退火工艺对大形变冷轧Ti-35Nb-9Zr-6Mo-4Sn医用钛合金组织和力学性能的影响

以新型医用钛合金Ti-35Nb-9Zr-6Mo-4Sn为对象，研究了该合金经固溶处理、85％冷变形和再结晶退火后的组织和力学性能。研究表明：该合金经固溶处理和85％冷变形后均由单-的β相构成。冷变形使合金强度显著上升，弹性模量降低，伸长率略有下降。经650℃再结晶退火后，合金仍由单一的β相构成，晶粒显著细化。随着退火时间的延长，缺陷减少，再结晶比例增高，合金的强度略有降低，弹性模量有所升高，塑性显著改善。形变率为85％的Ti-35Nb-9Zr-6Mo-4Sn合金经650℃退火30～60min后，合金的强度和伸长率显著优于Ti-6A1—4V，综合力学性能优异，适合作为医用种植材料。

Ti-35Nb合金中原子占位对β→ω相变的影响

利用第一性原理计算了Ti-35Nb(质量分数,%)合金的广义层错能,并讨论了合金中Nb原子占位对β→ω相变的影响。结果表明:在β相中沿{112}<111>滑移系开动会引起β→ω相变,形成ω相和孪晶相间隔的"三明治"结构,包含最近邻Nb原子链的{112}<111>滑移系的临界剪切应力约是2126.46 MPa,应力诱发的ω相最小尺寸约是长2.6444 nm,厚1.1297 nm;而包含次近邻Nb原子链的{112}<111>滑移系的临界剪切应力约是180.21 MPa,ω相最小尺寸约是长1.304 nm,厚0.3766 nm,较容易开动。

Microstructure and mechanical properties of cast Ti-47Al-2Cr-2Nb alloy melted in various crucibles

The main factors limiting the mass production of TiAl-based components are the high reactivity of TiAl-based alloys with the crucible or mould at high temperature.In this work,various crucibles (e.g.CaO,Y2O3 ceramic crucibles and water-cooled copper crucible) were used to fabricate the Ti-47Al-2Cr-2Nb alloy in a vacuum induction furnace.The effects of crucible materials and melting parameters on the microstructure and mechanical properties of the alloy were analyzed by means of microstructure observation,chemical analysis,tensile test and fracture surface observation.The possibilities of melting TiAl alloys in crucibles made of CaO and Y2O3 refractory materials were also discussed.

ON THE BURN RESISTANCE OF Ti-35V-15Cr-0.05C TITANIUM ALLOY

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.

Effects of solution time on microstructure and mechanical properties of Ti-22Al-24Nb alloy

In this research, the changing rules of billet forged Ti-22 Al-24 Nb alloy with various solution time were studied, and the mechanical properties of different microstructure were tested at the room temperature. The results indicate that the(α2+O+B2) three-phase microstructure with equiaxed grains was acquired by Ti-22 Al-24 Nb alloy billet forging, and the average size of the grains was about 300 μm. With the increase of solution time, the primary lath-shaped O phase began to dissolve, and then the equiaxial α2 phase started to dissolve, but the undissolved α2/O phase began to be equiaxial and grow. The grains of original B2 phase recrystallized and grew. After the 2 h solution treatment, the recrystallization of grains was completed basically and the average size of the grains was about 100 μm. After the 2.5 h solution treatment, the strength of the alloy decreased, and the plasticity increased. However, when the solution treatment increased to 3 h, the plasticity decreased but the strength increased. The optimal solution parameters of Ti-22 Al-24 Nb alloy were the holding time of 2 h, the solution temperature of 1 000 ?C, and water cooling. Excellent comprehensive mechanical properties can be accquired under these parameters. The tensile strength, the yield strength, the elasticity modulus, the elongation, and the section shrinkage were 950 MPa, 915 MPa, 90 GPa, 15.69% and 42.28%, respectively.

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

Ti-35Nb合金冷轧变形微观组织研究

本文研究了Ti-35Nb-2Ta-3Zr-O(Ti-35Nb)合金不同变形量下,微观组织特征。研究结果表明:Ti-35Nb合金随着冷轧变形量的增大,晶粒逐渐向RD方向拉长,并当变形量足够大时出现了剪切带几乎与轧制方向平行,剪切带延长并围绕变形拉长晶粒缠绕更加复杂;在bccβ相Ti-35Nb合金冷轧变形过程中其他取向晶粒绕特定的转轴逐渐转向较稳定的{001}和{111}面织构。

Impact of Microstructural and Surface Modifications on the Ti-45Nb Alloy’s Response to Bio-Environment

