consequently weakening the interfacial bonding strength.In metals with high work hardening rates,the conventional approach of enhancing interface interlocking and improving interfacial bonding strength by using a surface-hardened layer becomes less effective.展开更多
This study explored the coupling effects of microstructure,strain rate,and 3.5%NaCl solution on stress corrosion cracking(SCC)behaviors of low-cost Ti6411 and Ti52 titanium alloys,compared to those of marine TC4ELI an...This study explored the coupling effects of microstructure,strain rate,and 3.5%NaCl solution on stress corrosion cracking(SCC)behaviors of low-cost Ti6411 and Ti52 titanium alloys,compared to those of marine TC4ELI and Ti80 titanium alloys.Slow strain rate tensile(SSRT)tests were performed to evaluate SCC susceptibility.The SCC susceptibility index(I_(SSRT))was calculated,and the fracture morphologies were investigated to clarify the stress corrosion mechanisms.The experimental results show that the ISSRT of Ti6411 titanium alloy with a lamellar micro structure(LM)is the highest under a strain rate of 1×10^(-6)s^(-1),and the corresponding fracture mode shows a quasi-cleavage fracture with low ductility.TC4ELI alloy with an equiaxed microstructure exhibits excellent SCC resistance.However,the SCC behavior of the Ti80 alloy with a bimodal microstructure is relatively sensitive to high strain rates,and the Ti52 tube with a typical Widmanst?tten microstructure is sensitive to low strain rates.The stress corrosion mechanism can be attributed to the cyclic process of passive film rupture,anodic dissolution,and hydrogen-induced cracking due to a multifactor comprehensive interaction corresponding to specific microstructures,strain rates,and corrosive media.The LM of the Ti6411 plate allowed easy chloride penetration into the bare metal,thereby reducing the protection of the film and resulting in continuous anodic dissolution and hydrogen accumulation at the crack tip.The coupled effect of the internal hydrogen pressure and external tensile stress can easily cause crack propagation and failure under service conditions.展开更多
The properties of titanium carbonitride Ti（CxN1-x） inclusions precipitated during solidification of tire cord steels and the thermodynamic conditions for their decomposition and solid solution during billet heating ...The properties of titanium carbonitride Ti（CxN1-x） inclusions precipitated during solidification of tire cord steels and the thermodynamic conditions for their decomposition and solid solution during billet heating were investigated using a thermodynamics method. The solid solution of Ti（CxN1-x） inclusions during high-temperature heating was also studied experimentally. The results revealed that： （1） the higher the content of carbon in the tire cord steel is, the greater the value of .r in the Ti（CxN1-x） inclusions is; （2） the higher the content of carbon in the tire cord steel is, the earlier the Ti（CxN1-x） inclusions precipitated during the solidification process and the lower the solidification front temperature is during precipitation; （3） when an 82A steel sample was heated to 1087℃, the Ti（CxN1-x） inclusions possess the thermodynamic conditions of decomposition and solid solution; and （4） when 82A samples were heated to 1150 and 1 250℃, the total number of Ti（CxN1-x） inclusions larger than 5μm in diameter decreased by 55.0% and 70.3%, respectively. In addition, although smaller inclusions with diameter less than 2 μm continued to decompose when the sample was heated at 1 250℃ for 2 h and then cooled to 1000℃ in the furnace, the number of inclusions larger than 5 μm in diameter increased.展开更多
The microstructural evolution, mechanical properties and fracture mechanism of a Ti.5Al.5Mo.5V.3Cr.1Zr (Ti-55531) alloy after solution (760.820℃) plus aging (580.640℃) treatments were investigated. The results show ...The microstructural evolution, mechanical properties and fracture mechanism of a Ti.5Al.5Mo.5V.3Cr.1Zr (Ti-55531) alloy after solution (760.820℃) plus aging (580.640℃) treatments were investigated. The results show that the volume fraction of the primary α(αp) phase decreases with the increase of solution temperature, and the length of the secondary α phase (αs) decreases while its width increases with the increase of aging temperature. Yield and tensile strengths decrease with the increase of solution temperature, while increase with the increase of aging temperature. A good balance of tensile strength and ductility of the alloy is obtained under solution of 800℃ for 2 h plus aging of 640℃ for 8 h, in which the tensile strength is 1434 MPa and the elongation is 7.7%. The coarsening αs phase makes crack propagation paths deflected and tortuous, which increases the crack propagation resistance and improves the ductility and fracture toughness.展开更多
