TC4 titanium alloy(Ti-6Al-4V),known for its excellent specific strength,corrosion resistance,and weldability,is extensively applied in aerospace,marine engineering,and advanced manufacturing.This study focuses on the ...TC4 titanium alloy(Ti-6Al-4V),known for its excellent specific strength,corrosion resistance,and weldability,is extensively applied in aerospace,marine engineering,and advanced manufacturing.This study focuses on the microstructural uniformity and mechanical properties of TC4 ingots fabricated via the electron-beam cold hearth melting(EBCHM)process.A comprehensive analysis was performed using optical microscopy,scanning electron microscopy,electron backscatter diffraction,and energy-dispersive spectroscopy to investigate the ingot’s morphology,α-phase lamellar structure,and elemental distribution.Mechanical characterization included tensile testing,and microhardness and impact toughness assessments.Results reveal that EBCHM produces a well-defined and homogeneous microstructure,with the averageαlamellae thickness varying between 1.53 and 1.71μm and minimal fluctuations across the ingot regions,indicating high process consistency.Major alloying elements(Al and V)and impurity elements(O,N,H,C,and Fe)are evenly distributed,with no observable macrosegregation.The mechanical properties are stable and reliable,with a yield strength of 694.6-701.2 MPa,a tensile strength of 711.1-716.6 MPa,an elongation of 3.35%-3.84%,and an average impact toughness of 94.7 J/cm^(2).These results provide valuable data and technical references for the application of EBCHM in manufacturing premium-quality Ti-6Al-4V ingots.展开更多
Aiming at solve the difficulty and low dimensional accuracy in bending titanium alloy specimens at room temperature,we proposed a compound energy field(CEF)with laser and ultrasonic forming method.Through the conventi...Aiming at solve the difficulty and low dimensional accuracy in bending titanium alloy specimens at room temperature,we proposed a compound energy field(CEF)with laser and ultrasonic forming method.Through the conventional bending,laser-assisted energy field bending and CEF-assisted bending experiments on TC4 titanium alloy,the effects of bending force,laser-assisted energy field and CEF on the springback angle and fillet radius of TC4 titanium alloy specimens in V-shape bending were analyzed.The impact of the CEF-assisted bending process on the microstructure of TC4 titanium alloy was also investigated.The results show that CEF-assisted bending process has the advantages of high energy density,simple operation process and small influence area of the microstructure performances.It is effective in reducing the springback and fillet radius of bending specimens.Thus,CEF-assisted bending effectively improves the formability and surface quality of titanium alloy specimens.展开更多
The fiber laser welding tests for 3 mm thick TC4 titanium alloy plates are carried out,and the microstructures of the joints are analyzed by the OM and SEM,and the mechanical properties of the joints are described by ...The fiber laser welding tests for 3 mm thick TC4 titanium alloy plates are carried out,and the microstructures of the joints are analyzed by the OM and SEM,and the mechanical properties of the joints are described by tensile and hardness tests,and the SEM morpho-logies of the tensile fracture are observed.The results show that the weld zone is composed of columnarβphase with coarse grains and acicular martensiteα',and small secondaryα'phases in different directions are formed acicular martensiteα'.The microstructure at the boundary between the HAZ and the weld is composed ofα'andαphases,the microstructure at the boundary between the HAZ and the base metal is composed of the initial(αandβ)andαphases,and the microstructure of the middle transition zone of the HAZ is composed of a small amount ofα'andαphase of high temperatureβphase’transformation and initial(αandβ)phases.The average tensile strength of TC4 titanium alloy laser beam welded joints is 1056 MPa,and the average elongation is 9.0%,which are lower than the tensile strength and the elongation of the base metal respectively.The fracture is ductile fracture,and the hardness of the weld zone is the highest and that of the HAZ is the lowest.展开更多
The hot deformation behavior of Ti-6Al-4V （TC4） titanium alloy was investigated in the temperature range from 650℃ to 950℃ with the strain rate ranging from 7.7×10^-4 s^-1 to 7.7×10^-2 s^-1. The hot tens...The hot deformation behavior of Ti-6Al-4V （TC4） titanium alloy was investigated in the temperature range from 650℃ to 950℃ with the strain rate ranging from 7.7×10^-4 s^-1 to 7.7×10^-2 s^-1. The hot tension test results indicate that the flow stress decreases with increasing the deformation temperature and increases with increasing the strain rate. XRD analysis result reveals that only deformation temperature affects the phase constitution. The microstructure evolution under different deformation conditions was characterized by TEM observation. For the deformation of TC4 alloy, the work-hardening is dominant at low temperature, while the dynamic recovery and dynamic re-crystallization assisted softening is dominant at high temperature.展开更多
