Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot ...Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot isostatic pressing parameters on defects,composition uniformity,microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in detail.Results show that increasing temperature and pressure of hot isostatic pressing can reduce defects,especially,the internal defects are substantially eliminated when the temperature exceeds 920℃or the pressure exceeds 125 MPa.The higher temperature and pressure can improve the microstructure uniformity.Besides,the higher pressure can promote the composition uniformity.With the temperature increases from 880℃to 960℃,α-laths are coarsened.But with increasing pressure,the grain size of prior-βphase,the widths ofα-laths andα-colony are reduced.The tensile strength of Ti60 alloy is 949 MPa,yield strength is 827 MPa,and the elongation is 11%when the hot isostatic pressing parameters are 960℃/125 MPa/2 h,which exhibits the best match between the strength and plasticity.展开更多
We describe the new mineral species titanium, ideally Ti, found in the podiform chromitites of the Luobusha ophiolite in Tibet, People's Republic of China. The irregular crystals range from 0.1 to 0.6 mm in diameter ...We describe the new mineral species titanium, ideally Ti, found in the podiform chromitites of the Luobusha ophiolite in Tibet, People's Republic of China. The irregular crystals range from 0.1 to 0.6 mm in diameter and form an intergrowth with coesite and kyanite. Titanium is silver grey in colour, the luster is metallic, it is opaque, the streak is grayish black, and it is non-fluorescent. The mineral is malleable, has a rough to hackly fracture and has no apparent cleavage. The estimated Mohs hardness is 4, and the calculated density is 4.503 g/cm3. The composition is Ti 99.23-100.00 wt%. The mineral is hexagonal, space group P6flmmc. Unit-cell parameters are a 2.950 (2) ~, c 4.686 (1) A,V 35.32 (5) A3, Z = 2. The five strongest powder diffraction lines [d in A (hkl) (I/I0)] are: 2.569 (010) (32), 2.254(011) (100), 1.730 (012) (16), 1.478 (110) (21), and 0.9464 (121) (8). The species and name were approved by the CNMNC (IMA 2010-044).展开更多
Large quantities of CO_2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO_2 emission reduction and comprehensive utilization of t...Large quantities of CO_2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO_2 emission reduction and comprehensive utilization of the solid waste.This paper describes a novel route for indirect mineral carbonation of titanium-bearing blast furnace(TBBF) slag,in which the TBBF slag is roasted with recyclable(NH_4)_2SO_4(AS) at low temperatures and converted into the sulphates of various valuable metals, including calcium, magnesium, aluminium and titanium. High value added Ti-and Al-rich products can be obtained through stepwise precipitation of the leaching solution from the roasted slag. The NH_3 produced during the roasting is used to capture CO_2 from flue gases. The NH_4HCO_3 and(NH_4)_2CO_3 thus obtained are used to carbonate the CaSO_4-containing leaching residue and MgSO_4-rich leaching solution, respectively. In this study, the process parameters and efficiency for the roasting, carbonation and Ti and Al recovery were investigated in detail. The results showed that the sulfation ratios of calcium,magnesium, titanium and aluminium reached 92.6%, 87% and 84.4%, respectively, after roasting at an AS-to-TBBF slag mass ratio of 2:1 and 350 °C for 2 h. The leaching solution was subjected to hydrolysis at 102 °C for 4 h with a Ti hydrolysis ratio of 95.7% and the purity of TiO_2 in the calcined hydrolysate reached 98 wt%.99.7% of aluminium in the Ti-depleted leaching solution was precipitated by using NH_3. The carbonation products of Ca and Mg were CaCO_3 and(NH_4)_2 Mg(CO_3)_2·4H_2O, respectively. The latter can be decomposed into MgCO_3 at 100–200 °C with simultaneous recovery of the NH_3 for reuse. In this process, approximately 82.1% of Ca and 84.2%of Mg in the TBBF slag were transformed into stable carbonates and the total CO_2 sequestration capacity per ton of TBBF slag reached up to 239.7 kg. The TiO_2 obtained can be used directly as an end product, while the Al-rich precipitate and the two carbonation products can act, respectively, as raw materials for electrolytic aluminium,cement and light magnesium carbonate production for the replacement of natural resources.展开更多
