V-5Cr-5Ti alloys have been fabricated using a laser melting deposition(LMD)additive manufacturing process,showing precipitates aggregated near the grain/dendrite boundaries.Since the mechanical properties of vanadium ...V-5Cr-5Ti alloys have been fabricated using a laser melting deposition(LMD)additive manufacturing process,showing precipitates aggregated near the grain/dendrite boundaries.Since the mechanical properties of vanadium alloys considerably depend on the precipitates,solution and aging treatments have been applied to eliminating the aggregations of the precipitates.The results show that as the solution temperature increases from 800 to 1560℃,the densities and the lengths of the precipitates are reduced,while the widths of the precipitates are increased.When the solution temperature reaches 1560℃,most impurity elements diffuse into the matrix and form into a nearly uniform supersaturated solid solution.Aging treatments have been applied to the 1560℃solution treated samples.It shows that as the aging temperature increases from 800 to 1200℃,the precipitate length increases,and the shapes of precipitates change from near-spherical to lath-like.Compared to 800 and 1200℃,aging at 1000℃results in the highest precipitate density.Compared to the LMD and solution-treated samples,the aged samples have the highest micro-hardness,due to the precipitation strengthening.展开更多
To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level ...To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level orthogonal experiment design of factor levels.Results show that through range analysis,the significance order of process parameters is determined as follows:solution cooling method>solution temperature>aging time>aging temperature>solution time.Considering the strength-ductility matching and engineering application requirements,the benchmark parameters are selected as solution time of 1 h,solution cooling method of air cooling(AC),aging temperature of 525℃,and aging time of 4 h.Furthermore,the effects of solution temperature in the range of 790–870℃ on the impact toughness and micro-fracture characteristics of the alloy were studied.The results reveal that the larger the area of shear lip and fibrous zone,and the smaller the area of radiation zone,the better the toughness of the alloy.With the increase in solution temperature,the length of secondary cracks on the fracture surface increases,the number of dimples increases,and the toughness is enhanced.Based on the collaborative optimization of strength and toughness,the optimal heat treatment process for TB18 alloy is determined as 870℃/1 h,AC+525℃/4 h,AC.展开更多
The effects of heat treatment on microstructure and creep properties of β high-strength titanium alloy,Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe,were studied.After solution treatment at 790℃ and aging treatment(HT1),the microst...The effects of heat treatment on microstructure and creep properties of β high-strength titanium alloy,Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe,were studied.After solution treatment at 790℃ and aging treatment(HT1),the microstructure is composed of equiaxedαp phase,β phase,α_(p) phase,and becomes β phase and α_(s) phases after solution treatment at 840℃ and aging treatment(HT2).The creep behavior at 400℃ was analyzed.The stress exponents of both alloys are between 1 and 2,indicating that the diffusional creep mechanism is one of the dominant creep mechanisms.The alloy after HT2 treatment has better creep resistance and a subsequent creep test on this alloy was performed at 450℃ under 400 MPa.The creep fracture has the mixed ductile-brittle characteristics.The phase interfaces can hinder the dislocation movement,and theαs phase can coordinate with the matrix to deform,thereby reducing the occurrence of intragranular cracks.展开更多
The effects of different aging conditions on the microstructure,strength,corrosion resistance,cytotoxicity and antibacterial ability of Ti-15Zr-xCu(3≤x≤7,wt%)(TZC)alloys were systematically investigated.Microstructu...The effects of different aging conditions on the microstructure,strength,corrosion resistance,cytotoxicity and antibacterial ability of Ti-15Zr-xCu(3≤x≤7,wt%)(TZC)alloys were systematically investigated.Microstructural evolution and behavior were analyzed by X-ray diffraction(XRD)patterns and scanning electron microscopy with energy-dispersive spectroscopy(SEM-EDS),while potentiodynamic polarization technique was employed to characterize the corrosion response of the alloys after solution-treatment and aging(STA).High-temperature aging at 660℃ for 4 h(660-4)gave the best combination of properties by enabling significant precipitation of the Cu-rich Ti_(2)Cu and Zr_(2)Cu compounds,and mild formation of the Zr_(7)Cu_(10) secondary phase.The high kinetics at this condition was beneficial to the complete precipitation and more homogeneous distribution of the intermetallic particles.These led to the inhibition of dislocation movements and allowed for significantly improved mechanical strengths with added ductility,availability of more Cu ions for the desired oligodynamic activity without evoking cytotoxicity,better corrosion resistance and very high antibacterial ability(over 99.5%),thus improving the overall properties of the TZC alloys for biomedical applications.展开更多
