Texture Evaluation of α_2 Phase in Ti-25Al-10Nb-3V-1Mo Alloy Sheet

The texture evaluation of α2 phase in Ti-25Al-10Nb-3V-1Mo sheet during rolling and annealing has been investigated by means of microstructure observation and ODF analysis. From the weak initial {1010} (1210) and {0001}(1210) textures a {1210}(1010) texture and a {0001}(uvtw)fibre texture are formed after cold rolling. The {0001} (1210) texture is also strengthened simultaneously. The activation process of slip systems is discussed concerning formation of the rolling texture. Because of the disappearance of {0001} (nvtw) fibre texture the primary recrystallization process should occur and the {1210}(1010) texture forms during annealing

Ti-10Mo双相合金的吸氢性能

研究了低温(90℃以下)和高温(400—500℃)吸氢循环两种活化方法对Ti-10Mo双相合金吸氢动力学特性及吸氢后抗粉碎能力的影响。发现高温活化样品的抗破裂能力优于低温活化样品,但低温活化样品的吸氢动力学性能明显优于高温活化样品,这一现象可用样品具有不同的吸氢受控机制和相变过程来解释。

固溶处理对Ti-10Mo合金力学性能和腐蚀行为的影响

采用非自耗真空电弧炉制备了铸态Ti-10Mo(mass%)合金,分别在850、900和950℃下对该合金进行固溶处理。采用X-射线衍射仪(XRD)、光学显微镜(OM)、压缩实验及电化学测试研究了不同温度固溶处理对合金显微组织、力学性能及腐蚀性能的影响。结果表明:固溶处理后的合金的组织主要以β相和α″相为主,随着固溶温度的升高,α″相衍射峰强度逐渐降低,β相衍射峰向小角度偏移。此外,固溶处理后合金在压缩过程中均出现“双屈服”现象,塑性应变超过70%仍未断裂,表现出良好的塑性。动电位极化曲线和阻抗图谱表明,铸态与850℃固溶样品在3.5%NaCl溶液中的腐蚀电流密度(icorr)较小,耐蚀性较好。

Brazeability evaluation of Ti-Zr-Cu-Ni-Co-Mo filler for vacuum brazing TiAl-based alloy

Ti-47Al-2Nb-2Cr-0.15B(mole fraction,%)alloy was vacuum brazed with amorphous and crystalline Ti.25Zr-12.5Cu-12.5Ni-3.0Co-2.0Mo(mass fraction,%)filler alloys,and the melting,spreading and gap filling behaviors of the amorphous and crystalline filler alloys as well as the joints brazed with them were investigated in details.Results showed that the amorphous filler alloy possessed narrower melting temperature interval,lower liquidus temperature and melting active energy compared with the crystalline filler alloy,and it also exhibited better brazeability on the surface of the Ti.47Al.2Nb.2Cr.0.15B alloy.The TiAl joints brazed with crystalline and amorphous filler alloys were composed of two interfacial reaction layers and a central brazed layer.Under the same conditions,the tensile strength of the joint brazed with the amorphous filler alloy was always higher than that with the crystalline filler alloy.The maxmium tensile strength of the joint brazed at 1273 K with the amorphous filler alloy reached 254 MPa.

Effect of heat treatment processing on microstructure and tensile properties of Ti-6Al-4V-10Nb alloy

Effects of heat treatment processing on the microstructure and mechanical properties of Ti-6Al-4V-10Nb alloy were investigated. The microstructures were investigated by SEM, TEM and XRD, and the mechanical properties were evaluated by tensile tests at room and elevated temperatures. The results indicate that the lath-like and globular primary α phase, secondary α phase and β phase are obtained after forging and heat treatment processing. The size of secondary α phase is much smaller than that of primary α phase. After heat treatment, the volume fraction of primary α phase is decreased, and that of secondary α phase is increased. With the increase of solution temperature, the volume fraction of primary α phase is gradually decreased, and that of secondary α phase is obviously increased. The yield strength and tensile strength of Ti-6Al-4V-10Nb alloy are significantly enhanced with the solution temperature increasing.

