Bonding interface characteristic and shear strength of diffusion bonded Ti-17 titanium alloy

The bonding interface characteristic and shear strength of diffusion bonded Ti-17 titanium alloy at different bonding time were investigated. The results show that the average size of voids decreases while the amount of voids decreases after increasing to the maximum value with the increasing bonding time. The irregular void with a scraggly edge tends to an ellipse void with smooth surface and then changes to a tiny void with round shape. The grains across bonding interface occur at bonding time of 60 min. The shear strength of bond increases with increasing bonding time, and the highest shear strength of bond is 887.4 MPa at 60 min. The contribution of plastic deformation on the void closure and the increase of shear strength is significant even though the action time of plastic deformation is short.

Hot compressive behavior of Ti-3.0Al-3.7Cr-2.0Fe-0.1B titanium alloy

The hot deformation behavior of Ti-3.0Al-3.7Cr-2.0Fe-0.1B (TACFB) titanium alloy was investigated using a Gleeble-1500D thermal simulator in the temperature range of 800-950 °C, at constant strain rate from 0.01 s-1 to 10 s-1 and with height reduction of 70%. Flow stress and microstructure evolution during hot compression of TACFB alloy were investigated. The processing map of TACFB alloy was obtained. The results indicate that the hot deformation behavior of TACFB alloy is sensitive to the deformation temperature and strain rate. The peak flow stress decreases with increasing the test temperature and decreasing the strain rate. The constitutive relationship of TACFB alloy was obtained on the base of Arrhenius equations. When the strain rates are higher than 1.0 s-1, the dynamic recrystallization occurs, and the higher the strain rates are, the more the recrystallization is.

Stitch welding of Ti-6Al-4V titanium alloy by fiber laser

Stitch welding of plate covered skeleton structure of Ti-6Al-4V titanium alloys has a variety of applications in aerospace vehicle manufacture. The laser stitch welding of Ti-6Al-4V titanium alloys was carried out by a 4 kW ROFIN fiber laser. Influences of laser welding parameters on the macroscopic geometry, porosity, microstructure and mechanical properties of the stitch welded seams were investigated by digital microscope, optical microscope, scanning electron microscope and universal tensile testing machine. The results showed that the three-pipe nozzle with gas flow rate larger than 5 L/min could avoid oxidization, presenting better shielding effect in comparison with the single-pipe nozzle. Porosity formation could be suppressed with the gap between plate and skeleton less than 0.1 mm, while the existing porosity can be reduced with remelting. The maximum shear strength of stitch welding joint with minimal porosity was obtained by employing laser power of 1700 W, welding speed of 1.5 m/min and defocusing distance of ＋8 ram.

Electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel with copper interlayer sheet

Electron beam welding of Ti-15-3 titanium alloy to 304 stainless steel with a copper sheet as interlayer was carried out.Microstructures of the joint were studied by optical microscopy(OM),scanning electron microscopy(SEM) and X-ray diffractometry(XRD).In addition,the mechanical properties of the joint were evaluated by tensile test and the microhardness was measured.These two alloys were successfully welded by adding copper transition layer into the weld.Solid solution with a certain thickness was located at the interfaces between weld and base metal in both sides.Regions inside the weld and near the stainless steel were characterized by solid solution of copper with TiFe2 intermetallics dispersedly distributed in it.While weld near titanium alloy contained Ti-Cu and Ti-Fe-Cu intermetallics layer,in which the hardness of weld came to the highest value.Brittle fracture occurred in the intermetallics layer when the joint was stretched.

Structure and properties of micro-arc calcium phosphate coatings on pure titanium and Ti-40Nb alloy

The microstructure, physical and mechanical, and chemical properties of micro-arc calcium phosphate （CAP） coatings deposited under different process voltages in the range of 150-400 V on the commercially pure titanium （Ti） and Ti-40%Nb （Ti-40Nb） （mass fraction） alloy were investigated by the SEM, TEM, XRD and EDX methods. The coating thickness, roughness, and sizes of structural elements were measured and showed similar linear character depending on the process voltage for the coatings on both substrates. SEM results showed the porous morphology with spherical shape structural elements and rough surface relief of the coatings. XRD and TEM studies exhibited the amorphous structure of the CaP coating. With increasing the process voltage to 300-400 V, the crystalline phases, such as CaHPO4 and β-Ca2P207, were formed onto the coatings. The annealing leads to the formation of complex poly-phase structure with crystalline phases： CaTi4（PO4）6, β-Ca2P2O7, TiP2O7, TiNb（PO4）3, TiO2, NbO2, and Nb2O5. The applied voltage and process duration in the ranges of 200-250 V and 5-10 min, respectively, revealed the coating formed on Ti and Ti-40Nb with optimal properties： thickness of 40-70μm, porosity of 20%-25%, roughness （Ra） of 2.5-5.0 μm, adhesion strength of 15-30 MPa, and Ca/P mole ratio of 0.5-0.7.