Addition of rare earth elements for improving the tensile properties of aluminum alloys has attracted great attention. In this study, a systematic analysis on the microstructure and tensile properties of A356–0.13 Ti...Addition of rare earth elements for improving the tensile properties of aluminum alloys has attracted great attention. In this study, a systematic analysis on the microstructure and tensile properties of A356–0.13 Ti alloys with different contents of scandium(Sc) and scandium/zirconium(Sc/Zr) after solution and aging treatment process was carried out. The addition of Sc/Zr into A356–0.13 Ti alloys can greatly refine the grain size and modify the deleterious coarse eutectic Si structure and harmful acicular iron-containing phase morphology. As a result, the maximum value of strength(298 MPa) and ductility(elongation of 8.4%) are acquired by co-addition of Sc/Zr after solution and aging treatment process, which indicates that the tensile properties of A356 alloy are greatly enhanced by the synergistic effect of co-addition of Sc/Zr.展开更多
The solid solution and aging treatment for conventional manufacturing processes might not be suitable for laser additive manufactured titanium alloys due to the different lamellar microstructures.In this study,the inf...The solid solution and aging treatment for conventional manufacturing processes might not be suitable for laser additive manufactured titanium alloys due to the different lamellar microstructures.In this study,the influence of aging temperatures(600,700 and 800°C)on microstructure and mechanical properties of titanium alloy Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si was investigated.The results indicate that after solid solution treatment at 970°C followed by water quenching,the alloy mainly consists of coarsening lamellar a phase in martensite α' matrix.Aging at 600°C will not change the size of primary lamellar α phase but lead to huge amount of secondary a phases(α_(s))generating with very fine microstructure.By increasing the aging temperature,the number of α_(s) decreases but with coarsened microstructures.When aged at 800°C,the width of the asphase reaches 350 nm,almost 7 times wider than that aged at 600°C.The changing size of α_(s) obviously influences the property of the alloy.The fine α_(s) leads to high strength and microhardness but low plasticity,and specimen aged at 700°C with suitable assize has the best comprehensive properties.展开更多
The effects of the solution and aging treatment on microstructures and mechanical properties of the Mg-10Zn-5A1-0.1Sb-XCu cast magnesium alloys were investigated by brinell hardness measurement, scanning electron micr...The effects of the solution and aging treatment on microstructures and mechanical properties of the Mg-10Zn-5A1-0.1Sb-XCu cast magnesium alloys were investigated by brinell hardness measurement, scanning electron microscopy （SEM）, energy spectrum analyzing apparatus and X-ray diffraction （XRD）. The experimental results show that the strip-like t-Mg32 （A1, Zn）49 phase is shown at the grain boundaries and Mg2Cu phase become smaller, even granular after solution treatment at 350 ~C for 24 h. By ageing treatment at 180 ~C, the ternary strengthening phase （r phase） precipitates gradually at or around grain boundary. With increasing aging time, the micro-hardness improves obviously and up to the maximum （105.9 HV） at aging time of 36 h. In addition, the tensile-strengths at room temperature and at an elevated temperature respectively reach 228 MPa and 176 MPa, which is increased by 20% and 10%, respectively.展开更多