In order to improve the quality of the cord steel wire rod and achieve the effective control of titanium inclusion, the solid solution behavior of titanium inclusion in tire cord steel during the heating process was d...In order to improve the quality of the cord steel wire rod and achieve the effective control of titanium inclusion, the solid solution behavior of titanium inclusion in tire cord steel during the heating process was discussed in this paper, through the thermodynamic theory analysis, combined with the CLSM experiment. The conclusions are as follows: 1) According to the law of Ostwald repening, the coarsening rate of titanium carbonitride inclusion is very small, the coarsening behavior of titanium carbonitride inclusion cannot be considered in the heating and holding stage. 2) The solid solution behavior of titanium inclusion in the heating process is obviously existed. 3) Through the proper control of rolling temperature, holding time and the subsequent cooling rate, the size and quantity of large particle titanium inclusion in the high strength tire cord steel can be effectively controlled.展开更多
Through studying on the heating process of titanium microalloyed steels, the influence of heating temperature on the austenite grain size and the solid dissolution, precipitation law of Ti microalloying element were a...Through studying on the heating process of titanium microalloyed steels, the influence of heating temperature on the austenite grain size and the solid dissolution, precipitation law of Ti microalloying element were analyzed, and the results showed that, the austenite grain size increased with the increase of heating temperature, When the heating temperature reached 1050°C and 1250°C, the austenite grains appeared the obvious coarsening process twice. TiC particles dissolved gradually as the heating temperature increased. When the heating temperature rose to 1100°C, TiC particles disappeared basically, When the heating temperature rose to 1250°C, TiN particles began to be dissolved and grow up.展开更多
A series of nanocrystalline V-doped （0.0-3.0 at.%） TiO2 catalysts have been successfully prepared by the one-step solution combustion method using urea as a fuel. The obtained powders were characterized by XRD, SEM,...A series of nanocrystalline V-doped （0.0-3.0 at.%） TiO2 catalysts have been successfully prepared by the one-step solution combustion method using urea as a fuel. The obtained powders were characterized by XRD, SEM, Raman, XPS and UV-Vis DRS. The effects of V doping concentration on the phase structure and photocatalytic properties were investigated. XRD, Raman, and XPS show that V doping diffuses into TiO2 crystal lattice mainly in the form of V5＋ and causes a phase transition from anatase to mille. V doping can widen the light absorption range of TiO2, with the absorption threshold wavelength shifting from 425 to 625 nm. The photocatalytic activity of V-doped TiO2 powders were evaluated by the photocatalytic degradation of methyl orange （MO） under visible light irradiation. It is found that V doping enhances the photoeatalyilc activity under visible light irradiation and the optimal degradation rate of MO is about 95.8% with 1.0 at% V-doped TiO2.展开更多
The corrosion behavior of Ti60 alloy was investigated under continuous NaCl solution spraying at 600℃.Results indicate that the corrosion rate of the Ti60 alloy is lower than that obtained with the solid NaCl deposit...The corrosion behavior of Ti60 alloy was investigated under continuous NaCl solution spraying at 600℃.Results indicate that the corrosion rate of the Ti60 alloy is lower than that obtained with the solid NaCl deposit film in HO+O.The outer corrosion products are compact layers mainly containing NaTiOand nanocrystalline TiO.The inner layer is mainly composed of TiO,Ti O and SnO.TiO has a lamellar structure,and TiO has a strip-shaped structure.A mixed corrosion mechanism including classic oxidation and active oxidation occurred under NaCl solution spraying environment:the first stage was controlled by the classic oxidation mechanism with the promotion by the active oxidation following parabolic curves,and the second stage was controlled by the active oxidation mechanism following a linear rise in the mass gain curve.The mixed corrosion mechanism between classic oxidation and active oxidation produced a relatively dense Ti oxides scale,which decreased the corrosion rate.展开更多
