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
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
Ti - 40 alloy is a single β phase burn resistant titanium alloy.Its high temperature deformation mech- anism is studied and its stress - strain curves are examined he use of Gleeble - 1500 thermal -simulator. The r...Ti - 40 alloy is a single β phase burn resistant titanium alloy.Its high temperature deformation mech- anism is studied and its stress - strain curves are examined he use of Gleeble - 1500 thermal -simulator. The results reveal that there are abrupt flow stress drops followed b steady state.The magnitude of the flow stress drop increases with strain rote and decreases with temperature.Deformation activation energy, Q, is 247. 5 KJ/mol. The deformation mechanism of Ti - 40 alloy is controlled by the lattice diffusion Its constitutive equation is set up, i. e.展开更多
Ti-6AI-4V, among the Ti alloys, is the most widely used. In the present work, the behavior of Ti-6AI-4V alloy has been investigated by the uniaxial hot isothermal compression tests and a series of dilatometric experim...Ti-6AI-4V, among the Ti alloys, is the most widely used. In the present work, the behavior of Ti-6AI-4V alloy has been investigated by the uniaxial hot isothermal compression tests and a series of dilatometric experiments were also carried out to determine the transformation temperatures at different cooling rates. Specimens for hot compression tests were homogenized at 1050℃ for 10 min and then quickly cooled to different straining temperatures from 1050 to 850℃. Cooling rates were chosen fast enough to prevent high temperature transformation during cooling. Compression tests were conducted at temperatures from 1050 to 850℃ in steps of 50℃ at constant true strain rates of 10-3 or 10-2 s-1. The apparent activation energy for compression in two-phase region was calculated 420 kJ·mol-1. Partial globularization of a phase was observed in the specimen deformed at low strain rates and at temperatures near the transformation zone and annealed after deformation.展开更多
The microstrueture and various hydrides precipitated in Ti-6A1-4V alloys containing hydrogen 0.16,0.58,0.87,1.49 wt-%,respectively,have been studied by means of TEM and X-ray diffraction.The Ti_3Al phase may precipita...The microstrueture and various hydrides precipitated in Ti-6A1-4V alloys containing hydrogen 0.16,0.58,0.87,1.49 wt-%,respectively,have been studied by means of TEM and X-ray diffraction.The Ti_3Al phase may precipitate when H over 0.58 wt-%.In the same time,the morphology of hydrides gradually changed from rugged sheets to narrow laths as H contents increased.The microstructure of highly H-doped alloys is obviously fine.A mas- sive hydride and the hydride with tetragonal lattice were observed in the specimen containing 1.49 wt-%H.The twin hydrides were found in the alloys with different H contents and the electron diffraction patterns of the twin hydrides can be served as a simple criterion for distin- guishing the cubic and tetragonal structures.展开更多
High-resolution transmission electron microscope (HRTEM) was employed to investigate the deformation-induced α2→γ phase transformation phenomenon in a hot deformed Ti-45Al-10Nb alloy. Such a tronsformation can be n...High-resolution transmission electron microscope (HRTEM) was employed to investigate the deformation-induced α2→γ phase transformation phenomenon in a hot deformed Ti-45Al-10Nb alloy. Such a tronsformation can be nucleated either at α2/γ interfaces or at stacking faults on the basal planes of the α2 phase. The growth of deformation-induced γplate is accomplished by the motion of α/6<100> Shockley partials on alternate basal planes (0001)α2, and the α/6<100> Shockley partials move in coordination rather than sweep on (0001)α2 plane one by one. It appears that no atom transportation is involved in this stress-induced α2→γ transfromation.展开更多
Anodizing is expected to be an effective method to improve the osteoconductivity of the Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy because the bioactivity of anodized Ti is good. However, it is not known how the alloy elements i...Anodizing is expected to be an effective method to improve the osteoconductivity of the Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy because the bioactivity of anodized Ti is good. However, it is not known how the alloy elements influence the surface roughness, composition, hydrophilicity, and osteoconductivity of the anodized film on the Ti alloy. In this study, we investigated the effects of anodizing on the surface properties and the osteoconductivity of the anodized TNTZ alloy, focusing on the functions of the individual alloy elements. The anodized oxides of the Nb, Ta, and Zr metals were hydrophobic at all the voltages applied, in contrast to the anodized oxide of Ti. As well as pure Ti, a TiO2-based oxide film formed on TNTZ after anodizing. However, the oxide film also contained large amounts of Nb species and the molar Nb/Ti ratio in the TNTZ alloy was high, which makes the surface more hydrophobic than the anodized oxide on Ti. In vivo tests showed that the osteoconductivity of the TNTZ alloy was sensitive to both its surface roughness and hydrophilicity. When the TNTZ alloy was anodized, the process increased either the surface hydrophobicity or the surface roughness at the voltage used in this study. These changes in the surface properties did not improve its osteoconductivity.展开更多