Precipitation location of secondary phase and microstructural evolution during static recrystallization of as-cast Ti-25V-15Cr-0.3Si titanium alloy

The microstructural evolution and precipitation location of the secondary phase of an as-cast Ti-25 V-15 Cr-0.3 Si titanium alloy were investigated via isothermal compression experiments and heat treatment. The average aspect（length-to-width） ratio, average area and size of the grains at different heat treatment temperatures and holding time were analyzed and the effects of deformation and annealing time on the grain area and size were considered. It was found that the grain size was strongly influenced by the height reduction and holding time. Grain growth was significant when annealing time increased from 10 min to 2 h at 950 °C and height reduction of 30%; however, grain growth was minimal at annealing time between 2 and 4 h. Many dispersion particles were observed to form in continuous chains; the precipitation location was confirmed to be along initial grain boundaries, and the dispersion particles were identified to be Ti5 Si3 phase by TEM.

Evaluation of Oxidation of Ti-Al and Ti-Al-Cr Coatings Arc-ion Plated on Ti-60 High-temperature Titanium Alloy

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.

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.

HIGH TEMPERATURE DEFORMATION MECHANISM AND CONSTITUTIVE EQUATION OF Ti-40 BUREN RESISTANT TITANIUM ALLOY

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.

Preparation and osteoinduction of active micro-arc oxidation films on Ti-3Zr-2Sn-3Mo-25Nb alloy

A layer of porous film containing Ca and P was prepared by the micro-arc oxidation method on the surface of a novel near β biomedical Ti-3Zr-2Sn-3Mo-25Nb alloy, and then NH2- active group was introduced to the films by activation treatment. The phase composition, surface micro-topography and elemental characteristics of the micro-arc oxidation films were investigated with XRD, SEM, EDS and XPS, and the osteoinduction of the micro-arc oxidation films was tested using the simulated body fluid immersion, the in-vitro osteoblast cultivation test and animal experiment. The results show that the oxide layer is a kind of porous ceramic intermixture and contains Ca and P. The films in the simulated body fluid can induce apatite formation, resulting in excellent bioactivity. The cell test discovers that osteoblasts can grow well on the surface of micro-arc oxidation films. And the Ti-3Zr-2Sn-3Mo-25Nb biomedical alloy coated with active porous calcium-phosphate films shows better osteoinduction in vivo.

Ti-1023钛合金细晶化和组织控制工艺研究

钛合金的结构特点决定了该类金属不能单纯通过热处理细化晶粒调整组织形态 ,因此适当的变形工艺成为组织控制的有效手段。Ti 10 2 3合金的性能与组织形态、晶粒度有密切关系。通过变形得到了两种典型的近 β合金组织 ,测试分析了两种组织对应的性能 ,讨论了两种工艺得到的组织的优缺点。结果表明 ,采用传统的变形工艺只能得到个别性能突出的传统组织类型 ,如网兰组织、双态组织、等轴组织等 ,同时原始β晶粒大小不均匀 ,容易造成材料性能不均匀。必须采用现代研究手段 ,控制变形温度、变形量、变形火次 ,得到综合上述 3种组织优点的某种过渡组织类型 ,保证Ti 10 2 3合金发挥高强、高韧的综合优势。

Ti-1023钛合金棒材组织和性能的研究

制备了Ti-1023合金不同规格的棒材,对比分析了其低倍、高倍组织和室温拉伸力学性能。结果表明:准100mm和准350 mm棒材低倍组织呈模糊晶,而准150 mm棒材呈半模糊晶且组织均匀性较差;前两者的横截面高倍显微组织的初生α相为细小的球形,准150 mm棒材横截面的边缘区域α相等轴化良好,靠近中心区域的短棒状α相越多,说明准150 mm棒材锻压力不足和锻造道次变形量过小而导致坯料的锻透性较差。不同规格棒材及棒材不同位置的室温拉伸力学性能测试结果表明:随着显微组织的等轴初生α相增多和尺寸减小,室温强度提高;随着棒材的规格增大其强度略有降低。

