Optimum Design of Processing Parameters during ISM Process of Ti-47Ni-9Nb

［1］D.J.Chronister, S.W.Scott and D.R.Stickle: JOM.,1986, 38(9), 51. ［2］J.W.Sears: JOM., 1990, 42(3), 17. ［3］H.B.Bomberger and F.H.Froes: JOM., 1984, 36(12),39. ［4］B.C.Weber, W.M.Thompson and H.O.Bielstein: J. Am. Cer. Soc., 1957, 40(11), 363. ［5］G.H.Chippereit: JOM., 1961, 13(2), 140.     

SiC纤维增强Ti基复合材料的组织

采用真空热压扩散结合工艺制备出ＳｉＣｆ／Ｔｉ－１５－３复合板材，研究制备工艺，ＳｉＣｆ，基体合金特性，复合材料的显微组织及界面特征，结果表明，合适条件下国产射频加热ＣＶＤ法制备的ＳｉＣｆ与Ｔｉ－１５－３基体具有较好的相容性，界面结合良好，在拉伸条件下ＳｉＣｆ有从基体拔出的倾向，纤维具有脆性解理断口特 ，Ｔｉ－１５－３基体具有塑性断口特征。     

Ti－15－3钛合金的应用研究

研究了冷加工对Ｔｉ－１５－３合金时效性能的影响，并研究了该合金的冷成形性能及零件制造工艺，为Ｔｉ－１５－３高强钛合金钣金零件的应用提供了经验。     

Estimation of residual stresses in SiC/Ti-15-3 composites and their relaxation during a fatigue test

Residual stresses induced by cooling down from the elaboration process in SiC/Ti-15-3 composite were calculated by the finite element model using MARC and MENTAT software. An analytical model (derived from those of Eshelby and of Mikata and Taya) already used for ceramic matrix composites has also been used in this study for elementary composites. The influence of uncertainty on thermomechanical properties and also the influence of fibre packing and spacing were also studied. Then, evolution (relaxation) of the thermal residual stresses (TRS) during a fatigue test were investigated. Results show that the TRS decreased rapidly during the first cycles and then became almost constant at about one-third of their initial values. This revised version was published online in November 2006 with corrections to the Cover Date.     

Improved mechanical properties of Ti–15V–3Cr–3Sn–3Al alloy by electron beam welding process plus heat treatments and its microstructure evolution

Electron beam welding (EBW) and related heat treatments were carried out on Ti–15V–3Cr–3Sn–3Al (Ti-15-3) alloy plate materials. It was found that the operated parameters in the present EBW process together with suitable heat treatments significantly enhanced the mechanical properties as well as the elongations of the Ti-15-3 weldment, which may provide a promising way for further industrial application. Furthermore, the observed nano size phase of β, α, and here first reported TiCr₂ particle, may form from the solid solution matrix of the Ti-15-3 alloy. The possible mechanisms for these phase formation are discussed.     

Investigation of the Interaction of Sodium Chloride and Two Amino Sulfonic Acids,HEPES and MOPSO,by EMF Measurements

Ionic interactions in the two systems NaCl-HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid) and NaCl-MOPSO (3-(N-Morpholino)-2-hydroxypropanesulfonic acid) have been studied in terms of their mutual influence on the respective activity coefficients of each component. Activity coefficients for each component of the two systems and for corresponding buffers are calculated from emf measurements of solutions containing NaCl, the aminosulfonic acid, and its conjugate base in a NalSE/solution/AgCl-Ag cell at 5, 15, 25, and 37 °C.     

Fatigue behaviour of duplex metal coated SiC fibre reinforced Ti-15-3 matrix composites

Abstract

Duplex metal (Cu/Mo and Cu/W) coated SiC(SCS–6) fibre reinforced Ti-15-3 matrix composites have been prepared using a hot isostatic pressing process. The effect of the duplex metal coatings on the fatigue behaviour of unnotched SiC(SCS–6) fibre reinforced Ti-15-3 matrix composite has been studied. The fatigue resistance of this fibre reinforced composite is improved by use of the duplex metal coatings. The Cu/Mo and Cu/W duplex metal coating layers prevent debonding of the SCS coating layer from the SiC fibre surface, thus also effectively preventing a reduction in strength of the fibre. During the fatigue test, fibre bridging behind the matrix crack tip reduces the crack growth rate of the matrix; this mechanism is difficult to achieve with the pristine fibre composite. Evolution of the fatigue damage can be quantitatively evaluated by means of a fatigue damage parameter. Matrix crack propagation is the dominant factor responsible for the increase in damage parameter of the composites.     

Activity Interaction Coefficients of Si in Cu-Ti-Si Melts at 1550℃

Activitibs of Si in binary Cu-Si and ternary Cu-Ti-Si melts were measured at 1 550℃ by using a method of chemical equilIbrium between gas and liquid. The activity interaction coefficients of Si in the melts have been determined from the experimental data (lny = -5.69. s = 6.69. P2: = -26.22. E; =-43.96) and activity interaction coefficients of Ti in binary Cu-Ti melt at 1550℃ has been estimated from Sommer's data based on the regular solution model (lny =-1 .10. : = 2.95.p:=-2.10).     