In order to analyze the effect of grain size on stress relaxation(SR) mechanism,the SR tests of TC4 alloy with three kinds of grain size were performed in a temperature range of 650-750℃.A modified cubic delay functi...In order to analyze the effect of grain size on stress relaxation(SR) mechanism,the SR tests of TC4 alloy with three kinds of grain size were performed in a temperature range of 650-750℃.A modified cubic delay function was used to establish SR model for each grain size.A simplified algorithm was proposed for calculating the deformation activation energy based on classical Arrhenius equation.The grain size distribution and variation were observed by microstructural methods.The experimental results indicate that smaller grains are earlier to reach the relaxation limit at the same temperature due to lower initial stress and faster relaxation rate.The SR limit at 650℃ reduces with decreasing grain size.While the effect of grain size on SR limit is not evident at 700 and 750℃ since the relaxation is fully completed.With the increase of grain size,the deformation activation energy is improved and SR mechanism at 700℃ changes from grain rotation and grain boundary sliding to dislocation movement and dynamic recovery.展开更多
Electrolyte jet machining(EJM)is a promising method for shaping titanium alloys due to its lack of tool wear,thermal and residual stress,and cracks and burrs.Recently,macro-EJM has attracted increasing attention for i...Electrolyte jet machining(EJM)is a promising method for shaping titanium alloys due to its lack of tool wear,thermal and residual stress,and cracks and burrs.Recently,macro-EJM has attracted increasing attention for its high efficiency in machining wide grooves or planes.However,macro-EJM generates large amounts of electrolytic products,thereby increasing the difficulty of rapid product removal with a standard tool and reducing the surface quality.Therefore,for enhanced product transport,a novel tool with a back inclined end face was proposed for macroEJM of TC4 titanium alloy.For comparison,also proposed were ones with a standard flat end face,a front inclined end face,and both front and back inclined end faces.The flow field distributions of all proposed tools were simulated numerically,and experiments were also conducted to validate the simulation results.The results show that one with a 5°back inclined end face can decrease the lowvelocity flow zone in the machining area and increase the high-velocity flow zone at the back end of tool,thereby promoting rapid product removal.A relatively smooth bright-white groove surface was obtained.The same tool also resulted in the highest machining depth and material removal rate among the tested ones.In addition,rapid product removal was beneficial to the subsequent processing.Because of its rapid product removal,the machining depth and material removal rate during deep groove machining using the tool with a 5°back inclined end face were respectively 7%and14%higher than those produced using a standard one.Moreover,the lowest bottom height difference of 0.027 mm can be obtained when the step-over value was 8.2 mm,and a plane with a depth of0.285 mm and a bottom height difference of 0.03 mm was fabricated using the tool with a 5°back inclined end face.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
TC4 titanium alloy was welded by double-sided gas tungsten arc welding(GTAW) process in comparison with conventional GTAW process, the microstructure and mechanical performance of weld were also studied. The results i...TC4 titanium alloy was welded by double-sided gas tungsten arc welding(GTAW) process in comparison with conventional GTAW process, the microstructure and mechanical performance of weld were also studied. The results indicate that double-sided GTAW is superior over regular single-sided GTAW on the aspects of increasing penetration, reducing welding deformation and improving welding efficiency. Good weld joint was obtained, which can reach 96.14% tensile strength and 70.85% elongation percentage of the base metal. The grains in heat-affected zone(HAZ) are thin and equiaxed and the degree of grain coarsening increases as one moves to the weld center line, and the interior of grains are α and α′ structures. The coarse columned and equiaxed grains, which interlace martensitic structures α′ and acicular α structures, are observed in weld zone. The fracture mode is ductile fracture.展开更多
In this study,AZ91D(Mg-9Al-Zn)alloys reinforced with 2 vol%TC4(Ti-6Al-4V)particles fabricated by semi-solid stir casting were extruded at different ratios,resulting in observed grain refinement effects.The research fi...In this study,AZ91D(Mg-9Al-Zn)alloys reinforced with 2 vol%TC4(Ti-6Al-4V)particles fabricated by semi-solid stir casting were extruded at different ratios,resulting in observed grain refinement effects.The research findings demonstrate that both TC4 andβ-Mg_(17)Al_(12) phases contribute to promoting dynamic recrystallization(DRX)nucleation.With increasing extrusion ratio,theβ-phase(Mg_(17)Al_(12))gradually fractures into smaller particles,leading to progressive grain refinement.Furthermore,the transition from〈01-10〉fiber texture to non-basal texture in theα-Mg matrix after hot extrusion is attributed to improved DRX behavior and activation of non-basal slip.As the extrusion ratio increases,the tensile strength and elongation(EL)of TC4_(p)/AZ91D composite improve significantly,reaching optimum comprehensive mechanical properties at an extrusion of 40:1 with a yield strength(YS)of 257 MPa,an ultimate tensile strength(UTS)of 357 MPa,and an EL of 9.7%.This remarkable strengthening effect is primarily attributed toβ-phase reinforcement,grain refinement strengthening,and strain hardening.展开更多
基金funding recei-ved from the National Key R&D Program of China(No.2022YFB3705602)the Scientific Research Plan Project of Shanghai,P.R.China(No.22SQBS 00600).