The effects of picosecond Nd:YAG laser irradiation on chemical and morphological surface characteristics of the commercially pure titanium and Ti–13Nb–13Zr alloy in air and argon atmospheres were studied under diffe...The effects of picosecond Nd:YAG laser irradiation on chemical and morphological surface characteristics of the commercially pure titanium and Ti–13Nb–13Zr alloy in air and argon atmospheres were studied under different laser output energy values.During the interaction of laser irradiation with the investigated materials,a part of the energy was absorbed on the target surface,influencing surface modifications.Laser beam interaction with the target surface resulted in various morphological alterations,resulting in crater formation and the presence of microcracks and hydrodynamic structures.Moreover,different chemical changes were induced on the target materials’surfaces,resulting in the titanium oxide formation in the irradiation-affected area and consequently increasing the irradiation energy absorption.Given the high energy absorption at the site of interaction,the dimensions of the surface damaged area increased.Consequently,surface roughness increased.The appearance of surface oxides also led to the increased material hardness in the surface-modified area.Observed chemical and morphological changes were pronounced after laser irradiation of the Ti–13Nb–13Zr alloy surface.展开更多
In this work, the microstructure and the corresponding tensile properties of the rolled Ti-7Mo-3Nb-3Cr-3Al(Ti-7333) alloy before and after the thermal treatments were investigated. The results show that a strong α-fi...In this work, the microstructure and the corresponding tensile properties of the rolled Ti-7Mo-3Nb-3Cr-3Al(Ti-7333) alloy before and after the thermal treatments were investigated. The results show that a strong α-fiber texture is developed in the rolled Ti-7333 alloy. The deformed matrix and the texture significantly induce the variant selection of β phase. The high strength of the rolled Ti-7333 alloy is attributed to the <110> texture parallel to the tensile direction and the dispersed α phase within the matrix. After the solution treatment followed by the aging treatment, the texture decreases and the microstructure consists of the equiaxed β grains, the spheroidal α_p phase and various needle-like α variants. Eventually, the alloy could achieve an optimal combination with the strength of about 1450 MPa,the ductility of about 10.5% and a considerable shear strength of about 775 MPa. This balance can be ascribed to the performance of the spheroidal α_p phase and various needle-like α_s variants. The results indicate that the Ti-7333 alloy could be a promising candidate material for the high-strength fastener.展开更多
The compressive yielding phenomenon of titanium alloys is not as focused and sufficiently ascertain as the tensile yielding phenomenon.In the present work,the peculiar compressive yielding behavior and the different d...The compressive yielding phenomenon of titanium alloys is not as focused and sufficiently ascertain as the tensile yielding phenomenon.In the present work,the peculiar compressive yielding behavior and the different dynamic responses of three different initial microstructures(singleβ,clavateβand lamellarβ)were investigated in an attractive metastableβtitanium alloy Ti-5553 using electron microscopes/crystallographic calculation/crystal plastic finite element simulation.Results reveal that the distinct compressive yielding behavior,steep peaks of sudden drop in the initial stage(very small true strain 0.03)of stress loading have appeared in the compression stress-strain curves except for the lamellarβinitial microstructure.Dislocation slip is the essential mechanism of the initial yielding behavior.Interlaced multiple-slip bands formed in the singleβinitial microstructure during the warm deformation process.A small quantity of single slip bands was observed in the deformed clavateβinitial microstructure.The abundant varied nano/ultrafineβsprecipitates were nucleated dynamically and dispersedly in all the three deformed initial microstructures.The multiple-slip bands formation and substantial nanoscaleβsresult in the highest peak of flow stress for singleβinitial microstructure.The compressive slip bands are formed early in the elastic–plastic deformation stage.As the increasing strain,the sample showed a significant compressive bulge,or eventually forming a strong adiabatic shear band or crack.These results are expected to provide a reference for the study of deformation behavior and mechanical properties of metastableβtitanium alloys.展开更多
