The effects of MgO and TiO_2 on the viscosity, activation energy for viscous flow, and break-point temperature of titanium-bearing slag were studied. The correlation between viscosity and slag structure was analyzed b...The effects of MgO and TiO_2 on the viscosity, activation energy for viscous flow, and break-point temperature of titanium-bearing slag were studied. The correlation between viscosity and slag structure was analyzed by Fourier transform infrared（FTIR） spectroscopy. Subsequently, main phases in the slag and their content changes were investigated by X-ray diffraction and Factsage 6.4 software package. The results show that the viscosity decreases when the MgO content increases from 10.00wt% to 14.00wt%. Moreover, the break-point temperature increases, and the activation energy for viscous flow initially increases and subsequently decreases. In addition, with increasing TiO_2 content from 5.00wt% to 9.00wt%, the viscosity decreases, and the break-point temperature and activation energy for viscous flow initially decrease and subsequently increase. FTIR analyses reveal that the polymerization degree of complex viscous units in titanium-bearing slag decreases with increasing MgO and TiO_2 contents. The mechanism of viscosity variation was elucidated. The basic phase in experimental slags is melilite. Besides, as the MgO content increases, the amount of magnesia–alumina spinel in the slag increases. Similarly, the sum of pyroxene and perovskite phases in the slag increases with increasing TiO_2 content.展开更多
The isothermal precipitating behavior of perovskite phase in oxidized titanium bearing slag was studied by quenching method.The kinetics of precipitating process and crystal growth of perovskite phase was analyzed.The...The isothermal precipitating behavior of perovskite phase in oxidized titanium bearing slag was studied by quenching method.The kinetics of precipitating process and crystal growth of perovskite phase was analyzed.The results show that the precipitating and growth of perovskite are non-equilibrium process at the beginning of isothermal treatment.There are two factors influencing the growth rate of perovskite phase on non-equilibrium condition,one is the supersaturation concentration of perovskite and the other is the coarsening arising from the growth of larger perovskite at the expense of smaller ones.The precipitation kinetics of perovskite phase can be nearly described by the JMAK equation.展开更多
The precipitation of ordered alpha_2 phase in a near - alphaTi-6.3Al-4.8Sn-2.0Zr-1.0Mo-0.34Si-0.9Nd (mass fraction) alloy with duplex microstructure, duringaging at various temperatures, was investigated. It is conclu...The precipitation of ordered alpha_2 phase in a near - alphaTi-6.3Al-4.8Sn-2.0Zr-1.0Mo-0.34Si-0.9Nd (mass fraction) alloy with duplex microstructure, duringaging at various temperatures, was investigated. It is concluded that the precipitation and growthof the alpha_2 phase can be controlled by suitable selection of the aging temperature. Aging athigher temperatures can result in the uniform precipitation and growth of alpha_2 ordered phase inalpha_p whereas the alpha_2 ordered phase precipitated only at the lamella boundaries anddislocations in beta_t. Aging at a moderate temperature can promote the tendency of uniformprecipitation of alpha_2 phase in both alpha_p and beta_t. Aging at a relatively low temperature issuitable for the uniform precipitation and growth of fine alpha_2 particles throughout both thealpha_p and beta_t matrix.展开更多
For TA15 titanium alloy, slip is the dominant plastic deformation mechanism because of relatively high Al content. In order to reveal the grain-scale stress field and geometrically necessary dislocation（GND） density...For TA15 titanium alloy, slip is the dominant plastic deformation mechanism because of relatively high Al content. In order to reveal the grain-scale stress field and geometrically necessary dislocation（GND） density distribution around the slip traces and phase boundaries where the slip lines are blocked due to Burgers orientation relationship（OR） missing. We experimentally investigated tensile deformation on TA15 titanium alloy up to 2.0% strain at room temperature. The slip traces were observed and identified using high resolution scanning electron microscopy（SEM） and electron backscatter diffraction（EBSD） measurements. The grain-scale stress fields around the slip traces and phase boundaries were calculated by the cross-correlationbased method. Based on strain gradient theories, the density of GND was calculated and analyzed. The results indicate that the grain-scale stress is significantly concentrated at phase/grain boundaries and slip traces. Although there is an obvious GND accumulation in the vicinity of phase and subgrain boundaries, no GND density accumulation appears near the slip traces.展开更多