Prediction and Simulation of Microstructure of Ti-15-3 Alloy

Ti-15-3 alloy is a new metastableβ-type titanium. The influence of hot deformation parameters on the microstructureof Ti-15-3 alloy after solution treatment has been studied by isothermal compression tests as well as quantitativemetallographic analysis.     

Phenomena of nanotube nucleation and growth on new ternary titanium alloys

Ti-30Nb-xZr and Ti-30Ta-xNb alloys have been investigated using various methods of surface nanotube formation. Ternary Ti-30Nb-xZr (x = 3 and 15 wt%) and Ti-30Ta-xNb (x = 3 and 15 wt%) alloys were prepared by using high-purity sponge Ti (Grade 4, G&S Titanium, USA), Ta, Zr and Nb spheres. The two groups of ternary Ti alloys were prepared using a vacuum arc melting furnace. Nanotube formation was carried out with a conventional three-electrode configuration with the Ti alloy specimen, a platinum counterelectrode, and a saturated calomel (SCE) reference electrode. Experiments were performed in 1 M H3PO4 with small additions of NaF (0.1-0.8 wt%), using a potentiostat. Nanotubes formed on the surfaces of the two ternary Ti alloys were examined by field emission scanning electron microscopy, EDS and XRD. The Ti-30Ta-xZr alloys had microstructure with entirely needle-like constituents; the thickness of the needle-like alpha-phase increased as the Zr content increased. The Ti-30Nb-xZr alloys had equiaxed microstructures of the beta-phase, and increasing amounts of the needle-like alpha phase appeared at the grain boundaries of the beta-phase as the Zr content increased. The nanotubes were nucleated and grew mainly on the beta phase for the Ti-30Ta-3Zr and Ti-30Nb-3Zr alloys, which had nanotubes with uniform shape, but the nanotubes were nucleated at the alpha phase for the Ti-30Ta-15Zr and Ti-30Nb-15Zr alloys, which had nanotubes with irregular shape and diameters of two sizes. The diameter and depth of the nanotubes could be controlled, depending upon the alloy composition and composition of the surface oxide films (TiO2, Nb2O5, Ta2O5, and ZrO2). It is concluded that this research that selection of the appropriate alloying element can allow significant control of the nanotopography of these Ti alloy surfaces and that it is possible to control the surface nanotube size to promote long-term osseointegration for clinical dental or orthopedic use.     

Fractographic interpretation of failure mechanisms in titanium matrix composites

Titanium matrix composites (TMC) offer a combination of good mechanical properties and high temperature durability that make them attractive candidate materials for advanced engine components and high temperature structural applications. In such applications the material will be subjected to changing mechanical loads and temperature fluctuations, resulting in complex stress states within the constituents of the composite. This study examines how the various loading conditions on the TMCs are reflected in the fracture behaviour to gain insight into the damage mechanisms active in these materials. A fractographic study was conducted on several different TMC specimens, fabricated from Ti-15-3 and Timetal 21S alloys and SCS-6 fibres, that have been subjected to various thermomechanical loading conditions. The analysis showed that the Ti-15-3 composites were more susceptible to damage during sustained load at elevated temperature than the Timetal 21S composites. For both materials, striations only appear during elevated temperature fatigue when the residual processing stresses are relieved. During the Generic Hypersonic Flight Profile (GHFP) tests, the higher temperatures of the Mission 1 profile induce more damage in the Timetal 21S composites. The striations appear in the composites containing centre holes, unlike the unnotched specimens, indicating that the combined effect of stress concentration due to the hole and an underdeveloped fibre bridging zone may have resulted in crack closure.     

Forming Mechanism of Gaseous Defect in Ti-48A1-2Cr-2Nb Exhaust Valves Formed with Permanent Mold Centrifugal Casting Method

A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48AI-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathematical model of the filling process is established and the forming mechanism of internal gaseous defect is summarized. The results of calculation show that the melt fills the mould with varying cross-section area and inclined angle. The filling speed of the cross-section is a function of filling time. The cross-section area is directly proportional to the filling speed and the inclined angle is inversely proportional to the filling speed at a given rotating speed of the platform. Both of them changes more obvious near the mould entrance.The gaseous defect can be formed in several ways and the centrifugal field has an important influence on the formation of the defect. In addition, the filling process in centrifugal field has been verified by wax experiments and the theoretical analysis are consistent with experimental results.     

Superconducting properties of Ti-Nb-Hf alloys

To achieve improvements in superconducting properties of the Ti-Nb superconductor, effects of ternary additions of Hf have been extensively studied on 42 Ti-Nb-Hf alloys with compositions of 25 - 65at%Nb, 0- 15at%Hf and the balance Ti. Critical temperatures are found to depend upon Hf addition and aging temperature. In as-rolled Ti-40at%Nb-3at%Hf alloy the critical temperature is raised by about 0.3K over Ti- 40at%Nb alloy. Aging at 800°C can raise critical temperatures of high Hf alloys by 0.6 - 1.8K. The upper critical field at 4.2K of as-rolled Ti-40at%Nb-3at%Hf reaches 11.7 tesla, a value higher by 0.4 tesla than that of Ti-40at%Nb. High field critical current densities are also improved by the 3at%Hf addition. 2 step aging treatment is found effective in enhancing critical current densities of high Hf alloys. No degradation in fabricability is caused by a few at% Hf additions.     