The temperature and stress profiles of porous cubic Ti-6Al-4V titanium alloy grids by additive manufacturing via electron beam melting(EBM)based on finite element(FE)method were investigated.Three-dimensional FE model...The temperature and stress profiles of porous cubic Ti-6Al-4V titanium alloy grids by additive manufacturing via electron beam melting(EBM)based on finite element(FE)method were investigated.Three-dimensional FE models were developed to simulate the single-layer and five-layer girds under annular and lateral scanning.The results showed that the molten pool temperature in five-layer girds was higher than that in single-layer grids owing to the larger mass and higher heat capacity.More energies accumulated by the longer scanning time for annular path than lateral path led to the higher temperature and steeper temperature gradient.The thermal stress drastically fluctuated during EBM process and the residual stress decreased with the increase of powder layer where the largest stress appeared at the first layer along the build direction.The stress under lateral scanning was slightly larger but relatively more homogeneous distribution than those under annular scanning.The stress distribution showed anisotropy and the maximum Von Mises stress occurred around the central node.The stress profiles were explained by the temperature fields and grids structure.展开更多
In this work, the current understanding and development of fliction-stir welding and processing of Ti- 6Al-4V alloy are briefly reviewed. The critical issues of these processes are addressed, including welding tool ma...In this work, the current understanding and development of fliction-stir welding and processing of Ti- 6Al-4V alloy are briefly reviewed. The critical issues of these processes are addressed, including welding tool materials and design, tool wea,, processing temperature, material flow, processing window and residual stresses. A particular emphasis is given to microstructural aspects and microstructure-properties relationship. Potential engineering applications are highlighted.展开更多
The effect of hydrogen addition on the deformation behavior of coarse-grained Ti-55 alloys(~20μm)was studied by uniaxial tension tests at high temperature.The elongation of hydrogenated Ti-55 titanium alloy firstly i...The effect of hydrogen addition on the deformation behavior of coarse-grained Ti-55 alloys(~20μm)was studied by uniaxial tension tests at high temperature.The elongation of hydrogenated Ti-55 titanium alloy firstly increases and then decreases with hydrogen content increasing at 8750 C.The highest elongation of 243.8%is obtained in the hydrogenated alloy with 0.1 wt%H,and the peak stress reaches a minimum value of 29.0 MPa in the hydrogenated alloy with 0.3 wt%H.Compared with that of the unhydrogenated alloy,the elongation of the hydrogenated alloy with 0.1 wt%H increases by 41.3%and its peak stress decreases by 40.6%at 875℃.Hydrogen addition can promote the transformation of β phase and the dislocation movement.Appropriate hydrogen content can evidently improve the deformation properties of coarse-grained Ti-55 titanium alloy.展开更多
Titanium alloys are composed ofαandβphases and are classified as nearα,dual-phaseα+β,andβtypes.This study attempts to derive their general composition formulas within the cluster-plus-glue-atom model by interpre...Titanium alloys are composed ofαandβphases and are classified as nearα,dual-phaseα+β,andβtypes.This study attempts to derive their general composition formulas within the cluster-plus-glue-atom model by interpreting Ti-6A1-4V and other popular dual-phaseα+βTi alloy s with well-established chemical compositions.Our model identifiedαmolecule-like structural unit that covers onlyαnearest-neighbor cluster along withαfew next-neighbor glue atoms,which can be represented as"[cluster](glue atoms)x".The structural units of theαandβphases in Ti-6Al-4V,α-[Al-Ti_(12)](AlTi_(2)),andβ-[Al-Ti_(14)](V2Ti),were derived first and were in an unusual unit ratio of about 2.33:1.To obtain an alloy composition formula that satisfied this unit ratio,the two clusters were treated as hard spheres of different radii and packed according to the clusterplusglueatom model.Our calculations determined that the Ti-6A1-4V alloy unit is composed of 12α-[Al-Ti_(12)](AlTi_(2))and 5β-[Al-Ti_(14)](V2Ti)units(Ti-6.05A1-3.94V wt.%),with the fractional volume of theβphase being 32.5 vol.%,which is in agreement with experimental data.Finally,we describe how the chemical formulas of theαand p phases explain the high temperature near-a alloys(such as Ti-1100,[Al-(Ti_(0.97)Zr_(0.03))_(12)](Al_(0.67)Si_(0.12)Sn_(0.18)Mo_(0.03))_(1.01)Ti_(1.99))and high-strengthβ-Ti alloys(such as Ti-5553,[Al-Ti_(14)](Al_(0.24)Fe_(0.03)Cr_(0.20)-Mo_(0.18)V0.35)_(2.45)Ti_(0.55)),respectively.展开更多