Oxide powders of Zr1_xTixO2(x=0-1)solid solutions with micron-sized particles were synthesized via a solution combustion method.The synthesis process and Zr/Ti molar ratio were optimized to produce powders with the te...Oxide powders of Zr1_xTixO2(x=0-1)solid solutions with micron-sized particles were synthesized via a solution combustion method.The synthesis process and Zr/Ti molar ratio were optimized to produce powders with the tetragonal crystal structure.X-ray diffraction,Raman spectroscopy and transmission electron spectroscopy results confirm that a full crystallization microstructure with the single tetragonal phase is obtained after calcination at 600℃while maintaining the crystallite size<30 nm.Zr/Ti oxide mixtures with Zr>67 mol%exhibit a tetragonal crystal structure and the embedding Ti in ZrO2 improves the structure stability.The nitrogen sorption results indicate that the powders possess mesoporous morphology with medium specific surface areas(~10-50 m^2/g).Chemical stability tests show that these powders are relatively stable with negligible removal of titanium and zirconium after elution by 0.5 mol/L HC1.Density functional theory was used to calculate the most stable structure with low energy for the selected composition.展开更多
The effects of heat treatment on microstructure and creep properties of β high-strength titanium alloy,Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe,were studied.After solution treatment at 790℃ and aging treatment(HT1),the microst...The effects of heat treatment on microstructure and creep properties of β high-strength titanium alloy,Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe,were studied.After solution treatment at 790℃ and aging treatment(HT1),the microstructure is composed of equiaxedαp phase,β phase,α_(p) phase,and becomes β phase and α_(s) phases after solution treatment at 840℃ and aging treatment(HT2).The creep behavior at 400℃ was analyzed.The stress exponents of both alloys are between 1 and 2,indicating that the diffusional creep mechanism is one of the dominant creep mechanisms.The alloy after HT2 treatment has better creep resistance and a subsequent creep test on this alloy was performed at 450℃ under 400 MPa.The creep fracture has the mixed ductile-brittle characteristics.The phase interfaces can hinder the dislocation movement,and theαs phase can coordinate with the matrix to deform,thereby reducing the occurrence of intragranular cracks.展开更多
In order to improve the surface hardness and wear resistance of Ti and Ti alloy components, an oxygen permeation treatment (OPT) was developed. The oxygen permeation behaviors of three Ti alloys, TA2, TB5 and TC11, tr...In order to improve the surface hardness and wear resistance of Ti and Ti alloy components, an oxygen permeation treatment (OPT) was developed. The oxygen permeation behaviors of three Ti alloys, TA2, TB5 and TC11, treated in air with O-P medium at high temperature have been studied. The results show that the 0-P treatment can significantly improve the surface hardness of Ti alloys. The oxidation mass-gain of β-Ti alloy (TB5) is much higher than α-Ti alloy (TA2) under the same condition, while α+β Ti alloy (TC11) is the lowest. All the Ti alloys treated at this condition produce two surface layers: the outer layer consists mainly of TiO2, as well as trace of other oxides, and the inner layer consists of a Ti-O interstitial solid solution formed by the diffusion of oxygen in α crystal lattice. Thick scales of β Ti alloy (TB5) are easily formed depending mainly on the poor solid solution content of oxygen, while deep solution layer can be formed since partial β phase has been transformed into α phase. The scales of α-β Ti alloy (TC11) are very thin and compact. Aluminum-rich zone, as well as deficient zone, is found in oxide layers. A crystallographic characterization of oxygen solution layer has been performed and evaluated by crystallographic lattice constant.展开更多