A novel temperature fluctuation synthesis/simultaneous densification process was developed for the preparation of Ti3SiC2 bulk ceramics. In this process. Si is used as an in-situ liquid forming phase and it is favorab...A novel temperature fluctuation synthesis/simultaneous densification process was developed for the preparation of Ti3SiC2 bulk ceramics. In this process. Si is used as an in-situ liquid forming phase and it is favorable for both the solid-liquid synthesis and the densification of Ti3SiC2 rainies. The present work demonstrated that the temperature fluctuation synthesis/simultaneous densification process is one of the most effective and simple methods for the preparation of Ti3SiC2 bulk materials providing relatively low synthesis temperature. short reaction time; and simultaneous synthesis and densification. This work also showed the capability to control the microstructure, e.g., the preferred orientation, of the bulk Ti3SiC2 materials simply by applying the hot pressing pressure at different Stages of the temperature fluctuation process. And textured Ti3SiC2 bulk materials with {002} faces of laminated Ti3SiC2 grains normal to the hot pressing axis were prepared.展开更多
Electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel with a copper sheet as interlayer was carried out.Microstructures of the joint were studied by optical microscopy(OM),scanning electron microscopy...Electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel with a copper sheet as interlayer was carried out.Microstructures of the joint were studied by optical microscopy(OM),scanning electron microscopy(SEM) and X-ray diffractometry(XRD).In addition,the mechanical properties of the joint were evaluated by tensile test and the microhardness was measured.These two alloys were successfully welded by adding copper transition layer into the weld.Solid solution with a certain thickness was located at the interfaces between weld and base metal in both sides.Regions inside the weld and near the stainless steel were characterized by solid solution of copper with TiFe2 intermetallics dispersedly distributed in it.While weld near titanium alloy contained Ti-Cu and Ti-Fe-Cu intermetallics layer,in which the hardness of weld came to the highest value.Brittle fracture occurred in the intermetallics layer when the joint was stretched.展开更多
The electrochemical behaviour of Ti(Ⅲ) and Ti(Ⅱ) in LiCl-KCl eutectic system has been studied by cyclic voltammetry and chronoamperometry.The cathodic reduction of Ti(Ⅲ) and Ti(Ⅱ) has been found to be stepwise:Ti(...The electrochemical behaviour of Ti(Ⅲ) and Ti(Ⅱ) in LiCl-KCl eutectic system has been studied by cyclic voltammetry and chronoamperometry.The cathodic reduction of Ti(Ⅲ) and Ti(Ⅱ) has been found to be stepwise:Ti(Ⅲ)+e=Ti(Ⅱ),Ti(Ⅱ)+2e =Ti.The reductions are diffusion controlled.When an equilibrium between Ti subchlorides and excess metallic Ti was estab- lished by reaction 2TiCl_3+Ti=3TiCl_2 in LiCl-KCl melt at 475℃,then the average valence of Ti is less than 2.1.In this system the diffusion coefficient for Ti(Ⅱ) ion was calculated as D=2.5×10^(-5)cm^2·s^(-1).The chronoamperometric studies showed that the initial nucleation stage and growth of nuclei were observed when Ti ions were electrodeposited on low carbon steel substrate. The investigation of nucleation of metal may provide the method for obtaining smooth,coherent and adherent deposits of titanium.展开更多
For simulating the real deactivation of hollow titanium silicalite(HTS) zeolite in commercial ammoximation process, HTS was treated by 10% NH_3·H_2O solution at 120 ℃ in stirred autoclave. It is found that a par...For simulating the real deactivation of hollow titanium silicalite(HTS) zeolite in commercial ammoximation process, HTS was treated by 10% NH_3·H_2O solution at 120 ℃ in stirred autoclave. It is found that a part of HTS zeolite crystals dissolved in the hot NH_3·H_2O solution, and the specific surface area and pore volume continuously decreased with the increase in NH_3 hydrothermal treatment time. Meanwhile, the transformation of framework Ti species into extraframework Ti species was detected by the spectroscopic methods. However, the extraframework Ti species were still in a highly dispersed state after the hydrothermal and thermal treatments as shown by TEM images, while the formation of new acid sites was not detected. Upon combining the results of characterization with catalytic performance of HTS, the main deactivation reason for this material had been determined, which might be attributed to the reduction of specific surface area and active centers after basic treatment and calcination of HTS samples. And then the possible mechanism of simulated deactivation of HTS zeolite was proposed, which could describe the elemental reaction steps much more visually and directly.展开更多