Surgical implant-associated bacterial infection is becoming a serious clinical problem. A series of copper-bearing titanium alloy, Ti-6Al-4V-xCu (x = 1, 3, 5 wt%), were fabricated in the present study in order to re...Surgical implant-associated bacterial infection is becoming a serious clinical problem. A series of copper-bearing titanium alloy, Ti-6Al-4V-xCu (x = 1, 3, 5 wt%), were fabricated in the present study in order to reduce the hazard of the bacterial infection problem by means of the strong antibacterial ability of Cu element. The metallography, X-ray diffraction, antibacterial ability, corrosion resistance and cytotoxicity of Ti-6Al-4V-xCu alloys were preliminarily studied with comparison to the commercial medical Ti-6Al-4V alloy. The Ti-6Al- 4V-xCu alloys showed obvious antibacterial abilities with good corrosion resistance and cytocompatibility, and the antibacterial role was enhanced with increasing Cu content, which has significant potential for clinical applications as surgical implant materials.展开更多
Ti-62421S (Ti-6A1-2Sn-4Zr-2Nb-lMo-0.2Si) is a novel short-time using high-temperature titanium alloy. The effects of annealing on microstructure and tensile properties of Ti-62421S alloy plate were studied through o...Ti-62421S (Ti-6A1-2Sn-4Zr-2Nb-lMo-0.2Si) is a novel short-time using high-temperature titanium alloy. The effects of annealing on microstructure and tensile properties of Ti-62421S alloy plate were studied through optical microscopy (OM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), and tensile tests. The results show that, with annealing tem- perature increasing, the volume fraction of primary α(αp)- phase decreases while that of transformed β(βt)-structure and secondary α (αs)-phase increases. The room-temperature strength and plasticity are insensitive to annealing temperature. However, with annealing temperature increasing, the tensile strength decreases at 550℃, while increases at 600 and 650℃ instead. It is suggested that, at 550℃, the strengthening mechanism is mainly boundary strengthening and the biggest contributor is ap-phase by providing αp/β-boundary area. Above 600 ℃, the strengthening mechanism is grain strengthening, where αs-phase strengthens the β-phase.展开更多
This article studies the phase transformation of the metastable β-Ti-A1-Mo-V-Cr-Zr alloy (Ti-1300) to disclose the morphological reason for its high strength and high fracture toughness. It has been found that its ...This article studies the phase transformation of the metastable β-Ti-A1-Mo-V-Cr-Zr alloy (Ti-1300) to disclose the morphological reason for its high strength and high fracture toughness. It has been found that its ultrahigh strength (ultimate tensile strength exceeds 1 400 MPa) owes mainly to the spheroidization of the α-phase, while the high fracture toughness (exceeds 81 MPa·m^1/2) to the special lath-shaped α-particles. Compared to the needle-shaped second α-articles, the coarser lath-shaped ones remove the stress concentration at the lath tips and consequently benefit improvement of fracture toughness. The article also describes shape evolution of the α-particles during aging thermodynamically and kinetically, and suggests an optimized aging processing to achieve an ideal balance between high strength and high toughness for this alloy.展开更多
Ti2 AlNb-based alloy powder metallurgy(PM)compacts were prepared via hot isostatic pressing(HIP)under relatively low temperature(920 and 980℃)and at certain pressure(130 MPa).The microstructure,composition and orient...Ti2 AlNb-based alloy powder metallurgy(PM)compacts were prepared via hot isostatic pressing(HIP)under relatively low temperature(920 and 980℃)and at certain pressure(130 MPa).The microstructure,composition and orientation of B2,α2 and O phases in the compacts were characterized and analyzed with an aim to investigate the effect of unsuitable HIPping parameters on the appearance of prior particle boundary(PPB),which seriously affects the mechanical properties of the alloy.The results show that moreα2 phase is the characteristics of the PPB in Ti2AlNb-based alloy when HIPped at relatively low temperature.Increasing HIPping temperature to the upper part of the two-phase region can effectively inhibit the formation of PPB.Electron backscatter diffraction measurements show the specific orientation relationship between phases,which helps us understand the origin of a2 and O phase and the corresponding transformation path.The HIPping at a higher temperature can weaken the micro-texture intensity of theα2 and O phase due to the increase of misorientation in B2 phase.Theα2 phase at cell wall keeps the Burgers orientation relationship(BOR)with the grain on one side,and does not satisfy the BOR with the other.It is found that some O phase variants inside the cell HIPped at 980℃can only maintainα2-O OR withα2 owing to theα2→O phase transformation forming the O phase,while these O variants deviate from B2-O OR with B2 phase.展开更多
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.