Titanium based IrO2 +Ta2O5 oxide anodes with different compositions and pyrolysis temperatures were prepared by termodecompoisition method. By using X-ray diffraction (XRD), the structure and texture coefficient of th...Titanium based IrO2 +Ta2O5 oxide anodes with different compositions and pyrolysis temperatures were prepared by termodecompoisition method. By using X-ray diffraction (XRD), the structure and texture coefficient of the coatings, TC(hkl), of IrO2 rutile crystal have been tested. It showed that, the crystallization processes of IrO2 and Ta2O5 in xIrO2 +(100-x) Ta2 O5 (x is in mol%) films affected and confined each other.In the mixed system, IrO2 rutile phase existed as a solid solution with Ta, and attained the maximum solubility when x=70mol%, i.e. for the coating of 70% IrO2 +Ta2O5.For the coatings of low iridium content or at low preparing tem pemture, (110) and (101) pwtered orientations were dominant. However, preferred growth of IrO2 weakened with increasing either iridium content or temperature. Three typical surface morphologies were observed by using scanning electron tnicroscopy(SEM). The crystallite size of the mixed oxide coatings were finest for the the film of 70%IrO2 +30%Ta2O5,and decreased with the pyrolysis tempemture. As the results of the finest crystallite segregating on sudece and the maxitnum solid solubility of Ir and Ta component in deposits, the coatings with the composition of 70%IrO2 +Ta2O5 prepared at 450℃ presented the mdrimutn electrocatalgtic activitg for O2 evolution in 0. 5M H2SO4 solution.UP to 550℃, Ti base suffered to oxidation resulting in decreasing anode conductivity,therefore, coatings performed a low activity.展开更多
Highly localized and minute depassivation events are recorded using 50μm diametertitanium microelectrode in Ringer's physiological solution. These transient events are believed to be due to microscopic breakdown ...Highly localized and minute depassivation events are recorded using 50μm diametertitanium microelectrode in Ringer's physiological solution. These transient events are believed to be due to microscopic breakdown of passivity and occur well below the pitting potential of the metal. A mechanism is proposed to explain the observed phenomenon.Possible implications on passivity and the application of metallic biomaterials in vivo are also discussed.展开更多
The influence of surface pre-treatments, shot-peening (SP) and laser remelting (LR), on oxygen permeation behaviors of titanium alloy TC11 was investigated. Optical microscope, SEM with EDAX, XRD, and microhardness te...The influence of surface pre-treatments, shot-peening (SP) and laser remelting (LR), on oxygen permeation behaviors of titanium alloy TC11 was investigated. Optical microscope, SEM with EDAX, XRD, and microhardness tester were employed to characterize the microstructure, composition and hardness of this alloy. The results show that the surface roughness is increased by shot-peening, and the microstructure with fine-grain can be obtained by LR pre-treatment. The pre-treated samples were oxygen-permeated at (810± 10) ℃ for 10 h in atmospheric air. The outer layer consists essentially of TiO2, trace Ti2 N, Ti3Al and Ti3AlN for the SP pre-treatment and thin oxygen solution layer is found in the subsurface layer. As for LR pre-treatment, the outer layer consists mainly of TiO2 and small amounts of TiO, and the inner layer consists of alpha crystals, rich in interstitial atoms. Samples by LR pre-treatment has thicker hardened layer with higher hardness values in comparison with SP pre-treated ones.The boost diffusion of oxygen and hardening mechanisms were discussed based on the experimental results.展开更多
Presence of external electrical field plays a vital role in heat transfer and fluid flow phenomena. Keeping this in view present article is a numerical investigation of stagnation point flow of water based nanoparticl...Presence of external electrical field plays a vital role in heat transfer and fluid flow phenomena. Keeping this in view present article is a numerical investigation of stagnation point flow of water based nanoparticles suspended fluid under the influence of induced magnetic field. A detailed comparative analysis has been performed by considering Copper and Titanium dioxide nanoparticles. Utilization of similarity analysis leads to a simplified system of coupled nonlinear differential equations, which has been tackled numerically by means of shooting technique followed by Runge-Kutta of order 5. The solutions are computed correct up to 6 decimal places. Influence of pertinent parameters is examined for fluid flow, induced magnetic field, and temperature profile. One of the key findings includes that magnetic parameter plays a vital role in directing fluid flow and lowering temperature profile. Moreover, it is concluded that Cu-water based nanofluid high thermal conductivity contributes in enhancing heat transfer efficiently.展开更多
