The tribological conditions between tools and sheet are the major factors affecting the product quality,forming limits and service life of tools in thin-walled titanium components warm forming.Using the orthogonal des...The tribological conditions between tools and sheet are the major factors affecting the product quality,forming limits and service life of tools in thin-walled titanium components warm forming.Using the orthogonal design based twist compression test in the temperature range of 25-300 °C,the significant factors affecting the coefficient of friction（Co F） and the influencing rules in CP-3 titanium sheet warm forming are clarified and discussed by changing tribological conditions such as tool material,lubrication,temperature and normal pressure.The results show that the significant factors affecting the Co F are lubrication,surface roughness,tool material,sliding velocity,normal pressure and temperature;compared with unlubricated condition,the graphite and Mo S2 greatly improve the friction condition and the maximum reduction of the Co F is 0.318;the Co Fs of Cr12 Mo V/CP-3 and QAl10-3-1.5/CP-3 tribo-pairs show a similar tendency：the Co Fs increase with increasing surface roughness and sliding velocity,and increase firstly then decrease with increasing normal pressure and temperature.展开更多
Commercially pure titanium（CP Ti） has been actively used in the plate heat exchanger due to its light weight, high specific strength, and excellent corrosion resistance. However, researches for the plastic deformati...Commercially pure titanium（CP Ti） has been actively used in the plate heat exchanger due to its light weight, high specific strength, and excellent corrosion resistance. However, researches for the plastic deformation characteristics and press formability of the CP Ti sheet are not much in comparison with automotive steels and aluminum alloys. The mechanical properties and hardening behavior evaluated in stress-strain relation of the CP Ti sheet are clarified in relation with press formability. The flow curve denoting true stress-true strain relation for CP Ti sheet is fitted well by the Kim-Tuan hardening equation rather than Voce and Swift models. The forming limit curve（FLC） of CP Ti sheet as a criterion for press formability was experimentally evaluated by punch stretching test and analytically predicted via Hora＇s modified maximum force criterion. The predicted FLC by adopting Kim-Tuan hardening model and appropriate yield function shows good correlation with the experimental results of punch stretching test.展开更多
We investigated the influences of process parameters on the head curvature of pure titanium sheet in hot rolling process and proposed the controlling means. First, the thermal simulation experiments for pure titanium ...We investigated the influences of process parameters on the head curvature of pure titanium sheet in hot rolling process and proposed the controlling means. First, the thermal simulation experiments for pure titanium TA1 were carried out to investigate the hot deformation behaviors of pure titanium in the temperature range of 700-800 ℃ with strain rate range of 1-20 S-1, and the processing map was established to determine optimized deformation parameters. Then, the finite element model has been constructed and used to analyze the effect of process parameters on the direction and severity of head curvature of pure titanium sheet. The process parameters considered in the present study include workpiece temperature, work roll diameter, pass reduction, oxide scale thickness of workpiece surface, and interface friction coefficient. The simulation results show that the workpiece temperature and the interface friction coefficient are the two main factors. The proposed controlling means was carried out on a hot rolling production line and solved the head curvature problem effectively. The rolling practices indicate that the rolling yield is improved greatly.展开更多
By analyzing the influencing factors of part quality making of sheet alloy of titanium by vibra cutter, the shape of upper reamer is set as cylinder and wedge-shaped form, and the lower reamer as plain and hemicycle f...By analyzing the influencing factors of part quality making of sheet alloy of titanium by vibra cutter, the shape of upper reamer is set as cylinder and wedge-shaped form, and the lower reamer as plain and hemicycle form, and its main structural parameters are defined as well. Then it is validated further that such improved vibra cutter reamer can be used to process curve-edged parts of titanium alloy sheet. The experimental result shows that the titanium alloy sheet parts processed by above equipment have no sharpen angles for convex parts and evident crevasse of concave-edged part. In summary, such improvement can eliminate the free-waved edge and improve the manufacture quality of titanium alloy sheet parts greatly.展开更多
The relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation at 800℃was investigated.In the test,the original sheet exhibited relatively low flo...The relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation at 800℃was investigated.In the test,the original sheet exhibited relatively low flow stress and sound plasticity,and increasing the heat treatment temperature resulted in an increased ultimate tensile strength(UTS)and a decreased elongation(EL).The deformation mechanism of TA32 alloy was dominated by high angle grain boundaries sliding and coordinated by dislocation motion.The coarsening of grains and the annihilation of dislocations in heat-treated specimens weakened the deformation ability of material,which led to the increase in flow stress.Based on the high-temperature creep equation,the quantitative relationship between microstructure and flow stress was established.The grain size exponent andαphase strength constant of TA32 alloy were calculated to be 1.57 and 549.58 MPa,respectively.The flow stress was accurately predicted by combining with the corresponding phase volume fraction and grain size.Besides,the deformation behavior of TA32 alloy was also dependent on the orientation of predominantαphase,and the main slip mode was the activation of prismaticslip system.The decrease of near prism-oriented texture in heat-treated specimens resulted in the enhancement of strength of the material.展开更多
An annealed TC4 titanium alloy sheet was treated by high density electropulsing(Jmax=(5.09-5.26)×103A/mm2,tp=110μs)under ambient conditions.The effect of electropulsing treatment(EPT)on the plastic deformation b...An annealed TC4 titanium alloy sheet was treated by high density electropulsing(Jmax=(5.09-5.26)×103A/mm2,tp=110μs)under ambient conditions.The effect of electropulsing treatment(EPT)on the plastic deformation behavior of TC4 titanium alloysheet was studied using uniaxial tension tests.The experimental results indicate that electropulsing treatment significantly changesthe mechanical properties of sheet metal:the uniform elongation is increased by 35%,the yield stress is decreased by 19.8%and theyield to tensile ratio is decreased by 17.6%.It is of significant meaning to improve the formability of TC4 titanium alloy sheet.Theoptical microscope and scanning electron microscope(SEM)were used to examine the changes of the microstructure and the fracturemorphology before and after the electropulsing treatment.It is found that recrystallization occurs in the sheet metal and dimples infracture surface are large and deep after the electropulsing treatment.The research results show that the electropulsing treatment is aneffective method to improve the formability of titanium alloy sheets.展开更多
In order to investigate the influence of normal stress through thickness on the formability of sheet metal,the viscous pressure bulge(VPB)tests of an annealed TC1 titanium alloy sheet were carried out under two differ...In order to investigate the influence of normal stress through thickness on the formability of sheet metal,the viscous pressure bulge(VPB)tests of an annealed TC1 titanium alloy sheet were carried out under two different conditions:double-sided pressure bulging and conventional single-sided pressure bulging.The automated strain analysis,measurement environment(ASAME)and scanning electron microscope(SEM)were used to study the strain distributions and the fracture morphology of bulged specimens.It is found that thickness strain is increased for double-sided pressure bulging specimens,and the limiting dome height(LDH)of double-sided pressure bulging specimens is increased by 31.8% compared with conventional single-sided pressure bulging specimens.The dimples in fracture surface for double-sided pressure bulging specimens are larger and deeper than those for conventional single-sided pressure bulging specimens.The results indicate that normal stress through thickness is helpful in improving the formability of titanium alloy sheet metal.展开更多
This paper reports research into the microstructures and properties of electron beam welding （EBW） joints of a Ti alloy sheet. To control the TC4 sheet joint formation during electron beam welding is not an easy tas...This paper reports research into the microstructures and properties of electron beam welding （EBW） joints of a Ti alloy sheet. To control the TC4 sheet joint formation during electron beam welding is not an easy task. However, the electron beam current has a significant influence on joint formation and a good appearance of a T-joint can be obtained by increasing the heat input and using the electron beam scan method. It was found that all acicular martensite in the fusion zone （FZ） consisted primarily of α＇ phase titanium, with some β phase present. Grain coarsening occurred in the heat-affected zone （HAZ） due to transformation of the β phase. Butt joints possessed high strength, hardness of the fusion zone, and the heataffected zone of these joints performed better than that of the parent metal. The highest shear strength of T-joint was 615 MPa and the fracture mechanism was a gliding fracture.展开更多
Titanium dioxide sheet photocatalysts composed of interwoven microstrips were successfully synthesized using filter paper as templates. The synthesized samples were characterized by means of Fourier transform infrared...Titanium dioxide sheet photocatalysts composed of interwoven microstrips were successfully synthesized using filter paper as templates. The synthesized samples were characterized by means of Fourier transform infrared spectroscopy, surface area analyzer, thermogravimetric analysis, powder X-ray diffraction, and scanning electron microscopy. The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in an aqueous solution under UV-illumination. The results demonstrated that the paper-like TiO2 sheets with the optimum proportion of anatase/rutile （10/1） had the highest photoactivity. And the presence of the filter paper fiber can improve the crystallinity, raise the anatase-rutile transformation temperature and contribute to the formation of being paper-like. A detailed formation mechanism for TiO2 sheets is proposed.展开更多