Microstructure and Deformation Behavior of Ti-10V-2Fe-3Al Alloy during Hot Forming Process

The microstructure evolution and formability of Ti-10V-2Fe-3Al alloy related to the initial microstructures and processing variables were investigated during hot forming process. The experimental results show that the α-phase growth is controlled by solute diffusion during the heat treatment processes. Four different microstructures were established by combinations of several heat treatments, and Ti-10V-2Fe-3Al alloy shows excellent formability both above and below the β transus temperature. The alloy possesses low deformation resistance and active restoration mechanism during the deformation. A constitutive equation describing the hot deformation behavior of Ti-10V-2Fe-3Al alloy was obtained. Higher fl ow stress was observed for the acicular morphology of α phase in microstructures with large aspect ratios as compared with that of small aspect ratios. Due to the dynamic recovery in soft β phase, and the dynamic recrystallization and breakage of acicular α-phase, fl ow softening occurred signifi cantly during deformation. Dynamic recrystallization also occurred especially in the severely deformed regions of forged parts.

Superplasticity of a Ti-24Al-14Nb-3V-0.5Mo Intermetallic Alloy

Superplastic properties and microstructural evolution of a Ti-24Al-14Nb-3V-0.5Mo (at. pct) intermetallic alloy were studied. Optimum superplastic properties were obtained for temperatures in the interval 960℃≤5 T≤5980℃. The apparent activation energy in the superplastic regime was determined and the deformation mechanism was also discussed. Based on the studies, a curve panel with three sheets sandwich structure was fabricated successfully. The microstructures corresponding to different strain in the part were also studied.

DEFORMATION-INDUCED α2→γ TRANSFORMATION IN A HOT DEFORMED Ti-45A1-10Nb ALLOY

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.

Deformation-induced α_2/γ Interfaces in a Hot-deformed Ti-45Al-10Nb Alloy

The structure change of α2/γ interface in a Ti-45Al-10Nb alloy induced by hot deformation was investigated by conventional and high-resolution transmission eIectron microscopy. Two types of hot deformation induced special α2/γ intedeces, coherent intedeces with high density of ledges and semi-coherent α2/γ intedeces were found to be due to the absorption of mobile dislocations into the α2/γ inteface. For the misoriented semi-coherent α2/γ interfaces, the densities of dislocation ledges increase with the misoriented angle between (111)γ and (0001)α2 planes, and 1/3[111] Frank partial dislocations were involved in the dislocation ledges. Formation mechanism of these deformation-induced α2/γ interfaces was discussed to be related to the role of α2/γ interface5 adjusting the deformation as a dislocation sink absorbing the slipping dislocations in the γ phase

EFFECT OF β-FLECKS ON MECHANICAL PROPERTIES OF Ti-10V-2Fe-3Al ALLOY

Effect of β-flecks on properties of tensile elongation and low cycle.fatigue life at room tern. perature for Ti-10V-2Fe-3Al alloy has been investigated.The cracks along initial β-grain boundaries in the β-fleck region may propagate to form intergranular brittle fracture.Under alternating load,the β-fleck often becomes a fatigue origin.While under higher strain,the cracks initiate and propagate to fracture early at the original β-grain boundaries in β-fleck region and at α-grain boundaries.

Characteristics of Faigue Crack Initiation in Ti-5Al-4Sn-2Zr-1Mo-0.7Nd-0.25Si Alloy

The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue crack initiation than the matrix at lower stress.

Ti-37.5Zr-15Cu-10Ni钎焊钼的钎缝组织分析

采用Ti-37.5Zr-15Cu-10Ni非晶钎料真空钎焊钼,获得Mo/Mo钎焊接头,研究钎焊过程液态钎料与母材的相互作用.结果表明,液态Ti-37.5Zr-15Cu-10Ni钎料与钼发生扩散–溶解,即母材钼向钎料中的溶解和钎料组分向母材的扩散.随钎焊温度的升高,钼向钎料中溶解量增加,凝固后钼主要固溶在Ti基固溶体内;随钎焊温度的升高,发生钎料组分向母材晶间的扩散,当温度为900℃时,发生显著的晶间渗入现象.为得到良好的钎焊接头,避免母材过量溶解和晶间渗入的发生,Ti-37.5Zr-15Cu-10Ni钎料真空钎焊钼温度不宜高于900℃.