基金supported by the National Key R&D Program of China (No. 2018YFA0707300)the National Natural Science Foundation of China (No. 52374376)the Introduction Plan for High end Foreign Experts, China (No. G2023105001L)。
文摘Titanium plates with a Ti−O solid solution surface-hardened layer were cold roll-bonded with 304 stainless steel plates with high work hardening rates.The evolution and mechanisms affecting the interfacial bonding strength in titanium/stainless steel laminated composites were investigated.Results indicate that the hardened layer reduces the interfacial bonding strength from over 261 MPa to less than 204 MPa.During the cold roll-bonding process,the hardened layer fractures,leading to the formation of multi-scale cracks that are difficult for the stainless steel to fill.This not only hinders the development of an interlocking interface but also leads to the presence of numerous microcracks and hardened blocks along the nearly straight interface,consequently weakening the interfacial bonding strength.In metals with high work hardening rates,the conventional approach of enhancing interface interlocking and improving interfacial bonding strength by using a surface-hardened layer becomes less effective.
基金the financial support from the National Key R&D Program of China(No.2022YFB3705605)。
文摘This study explored the coupling effects of microstructure,strain rate,and 3.5%NaCl solution on stress corrosion cracking(SCC)behaviors of low-cost Ti6411 and Ti52 titanium alloys,compared to those of marine TC4ELI and Ti80 titanium alloys.Slow strain rate tensile(SSRT)tests were performed to evaluate SCC susceptibility.The SCC susceptibility index(I_(SSRT))was calculated,and the fracture morphologies were investigated to clarify the stress corrosion mechanisms.The experimental results show that the ISSRT of Ti6411 titanium alloy with a lamellar micro structure(LM)is the highest under a strain rate of 1×10^(-6)s^(-1),and the corresponding fracture mode shows a quasi-cleavage fracture with low ductility.TC4ELI alloy with an equiaxed microstructure exhibits excellent SCC resistance.However,the SCC behavior of the Ti80 alloy with a bimodal microstructure is relatively sensitive to high strain rates,and the Ti52 tube with a typical Widmanst?tten microstructure is sensitive to low strain rates.The stress corrosion mechanism can be attributed to the cyclic process of passive film rupture,anodic dissolution,and hydrogen-induced cracking due to a multifactor comprehensive interaction corresponding to specific microstructures,strain rates,and corrosive media.The LM of the Ti6411 plate allowed easy chloride penetration into the bare metal,thereby reducing the protection of the film and resulting in continuous anodic dissolution and hydrogen accumulation at the crack tip.The coupled effect of the internal hydrogen pressure and external tensile stress can easily cause crack propagation and failure under service conditions.
基金Item Sponsored by Science Research Plan of Wuhan Science and Technology Bureau of China(201210321098)
文摘The properties of titanium carbonitride Ti（CxN1-x） inclusions precipitated during solidification of tire cord steels and the thermodynamic conditions for their decomposition and solid solution during billet heating were investigated using a thermodynamics method. The solid solution of Ti（CxN1-x） inclusions during high-temperature heating was also studied experimentally. The results revealed that： （1） the higher the content of carbon in the tire cord steel is, the greater the value of .r in the Ti（CxN1-x） inclusions is; （2） the higher the content of carbon in the tire cord steel is, the earlier the Ti（CxN1-x） inclusions precipitated during the solidification process and the lower the solidification front temperature is during precipitation; （3） when an 82A steel sample was heated to 1087℃, the Ti（CxN1-x） inclusions possess the thermodynamic conditions of decomposition and solid solution; and （4） when 82A samples were heated to 1150 and 1 250℃, the total number of Ti（CxN1-x） inclusions larger than 5μm in diameter decreased by 55.0% and 70.3%, respectively. In addition, although smaller inclusions with diameter less than 2 μm continued to decompose when the sample was heated at 1 250℃ for 2 h and then cooled to 1000℃ in the furnace, the number of inclusions larger than 5 μm in diameter increased.