文摘Ti - 40 alloy is a single β phase burn resistant titanium alloy.Its high temperature deformation mech- anism is studied and its stress - strain curves are examined he use of Gleeble - 1500 thermal -simulator. The results reveal that there are abrupt flow stress drops followed b steady state.The magnitude of the flow stress drop increases with strain rote and decreases with temperature.Deformation activation energy, Q, is 247. 5 KJ/mol. The deformation mechanism of Ti - 40 alloy is controlled by the lattice diffusion Its constitutive equation is set up, i. e.
文摘Ti-6AI-4V, among the Ti alloys, is the most widely used. In the present work, the behavior of Ti-6AI-4V alloy has been investigated by the uniaxial hot isothermal compression tests and a series of dilatometric experiments were also carried out to determine the transformation temperatures at different cooling rates. Specimens for hot compression tests were homogenized at 1050℃ for 10 min and then quickly cooled to different straining temperatures from 1050 to 850℃. Cooling rates were chosen fast enough to prevent high temperature transformation during cooling. Compression tests were conducted at temperatures from 1050 to 850℃ in steps of 50℃ at constant true strain rates of 10-3 or 10-2 s-1. The apparent activation energy for compression in two-phase region was calculated 420 kJ·mol-1. Partial globularization of a phase was observed in the specimen deformed at low strain rates and at temperatures near the transformation zone and annealed after deformation.
文摘The microstrueture and various hydrides precipitated in Ti-6A1-4V alloys containing hydrogen 0.16,0.58,0.87,1.49 wt-%,respectively,have been studied by means of TEM and X-ray diffraction.The Ti_3Al phase may precipitate when H over 0.58 wt-%.In the same time,the morphology of hydrides gradually changed from rugged sheets to narrow laths as H contents increased.The microstructure of highly H-doped alloys is obviously fine.A mas- sive hydride and the hydride with tetragonal lattice were observed in the specimen containing 1.49 wt-%H.The twin hydrides were found in the alloys with different H contents and the electron diffraction patterns of the twin hydrides can be served as a simple criterion for distin- guishing the cubic and tetragonal structures.
文摘High-resolution transmission electron microscope (HRTEM) was employed to investigate the deformation-induced α2→γ phase transformation phenomenon in a hot deformed Ti-45Al-10Nb alloy. Such a tronsformation can be nucleated either at α2/γ interfaces or at stacking faults on the basal planes of the α2 phase. The growth of deformation-induced γplate is accomplished by the motion of α/6<100> Shockley partials on alternate basal planes (0001)α2, and the α/6<100> Shockley partials move in coordination rather than sweep on (0001)α2 plane one by one. It appears that no atom transportation is involved in this stress-induced α2→γ transfromation.
文摘Anodizing is expected to be an effective method to improve the osteoconductivity of the Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy because the bioactivity of anodized Ti is good. However, it is not known how the alloy elements influence the surface roughness, composition, hydrophilicity, and osteoconductivity of the anodized film on the Ti alloy. In this study, we investigated the effects of anodizing on the surface properties and the osteoconductivity of the anodized TNTZ alloy, focusing on the functions of the individual alloy elements. The anodized oxides of the Nb, Ta, and Zr metals were hydrophobic at all the voltages applied, in contrast to the anodized oxide of Ti. As well as pure Ti, a TiO2-based oxide film formed on TNTZ after anodizing. However, the oxide film also contained large amounts of Nb species and the molar Nb/Ti ratio in the TNTZ alloy was high, which makes the surface more hydrophobic than the anodized oxide on Ti. In vivo tests showed that the osteoconductivity of the TNTZ alloy was sensitive to both its surface roughness and hydrophilicity. When the TNTZ alloy was anodized, the process increased either the surface hydrophobicity or the surface roughness at the voltage used in this study. These changes in the surface properties did not improve its osteoconductivity.