High-temperature titanium alloy for aeroengine compressor applications suffers from high-temperature oxidation and environmental corrosion, which prohibits long-term service of this kind alloy at temperatures above 60...High-temperature titanium alloy for aeroengine compressor applications suffers from high-temperature oxidation and environmental corrosion, which prohibits long-term service of this kind alloy at temperatures above 600℃. In an attempt to tackle this problem, Ti-48Al (at. pct) and Ti-48Al-12Cr (at. pct) protective coatings were plated on the substrate of alloy Ti-60 by arc ion plating (ALP) method. Isothermal and cyclic oxidation tests were performed in static air at elevated temperatures. Phase composition, morphology of the coatings and distribution of elements were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The results showed that the Ti-48Al coating exhibited good isothermal oxidation resistance during exposure at 800℃, but poorer resistance against oxidation at 900℃. By contrast Ti-48Al-12Cr coating demonstrated excellent isothermal oxidation resistance at both temperatures. Cyclic oxidation tests performed at 800℃ indicated that resistance and no spallation of coatings was observed. But both coatings demonstrated good cyclic oxidation at 900℃ only Ti-48Al-12Cr coating demonstrated excellent cyclic oxidation resistance.展开更多
In this paper, cold bulge forming of titanium alloy Ti55 was investigated. This process was done successfully and titanium alloy Ti55 was formed completely. Also, in the numerical work, this process has been investiga...In this paper, cold bulge forming of titanium alloy Ti55 was investigated. This process was done successfully and titanium alloy Ti55 was formed completely. Also, in the numerical work, this process has been investigated using Abaqus/ Explicit code. The results show that there is a good agreement between experimental and numerical results. Mechanical properties of Titanium alloy Ti55 have been investigated before and after bulge forming. The results show that mechanical properties of titanium alloy Ti55 have been improved during bulge forming. Also, hardness, and thickness variation tests of sheet metal before and after bulge forming were performed and the same results to mechanical properties were obtained.展开更多
The Ti-35V-15Cr-0.05C (wt% is a new nonburning titanium alloy. The test for alloy combustibility was carried out by using CO2 laser. A 430 watt and 6mm diameter laser spot impinges directly on the sample within normal...The Ti-35V-15Cr-0.05C (wt% is a new nonburning titanium alloy. The test for alloy combustibility was carried out by using CO2 laser. A 430 watt and 6mm diameter laser spot impinges directly on the sample within normal atmospheric pressure and temperature. The results show that the ignition time of the nonburning titanium alloy is the longest in the eight examined titanium alloys, and is 3.5 times that of TC4 alloy. The ignition tempeerature of the nonburning alloy is 2991° C, and is higher than that of TC4 alloy by 1976°C. On the condition of high tempeerature and rich oxygen,the surface of alloy forms a melting layer which plays roles of oxygen insulation, heat insulation and burning products insulation. This is the mechanism of combustion resistance.展开更多
基金the financial support from the Fundamental Research Program of Shanxi Province,China(No.202203021211130)the National Natural Science Foundation of China(Nos.51801132,52075359)。
基金financially supported by the National Key Research and Development Program of China(Grant No.2020YFB2008300)。
文摘Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot isostatic pressing parameters on defects,composition uniformity,microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in detail.Results show that increasing temperature and pressure of hot isostatic pressing can reduce defects,especially,the internal defects are substantially eliminated when the temperature exceeds 920℃or the pressure exceeds 125 MPa.The higher temperature and pressure can improve the microstructure uniformity.Besides,the higher pressure can promote the composition uniformity.With the temperature increases from 880℃to 960℃,α-laths are coarsened.But with increasing pressure,the grain size of prior-βphase,the widths ofα-laths andα-colony are reduced.The tensile strength of Ti60 alloy is 949 MPa,yield strength is 827 MPa,and the elongation is 11%when the hot isostatic pressing parameters are 960℃/125 MPa/2 h,which exhibits the best match between the strength and plasticity.
基金supported by the National Natural Science Foundation of China (40472025, 40620120098,40872043)
文摘We describe the new mineral species titanium, ideally Ti, found in the podiform chromitites of the Luobusha ophiolite in Tibet, People's Republic of China. The irregular crystals range from 0.1 to 0.6 mm in diameter and form an intergrowth with coesite and kyanite. Titanium is silver grey in colour, the luster is metallic, it is opaque, the streak is grayish black, and it is non-fluorescent. The mineral is malleable, has a rough to hackly fracture and has no apparent cleavage. The estimated Mohs hardness is 4, and the calculated density is 4.503 g/cm3. The composition is Ti 99.23-100.00 wt%. The mineral is hexagonal, space group P6flmmc. Unit-cell parameters are a 2.950 (2) ~, c 4.686 (1) A,V 35.32 (5) A3, Z = 2. The five strongest powder diffraction lines [d in A (hkl) (I/I0)] are: 2.569 (010) (32), 2.254(011) (100), 1.730 (012) (16), 1.478 (110) (21), and 0.9464 (121) (8). The species and name were approved by the CNMNC (IMA 2010-044).