基金Project(SKLSP201853) supported by the Fund of the State Key Laboratory of Solidification Processing in NWPU,ChinaProject(51625505) supported by the National Science Fund for Distinguished Young Scholars of China+1 种基金Project(U1537203) supported by the Key Program Project of the Joint Fund of Astronomy and National Natural Science Foundation of ChinaProject(KYQD1801) supported by the Scientific Research Foundation of Tianjin University of Technology and Education,China
文摘The microstructural evolution, mechanical properties and fracture mechanism of a Ti.5Al.5Mo.5V.3Cr.1Zr (Ti-55531) alloy after solution (760.820℃) plus aging (580.640℃) treatments were investigated. The results show that the volume fraction of the primary α(αp) phase decreases with the increase of solution temperature, and the length of the secondary α phase (αs) decreases while its width increases with the increase of aging temperature. Yield and tensile strengths decrease with the increase of solution temperature, while increase with the increase of aging temperature. A good balance of tensile strength and ductility of the alloy is obtained under solution of 800℃ for 2 h plus aging of 640℃ for 8 h, in which the tensile strength is 1434 MPa and the elongation is 7.7%. The coarsening αs phase makes crack propagation paths deflected and tortuous, which increases the crack propagation resistance and improves the ductility and fracture toughness.
文摘In order to improve the quality of the cord steel wire rod and achieve the effective control of titanium inclusion, the solid solution behavior of titanium inclusion in tire cord steel during the heating process was discussed in this paper, through the thermodynamic theory analysis, combined with the CLSM experiment. The conclusions are as follows: 1) According to the law of Ostwald repening, the coarsening rate of titanium carbonitride inclusion is very small, the coarsening behavior of titanium carbonitride inclusion cannot be considered in the heating and holding stage. 2) The solid solution behavior of titanium inclusion in the heating process is obviously existed. 3) Through the proper control of rolling temperature, holding time and the subsequent cooling rate, the size and quantity of large particle titanium inclusion in the high strength tire cord steel can be effectively controlled.
文摘Through studying on the heating process of titanium microalloyed steels, the influence of heating temperature on the austenite grain size and the solid dissolution, precipitation law of Ti microalloying element were analyzed, and the results showed that, the austenite grain size increased with the increase of heating temperature, When the heating temperature reached 1050°C and 1250°C, the austenite grains appeared the obvious coarsening process twice. TiC particles dissolved gradually as the heating temperature increased. When the heating temperature rose to 1100°C, TiC particles disappeared basically, When the heating temperature rose to 1250°C, TiN particles began to be dissolved and grow up.
基金Funded by the National Natural Science Foundation of China(Nos.51002054,51272079)the Fundamental Research Fundsfor the Central Universities,HUST(No.2011TS014)
文摘A series of nanocrystalline V-doped （0.0-3.0 at.%） TiO2 catalysts have been successfully prepared by the one-step solution combustion method using urea as a fuel. The obtained powders were characterized by XRD, SEM, Raman, XPS and UV-Vis DRS. The effects of V doping concentration on the phase structure and photocatalytic properties were investigated. XRD, Raman, and XPS show that V doping diffuses into TiO2 crystal lattice mainly in the form of V5＋ and causes a phase transition from anatase to mille. V doping can widen the light absorption range of TiO2, with the absorption threshold wavelength shifting from 425 to 625 nm. The photocatalytic activity of V-doped TiO2 powders were evaluated by the photocatalytic degradation of methyl orange （MO） under visible light irradiation. It is found that V doping enhances the photoeatalyilc activity under visible light irradiation and the optimal degradation rate of MO is about 95.8% with 1.0 at% V-doped TiO2.