基金This work was financially supported by the Ministry of Education,Science and Technological Development of the Republic of Serbia through Project Nos.ON174004 and ON172019the PhD fellowship of Slađana Laketić.
文摘The effects of picosecond Nd:YAG laser irradiation on chemical and morphological surface characteristics of the commercially pure titanium and Ti–13Nb–13Zr alloy in air and argon atmospheres were studied under different laser output energy values.During the interaction of laser irradiation with the investigated materials,a part of the energy was absorbed on the target surface,influencing surface modifications.Laser beam interaction with the target surface resulted in various morphological alterations,resulting in crater formation and the presence of microcracks and hydrodynamic structures.Moreover,different chemical changes were induced on the target materials’surfaces,resulting in the titanium oxide formation in the irradiation-affected area and consequently increasing the irradiation energy absorption.Given the high energy absorption at the site of interaction,the dimensions of the surface damaged area increased.Consequently,surface roughness increased.The appearance of surface oxides also led to the increased material hardness in the surface-modified area.Observed chemical and morphological changes were pronounced after laser irradiation of the Ti–13Nb–13Zr alloy surface.
基金financially supported by the National Natural Science Foundation of China(Grant No.51711530151)the Major State Research Development Program of China(Nos.2016YFB0701303 and 2016YFB0701305)
文摘In this work, the microstructure and the corresponding tensile properties of the rolled Ti-7Mo-3Nb-3Cr-3Al(Ti-7333) alloy before and after the thermal treatments were investigated. The results show that a strong α-fiber texture is developed in the rolled Ti-7333 alloy. The deformed matrix and the texture significantly induce the variant selection of β phase. The high strength of the rolled Ti-7333 alloy is attributed to the <110> texture parallel to the tensile direction and the dispersed α phase within the matrix. After the solution treatment followed by the aging treatment, the texture decreases and the microstructure consists of the equiaxed β grains, the spheroidal α_p phase and various needle-like α variants. Eventually, the alloy could achieve an optimal combination with the strength of about 1450 MPa,the ductility of about 10.5% and a considerable shear strength of about 775 MPa. This balance can be ascribed to the performance of the spheroidal α_p phase and various needle-like α_s variants. The results indicate that the Ti-7333 alloy could be a promising candidate material for the high-strength fastener.
基金supported by National Natural Science Foundation of China(51801156)Major State Research Development Program of China(2016YFB0701305)+1 种基金Natural Science Basic Research Plan in Shaanxi Province of China(2018JQ5035)the Fundamental Research Funds for the Central Universities(G2017KY0310).
文摘The compressive yielding phenomenon of titanium alloys is not as focused and sufficiently ascertain as the tensile yielding phenomenon.In the present work,the peculiar compressive yielding behavior and the different dynamic responses of three different initial microstructures(singleβ,clavateβand lamellarβ)were investigated in an attractive metastableβtitanium alloy Ti-5553 using electron microscopes/crystallographic calculation/crystal plastic finite element simulation.Results reveal that the distinct compressive yielding behavior,steep peaks of sudden drop in the initial stage(very small true strain 0.03)of stress loading have appeared in the compression stress-strain curves except for the lamellarβinitial microstructure.Dislocation slip is the essential mechanism of the initial yielding behavior.Interlaced multiple-slip bands formed in the singleβinitial microstructure during the warm deformation process.A small quantity of single slip bands was observed in the deformed clavateβinitial microstructure.The abundant varied nano/ultrafineβsprecipitates were nucleated dynamically and dispersedly in all the three deformed initial microstructures.The multiple-slip bands formation and substantial nanoscaleβsresult in the highest peak of flow stress for singleβinitial microstructure.The compressive slip bands are formed early in the elastic–plastic deformation stage.As the increasing strain,the sample showed a significant compressive bulge,or eventually forming a strong adiabatic shear band or crack.These results are expected to provide a reference for the study of deformation behavior and mechanical properties of metastableβtitanium alloys.
基金The work was financially supported by the Natural Science Foundation of Shandong Province,China(No.ZR2019MEM012)the Major Scientific and Technological Innovation Program of Shandong Province,China(No.2019JZZY010325)+1 种基金the Key Research Program of Frontier Sciences,CAS(No.QYZDJ-SSW-JSC031-02)the National Natural Science Foundation of China(No.51871220).