基金Supported by the National Key Projects for Fundamental Research and Development of China(2016YFB0600904)
文摘Large quantities of CO_2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO_2 emission reduction and comprehensive utilization of the solid waste.This paper describes a novel route for indirect mineral carbonation of titanium-bearing blast furnace(TBBF) slag,in which the TBBF slag is roasted with recyclable(NH_4)_2SO_4(AS) at low temperatures and converted into the sulphates of various valuable metals, including calcium, magnesium, aluminium and titanium. High value added Ti-and Al-rich products can be obtained through stepwise precipitation of the leaching solution from the roasted slag. The NH_3 produced during the roasting is used to capture CO_2 from flue gases. The NH_4HCO_3 and(NH_4)_2CO_3 thus obtained are used to carbonate the CaSO_4-containing leaching residue and MgSO_4-rich leaching solution, respectively. In this study, the process parameters and efficiency for the roasting, carbonation and Ti and Al recovery were investigated in detail. The results showed that the sulfation ratios of calcium,magnesium, titanium and aluminium reached 92.6%, 87% and 84.4%, respectively, after roasting at an AS-to-TBBF slag mass ratio of 2:1 and 350 °C for 2 h. The leaching solution was subjected to hydrolysis at 102 °C for 4 h with a Ti hydrolysis ratio of 95.7% and the purity of TiO_2 in the calcined hydrolysate reached 98 wt%.99.7% of aluminium in the Ti-depleted leaching solution was precipitated by using NH_3. The carbonation products of Ca and Mg were CaCO_3 and(NH_4)_2 Mg(CO_3)_2·4H_2O, respectively. The latter can be decomposed into MgCO_3 at 100–200 °C with simultaneous recovery of the NH_3 for reuse. In this process, approximately 82.1% of Ca and 84.2%of Mg in the TBBF slag were transformed into stable carbonates and the total CO_2 sequestration capacity per ton of TBBF slag reached up to 239.7 kg. The TiO_2 obtained can be used directly as an end product, while the Al-rich precipitate and the two carbonation products can act, respectively, as raw materials for electrolytic aluminium,cement and light magnesium carbonate production for the replacement of natural resources.
基金the National Outstanding YOung Scientist Foundation Under Grant !No.59925208 the National Natural Science Foundation of China
文摘A novel temperature fluctuation synthesis/simultaneous densification process was developed for the preparation of Ti3SiC2 bulk ceramics. In this process. Si is used as an in-situ liquid forming phase and it is favorable for both the solid-liquid synthesis and the densification of Ti3SiC2 rainies. The present work demonstrated that the temperature fluctuation synthesis/simultaneous densification process is one of the most effective and simple methods for the preparation of Ti3SiC2 bulk materials providing relatively low synthesis temperature. short reaction time; and simultaneous synthesis and densification. This work also showed the capability to control the microstructure, e.g., the preferred orientation, of the bulk Ti3SiC2 materials simply by applying the hot pressing pressure at different Stages of the temperature fluctuation process. And textured Ti3SiC2 bulk materials with {002} faces of laminated Ti3SiC2 grains normal to the hot pressing axis were prepared.
文摘Electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel with a copper sheet as interlayer was carried out.Microstructures of the joint were studied by optical microscopy(OM),scanning electron microscopy(SEM) and X-ray diffractometry(XRD).In addition,the mechanical properties of the joint were evaluated by tensile test and the microhardness was measured.These two alloys were successfully welded by adding copper transition layer into the weld.Solid solution with a certain thickness was located at the interfaces between weld and base metal in both sides.Regions inside the weld and near the stainless steel were characterized by solid solution of copper with TiFe2 intermetallics dispersedly distributed in it.While weld near titanium alloy contained Ti-Cu and Ti-Fe-Cu intermetallics layer,in which the hardness of weld came to the highest value.Brittle fracture occurred in the intermetallics layer when the joint was stretched.