基金the National Natural Science Foundation of China(Nos.U20B2026 and 51871049)。
文摘The corrosion behavior of Ti60 alloy was investigated under continuous NaCl solution spraying at 600℃.Results indicate that the corrosion rate of the Ti60 alloy is lower than that obtained with the solid NaCl deposit film in HO+O.The outer corrosion products are compact layers mainly containing NaTiOand nanocrystalline TiO.The inner layer is mainly composed of TiO,Ti O and SnO.TiO has a lamellar structure,and TiO has a strip-shaped structure.A mixed corrosion mechanism including classic oxidation and active oxidation occurred under NaCl solution spraying environment:the first stage was controlled by the classic oxidation mechanism with the promotion by the active oxidation following parabolic curves,and the second stage was controlled by the active oxidation mechanism following a linear rise in the mass gain curve.The mixed corrosion mechanism between classic oxidation and active oxidation produced a relatively dense Ti oxides scale,which decreased the corrosion rate.
文摘Oxide powders of Zr1_xTixO2(x=0-1)solid solutions with micron-sized particles were synthesized via a solution combustion method.The synthesis process and Zr/Ti molar ratio were optimized to produce powders with the tetragonal crystal structure.X-ray diffraction,Raman spectroscopy and transmission electron spectroscopy results confirm that a full crystallization microstructure with the single tetragonal phase is obtained after calcination at 600℃while maintaining the crystallite size<30 nm.Zr/Ti oxide mixtures with Zr>67 mol%exhibit a tetragonal crystal structure and the embedding Ti in ZrO2 improves the structure stability.The nitrogen sorption results indicate that the powders possess mesoporous morphology with medium specific surface areas(~10-50 m^2/g).Chemical stability tests show that these powders are relatively stable with negligible removal of titanium and zirconium after elution by 0.5 mol/L HC1.Density functional theory was used to calculate the most stable structure with low energy for the selected composition.
基金supported by the National Natural Science Foundation of China(No.51975147)。
文摘The effects of heat treatment on microstructure and creep properties of β high-strength titanium alloy,Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe,were studied.After solution treatment at 790℃ and aging treatment(HT1),the microstructure is composed of equiaxedαp phase,β phase,α_(p) phase,and becomes β phase and α_(s) phases after solution treatment at 840℃ and aging treatment(HT2).The creep behavior at 400℃ was analyzed.The stress exponents of both alloys are between 1 and 2,indicating that the diffusional creep mechanism is one of the dominant creep mechanisms.The alloy after HT2 treatment has better creep resistance and a subsequent creep test on this alloy was performed at 450℃ under 400 MPa.The creep fracture has the mixed ductile-brittle characteristics.The phase interfaces can hinder the dislocation movement,and theαs phase can coordinate with the matrix to deform,thereby reducing the occurrence of intragranular cracks.
基金The project was supported by the National Natural Science Foundation of China(Grant 50171073).
文摘In order to improve the surface hardness and wear resistance of Ti and Ti alloy components, an oxygen permeation treatment (OPT) was developed. The oxygen permeation behaviors of three Ti alloys, TA2, TB5 and TC11, treated in air with O-P medium at high temperature have been studied. The results show that the 0-P treatment can significantly improve the surface hardness of Ti alloys. The oxidation mass-gain of β-Ti alloy (TB5) is much higher than α-Ti alloy (TA2) under the same condition, while α+β Ti alloy (TC11) is the lowest. All the Ti alloys treated at this condition produce two surface layers: the outer layer consists mainly of TiO2, as well as trace of other oxides, and the inner layer consists of a Ti-O interstitial solid solution formed by the diffusion of oxygen in α crystal lattice. Thick scales of β Ti alloy (TB5) are easily formed depending mainly on the poor solid solution content of oxygen, while deep solution layer can be formed since partial β phase has been transformed into α phase. The scales of α-β Ti alloy (TC11) are very thin and compact. Aluminum-rich zone, as well as deficient zone, is found in oxide layers. A crystallographic characterization of oxygen solution layer has been performed and evaluated by crystallographic lattice constant.