Forming mechanism of gaseous defect in Ti-48Al-2Cr-2Nb exhaust valves formed with permanent mold centrifugal casting method

A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48Al-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathematical model of the filling process is established and the forming mechanism of internal gaseous defect is summarized. The results of calculation show that the melt fills the mould with varying cross-section area and inclined angle. The filling speed of the cross-section is a function of filling time. The cross-section area is directly proportional to the filling speed and the inclined angle is inversely proportional to the filling speed at a given rotating speed of the platform. Both of them changes more obvious near the mould entrance. The gaseous defect can be formed in several ways and the centrifugal field has an important influence on the formation of the defect. In addition, the filling process in centrifugal field has been verified by wax experiments and the theoretical analysis are consistent with experimental results.     

Influence of 0.2 wt-%C on the aging response of Ti-15-3

Abstract

The effect of aging time and temperature on the microstructure and mechanical properties of Ti-15-3 (Ti – 3Cr – 3Sn – 3Al) with and without carbon addition has been studied. It has been found that carbon addition has a significant effect on the age hardenability and microstructural stability at higher aging temperatures in Ti-15-3, whereas it has a smaller effect at lower aging temperatures, where precipitation of α appears to influence precipitation of ω. The presence of carbides in Ti-15-3 accelerates the precipitation and inhibits the growth of α phase. The gettering of oxygen by the Ti₂C precipitates reduces the tendency of grain boundary α precipitation and improves the homogeneity of α precipitation. The significance of these observations is discussed in terms of the effect of the microstructural changes in quenched and aged samples associated with the presence of Ti₂C precipitates.     

Ti－15－3合金的性能数据

研究了可冷成形的Ｔｉ－１５－３高强钛合金两种时效制度的全面力学性能，为该合金的扩大应用提供了依据。     

Fabrication of low-cost Ti-1Al-8V-5Fe by powder metallurgy with TiH2 and FeV80 alloy

The low-cost Ti-1Al-8V-5Fe (Ti-185) alloy with a high strength is prepared by cold-compaction-and-sintering powder metallurgy process with low-cost titanium hydride (TiH₂) powders and FeV₈₀ master alloy powders. The use of simple technique process and cheap alloying elements can lead to the cost reduction for titanium alloys. The thermal decomposition of TiH₂-1Al-8V-5Fe is analyzed by thermal gravimetric analyses and differential scanning calorimetry simultaneous thermal analyzer. The shrinkage behavior of TiH₂-1Al-8V-5Fe during the sintering process is employed by the high-sensitivity dilatometer system. The microstructure of sintered Ti-185 consists of β-phase and lamellar α-phase. The results show that the sintered Ti-185 alloys have the relative density of 97.8%, homogeneous composition, and fine grains. The yield strength and the hardness are 1461?MPa and 40.1?±?1.0 HRC (unit of Rockwell hardness), which are better than that of as-cast Ti-185.     

Ti－15－3合金管材的试制及组织性能研究

本文介绍了Ｔｉ－１５－３合金管材的加工工艺及工艺性能，研究了热处理条件对其性能的影响，并分析观察了不同状态下的组织特征。实验中还利用Ｘ射线衍射方法对Ｔｉ－１５－３合金管材的织构类型进行了确定。     

Ti153合金ISM熔炼过程中氮元素的溶解与控制

建立了氮元素溶解到Ｔｉ１５３合金熔体中的热力学模型,并以此计算了氮在Ｔｉ１５３合金熔体中的溶解度,分析了ＩＳＭ熔炼过程中影响氮元素在Ｔｉ１５３合金熔体中溶解的几个因素。结果表明,熔体温度对Ｔｉ１５３合金熔体中氮的溶解度影响较大,而熔化室内氮气分压是决定Ｔｉ１５３合金熔体中氮溶解度的主要因素,需要合理控制,并提出了利用多次抽真空反充氩气以降低熔化室内氮气分压的方法,来进一步降低Ｔｉ１５３合金窝熔体中     

XPS characterization of surface modified titanium alloys for use as biomaterials

Three different Ti alloys of biomedical interest have been studied by means of X-ray photoelectron spectroscopy (XPS) to determine their surface chemical composition in both as-received condition and after oxidation at 750 °C in air for different times. Compositions of the investigated alloys were, in wt.%, Ti-7Nb-6Al, Ti-13Nb-13Zr and Ti-15Zr-4Nb. XPS analyses showed a behaviour of the Ti-7Nb-6Al alloy different from that of the two TiNbZr alloys, evidencing the role of the chemical composition of the alloys on the oxidation mechanisms. The oxidation process generates an aluminium-oxide rich surface on the Ti-7Nb-6Al, while in the case of the TiNbZr alloys a titanium-oxide rich layer is formed. The effect of the heat treatment on the contribution of the minority elements at the surface is also discussed.