Laser powder bed fusion(LPBF)of Mg alloys mainly focuses on the traditional commercial casting Mg alloys such as AZ91D,ZK60 and WE43,which usually display relatively low tensile strengths.Herein we developed a novel h...Laser powder bed fusion(LPBF)of Mg alloys mainly focuses on the traditional commercial casting Mg alloys such as AZ91D,ZK60 and WE43,which usually display relatively low tensile strengths.Herein we developed a novel high-strength Mg-12 Gd-2 Y-1 Zn-0.5 Mn(wt.%,GWZ1221M)alloy for the LPBF additive manufacturing process,and the evolution of microstructure and mechanical properties from the as-built state to LPBF-T4 and LPBF-T6 states was systematically investigated.The as-built GWZ1221M alloy exhibited fine equiaxed grains with an average grain size of only 4.3±2.2μm,while the as-cast alloy displayed typical coarse dendrite grains(178.2±73.6μm).Thus,the as-built alloy showed significantly higher tensile strengths than the as-cast counterpart,and its yield strength(YS),ultimate tensile strength(UTS)and elongation(EL)were 315±8 MPa,340±7 MPa and 2.7±0.5%respectively.Solution treatment transformed hard and brittleβ-(Mg,Zn)_(3)(Gd,Y)phase into basal X phase and lamellar long period stacking ordered(LPSO)with better plastic deformability,leading to the improvement of EL.Then peak-aging heat treatment introduced numerous nano-sized prismaticβprecipitates inside grains,resulting in the enhancement of YS.Finally,the LPBF-T6 alloy achieved appreciably high strength with YS,UTS and EL of 320±3 MPa,395±4 MPa and 2.1±0.4%respectively.Both as-built and LPBF-T6 GWZ1221M alloys showed remarkably higher tensile strengths than the as-cast counterparts and as-built commercial Mg alloys,highlighting the great potential of high-strength as-built Mg-Gd based alloys for structural applications.展开更多
The effects of solution and ageing treatment (T6) on microstructure and tensile properties of as-extruded Mg-10Gd-3Y-0.6Zr (mass fraction. %) alloy were investigated. The results show that after T6 treatment, the diam...The effects of solution and ageing treatment (T6) on microstructure and tensile properties of as-extruded Mg-10Gd-3Y-0.6Zr (mass fraction. %) alloy were investigated. The results show that after T6 treatment, the diameter of grain increases to 20 μm. As the second phases dissolve into the matrix, the smaller and denser β′ phases precipitate inside the grains. After T6-treatment, both yield strength (TYS) and ultimate tensile strength (UTS) are increased. Comparing with that in only ageing condition (T5), the UTS and TYS increased from 365 MPa,285 MPa to 400 MPa,310 MPa, respectively, but the elongation decreased from 7.0% to 3.5%. It has been found that the effects of precipitates on the strength are stronger than that of the growth of grain size.展开更多
The microstructures of the Zn-27Al alloy after modification, solid-solution treatment, and natural aging were studied. It was clarified why the damping properties of Zn-27Al alloys, after treatment, had advanced most ...The microstructures of the Zn-27Al alloy after modification, solid-solution treatment, and natural aging were studied. It was clarified why the damping properties of Zn-27Al alloys, after treatment, had advanced most on the basis of analyzing the microstructures. Approximate expressions have been educed, which can be used to quantificationally work out the damping of the Zn-27Al alloy on the basis of the micro interface sliding model. By comparing the testing damping properties of the foundry Zn-27Al alloys and the Zn-27Al alloys after modification, solid solution, and natural aging, it was shown that the expressions were rational.展开更多
The alloy Ni-Al26.6-Cr13.4-Co8.1-Ti4.3-W1.3-Mo0.9 （at. pct） was fabricated from superalloy K44 and Al element using vacuum induction and casting technique. Investigations to this alloy reveal that a new phase Cr3Ni2...The alloy Ni-Al26.6-Cr13.4-Co8.1-Ti4.3-W1.3-Mo0.9 （at. pct） was fabricated from superalloy K44 and Al element using vacuum induction and casting technique. Investigations to this alloy reveal that a new phase Cr3Ni2 possessing low melting point and poor ductility is formed, which is distributed as a network along NiAI matrix grain boundaries. Subsequent different solution and aging treatments are carried out and lead to microstructural changes to various extents. Rapid cooling after solution at 1250℃ for 20 h gives rise to macrocracks in the specimen while slow cooling after the same treatment results in the formation of spheric α-Cr solid solution and needle-like Ni3Al phase, which are embedded in NiAl matrix. It is comfirmed that aging treatments initiate lath-shaped Ni3Al phase and pearl-shaped α-Cr phase to precipitate from the NiAl matrix, which own orientation relationships with these precipitates.展开更多
基金Project(51871203)supported by the National Natural Science Foundation of ChinaProject(TZ2018006-0303-02)supported by the Science Challenge Project,ChinaProjects(2020ZDZX0017,2019YFG0217)supported by the Sichuan Science and Technology Program,China。