文摘The temperature and stress profiles of porous cubic Ti-6Al-4V titanium alloy grids by additive manufacturing via electron beam melting(EBM)based on finite element(FE)method were investigated.Three-dimensional FE models were developed to simulate the single-layer and five-layer girds under annular and lateral scanning.The results showed that the molten pool temperature in five-layer girds was higher than that in single-layer grids owing to the larger mass and higher heat capacity.More energies accumulated by the longer scanning time for annular path than lateral path led to the higher temperature and steeper temperature gradient.The thermal stress drastically fluctuated during EBM process and the residual stress decreased with the increase of powder layer where the largest stress appeared at the first layer along the build direction.The stress under lateral scanning was slightly larger but relatively more homogeneous distribution than those under annular scanning.The stress distribution showed anisotropy and the maximum Von Mises stress occurred around the central node.The stress profiles were explained by the temperature fields and grids structure.
文摘In this work, the current understanding and development of fliction-stir welding and processing of Ti- 6Al-4V alloy are briefly reviewed. The critical issues of these processes are addressed, including welding tool materials and design, tool wea,, processing temperature, material flow, processing window and residual stresses. A particular emphasis is given to microstructural aspects and microstructure-properties relationship. Potential engineering applications are highlighted.
基金financially supported by the Equipment Pre-research Fund(No.61409230408)the National Natural Science Foundation of China(No.51875350)the Program of Shanghai Excellent Academic Research Leadership(No.19XD1401900)。
文摘The effect of hydrogen addition on the deformation behavior of coarse-grained Ti-55 alloys(~20μm)was studied by uniaxial tension tests at high temperature.The elongation of hydrogenated Ti-55 titanium alloy firstly increases and then decreases with hydrogen content increasing at 8750 C.The highest elongation of 243.8%is obtained in the hydrogenated alloy with 0.1 wt%H,and the peak stress reaches a minimum value of 29.0 MPa in the hydrogenated alloy with 0.3 wt%H.Compared with that of the unhydrogenated alloy,the elongation of the hydrogenated alloy with 0.1 wt%H increases by 41.3%and its peak stress decreases by 40.6%at 875℃.Hydrogen addition can promote the transformation of β phase and the dislocation movement.Appropriate hydrogen content can evidently improve the deformation properties of coarse-grained Ti-55 titanium alloy.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFB1100103)the Science Research Project of Liaoning Province Education Department(Grant No.JDL2019023)+1 种基金the Natural Science Foundation of Liaoning Province(Grant No.2020-BS-208)the Open Project of Key Laboratory of Materials Modification by Laser,Ion and Electron Beams(Grant No.KF2006)。
文摘Titanium alloys are composed ofαandβphases and are classified as nearα,dual-phaseα+β,andβtypes.This study attempts to derive their general composition formulas within the cluster-plus-glue-atom model by interpreting Ti-6A1-4V and other popular dual-phaseα+βTi alloy s with well-established chemical compositions.Our model identifiedαmolecule-like structural unit that covers onlyαnearest-neighbor cluster along withαfew next-neighbor glue atoms,which can be represented as"[cluster](glue atoms)x".The structural units of theαandβphases in Ti-6Al-4V,α-[Al-Ti_(12)](AlTi_(2)),andβ-[Al-Ti_(14)](V2Ti),were derived first and were in an unusual unit ratio of about 2.33:1.To obtain an alloy composition formula that satisfied this unit ratio,the two clusters were treated as hard spheres of different radii and packed according to the clusterplusglueatom model.Our calculations determined that the Ti-6A1-4V alloy unit is composed of 12α-[Al-Ti_(12)](AlTi_(2))and 5β-[Al-Ti_(14)](V2Ti)units(Ti-6.05A1-3.94V wt.%),with the fractional volume of theβphase being 32.5 vol.%,which is in agreement with experimental data.Finally,we describe how the chemical formulas of theαand p phases explain the high temperature near-a alloys(such as Ti-1100,[Al-(Ti_(0.97)Zr_(0.03))_(12)](Al_(0.67)Si_(0.12)Sn_(0.18)Mo_(0.03))_(1.01)Ti_(1.99))and high-strengthβ-Ti alloys(such as Ti-5553,[Al-Ti_(14)](Al_(0.24)Fe_(0.03)Cr_(0.20)-Mo_(0.18)V0.35)_(2.45)Ti_(0.55)),respectively.
