Ti6Al7Nb和Ti6Al4V合金的热氧化行为

在600～900℃温度下,0.5～72 h时间范围内空气气氛下对Ti6Al7Nb进行热氧化,根据增重曲线计算其氧化动力学规律,利用XRD、XPS分析表面氧化层的相组成、成分和价态,并以Ti6Al4V合金做为比照.结果表明,Ti6Al7Nb合金较Ti6Al4V合金抗氧化能力更强.同等氧化条件下,Ti6Al7Nb合金的氧化速率常数(k)更小.对短时间(1 h)氧化的样品的表面分析显示:各合金元素均以最高价态或稳定价态存在,其中Al和V被富集,而Nb则贫化;另外,Ti6Al7Nb合金和Ti6Al4V合金氧化层主要由金红石型TiO2(R-TiO2)组成,Al2O3相仅出现在900 ℃Ti6Al4V合金样品中.     

Laser welding of Ti6Al4V titanium alloys

The high strength to weight ratio and excellent corrosion resistance of titanium alloys allow diverse application in various fields including the medical and aerospace industry. Several techniques have been considered to achieve reliable welds with minimum distortion for the fabrication of components in these industries. Of these techniques, laser welding can provide a significant benefit for the welding of titanium alloys because of its precision and rapid processing capability. For pulse mode Nd:YAG laser welding, pulse shape, energy, duration, repetition rate and peak power are the most important parameters that influence directly or synergistically the quality of pulsed seam welds. In this study, experimental work involved examination of the welding parameters for joining a 3-mm thick titanium alloy using the Lumonics JK760TR Nd:YAG pulsed laser. It has been determined that the ratio between the pulse energy and pulse duration is the most important parameter in defining the penetration depth. Also it has been observed the variation of pulse duration at constant peak power has no influence on the penetration depth. Consequently, to increase the penetration depth during welding, the role of the laser parameters such as pulse energy and duration and peak power have been investigated to join 3 mm thick Ti6Al4V.     

Ti6Al4V合金吸氢行为研究

研究了Ti6Al4V合金在不同置氢温度、保温时间和氢压下的吸氢行为,利用光学显微镜研究了氢在钛合金中的分布规律。研究结果表明,Ti6Al4V合金的氢含量是由置氢温度、保温时间和氢压来控制的。随着置氢温度的升高,氢含量先增加后降低。随着氢压的增加,氢含量直线增加。钛合金的吸氢过程实质上是氢的扩散过程,随着保温时间的增加,合金中的氢分布逐渐趋于一致。     

Machinability of titanium alloys (Ti6Al4V and Ti555.3)

Near-beta titanium alloys like Ti555.3 are increasingly being used in aeronautics replacing in some critical applications the most common Ti6Al4V. However, these near-beta titanium alloys have a poor machinability rating which needs to be overcome so as to maintain at least the same productivity levels as in Ti6Al4V.This paper presents the machinability results carried out for Ti555.3 compared with the commonly used Ti6Al4V. The aim of this research work is to understand tool wear mechanisms when machining Ti555.3. Analysis of variables such as cutting forces, chip geometry and tool wear shows that: (I) greater difficulty is encounterd when machining Ti555.3 alloy compared with Ti6Al4V alloy which can be machined at higher speeds up to 90 m min^?1; (II) there was a correlation between the mechanical properties of work material, tool wear, and component forces; (III) the occurrence of the diffusion process leads to the formation of a layer of adhered material composed of Ti and TiC on the tool's rake face for both Ti alloys.     

真空热处理对多孔Ti6Al4V拉伸和疲劳性能的影响研究

本研究采用钛网层叠扩散连接法制备多孔Ti-6Al-4V合金,通过780℃/2h,FC;950℃ /2h,FC;950℃/2h,FC+540 /4h,FC三种不同真空热处理方法,获得具有不同显微组织的多孔Ti6Al4V合金。研究了孔壁显微组织对合金力学性能的影响。研究结果表明：多孔Ti-6Al-4V合金的弹性模量、抗拉强度可分别在9.5~12.2GPa和360~505MPa范围内调整,并获得在R=-1,f=10Hz,N=5×10₆循环载荷条件下疲劳强度水平为40~80MPa。另外发现,热处理工艺对抗拉强度的影响程度远大于对弹性模量的影响。     

Plasma nitriding behavior of Ti6Al4V orthopedic alloy

The influence of plasma nitriding on mechanical, corrosion and tribological properties of Ti6Al4V has been investigated using X-ray diffraction, microhardness tester, scanning electron microscopy, pin-on-disc tribotester, electrochemical polarization and impedance spectroscopy. Plasma nitriding treatment of Ti6Al4V has been performed in 25%Ar-75%N₂ gas mixture, for treatment times of 1-4 h at the temperatures of 650-750 °C. The corrosion tests were carried out in Ringer solution at 37 °C, and the wear tests were performed in dry sliding conditions. XRD analyses confirm the formation of δ-TiN and tetragonal ?-Ti₂N phases in the modified layer. It was observed that the surface hardness and wear resistance increase as the treatment time and temperature increase. The electrochemical impedance measurements indicate a decrease in double layer capacitance value and increase in charge transfer resistance for the nitrided specimens compared to the untreated ones.     