Ribbons of the two-phase titanium alloy were fabricated by single-roller rapid solidification technique,and aged at high temperature. The microstructure of ribbon samples were characterized with X-ray diffractometer(X...Ribbons of the two-phase titanium alloy were fabricated by single-roller rapid solidification technique,and aged at high temperature. The microstructure of ribbon samples were characterized with X-ray diffractometer(XRD) and environmental scanning electron microscope(ESEM). The microstructures of the alloy are composed of α phase and supersaturated β phase,and X-ray diffraction results show that all peaks of the α and β phases shift slightly to smaller angles,which can be explained by the disordering growth pattern caused by the rapid solidification process. After aging at 960 ℃ in vacuum,the ribbon is composed of homogeneous α phase and β phase.展开更多
Chitosan （CTS） coatings contained calcium （Ca） and phosphorus （P） on titanium （Ti） surface are prepared by the cathode liquid phase plasma technology （CLPT）, in a certain concentration electrolyte solution w...Chitosan （CTS） coatings contained calcium （Ca） and phosphorus （P） on titanium （Ti） surface are prepared by the cathode liquid phase plasma technology （CLPT）, in a certain concentration electrolyte solution with selective additions of ammonium dihydrogen phosphate and calcium nitrate. It is indicated that the parameters for a stable discharge are voltage of 400 V, frequency of 100 Hz, duty cycle of 30% based on a large amount of experiment data. The morphology, structure and composition of the coated samples are studied by SEM, FTIR, XRD, XPS. The results demonstrate that the composite coatings are uniform, and some solid particles of inorganic salt containing calcium and phosphorus dispersed on the coatings. CA tests show that the samples treated by the liquid plasma became less hydrophilic. The variation of hydrophilicity on the CLPT treated titanium is attributed to the change of the function groups on the sample surface. Meanwhile, a possible formation mechanism of the composite coatings is discussed.展开更多
Some experimental α+α2 alloys were prepared by the addition of tin or aluminum elements into Ti-55 alloy. These alloys were designed with varied electron concentration values and named as Sn-rich alloys...Some experimental α+α2 alloys were prepared by the addition of tin or aluminum elements into Ti-55 alloy. These alloys were designed with varied electron concentration values and named as Sn-rich alloys and Al-rich alloys, respectively. The precipita- tion and growth of α2 ordered phase in the tested alloys under various heat treatment conditions were investigated. Some compari- sons among the experimental results were performed and discussed in detail. Stronger precipitation and growth of α2 ordered phase were caused in Al-rich alloys but relatively weak change in Sn-rich alloys with increasing the electron concentration. The precipita- tion of α2 ordered phase in Al-rich alloys is stronger than that in Sn-rich alloys when the electron concentration value is the same for the two alloys.展开更多
A new method by liquid–liquid–liquid three phase system, consisting of acidified primary amine N1923(abbreviated as A-N1923), poly(ethylene glycol)(PEG) and (NH_4)_2SO_4 aqueous solution, was suggested for the separ...A new method by liquid–liquid–liquid three phase system, consisting of acidified primary amine N1923(abbreviated as A-N1923), poly(ethylene glycol)(PEG) and (NH_4)_2SO_4 aqueous solution, was suggested for the separation and simultaneous extraction of V(V) and Cr(VI) from the acidic leach solutions of highchromium vanadium–titanium magnetite. Experimental results indicated that V(V) and Cr(VI) could be selectively enriched into the A-N1923 organic top phase and PEG-rich middle phase, respectively, while Al(III)and other co-existing impurity ions, such as Si(IV), Fe(III), Ti(IV), Mg(II) and Ca(II) in acidic leach solutions,could be enriched in the(NH_4)_2SO_4 bottom aqueous phase. During the process for extraction and separation of V(V) and Cr(VI), almost all of impurity ions could be removed. The separation factors between V(V) and Cr(VI) could reach 630 and 908, respectively in the organic top phase and PEG middle phase, and yields of recovered V(V) and Cr(VI) in the top phase and middle phase respectively were all above 90%.Various effects including aqueous p H, A-N1923 concentration, PEG added amount and(NH_4)_2SO_4 concentration on three-phase partitioning of V(V) and Cr(VI) were discussed. It was found that the partition of Cr(VI) into the PEG-rich middle phase was driven by hydrophobic interaction, while extraction of V(V) by A-N1923 resulted of anion exchange between NO_3^- and H_2V_(10)O_(28)^(-4). Stripping of V(V) and Cr(VI) from the top organic phase and the middle PEG-rich phase were achieved by mixing respectively with NaNO_3 aqueous solutions and Na OH-((NH_4)_2SO_4 solutions. The present work highlights a new approach for the extraction and purification of V and Cr from the complex multi-metal co-existing acidic leach solutions of high-chromium vanadium–titanium magnetite.展开更多