基金financially supported by the National Basic Research Program of China(No.2012CB619101)the National Natural Science Foundation of China(No.81271957)the Basic Research Project of Shenzhen,China(No. JCYJ20120616142847342)
文摘Surgical implant-associated bacterial infection is becoming a serious clinical problem. A series of copper-bearing titanium alloy, Ti-6Al-4V-xCu (x = 1, 3, 5 wt%), were fabricated in the present study in order to reduce the hazard of the bacterial infection problem by means of the strong antibacterial ability of Cu element. The metallography, X-ray diffraction, antibacterial ability, corrosion resistance and cytotoxicity of Ti-6Al-4V-xCu alloys were preliminarily studied with comparison to the commercial medical Ti-6Al-4V alloy. The Ti-6Al- 4V-xCu alloys showed obvious antibacterial abilities with good corrosion resistance and cytocompatibility, and the antibacterial role was enhanced with increasing Cu content, which has significant potential for clinical applications as surgical implant materials.
基金financially supported by the National Natural Science Foundation of China (No. 51201016)
文摘Ti-62421S (Ti-6A1-2Sn-4Zr-2Nb-lMo-0.2Si) is a novel short-time using high-temperature titanium alloy. The effects of annealing on microstructure and tensile properties of Ti-62421S alloy plate were studied through optical microscopy (OM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), and tensile tests. The results show that, with annealing tem- perature increasing, the volume fraction of primary α(αp)- phase decreases while that of transformed β(βt)-structure and secondary α (αs)-phase increases. The room-temperature strength and plasticity are insensitive to annealing temperature. However, with annealing temperature increasing, the tensile strength decreases at 550℃, while increases at 600 and 650℃ instead. It is suggested that, at 550℃, the strengthening mechanism is mainly boundary strengthening and the biggest contributor is ap-phase by providing αp/β-boundary area. Above 600 ℃, the strengthening mechanism is grain strengthening, where αs-phase strengthens the β-phase.
基金National Basic Research Program of China (2007CB613805)
文摘This article studies the phase transformation of the metastable β-Ti-A1-Mo-V-Cr-Zr alloy (Ti-1300) to disclose the morphological reason for its high strength and high fracture toughness. It has been found that its ultrahigh strength (ultimate tensile strength exceeds 1 400 MPa) owes mainly to the spheroidization of the α-phase, while the high fracture toughness (exceeds 81 MPa·m^1/2) to the special lath-shaped α-particles. Compared to the needle-shaped second α-articles, the coarser lath-shaped ones remove the stress concentration at the lath tips and consequently benefit improvement of fracture toughness. The article also describes shape evolution of the α-particles during aging thermodynamically and kinetically, and suggests an optimized aging processing to achieve an ideal balance between high strength and high toughness for this alloy.
基金The supports from the National Key Research and Development Program of China (No.2016YFB0701304)the CAS Informatization Project (No.XXH13506-304)the Doctoral Scientific Research Foundation of Liaoning Province (No.20180540133)
文摘Ti2 AlNb-based alloy powder metallurgy(PM)compacts were prepared via hot isostatic pressing(HIP)under relatively low temperature(920 and 980℃)and at certain pressure(130 MPa).The microstructure,composition and orientation of B2,α2 and O phases in the compacts were characterized and analyzed with an aim to investigate the effect of unsuitable HIPping parameters on the appearance of prior particle boundary(PPB),which seriously affects the mechanical properties of the alloy.The results show that moreα2 phase is the characteristics of the PPB in Ti2AlNb-based alloy when HIPped at relatively low temperature.Increasing HIPping temperature to the upper part of the two-phase region can effectively inhibit the formation of PPB.Electron backscatter diffraction measurements show the specific orientation relationship between phases,which helps us understand the origin of a2 and O phase and the corresponding transformation path.The HIPping at a higher temperature can weaken the micro-texture intensity of theα2 and O phase due to the increase of misorientation in B2 phase.Theα2 phase at cell wall keeps the Burgers orientation relationship(BOR)with the grain on one side,and does not satisfy the BOR with the other.It is found that some O phase variants inside the cell HIPped at 980℃can only maintainα2-O OR withα2 owing to theα2→O phase transformation forming the O phase,while these O variants deviate from B2-O OR with B2 phase.