文摘TC4 titanium alloy(Ti-6Al-4V),known for its excellent specific strength,corrosion resistance,and weldability,is extensively applied in aerospace,marine engineering,and advanced manufacturing.This study focuses on the microstructural uniformity and mechanical properties of TC4 ingots fabricated via the electron-beam cold hearth melting(EBCHM)process.A comprehensive analysis was performed using optical microscopy,scanning electron microscopy,electron backscatter diffraction,and energy-dispersive spectroscopy to investigate the ingot’s morphology,α-phase lamellar structure,and elemental distribution.Mechanical characterization included tensile testing,and microhardness and impact toughness assessments.Results reveal that EBCHM produces a well-defined and homogeneous microstructure,with the averageαlamellae thickness varying between 1.53 and 1.71μm and minimal fluctuations across the ingot regions,indicating high process consistency.Major alloying elements(Al and V)and impurity elements(O,N,H,C,and Fe)are evenly distributed,with no observable macrosegregation.The mechanical properties are stable and reliable,with a yield strength of 694.6-701.2 MPa,a tensile strength of 711.1-716.6 MPa,an elongation of 3.35%-3.84%,and an average impact toughness of 94.7 J/cm^(2).These results provide valuable data and technical references for the application of EBCHM in manufacturing premium-quality Ti-6Al-4V ingots.
基金Funded by the National Natural Science Foundation of China(Nos.52075347,51575364)the Natural Science Foundation of Liaoning Provincial(No.2022-MS-295)。
文摘Aiming at solve the difficulty and low dimensional accuracy in bending titanium alloy specimens at room temperature,we proposed a compound energy field(CEF)with laser and ultrasonic forming method.Through the conventional bending,laser-assisted energy field bending and CEF-assisted bending experiments on TC4 titanium alloy,the effects of bending force,laser-assisted energy field and CEF on the springback angle and fillet radius of TC4 titanium alloy specimens in V-shape bending were analyzed.The impact of the CEF-assisted bending process on the microstructure of TC4 titanium alloy was also investigated.The results show that CEF-assisted bending process has the advantages of high energy density,simple operation process and small influence area of the microstructure performances.It is effective in reducing the springback and fillet radius of bending specimens.Thus,CEF-assisted bending effectively improves the formability and surface quality of titanium alloy specimens.
基金supported by the Science and Technology Plan Foundation of Guizhou(Guizhou Science Support[2021]General 337)Anhui University Natural Science Key Research Project(2022AH052357).
文摘The fiber laser welding tests for 3 mm thick TC4 titanium alloy plates are carried out,and the microstructures of the joints are analyzed by the OM and SEM,and the mechanical properties of the joints are described by tensile and hardness tests,and the SEM morpho-logies of the tensile fracture are observed.The results show that the weld zone is composed of columnarβphase with coarse grains and acicular martensiteα',and small secondaryα'phases in different directions are formed acicular martensiteα'.The microstructure at the boundary between the HAZ and the weld is composed ofα'andαphases,the microstructure at the boundary between the HAZ and the base metal is composed of the initial(αandβ)andαphases,and the microstructure of the middle transition zone of the HAZ is composed of a small amount ofα'andαphase of high temperatureβphase’transformation and initial(αandβ)phases.The average tensile strength of TC4 titanium alloy laser beam welded joints is 1056 MPa,and the average elongation is 9.0%,which are lower than the tensile strength and the elongation of the base metal respectively.The fracture is ductile fracture,and the hardness of the weld zone is the highest and that of the HAZ is the lowest.
文摘The hot deformation behavior of Ti-6Al-4V （TC4） titanium alloy was investigated in the temperature range from 650℃ to 950℃ with the strain rate ranging from 7.7×10^-4 s^-1 to 7.7×10^-2 s^-1. The hot tension test results indicate that the flow stress decreases with increasing the deformation temperature and increases with increasing the strain rate. XRD analysis result reveals that only deformation temperature affects the phase constitution. The microstructure evolution under different deformation conditions was characterized by TEM observation. For the deformation of TC4 alloy, the work-hardening is dominant at low temperature, while the dynamic recovery and dynamic re-crystallization assisted softening is dominant at high temperature.