The effect of heat treatment and rolling process on the properties and microstructures of Ti-26(Ti-15V-3Al-3Cr-3Sn-Forming) sheet was studied. The results show that the best rolling temperature for Ti-26 alloy is in t...The effect of heat treatment and rolling process on the properties and microstructures of Ti-26(Ti-15V-3Al-3Cr-3Sn-Forming) sheet was studied. The results show that the best rolling temperature for Ti-26 alloy is in the temperature range from 900 ℃ to 950℃. Under this condition,the resistance of deformation and yield ratio are low and the alloy has better hot work ability. The alloy will achieve better mechanical properties and completely recrystallized β microstructure when the deformation ratio is not less than 60% and the solution temperature is 30 ℃ above the phase transformation temperature. The best heat treatment conditions are recommended as:790℃,30 min,AC or WQ followed by 510 ℃,10 h,AC. Under this heat treatment condition the strength of the Ti-26 alloy is 1 230 MPa and the elongation is 15%.展开更多
Ultra-thin sheets of titanium for fabricating microchannels have been used in fuel cells due to their good corrosion resistance and high strength-weight ratio. This paper presents a constitutive model for studying the...Ultra-thin sheets of titanium for fabricating microchannels have been used in fuel cells due to their good corrosion resistance and high strength-weight ratio. This paper presents a constitutive model for studying the anisotropy effects of pure titanium(CP-Ti) sheet on the springback behavior and forming properties during the microstamping process. Thin sheets of CP-Ti specimens with different orientations were examined using uniaxial tensile tests to assess the effects of anisotropy on their mechanical properties. Then an anisotropic constitutive model considering the off-axis elastic modulus was developed based on orthotropic elasticity and Hill's yield criterion. Numerical modeling and simulation of the microstamping process for fabricating multi-channel structures were performed. The effects of anisotropy on the springback of multi-channels were investigated and compared with experimental results;the effects of tool dimension parameters on the formability of microchannel structures were also analyzed. The results showed that the anisotropy of thin titanium sheets causes various degrees of forming loads and springback in the microstamping of microchannels at different orientations. This study accurately predicts the springback of thin titanium sheet used to fabricate microchannel structures and is a good guide to the formation of such structures.展开更多
基金Projects(50905144,51275415)supported by the National Natural Science Foundation of ChinaProject(3102014KYJD001)supported by Fundamental Research Funds for the Central Universities,ChinaProject(B08040)supported by the Program of Introducing Talents of Discipline to Universities("111"Project)
文摘The tribological conditions between tools and sheet are the major factors affecting the product quality,forming limits and service life of tools in thin-walled titanium components warm forming.Using the orthogonal design based twist compression test in the temperature range of 25-300 °C,the significant factors affecting the coefficient of friction（Co F） and the influencing rules in CP-3 titanium sheet warm forming are clarified and discussed by changing tribological conditions such as tool material,lubrication,temperature and normal pressure.The results show that the significant factors affecting the Co F are lubrication,surface roughness,tool material,sliding velocity,normal pressure and temperature;compared with unlubricated condition,the graphite and Mo S2 greatly improve the friction condition and the maximum reduction of the Co F is 0.318;the Co Fs of Cr12 Mo V/CP-3 and QAl10-3-1.5/CP-3 tribo-pairs show a similar tendency：the Co Fs increase with increasing surface roughness and sliding velocity,and increase firstly then decrease with increasing normal pressure and temperature.
基金supported by the National Research Foundation of Korea (NRF) granted by the Korea government [2014R1A2A2A01005903]Priority Research Centers Program (2010-0020089)support from a grant [R0003356] (Tuning Professional Support Center in Daegu Metropolitan City) funded by the Ministry of Trade, Industry and Energy (MOTIE, Korea)
文摘Commercially pure titanium（CP Ti） has been actively used in the plate heat exchanger due to its light weight, high specific strength, and excellent corrosion resistance. However, researches for the plastic deformation characteristics and press formability of the CP Ti sheet are not much in comparison with automotive steels and aluminum alloys. The mechanical properties and hardening behavior evaluated in stress-strain relation of the CP Ti sheet are clarified in relation with press formability. The flow curve denoting true stress-true strain relation for CP Ti sheet is fitted well by the Kim-Tuan hardening equation rather than Voce and Swift models. The forming limit curve（FLC） of CP Ti sheet as a criterion for press formability was experimentally evaluated by punch stretching test and analytically predicted via Hora＇s modified maximum force criterion. The predicted FLC by adopting Kim-Tuan hardening model and appropriate yield function shows good correlation with the experimental results of punch stretching test.