The Ti-45Nb (mass%) alloy’s corrosive and biocompatible response in simulated physiological conditions was investigated before and after its additional high-pressure torsion (HPT) and laser irradiation processing. The grain size reduction from 2.76 µm to ~ 200 nm and the appearance of laser-induced morphologically altered and highly oxidized surface led to the significant improvement of alloy corrosion resistance and cell–implant interaction. Moreover, an additional increase of the laser pulse energy from 5 to 15 mJ during the alloy irradiation in the air led to an increase in the surface oxygen content from 13.64 to 23.89% accompanied by an increase of excellent cell viability from 127.18 to 134.42%. As a result of the controlled alloy microstructural and surface modifications, the formation of protective bi-modal mixed Ti- and Nb-oxide external scale was enabled. The presence of this surface oxide scale enhanced the alloy’s resistance to corrosion deterioration and simultaneously boosted cell viability and proliferation.

Plasma Spray Deposition of HA-TiO2 on β-phase Ti-35Nb-7Ta-5Zr Alloy for Hip Stem: Characterization of Bio-mechanical Properties, Wettability, and Wear Resistance

In this work,a biomimetic coating of hydroxyapatite(HA)-and titania(TiO2)was deposited on low elastic β-phase Ti-35Nb-7Ta-5Zr(β-TNTZ)alloy by plasma spray deposition technique for orthopedic applications.The effect of TiO2 reinforcement on microstructure,mechanical properties,and bioactivity was investigated.The morphology,coating thickness,elemental composition,and phase composition of the developed coatings were characterized.The biomechanical behavior of the deposited coatings was investigated in terms of surface hardness,elastic modulus,and adhesion strength.It was found from the morphological investigation that the TiO2 reinforcement improves the microstructure and prevents the formation of defects in the coating.The biomimetic HA-TiO2 coated surface possessed pores,size ranging from 200 nm-600 nm that benefits the apatite growth and osseointegration.The EDS spectrum,mapping,and XRD analysis show that the deposited layerβ-TCP,CaO,TTCP,TiO2 phases.The HA-TiO2 coating exhibits a very dense and thick layer of 100μm-125am that exhibits excellent adhesion strength to offer mechanical interlocking to prevent delamination.The alloying of TiO2 improves the hardness from 1.67 GPa to 2.95 GPa that enhances the wear resistance.It was found that HA-TiO2 coating exhibits better hydrophilic and biocompatible surface as compared to HA-coating.

Ti-35Zr-10Nb合金板材的固溶处理与力学性能

Ti-35Zr-10Nb为一种β合金元素含量较高的钛合金,其固溶处理制度是决定产品性能的重要因素。本文研究了该合金板材在600～850℃不同温度固溶处理和不同冷却速度下固溶处理后的力学性能,得出了该合金的固溶处理制度与力学性能关系。研究表明该合金固溶处理700～800℃保温,冷却采用水冷将会获得较好的塑性。

Hot deformation behavior and process parameters optimization of Ti-6Al-7Nb alloy using constitutive modeling and 3D processing map

The isothermal compression test for Ti-6Al-7Nb alloy was conducted by using Gleeble-3800 thermal simulator.The hot deformation behavior of Ti-6Al-7Nb alloy was investigated in the deformation temperature ranges of 940-1030℃and the strain rate ranges of 0.001-10 s^(-1).Meanwhile,the activation energy of thermal deformation was computed.The results show that the flow stress of Ti-6Al-7Nb alloy increases with increasing the strain rate and decreasing the deformation temperature.The activation energy of thermal deformation for Ti-6Al-7Nb alloy is much greater than that for self-diffusion ofα-Ti andβ-Ti.Considering the influence of strain on flow stress,the strain-compensated Arrhenius constitutive model of Ti-6Al-7Nb alloy was established.The error analysis shows that the model has higher accuracy,and the correlation coefficient r and average absolute relative error are 0.9879 and 4.11%,respectively.The processing map(PM)of Ti-6Al-7Nb alloy was constructed by the dynamic materials model and Prasad instability criterion.According to PM and microstructural observation,it is found that the main form of instability zone is local flow,and the deformation mechanisms of the stable zone are mainly superplasticity and dynamic recrystallization.The optimal processing parameters of Ti-6Al-7Nb alloy are determined as follows:960-995℃/0.01-0.18 s^(-1)and 1000-1030℃/0.001-0.01 s^(-1).