Phase precipitation and mechanical properties of TC21 titanium alloy with two different initial microstructures during heat treatment were determined. Result indicated that compared with coarse microstructure alloy, f...Phase precipitation and mechanical properties of TC21 titanium alloy with two different initial microstructures during heat treatment were determined. Result indicated that compared with coarse microstructure alloy, fine microstructure alloy developed finer microstructure, more unstable <em>ω</em> and <em>α</em><sub>2</sub> precipitates with much smaller size and lower volume fraction, and obtained better mechanical properties during heat treatment.展开更多
基金financial support by the Fundamental Research Funds for the Central Universities (No. N130602003)National High Technology Research and Development Program of China (No. 2012AA062302)the National Natural Science Foundation of China (No. 51574067)
文摘The effects of MgO and TiO_2 on the viscosity, activation energy for viscous flow, and break-point temperature of titanium-bearing slag were studied. The correlation between viscosity and slag structure was analyzed by Fourier transform infrared（FTIR） spectroscopy. Subsequently, main phases in the slag and their content changes were investigated by X-ray diffraction and Factsage 6.4 software package. The results show that the viscosity decreases when the MgO content increases from 10.00wt% to 14.00wt%. Moreover, the break-point temperature increases, and the activation energy for viscous flow initially increases and subsequently decreases. In addition, with increasing TiO_2 content from 5.00wt% to 9.00wt%, the viscosity decreases, and the break-point temperature and activation energy for viscous flow initially decrease and subsequently increase. FTIR analyses reveal that the polymerization degree of complex viscous units in titanium-bearing slag decreases with increasing MgO and TiO_2 contents. The mechanism of viscosity variation was elucidated. The basic phase in experimental slags is melilite. Besides, as the MgO content increases, the amount of magnesia–alumina spinel in the slag increases. Similarly, the sum of pyroxene and perovskite phases in the slag increases with increasing TiO_2 content.
基金Project supported by the Postdoctoral Science Foundation of Central South University,ChinaProject(76112037)supported by theScience Foundation of Central South University,China
文摘The isothermal precipitating behavior of perovskite phase in oxidized titanium bearing slag was studied by quenching method.The kinetics of precipitating process and crystal growth of perovskite phase was analyzed.The results show that the precipitating and growth of perovskite are non-equilibrium process at the beginning of isothermal treatment.There are two factors influencing the growth rate of perovskite phase on non-equilibrium condition,one is the supersaturation concentration of perovskite and the other is the coarsening arising from the growth of larger perovskite at the expense of smaller ones.The precipitation kinetics of perovskite phase can be nearly described by the JMAK equation.
文摘The precipitation of ordered alpha_2 phase in a near - alphaTi-6.3Al-4.8Sn-2.0Zr-1.0Mo-0.34Si-0.9Nd (mass fraction) alloy with duplex microstructure, duringaging at various temperatures, was investigated. It is concluded that the precipitation and growthof the alpha_2 phase can be controlled by suitable selection of the aging temperature. Aging athigher temperatures can result in the uniform precipitation and growth of alpha_2 ordered phase inalpha_p whereas the alpha_2 ordered phase precipitated only at the lamella boundaries anddislocations in beta_t. Aging at a moderate temperature can promote the tendency of uniformprecipitation of alpha_2 phase in both alpha_p and beta_t. Aging at a relatively low temperature issuitable for the uniform precipitation and growth of fine alpha_2 particles throughout both thealpha_p and beta_t matrix.
基金Funded by National Natural Science Foundation of China(No.51401226)
文摘For TA15 titanium alloy, slip is the dominant plastic deformation mechanism because of relatively high Al content. In order to reveal the grain-scale stress field and geometrically necessary dislocation（GND） density distribution around the slip traces and phase boundaries where the slip lines are blocked due to Burgers orientation relationship（OR） missing. We experimentally investigated tensile deformation on TA15 titanium alloy up to 2.0% strain at room temperature. The slip traces were observed and identified using high resolution scanning electron microscopy（SEM） and electron backscatter diffraction（EBSD） measurements. The grain-scale stress fields around the slip traces and phase boundaries were calculated by the cross-correlationbased method. Based on strain gradient theories, the density of GND was calculated and analyzed. The results indicate that the grain-scale stress is significantly concentrated at phase/grain boundaries and slip traces. Although there is an obvious GND accumulation in the vicinity of phase and subgrain boundaries, no GND density accumulation appears near the slip traces.