基金Projects(2016ZE57008,20163657004)supported by Aeronautical Science Foundation of ChinaProject(USCAST2016-20)supported by the SAST-SJTU Joint Research Centre of Advanced Aerospace Technology,ChinaProject(51875350)supported by the National Natural Science Foundation of China
文摘In order to analyze the effect of grain size on stress relaxation(SR) mechanism,the SR tests of TC4 alloy with three kinds of grain size were performed in a temperature range of 650-750℃.A modified cubic delay function was used to establish SR model for each grain size.A simplified algorithm was proposed for calculating the deformation activation energy based on classical Arrhenius equation.The grain size distribution and variation were observed by microstructural methods.The experimental results indicate that smaller grains are earlier to reach the relaxation limit at the same temperature due to lower initial stress and faster relaxation rate.The SR limit at 650℃ reduces with decreasing grain size.While the effect of grain size on SR limit is not evident at 700 and 750℃ since the relaxation is fully completed.With the increase of grain size,the deformation activation energy is improved and SR mechanism at 700℃ changes from grain rotation and grain boundary sliding to dislocation movement and dynamic recovery.
基金supported by the National Natural Science Foundation of China(No.91860208)the National Natural Science Foundation of China for Creative Research Groups(No.51921003)。
文摘Electrolyte jet machining(EJM)is a promising method for shaping titanium alloys due to its lack of tool wear,thermal and residual stress,and cracks and burrs.Recently,macro-EJM has attracted increasing attention for its high efficiency in machining wide grooves or planes.However,macro-EJM generates large amounts of electrolytic products,thereby increasing the difficulty of rapid product removal with a standard tool and reducing the surface quality.Therefore,for enhanced product transport,a novel tool with a back inclined end face was proposed for macroEJM of TC4 titanium alloy.For comparison,also proposed were ones with a standard flat end face,a front inclined end face,and both front and back inclined end faces.The flow field distributions of all proposed tools were simulated numerically,and experiments were also conducted to validate the simulation results.The results show that one with a 5°back inclined end face can decrease the lowvelocity flow zone in the machining area and increase the high-velocity flow zone at the back end of tool,thereby promoting rapid product removal.A relatively smooth bright-white groove surface was obtained.The same tool also resulted in the highest machining depth and material removal rate among the tested ones.In addition,rapid product removal was beneficial to the subsequent processing.Because of its rapid product removal,the machining depth and material removal rate during deep groove machining using the tool with a 5°back inclined end face were respectively 7%and14%higher than those produced using a standard one.Moreover,the lowest bottom height difference of 0.027 mm can be obtained when the step-over value was 8.2 mm,and a plane with a depth of0.285 mm and a bottom height difference of 0.03 mm was fabricated using the tool with a 5°back inclined end face.
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TC4 titanium alloy was welded by double-sided gas tungsten arc welding(GTAW) process in comparison with conventional GTAW process, the microstructure and mechanical performance of weld were also studied. The results indicate that double-sided GTAW is superior over regular single-sided GTAW on the aspects of increasing penetration, reducing welding deformation and improving welding efficiency. Good weld joint was obtained, which can reach 96.14% tensile strength and 70.85% elongation percentage of the base metal. The grains in heat-affected zone(HAZ) are thin and equiaxed and the degree of grain coarsening increases as one moves to the weld center line, and the interior of grains are α and α′ structures. The coarse columned and equiaxed grains, which interlace martensitic structures α′ and acicular α structures, are observed in weld zone. The fracture mode is ductile fracture.
基金the Guangdong Major Project of Basic and Applied Basic Research(2020B0301030006)the Guangdong Provincial Academy of Sciences Fund(2020GDASYL-20200101001)the Natural Science Foundation of Hubei Province,China(2023AFB1033).
文摘In this study,AZ91D(Mg-9Al-Zn)alloys reinforced with 2 vol%TC4(Ti-6Al-4V)particles fabricated by semi-solid stir casting were extruded at different ratios,resulting in observed grain refinement effects.The research findings demonstrate that both TC4 andβ-Mg_(17)Al_(12) phases contribute to promoting dynamic recrystallization(DRX)nucleation.With increasing extrusion ratio,theβ-phase(Mg_(17)Al_(12))gradually fractures into smaller particles,leading to progressive grain refinement.Furthermore,the transition from〈01-10〉fiber texture to non-basal texture in theα-Mg matrix after hot extrusion is attributed to improved DRX behavior and activation of non-basal slip.As the extrusion ratio increases,the tensile strength and elongation(EL)of TC4_(p)/AZ91D composite improve significantly,reaching optimum comprehensive mechanical properties at an extrusion of 40:1 with a yield strength(YS)of 257 MPa,an ultimate tensile strength(UTS)of 357 MPa,and an EL of 9.7%.This remarkable strengthening effect is primarily attributed toβ-phase reinforcement,grain refinement strengthening,and strain hardening.