Ag掺杂Mo-12Si-8.5B合金在25~600℃的摩擦学行为

本文中采用放电等离子烧结法制备了Mo-12Si-8.5B和Mo-12Si-8.5B-10%Ag这2种合金,通过高温真空摩擦磨损试验仪测试了2种合金与Al_(2)O_(3)摩擦副在25~600℃间的干摩擦学性能.结果表明:与Mo-12Si-8.5B合金相比,在25~600℃区间Mo-12Si-8.5B-10%Ag合金表现出更低的摩擦系数和磨损率.在600℃时,Mo-12Si-8.5B-10%Ag合金的摩擦系数和磨损率均可达到最小值,其值分别为0.41和1.14×10^(-5)mm^(3)/(N·m),此时Mo-12Si-8.5B-10%Ag合金的干摩擦性能表现最佳,这与Mo-12Si-8.5B-10%Ag合金磨损表面的MoO_(3)、SiO_(2)和Ag_(2)MoO_(4)等润滑相的存在及Ag在25~600℃范围内起到的润滑效果有关.此外,在25~200℃区间,Mo-12Si-8.5B-10%Ag合金的磨损机制主要为黏着磨损和剥层磨损,在400~600℃范围内,则以黏着磨损和氧化磨损为主.

FEATURES OF ANNEALING MICROSTRUCTURE AND TEXTURE IN Ti－25Al－10Nb－3V－1Mo SHEET

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Microstructure refinement of a dual phase titanium alloy by severe room temperature compression

Microstructure refinement of a dual phase titanium alloy, Ti-3AI-4.5V-5Mo, by severe room temperature compression was investigated. Nanocrystalline grains were observed in the sample with 75% reduction, in which the grain sizes of a phase and β phase were approximately 50 and 100 nm. Conversely, the average thicknesses of a phase and β phase in as-received microstructure were measured to be 0.7 and 0.5 μm, respectively. TEM and XRD methods were used to analyze the microstructure and texture changes after severe deformation. Microstructure refinement was deduced to the complex interaction among slip dislocations in the a phase, the complex interaction among slip dislocations and martensites in the β phases. In addition, the interaction between the a phase and the β phase also contributed to the microstructure refinement.

Characteristics of novel Ti-10Mo-xCu alloy by powder metallurgy for potential biomedical implant applications

When biomaterials are implanted in the human body,the surfaces of the implants become favorable sites for microbial adhesion and biofilm formation,causing peri-implant infection which frequently results in the failure of prosthetics and revision surgery.Ti-Mo alloy is one of the commonly used implant materials for load-bearing bone replacement,and the prevention of infection of Ti-Mo implants is therefore crucial.In this study,bacterial inhibitory copper(Cu)was added to Ti-Mo matrix to develop a novel Ti-Mo-Cu alloy with bacterial inhibitory property.The effects of Cu content on microstructure,tensile properties,cytocompatibility,and bacterial inhibitory ability of Ti-Mo-Cu alloy were systematically investigated.Results revealed that Ti-10Mo-1Cu alloy consisted ofαandβphases,while there were a few Ti2Cu intermetallic compounds existed for Ti-10Mo-3Cu and Ti-10Mo-5Cu alloys,in addition toαandβphases.The tensile strength of Ti-10Mo-xCu alloy increased with Cu content while elongation decreased.Ti-10Mo-3Cu alloy exhibited an optimal tensile strength of 1098.1 MPa and elongation of 5.2%.Cytocompatibility study indicated that none of the Ti-10Mo-xCu alloys had a negative effect on MC3T3-E1 cell proliferation.Bacterial inhibitory rates against S.aureus and E.coli increased with the increase in Cu content of Ti-10Mo-xCu alloy,within the ranges of 20-60%and 15-50%,respectively.Taken together,this study suggests that Ti-10Mo-3Cu alloy with high strength,acceptable elongation,excellent cytocompatibility,and the bacterial inhibitory property is a promising candidate for biomedical implant applications.

Effect of shot peening on microstructure,nanocrystallization and microhardness of Ti-10V-2Fe-3Al alloy surface

Severe plastic deformation of Ti-10V-2Fe-3Al alloy in the surface region was caused by shot peening at air pressure of 0.6 MPa with processing time ranging from 1 to 45 min.The results showed that the thickness of surface deformation layer was proportio nal to the processing time,the microhardness of the shot-peened surface in creased from 280 to 385 HV,and the depth of highly hardening layers arrived at 200μm.It was worth noting that a grain size gradient from nanocrystalline on the surface toward coarse grain in the matrix was obtained during the shot peening process and the minimum grain size in the top surface after shot peening was about 100-200 nm.