文摘The electrochemical behaviour of Ti(Ⅲ) and Ti(Ⅱ) in LiCl-KCl eutectic system has been studied by cyclic voltammetry and chronoamperometry.The cathodic reduction of Ti(Ⅲ) and Ti(Ⅱ) has been found to be stepwise:Ti(Ⅲ)+e=Ti(Ⅱ),Ti(Ⅱ)+2e =Ti.The reductions are diffusion controlled.When an equilibrium between Ti subchlorides and excess metallic Ti was estab- lished by reaction 2TiCl_3+Ti=3TiCl_2 in LiCl-KCl melt at 475℃,then the average valence of Ti is less than 2.1.In this system the diffusion coefficient for Ti(Ⅱ) ion was calculated as D=2.5×10^(-5)cm^2·s^(-1).The chronoamperometric studies showed that the initial nucleation stage and growth of nuclei were observed when Ti ions were electrodeposited on low carbon steel substrate. The investigation of nucleation of metal may provide the method for obtaining smooth,coherent and adherent deposits of titanium.
基金financially supported by the National Basic Research Program of China(973 Program,2006CB202508)the China Petrochemical Corporation(SINOPEC Group 20673054)
文摘For simulating the real deactivation of hollow titanium silicalite(HTS) zeolite in commercial ammoximation process, HTS was treated by 10% NH_3·H_2O solution at 120 ℃ in stirred autoclave. It is found that a part of HTS zeolite crystals dissolved in the hot NH_3·H_2O solution, and the specific surface area and pore volume continuously decreased with the increase in NH_3 hydrothermal treatment time. Meanwhile, the transformation of framework Ti species into extraframework Ti species was detected by the spectroscopic methods. However, the extraframework Ti species were still in a highly dispersed state after the hydrothermal and thermal treatments as shown by TEM images, while the formation of new acid sites was not detected. Upon combining the results of characterization with catalytic performance of HTS, the main deactivation reason for this material had been determined, which might be attributed to the reduction of specific surface area and active centers after basic treatment and calcination of HTS samples. And then the possible mechanism of simulated deactivation of HTS zeolite was proposed, which could describe the elemental reaction steps much more visually and directly.
文摘High-temperature titanium alloy for aeroengine compressor applications suffers from high-temperature oxidation and environmental corrosion, which prohibits long-term service of this kind alloy at temperatures above 600℃. In an attempt to tackle this problem, Ti-48Al (at. pct) and Ti-48Al-12Cr (at. pct) protective coatings were plated on the substrate of alloy Ti-60 by arc ion plating (ALP) method. Isothermal and cyclic oxidation tests were performed in static air at elevated temperatures. Phase composition, morphology of the coatings and distribution of elements were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The results showed that the Ti-48Al coating exhibited good isothermal oxidation resistance during exposure at 800℃, but poorer resistance against oxidation at 900℃. By contrast Ti-48Al-12Cr coating demonstrated excellent isothermal oxidation resistance at both temperatures. Cyclic oxidation tests performed at 800℃ indicated that resistance and no spallation of coatings was observed. But both coatings demonstrated good cyclic oxidation at 900℃ only Ti-48Al-12Cr coating demonstrated excellent cyclic oxidation resistance.
文摘In this paper, cold bulge forming of titanium alloy Ti55 was investigated. This process was done successfully and titanium alloy Ti55 was formed completely. Also, in the numerical work, this process has been investigated using Abaqus/ Explicit code. The results show that there is a good agreement between experimental and numerical results. Mechanical properties of Titanium alloy Ti55 have been investigated before and after bulge forming. The results show that mechanical properties of titanium alloy Ti55 have been improved during bulge forming. Also, hardness, and thickness variation tests of sheet metal before and after bulge forming were performed and the same results to mechanical properties were obtained.
文摘The Ti-35V-15Cr-0.05C (wt% is a new nonburning titanium alloy. The test for alloy combustibility was carried out by using CO2 laser. A 430 watt and 6mm diameter laser spot impinges directly on the sample within normal atmospheric pressure and temperature. The results show that the ignition time of the nonburning titanium alloy is the longest in the eight examined titanium alloys, and is 3.5 times that of TC4 alloy. The ignition tempeerature of the nonburning alloy is 2991° C, and is higher than that of TC4 alloy by 1976°C. On the condition of high tempeerature and rich oxygen,the surface of alloy forms a melting layer which plays roles of oxygen insulation, heat insulation and burning products insulation. This is the mechanism of combustion resistance.