基金Funded by the National Natural Science Foundation of China(51275445)
文摘We investigated the influences of process parameters on the head curvature of pure titanium sheet in hot rolling process and proposed the controlling means. First, the thermal simulation experiments for pure titanium TA1 were carried out to investigate the hot deformation behaviors of pure titanium in the temperature range of 700-800 ℃ with strain rate range of 1-20 S-1, and the processing map was established to determine optimized deformation parameters. Then, the finite element model has been constructed and used to analyze the effect of process parameters on the direction and severity of head curvature of pure titanium sheet. The process parameters considered in the present study include workpiece temperature, work roll diameter, pass reduction, oxide scale thickness of workpiece surface, and interface friction coefficient. The simulation results show that the workpiece temperature and the interface friction coefficient are the two main factors. The proposed controlling means was carried out on a hot rolling production line and solved the head curvature problem effectively. The rolling practices indicate that the rolling yield is improved greatly.
文摘By analyzing the influencing factors of part quality making of sheet alloy of titanium by vibra cutter, the shape of upper reamer is set as cylinder and wedge-shaped form, and the lower reamer as plain and hemicycle form, and its main structural parameters are defined as well. Then it is validated further that such improved vibra cutter reamer can be used to process curve-edged parts of titanium alloy sheet. The experimental result shows that the titanium alloy sheet parts processed by above equipment have no sharpen angles for convex parts and evident crevasse of concave-edged part. In summary, such improvement can eliminate the free-waved edge and improve the manufacture quality of titanium alloy sheet parts greatly.
基金Project(51805256)supported by the National Natural Science Foundation of China。
文摘The relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation at 800℃was investigated.In the test,the original sheet exhibited relatively low flow stress and sound plasticity,and increasing the heat treatment temperature resulted in an increased ultimate tensile strength(UTS)and a decreased elongation(EL).The deformation mechanism of TA32 alloy was dominated by high angle grain boundaries sliding and coordinated by dislocation motion.The coarsening of grains and the annihilation of dislocations in heat-treated specimens weakened the deformation ability of material,which led to the increase in flow stress.Based on the high-temperature creep equation,the quantitative relationship between microstructure and flow stress was established.The grain size exponent andαphase strength constant of TA32 alloy were calculated to be 1.57 and 549.58 MPa,respectively.The flow stress was accurately predicted by combining with the corresponding phase volume fraction and grain size.Besides,the deformation behavior of TA32 alloy was also dependent on the orientation of predominantαphase,and the main slip mode was the activation of prismaticslip system.The decrease of near prism-oriented texture in heat-treated specimens resulted in the enhancement of strength of the material.
文摘An annealed TC4 titanium alloy sheet was treated by high density electropulsing(Jmax=(5.09-5.26)×103A/mm2,tp=110μs)under ambient conditions.The effect of electropulsing treatment(EPT)on the plastic deformation behavior of TC4 titanium alloysheet was studied using uniaxial tension tests.The experimental results indicate that electropulsing treatment significantly changesthe mechanical properties of sheet metal:the uniform elongation is increased by 35%,the yield stress is decreased by 19.8%and theyield to tensile ratio is decreased by 17.6%.It is of significant meaning to improve the formability of TC4 titanium alloy sheet.Theoptical microscope and scanning electron microscope(SEM)were used to examine the changes of the microstructure and the fracturemorphology before and after the electropulsing treatment.It is found that recrystallization occurs in the sheet metal and dimples infracture surface are large and deep after the electropulsing treatment.The research results show that the electropulsing treatment is aneffective method to improve the formability of titanium alloy sheets.
文摘In order to investigate the influence of normal stress through thickness on the formability of sheet metal,the viscous pressure bulge(VPB)tests of an annealed TC1 titanium alloy sheet were carried out under two different conditions:double-sided pressure bulging and conventional single-sided pressure bulging.The automated strain analysis,measurement environment(ASAME)and scanning electron microscope(SEM)were used to study the strain distributions and the fracture morphology of bulged specimens.It is found that thickness strain is increased for double-sided pressure bulging specimens,and the limiting dome height(LDH)of double-sided pressure bulging specimens is increased by 31.8% compared with conventional single-sided pressure bulging specimens.The dimples in fracture surface for double-sided pressure bulging specimens are larger and deeper than those for conventional single-sided pressure bulging specimens.The results indicate that normal stress through thickness is helpful in improving the formability of titanium alloy sheet metal.