文摘V-5Cr-5Ti alloys have been fabricated using a laser melting deposition(LMD)additive manufacturing process,showing precipitates aggregated near the grain/dendrite boundaries.Since the mechanical properties of vanadium alloys considerably depend on the precipitates,solution and aging treatments have been applied to eliminating the aggregations of the precipitates.The results show that as the solution temperature increases from 800 to 1560℃,the densities and the lengths of the precipitates are reduced,while the widths of the precipitates are increased.When the solution temperature reaches 1560℃,most impurity elements diffuse into the matrix and form into a nearly uniform supersaturated solid solution.Aging treatments have been applied to the 1560℃solution treated samples.It shows that as the aging temperature increases from 800 to 1200℃,the precipitate length increases,and the shapes of precipitates change from near-spherical to lath-like.Compared to 800 and 1200℃,aging at 1000℃results in the highest precipitate density.Compared to the LMD and solution-treated samples,the aged samples have the highest micro-hardness,due to the precipitation strengthening.
基金Key Program of National Natural Science Foundation of China(52431001)。
文摘To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level orthogonal experiment design of factor levels.Results show that through range analysis,the significance order of process parameters is determined as follows:solution cooling method>solution temperature>aging time>aging temperature>solution time.Considering the strength-ductility matching and engineering application requirements,the benchmark parameters are selected as solution time of 1 h,solution cooling method of air cooling(AC),aging temperature of 525℃,and aging time of 4 h.Furthermore,the effects of solution temperature in the range of 790–870℃ on the impact toughness and micro-fracture characteristics of the alloy were studied.The results reveal that the larger the area of shear lip and fibrous zone,and the smaller the area of radiation zone,the better the toughness of the alloy.With the increase in solution temperature,the length of secondary cracks on the fracture surface increases,the number of dimples increases,and the toughness is enhanced.Based on the collaborative optimization of strength and toughness,the optimal heat treatment process for TB18 alloy is determined as 870℃/1 h,AC+525℃/4 h,AC.
基金supported by the National Natural Science Foundation of China(No.51975147)。
文摘The effects of heat treatment on microstructure and creep properties of β high-strength titanium alloy,Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe,were studied.After solution treatment at 790℃ and aging treatment(HT1),the microstructure is composed of equiaxedαp phase,β phase,α_(p) phase,and becomes β phase and α_(s) phases after solution treatment at 840℃ and aging treatment(HT2).The creep behavior at 400℃ was analyzed.The stress exponents of both alloys are between 1 and 2,indicating that the diffusional creep mechanism is one of the dominant creep mechanisms.The alloy after HT2 treatment has better creep resistance and a subsequent creep test on this alloy was performed at 450℃ under 400 MPa.The creep fracture has the mixed ductile-brittle characteristics.The phase interfaces can hinder the dislocation movement,and theαs phase can coordinate with the matrix to deform,thereby reducing the occurrence of intragranular cracks.
基金financially supported by the National Natural Science Foundation of China(Nos.51631009 and 31870954).S.K.Kolawole graciously appreciates CAS-TWAS President Fellowship for the scholarship aid。
文摘The effects of different aging conditions on the microstructure,strength,corrosion resistance,cytotoxicity and antibacterial ability of Ti-15Zr-xCu(3≤x≤7,wt%)(TZC)alloys were systematically investigated.Microstructural evolution and behavior were analyzed by X-ray diffraction(XRD)patterns and scanning electron microscopy with energy-dispersive spectroscopy(SEM-EDS),while potentiodynamic polarization technique was employed to characterize the corrosion response of the alloys after solution-treatment and aging(STA).High-temperature aging at 660℃ for 4 h(660-4)gave the best combination of properties by enabling significant precipitation of the Cu-rich Ti_(2)Cu and Zr_(2)Cu compounds,and mild formation of the Zr_(7)Cu_(10) secondary phase.The high kinetics at this condition was beneficial to the complete precipitation and more homogeneous distribution of the intermetallic particles.These led to the inhibition of dislocation movements and allowed for significantly improved mechanical strengths with added ductility,availability of more Cu ions for the desired oligodynamic activity without evoking cytotoxicity,better corrosion resistance and very high antibacterial ability(over 99.5%),thus improving the overall properties of the TZC alloys for biomedical applications.