文摘Titanium based IrO2 +Ta2O5 oxide anodes with different compositions and pyrolysis temperatures were prepared by termodecompoisition method. By using X-ray diffraction (XRD), the structure and texture coefficient of the coatings, TC(hkl), of IrO2 rutile crystal have been tested. It showed that, the crystallization processes of IrO2 and Ta2O5 in xIrO2 +(100-x) Ta2 O5 (x is in mol%) films affected and confined each other.In the mixed system, IrO2 rutile phase existed as a solid solution with Ta, and attained the maximum solubility when x=70mol%, i.e. for the coating of 70% IrO2 +Ta2O5.For the coatings of low iridium content or at low preparing tem pemture, (110) and (101) pwtered orientations were dominant. However, preferred growth of IrO2 weakened with increasing either iridium content or temperature. Three typical surface morphologies were observed by using scanning electron tnicroscopy(SEM). The crystallite size of the mixed oxide coatings were finest for the the film of 70%IrO2 +30%Ta2O5,and decreased with the pyrolysis tempemture. As the results of the finest crystallite segregating on sudece and the maxitnum solid solubility of Ir and Ta component in deposits, the coatings with the composition of 70%IrO2 +Ta2O5 prepared at 450℃ presented the mdrimutn electrocatalgtic activitg for O2 evolution in 0. 5M H2SO4 solution.UP to 550℃, Ti base suffered to oxidation resulting in decreasing anode conductivity,therefore, coatings performed a low activity.
文摘Highly localized and minute depassivation events are recorded using 50μm diametertitanium microelectrode in Ringer's physiological solution. These transient events are believed to be due to microscopic breakdown of passivity and occur well below the pitting potential of the metal. A mechanism is proposed to explain the observed phenomenon.Possible implications on passivity and the application of metallic biomaterials in vivo are also discussed.
基金Project (50171073) supported by the National Natural Science Foundation of China
文摘The influence of surface pre-treatments, shot-peening (SP) and laser remelting (LR), on oxygen permeation behaviors of titanium alloy TC11 was investigated. Optical microscope, SEM with EDAX, XRD, and microhardness tester were employed to characterize the microstructure, composition and hardness of this alloy. The results show that the surface roughness is increased by shot-peening, and the microstructure with fine-grain can be obtained by LR pre-treatment. The pre-treated samples were oxygen-permeated at (810± 10) ℃ for 10 h in atmospheric air. The outer layer consists essentially of TiO2, trace Ti2 N, Ti3Al and Ti3AlN for the SP pre-treatment and thin oxygen solution layer is found in the subsurface layer. As for LR pre-treatment, the outer layer consists mainly of TiO2 and small amounts of TiO, and the inner layer consists of alpha crystals, rich in interstitial atoms. Samples by LR pre-treatment has thicker hardened layer with higher hardness values in comparison with SP pre-treated ones.The boost diffusion of oxygen and hardening mechanisms were discussed based on the experimental results.
文摘Presence of external electrical field plays a vital role in heat transfer and fluid flow phenomena. Keeping this in view present article is a numerical investigation of stagnation point flow of water based nanoparticles suspended fluid under the influence of induced magnetic field. A detailed comparative analysis has been performed by considering Copper and Titanium dioxide nanoparticles. Utilization of similarity analysis leads to a simplified system of coupled nonlinear differential equations, which has been tackled numerically by means of shooting technique followed by Runge-Kutta of order 5. The solutions are computed correct up to 6 decimal places. Influence of pertinent parameters is examined for fluid flow, induced magnetic field, and temperature profile. One of the key findings includes that magnetic parameter plays a vital role in directing fluid flow and lowering temperature profile. Moreover, it is concluded that Cu-water based nanofluid high thermal conductivity contributes in enhancing heat transfer efficiently.