基金Supported by National Basic Research Program （2010CB731704） and National Natural Science Foundation of China（No. 51075089）.
文摘This paper reports research into the microstructures and properties of electron beam welding （EBW） joints of a Ti alloy sheet. To control the TC4 sheet joint formation during electron beam welding is not an easy task. However, the electron beam current has a significant influence on joint formation and a good appearance of a T-joint can be obtained by increasing the heat input and using the electron beam scan method. It was found that all acicular martensite in the fusion zone （FZ） consisted primarily of α＇ phase titanium, with some β phase present. Grain coarsening occurred in the heat-affected zone （HAZ） due to transformation of the β phase. Butt joints possessed high strength, hardness of the fusion zone, and the heataffected zone of these joints performed better than that of the parent metal. The highest shear strength of T-joint was 615 MPa and the fracture mechanism was a gliding fracture.
基金This work was supported by the Natural Science Foundation of Shanxi Province （No.2009011099）, the Program for the Top Science and Technology Innovation Team of Higher Learning Institutions of Shanxi, and the Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxi.
文摘Titanium dioxide sheet photocatalysts composed of interwoven microstrips were successfully synthesized using filter paper as templates. The synthesized samples were characterized by means of Fourier transform infrared spectroscopy, surface area analyzer, thermogravimetric analysis, powder X-ray diffraction, and scanning electron microscopy. The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in an aqueous solution under UV-illumination. The results demonstrated that the paper-like TiO2 sheets with the optimum proportion of anatase/rutile （10/1） had the highest photoactivity. And the presence of the filter paper fiber can improve the crystallinity, raise the anatase-rutile transformation temperature and contribute to the formation of being paper-like. A detailed formation mechanism for TiO2 sheets is proposed.
基金Project(2007CB613807) supported by the National Basic Research Program of Chin
文摘The effect of heat treatment and rolling process on the properties and microstructures of Ti-26(Ti-15V-3Al-3Cr-3Sn-Forming) sheet was studied. The results show that the best rolling temperature for Ti-26 alloy is in the temperature range from 900 ℃ to 950℃. Under this condition,the resistance of deformation and yield ratio are low and the alloy has better hot work ability. The alloy will achieve better mechanical properties and completely recrystallized β microstructure when the deformation ratio is not less than 60% and the solution temperature is 30 ℃ above the phase transformation temperature. The best heat treatment conditions are recommended as:790℃,30 min,AC or WQ followed by 510 ℃,10 h,AC. Under this heat treatment condition the strength of the Ti-26 alloy is 1 230 MPa and the elongation is 15%.
基金supported by the National Key R&D Program of China(No.2019YFC1509503)the National Natural Science Foundation of China(No.U1809220)the Key Research and Development Program of Zhejiang Province(No.2022C01113),China.
文摘Ultra-thin sheets of titanium for fabricating microchannels have been used in fuel cells due to their good corrosion resistance and high strength-weight ratio. This paper presents a constitutive model for studying the anisotropy effects of pure titanium(CP-Ti) sheet on the springback behavior and forming properties during the microstamping process. Thin sheets of CP-Ti specimens with different orientations were examined using uniaxial tensile tests to assess the effects of anisotropy on their mechanical properties. Then an anisotropic constitutive model considering the off-axis elastic modulus was developed based on orthotropic elasticity and Hill's yield criterion. Numerical modeling and simulation of the microstamping process for fabricating multi-channel structures were performed. The effects of anisotropy on the springback of multi-channels were investigated and compared with experimental results;the effects of tool dimension parameters on the formability of microchannel structures were also analyzed. The results showed that the anisotropy of thin titanium sheets causes various degrees of forming loads and springback in the microstamping of microchannels at different orientations. This study accurately predicts the springback of thin titanium sheet used to fabricate microchannel structures and is a good guide to the formation of such structures.
基金the National Natural Science Foundation of China(Nos.51801156 and 52074231)the Chongqing Natural Science Foundation,China(No.cstc2020jcyj-msxm X1056)for the financial support to this work。