表面加工状态对Ti-1023钛合金疲劳性能的影响

通过热处理得到3种强度级别的Ti-1023合金材料。拉伸和疲劳试验结果表明，在时效温度为510--660℃的范围内，Ti-1023合金的轴向拉压疲劳极限随屈服强度的提高而提高。拉伸断口分析表明，高强度Ti-1023的断裂模式为沿晶断裂，在较低强度Ti-1023断裂模式以韧性断裂为主的韧性和沿晶断裂的混合断裂模式。疲劳断口分析则表明，在较低载荷时，时效温度对断口疲劳区域的影响较小。

Ti-1023钛合金的低周疲劳行为

研究了室温Ti-1023钛合金由应变控制的低周疲劳行为。对循环应力-应变数据和应变-疲劳寿命数据进行了分析，通过双对数线性回归处理，得出了Coffin-Mason处理模型的疲劳参数。结果表明：合金总应变幅在0．6％-0．8％时，循环初期表现出轻微的循环硬化，然后循环稳定；总应变幅超过0．8％时则表现为循环软化。表明合金的循环应力响应行为取决于外加总应变幅。

Ti-1023合金的研究现状

Ti-1023合金是一种为适应损伤容限性设计原则而生产的高结构效益、高可靠性和低制造成本的锻造钛合金。本文主要介绍了Ti-1023合金组织性能、工艺性能及应用现状。

硼对Ti-1023合金组织与性能的影响

采用真空自耗电弧炉熔炼添加硼元素的Ti-1023合金铸锭，对其进行一定的变形得到锻造棒材。利用金相显微镜、电子探针、万能材料试验机等设备对其进行宏观、微观组织及性能分析，研究硼元素对铸态与锻态Ti-1023合金组织与性能的影响。研究发现，硼元素作为一种高效的细化剂，能显著细化Ti一-1023合金的铸态组织。硼化物倾向于以链状析出，对合金进行充分变形，能使硼化物充分破碎。微量的硼可以显著提高钛合金的强度，当硼含量在0．1％～0．2％（质量分数）时，Ti-1023合金的抗拉强度与屈服强度变化不大，但是塑性下降明显。为了得到良好的强度一塑性匹配，最佳硼添加量不应大于0．1％。

Ti-1023钛合金热塑性变形行为及加工图

利用Gleeble3800热模拟试验机,在温度1123-1423 K和应变速率0.01-10 s-1的变形条件下对Ti-1023钛合金进行了等温压缩试验,并绘制了其流变应力曲线。基于热压缩数据,建立了该合金的Arrhenius双曲正弦型本构方程。根据动态材料模型理论,建立了合金在不同真应变下的热加工图。结果表明该合金的失稳区主要集中在高应变速率的区域内。最终通过Prasad判据确定了Ti-1023合金热变形时的失稳区和安全区。

Hot deformation behavior of Ti-6Al-4V-0.1Ru alloy during isothermal compression

The hot deformation behavior of Ti-6 Al-4 V-0.1 Ru titanium alloy was investigated by isothermal compression tests on a Gleeble-3500 thermal simulator over deformation temperature range of 1023-1423 K and strain rate of 0.01-10 s-1.Arrhenius-type constitutive models were developed for temperature ranges of bothα+βdual phase andβsingle phase at strain of 0.1.Afterwards,a series of material constants(including activation energy Q,material constants n,αand ln A)as polynomial functions of strain were introduced into Arrhenius-type models.Finally,the improved Arrhenius-type models in temperature field ofα+βandβphase were constructed.The results show that the improved Arrhenius-type models contribute to the calculation of Zener-Hollomon(Z)parameter,and the microstructural evolution mechanism is uncovered by combining microstructure observations with Z-parameter.Furthermore,the improved Arrhenius-type models are also helpful to improve the accuracy of finite element method(FEM)simulation in the deformation process of Ti-6 Al-4 V-0.1 Ru titanium alloy.

Hot deformation behavior of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy with acicular microstructure

The characteristics of hot deformation of an α＋β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si with acicular microstructure were studied using isothermal hot compressive tests in a strain rate range of 0.01-10 s^-1 at 860-1 100 ℃. The true stress-tree strain curves of alloy hot-compressed in the α＋β region exhibit a peak stress followed by continuous flow softening; whereas in the β region, the flow stress attains a steady-state regime. At a strain rate of 10 s^-1 and in a wide temperature range, the alloy exhibits plastic flow instability. According to the kinetic rate equation, the apparent activation energies are estimated to be about 633 kJ/mol in the α＋β region and 281 kJ/mol in the β region, respectively. The processing maps show a domain of the globularization process of a colony structure and α dynamic recrystallization in the temperature range of 860-960 ℃ with a peak efficiency of about 60%, and a domain of β dynamic recrystallization in the β region with a peak efficiency of 80%.

Thermomechanical Behavior of Ti-6Al-4V Alloy

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.