Preparation and bioactive surface modification of the microwave sintered porous Ti-15Mo alloys for biomedical application

Biomedical porous Ti-15 Mo alloys were prepared by microwave sintering using ammonium hydrogen carbonate（NH4HCO3） as the space holder agent to adjust the porosity and mechanical properties. The porous Ti-15 Mo alloys are dominated by β-Ti phase with a little α-Ti phase, and the proportion of α and β phase has no significant difference as the NH4HCO3 content increases. The porosities and the average pore sizes of the porous Ti-15 Mo alloys increase with increase of the contents of NH4HCO3, while all of the compressive strength, elastic modulus and bending strength decrease. However, the compressive strength, bending strength and the elastic modulus are higher or close to those of natural bone. The surface of the porous Ti-15 Mo alloy was further modified by hydrothermal treatment, after which Na2Ti6O13 layers with needle and flake-like clusters were formed on the outer and inner surface of the porous Ti-15 Mo alloy. The hydrothermally treated porous Ti-15 Mo alloy is completely covered by the Ca-deficient apatite layers after immersed in SBF solution for 14 d, indicating that it possesses high apatiteforming ability and bioactivity. These results demonstrate that the hydrothermally treated microwave sintered porous Ti-15 Mo alloys could be a promising candidate as the bone implant.

Synergistic antibacterial photocatalytic and photothermal properties over bowl-shaped TiO_(2)nanostructures on Ti-19Zr-10Nb-1Fe alloy

As implant substitutes are increasingly applied to the clinic,the infection caused by implants has become one of the most common complications,and the modification of the antibacterial function of the implant can reduce such complications.In this work,a well-defined bowl-shaped nanostructure coating with photocatalytic and photothermal synergistic antibacterial properties was prepared on Ti-19Zr-10Nb-1Fe(TZNF)alloy.The coating is obtained by spin-coating and sintering TiO_(2)precursors templated from self-assembled microspheres of polystyrenepoly(4-vinylpyridine)(PS-P4VP)amphiphilic block polymer on TZNF alloy.PS-P4VP provides the bowl-shaped TiO_(2)nanostructures doped with C,N elements,reducing the band-gap of TiO_(2),which can absorb near-infrared(NIR)light to release reactive oxygen species and produce photothermal conversion.The bowl structure is expected to enhance the utilization of light via the reflection in the confined space.The bowl-shaped surface has 100%antibacterial rates after 30 min of NIR light irradiation.In addition to antibacterial properties,the bowl-shaped surface has better hydrophilicity and protein adsorption capacity.The amount of protein adsorbed on TZNF with the bowl-shaped structures was six times that of TZNF.Hence,the bowl-shaped nanostructure can promote the proliferation and adhesion of osteoblasts,the cell proliferation rate was increased by 10–30%.

Effect of stress ratio on very high cycle fatigue properties of Ti-10V-2Fe-3Al alloy with duplex microstructure

In fatigue critical applications, Ti-10V-2Fe-3Al alloy components are expected to endure cyclic loading with cycles above 109. To assess their operating safety, S-N relations of Ti-10V-2Fe-3Al alloy in very high cycle fatigue （VHCF） regime are of concern and have been investigated in this work. Fatigue behavior including S-N curves and crack initiation mechanisms is reported. Two transitions of fatigue crack initi- ation mechanism, from internal crack initiation to surface crack initiation and from αp cleavage to αS/β decohesion, occur when the stress ratio （R） and stress level are reduced. Fatigue limits exist at Nr = 6×10^7 cycles for all stress ratios except for 0.5. In the VHCF regime two kinds of internal crack initiation mechanisms exist, i.e., coalescence of cluster of αp facets and αS/β decohesion. Their mutual competition depends on the stress ratio and can be interpreted in terms of different stress character required for promotion on different internal crack initiation mechanism. Small crack propagation is discussed to be life controlling process under the stress ratio range from -0.5 to 0.1 during VHCF regime while under the stress ratio 0.5 VHCF, life almost refers to the life required for crack initiation.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.