基金Projects(0552nm028 04DZ05616) supported by Shanghai Science and Technology Committee
文摘Ribbons of the two-phase titanium alloy were fabricated by single-roller rapid solidification technique,and aged at high temperature. The microstructure of ribbon samples were characterized with X-ray diffractometer(XRD) and environmental scanning electron microscope(ESEM). The microstructures of the alloy are composed of α phase and supersaturated β phase,and X-ray diffraction results show that all peaks of the α and β phases shift slightly to smaller angles,which can be explained by the disordering growth pattern caused by the rapid solidification process. After aging at 960 ℃ in vacuum,the ribbon is composed of homogeneous α phase and β phase.
基金supported by National Natural Science Foundation of China (No.10675078)
文摘Chitosan （CTS） coatings contained calcium （Ca） and phosphorus （P） on titanium （Ti） surface are prepared by the cathode liquid phase plasma technology （CLPT）, in a certain concentration electrolyte solution with selective additions of ammonium dihydrogen phosphate and calcium nitrate. It is indicated that the parameters for a stable discharge are voltage of 400 V, frequency of 100 Hz, duty cycle of 30% based on a large amount of experiment data. The morphology, structure and composition of the coated samples are studied by SEM, FTIR, XRD, XPS. The results demonstrate that the composite coatings are uniform, and some solid particles of inorganic salt containing calcium and phosphorus dispersed on the coatings. CA tests show that the samples treated by the liquid plasma became less hydrophilic. The variation of hydrophilicity on the CLPT treated titanium is attributed to the change of the function groups on the sample surface. Meanwhile, a possible formation mechanism of the composite coatings is discussed.
基金This work was financially supported by the National Natural Science Foundation of China (No.50471085).
文摘Some experimental α+α2 alloys were prepared by the addition of tin or aluminum elements into Ti-55 alloy. These alloys were designed with varied electron concentration values and named as Sn-rich alloys and Al-rich alloys, respectively. The precipita- tion and growth of α2 ordered phase in the tested alloys under various heat treatment conditions were investigated. Some compari- sons among the experimental results were performed and discussed in detail. Stronger precipitation and growth of α2 ordered phase were caused in Al-rich alloys but relatively weak change in Sn-rich alloys with increasing the electron concentration. The precipita- tion of α2 ordered phase in Al-rich alloys is stronger than that in Sn-rich alloys when the electron concentration value is the same for the two alloys.
基金Supported by the National Basic Research and Development Program of China(973ProgramNo.2013CB632602)the National Natural Science Foundation of China(Nos.51574213,51074150)
文摘A new method by liquid–liquid–liquid three phase system, consisting of acidified primary amine N1923(abbreviated as A-N1923), poly(ethylene glycol)(PEG) and (NH_4)_2SO_4 aqueous solution, was suggested for the separation and simultaneous extraction of V(V) and Cr(VI) from the acidic leach solutions of highchromium vanadium–titanium magnetite. Experimental results indicated that V(V) and Cr(VI) could be selectively enriched into the A-N1923 organic top phase and PEG-rich middle phase, respectively, while Al(III)and other co-existing impurity ions, such as Si(IV), Fe(III), Ti(IV), Mg(II) and Ca(II) in acidic leach solutions,could be enriched in the(NH_4)_2SO_4 bottom aqueous phase. During the process for extraction and separation of V(V) and Cr(VI), almost all of impurity ions could be removed. The separation factors between V(V) and Cr(VI) could reach 630 and 908, respectively in the organic top phase and PEG middle phase, and yields of recovered V(V) and Cr(VI) in the top phase and middle phase respectively were all above 90%.Various effects including aqueous p H, A-N1923 concentration, PEG added amount and(NH_4)_2SO_4 concentration on three-phase partitioning of V(V) and Cr(VI) were discussed. It was found that the partition of Cr(VI) into the PEG-rich middle phase was driven by hydrophobic interaction, while extraction of V(V) by A-N1923 resulted of anion exchange between NO_3^- and H_2V_(10)O_(28)^(-4). Stripping of V(V) and Cr(VI) from the top organic phase and the middle PEG-rich phase were achieved by mixing respectively with NaNO_3 aqueous solutions and Na OH-((NH_4)_2SO_4 solutions. The present work highlights a new approach for the extraction and purification of V and Cr from the complex multi-metal co-existing acidic leach solutions of high-chromium vanadium–titanium magnetite.
文摘Phase precipitation and mechanical properties of TC21 titanium alloy with two different initial microstructures during heat treatment were determined. Result indicated that compared with coarse microstructure alloy, fine microstructure alloy developed finer microstructure, more unstable <em>ω</em> and <em>α</em><sub>2</sub> precipitates with much smaller size and lower volume fraction, and obtained better mechanical properties during heat treatment.
基金supported by the National Natural Science Foundation of China (No. 51975596)the Fundamental Research Funds for the Central Universities of Central South University, China (No. CX20220285)。