基金financially supported by the National Natural Science Foundation of China(Nos.51422104,51472177 and 51531004)the Foundation for the Author of National Excellent Doctoral Dissertation of China(No.201145)the Program for New Century Excellent Talents in University(No.NCET12-0408)。
文摘Addition of rare earth elements for improving the tensile properties of aluminum alloys has attracted great attention. In this study, a systematic analysis on the microstructure and tensile properties of A356–0.13 Ti alloys with different contents of scandium(Sc) and scandium/zirconium(Sc/Zr) after solution and aging treatment process was carried out. The addition of Sc/Zr into A356–0.13 Ti alloys can greatly refine the grain size and modify the deleterious coarse eutectic Si structure and harmful acicular iron-containing phase morphology. As a result, the maximum value of strength(298 MPa) and ductility(elongation of 8.4%) are acquired by co-addition of Sc/Zr after solution and aging treatment process, which indicates that the tensile properties of A356 alloy are greatly enhanced by the synergistic effect of co-addition of Sc/Zr.
基金financially supported by the Beijing Municipal Science and Technology Project(No.Z171100000817002)the Young Elite Scientist Sponsorship Program by CAST and the National Key Research and Development Program of China(No.2016YFB1100401)。
文摘The solid solution and aging treatment for conventional manufacturing processes might not be suitable for laser additive manufactured titanium alloys due to the different lamellar microstructures.In this study,the influence of aging temperatures(600,700 and 800°C)on microstructure and mechanical properties of titanium alloy Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si was investigated.The results indicate that after solid solution treatment at 970°C followed by water quenching,the alloy mainly consists of coarsening lamellar a phase in martensite α' matrix.Aging at 600°C will not change the size of primary lamellar α phase but lead to huge amount of secondary a phases(α_(s))generating with very fine microstructure.By increasing the aging temperature,the number of α_(s) decreases but with coarsened microstructures.When aged at 800°C,the width of the asphase reaches 350 nm,almost 7 times wider than that aged at 600°C.The changing size of α_(s) obviously influences the property of the alloy.The fine α_(s) leads to high strength and microhardness but low plasticity,and specimen aged at 700°C with suitable assize has the best comprehensive properties.
基金Funded by the National Natural Science Foundation of China(NO.51044007,51001079,50571073)the National Natural Science Foundation of Shanxi Province(2009011028-3)the Research Fund for the Dectoral Program of Higher Education of China(20111402110004)
文摘The effects of the solution and aging treatment on microstructures and mechanical properties of the Mg-10Zn-5A1-0.1Sb-XCu cast magnesium alloys were investigated by brinell hardness measurement, scanning electron microscopy （SEM）, energy spectrum analyzing apparatus and X-ray diffraction （XRD）. The experimental results show that the strip-like t-Mg32 （A1, Zn）49 phase is shown at the grain boundaries and Mg2Cu phase become smaller, even granular after solution treatment at 350 ~C for 24 h. By ageing treatment at 180 ~C, the ternary strengthening phase （r phase） precipitates gradually at or around grain boundary. With increasing aging time, the micro-hardness improves obviously and up to the maximum （105.9 HV） at aging time of 36 h. In addition, the tensile-strengths at room temperature and at an elevated temperature respectively reach 228 MPa and 176 MPa, which is increased by 20% and 10%, respectively.