Quantitative analysis on microstructure evolution of Ti-6Al-2Zr-2Sn-2Mo-1.5Cr-2Nb alloy during isothermal compression

Isothermal compression tests of Ti-6Al-2Zr-2Sn-2Mo-1.5Cr-2Nb alloy were conducted at a Gleeble-1500 simulator in deformation temperature range of 1103–1243K, strain rate range of 0.01–5.00 s-1and height reduction range of 50 %–70 %. The effects of processing parameters on morphology, grain size and contents of a and b phases were discussed based on the quantitative microstructure examination, and the detailed explanation was shown. The results show that b transformed matrix will obviously grow up at higher deformation temperature or lower strain rate because of low grain growth activation energies. The content of a phase will decrease at higher deformation temperature or higher strain rate due to the phase transformation. Some elongated a or b grains exist at higher strain rate, implying that the dominant softening mechanism is dynamic recovery. The effect of height reduction on b transformed matrix is negligible, but the height reduction has some effects on the morphology of primary a phase.

Mechanism and morphology evolution of the O phase transformation in Ti-22Al-25Nb alloy

The phase transformation and microstructure in Ti-22Al-25Nb alloy are extremely complex.In this work,the morphology evolution of the O phase during the heating and cooling process was investigated by electron backscatter diffraction(EBSD)and first-principles calculations.The results show that the O→α_(2)phase transformation process during the heating process is as follows:spheroidization of the O phase occurs first,then theα_(2)phase nucleates in the spheroidized O phase,grows and replaces the O phase,completing the O→α_(2)phase transformation.In the meanwhile,the diffusion of Nb from Nb-poor O to Nb-rich B2 phases is a back-diffusion process.According to first-principles calculations,the driving force of the O→α_(2)phase transformation is the difference in the free energies of formation for the two phases(0.09 eV/atom).When the Nb content is greater than 15.625%,the lattice distortion of theα_(2)phase sharply increases,and the distortion energy drives the back-diffusion of Nb.During the cooling process,theα_(2)→O phase transformation is difficult and slow due to the difficult diffusion of Nb from the B2 toα_(2)phases.When holding for 60 min at 960℃,the coarseα_(2)phase gradually transforms to the O phase from the margin to the inside,forming a dispersed mixed structure of the O andα_(2)phases.During the B2→O transformation,the nucleation of the O phase induces a high stress region,in the range of approximately 200 nm.

Mechanobiologically optimized Ti-35Nb-2Ta-3Zr improves load transduction and enhances bone remodeling in tilted dental implant therapy

The tilted implant with immediate function is increasingly used in clinical dental therapy for edentulous and partially edentulous patients with excessive bone resorption and the anatomic limitations in the alveolar ridge.However,peri-implant cervical bone loss can be caused by the stress shielding effect.Herein,inspired by the concept of“materiobiology”,the mechanical characteristics of materials were considered along with bone biology for tilted implant design.In this study,a novel Ti-35Nb-2Ta-3Zr alloy(TNTZ)implant with low elastic modulus,high strength and favorable biocompatibility was developed.Then the human alveolar bone environment was mimicked in goat and finite element(FE)models to investigate the mechanical property and the related peri-implant bone remodeling of TNTZ compared to commonly used Ti-6Al-4V(TC4)in tilted implantation under loading condition.Next,a layer-by-layer quantitative correlation of the FE and X-ray Microscopy(XRM)analysis suggested that the TNTZ implant present better mechanobiological characteristics including improved load transduction and increased bone area in the tilted implantation model compared to TC4 implant,especially in the upper 1/3 region of peri-implant bone that is“lower stress”.Finally,combining the static and dynamic parameters of bone,it was further verified that TNTZ enhanced bone remodeling in“lower stress”upper 1/3 region.This study demonstrates that TNTZ is a mechanobiological optimized tilted implant material that enhances load transduction and bone remodeling.

Effects of Nb content in Ti–Ni–Nb brazing alloys on the microstructure and mechanical properties of Ti–22Al–25Nb alloy brazed joints

Vacuum brazing was successfully used to join Ti-22Al-25Nb alloy using Ti-Ni-Nb brazing alloys prepared by arc-melting. The influence of Nb content in the Ti-Ni-Nb brazing alloys on the interfacial microstructure and mechanical properties of the brazed joints was investigated. The results showed that the interfacial microstructure of brazed joint consisted of B2, O, ？3, and Ti2 Ni phase, while the width of brazing seams varied at different Nb contents. The room temperature shear strength reached359 MPa when the joints were brazed with eutectic Ti40Ni40Nb20 alloy at 1180？C for 20 min, and it was321, 308 and 256 MPa at 500, 650 and 800？C, respectively. Cracks primarily initiated and propagated in ？3compounds, and partially traversed B2＋O region. Moreover, the fracture surface displayed typical ductile dimples when cracks propagated through B2＋O region, which was favorable for the mechanical properties of the brazed joint.