基金supported by the National Key Research and Development Program of China(No.2021YFB3701000)the National Natural Science Foundation of China(Nos.51971130,52201129,U21A2047,51821001,U2037601)。
文摘Laser powder bed fusion(LPBF)of Mg alloys mainly focuses on the traditional commercial casting Mg alloys such as AZ91D,ZK60 and WE43,which usually display relatively low tensile strengths.Herein we developed a novel high-strength Mg-12 Gd-2 Y-1 Zn-0.5 Mn(wt.%,GWZ1221M)alloy for the LPBF additive manufacturing process,and the evolution of microstructure and mechanical properties from the as-built state to LPBF-T4 and LPBF-T6 states was systematically investigated.The as-built GWZ1221M alloy exhibited fine equiaxed grains with an average grain size of only 4.3±2.2μm,while the as-cast alloy displayed typical coarse dendrite grains(178.2±73.6μm).Thus,the as-built alloy showed significantly higher tensile strengths than the as-cast counterpart,and its yield strength(YS),ultimate tensile strength(UTS)and elongation(EL)were 315±8 MPa,340±7 MPa and 2.7±0.5%respectively.Solution treatment transformed hard and brittleβ-(Mg,Zn)_(3)(Gd,Y)phase into basal X phase and lamellar long period stacking ordered(LPSO)with better plastic deformability,leading to the improvement of EL.Then peak-aging heat treatment introduced numerous nano-sized prismaticβprecipitates inside grains,resulting in the enhancement of YS.Finally,the LPBF-T6 alloy achieved appreciably high strength with YS,UTS and EL of 320±3 MPa,395±4 MPa and 2.1±0.4%respectively.Both as-built and LPBF-T6 GWZ1221M alloys showed remarkably higher tensile strengths than the as-cast counterparts and as-built commercial Mg alloys,highlighting the great potential of high-strength as-built Mg-Gd based alloys for structural applications.
基金Project supported by program for Changjiang Scholars and Innovative Research Teamin University(IRT0713)National Basic Research Program ofChina (2007CB613702, 2007CB613701)
文摘The effects of solution and ageing treatment (T6) on microstructure and tensile properties of as-extruded Mg-10Gd-3Y-0.6Zr (mass fraction. %) alloy were investigated. The results show that after T6 treatment, the diameter of grain increases to 20 μm. As the second phases dissolve into the matrix, the smaller and denser β′ phases precipitate inside the grains. After T6-treatment, both yield strength (TYS) and ultimate tensile strength (UTS) are increased. Comparing with that in only ageing condition (T5), the UTS and TYS increased from 365 MPa,285 MPa to 400 MPa,310 MPa, respectively, but the elongation decreased from 7.0% to 3.5%. It has been found that the effects of precipitates on the strength are stronger than that of the growth of grain size.
文摘The microstructures of the Zn-27Al alloy after modification, solid-solution treatment, and natural aging were studied. It was clarified why the damping properties of Zn-27Al alloys, after treatment, had advanced most on the basis of analyzing the microstructures. Approximate expressions have been educed, which can be used to quantificationally work out the damping of the Zn-27Al alloy on the basis of the micro interface sliding model. By comparing the testing damping properties of the foundry Zn-27Al alloys and the Zn-27Al alloys after modification, solid solution, and natural aging, it was shown that the expressions were rational.
文摘The alloy Ni-Al26.6-Cr13.4-Co8.1-Ti4.3-W1.3-Mo0.9 （at. pct） was fabricated from superalloy K44 and Al element using vacuum induction and casting technique. Investigations to this alloy reveal that a new phase Cr3Ni2 possessing low melting point and poor ductility is formed, which is distributed as a network along NiAI matrix grain boundaries. Subsequent different solution and aging treatments are carried out and lead to microstructural changes to various extents. Rapid cooling after solution at 1250℃ for 20 h gives rise to macrocracks in the specimen while slow cooling after the same treatment results in the formation of spheric α-Cr solid solution and needle-like Ni3Al phase, which are embedded in NiAl matrix. It is comfirmed that aging treatments initiate lath-shaped Ni3Al phase and pearl-shaped α-Cr phase to precipitate from the NiAl matrix, which own orientation relationships with these precipitates.