新型网状增强体分布的原位自生TiB_w/Ti6Al4V复合材料的热变形行为(英文)

通过原位自生反应热压法制备出TiB晶须增强Ti6Al4V(TC4)合金基复合材料(TiBw/Ti64)。通过热压缩实验研究这种新型复合材料的高温变形行为,变形温度区间为900~1100°C,变形应变速率区间为0.001~10s1。结果显示,该复合材料的流变应力随变形温度的升高与应变速率的降低而降低。当应变速率达到10s1时,出现了非连续屈服与流变失稳现象,特别是在β相区变形时,这种现象更加明显。根据应力—应变曲线上获得的峰值流变应力,分别获得了α+β双相区与单一β相区的流变应力方程。根据流变应力方程,获得了α+β双相区塑性变形激活能为822.3kJ/mol,单一β相区塑性变形激活能为209.4kJ/mol。增强体网状组织结构与基体组织结构变形形态较大程度上取决于变形区域与变形参数。     

水基凝胶注Ti-6Al-4V合金坯体

将凝胶注模工艺应用于金属Ti6Al4V合金粉末的成形,研究了高固相含量的Ti6Al4V合金粉末的料浆的制备,比较了金属浆料与陶瓷浆料的不同。结果表明粉末的颗粒形状是影响浆料固相含量的重要因素,浆料的固相含量随分散剂的增加而增加。最后制备出了固相含量为54%(体积分数,下同)的钛合金粉末浆料和形状复杂的坯体。坯体的抗弯强度随气雾化(GA)Ti6Al4V含量增加先增大后减小,随着坯体的固相含量增大而减小。当GA-Ti6Al4V含量为80%,固相含量为50%时生坯抗弯强度最大,为18.5 MPa。     

Ti/Al/Mg/Al/Ti层合板变形行为及断裂形式的原位研究

为阐明Ti/Al/Mg/Al/Ti层合板的变形行为及断裂形式,对轧制态和退火态的层合板进行原位弯曲和拉伸试验,研究组元板和金属间化合物的裂纹萌生和扩展情况.结果表明:无论Al/Mg界面有无金属间化合物,Al/Mg界面分层都是最先出现的断裂形式,因此Al/Mg界面结合强度决定层合板的力学性能.在退火态层合板中,金属间化合...     

Infrared brazing of Ti–6Al–4V using two silver-based braze alloys

Infrared brazing of Ti–6Al–4V using two silver-based alloys is evaluated in the study. For the 72Ag–28Cu brazed specimen, Ag-rich matrix, eutectic Ag–Cu and Cu–Ti interfacial reaction layer(s) are observed in the experiment. In contrast, both Ag-rich matrix and interfacial titanium aluminides, TiAl or Ti₃Al, are found in the 95Ag–5Al brazed joint. In general, the shear strength of 72Ag–28Cu brazed joint is much higher than that of 95Ag–5Al brazed specimen. Additionally, the use of infrared brazing with lower brazing temperature and/or less time can significantly decrease both dissolution of the substrate into molten braze as well as excessive growth of the interfacial reaction layer(s) in the joint. Therefore, infrared brazing has the potential to be applied in industry.     

Electrochemical behavior of the Ti6Al4V alloy implanted by nitrogen PIII

Plasma surface treatments have been used very often to enhance the surface properties of metallic materials. In this work, Ti6Al4V titanium alloy was treated by nitrogen plasma immersion ion implantation (NPIII) in order to obtain improvements in its surface properties, such as corrosion resistance evaluated here. The microstructure and corrosion behavior of the implanted and unimplanted samples were evaluated, using, XRD, GDOES and potentiodynamic polarization and impedance electrochemical spectroscopy tests in 0.6 M NaCl solution. It was verified that the NPIII created resistant layers to corrosive attacks. In corrosion tests by polarization, the implanted samples showed corrosion current density reduction of about 10 times compared to the Ti6Al4V alloy without treatment. Besides that, it was also observed a reduction of the passive current density of one order of the magnitude. In all the studied cases, the polarization curves were shifted to more positive values of potentials, indicating a lower tendency of these PIII treated surfaces to corrosion. The implantation process produced a thin TiN surface layer followed by Ti₂N and then a layer with nitrogen in solid solution, all detected by GDOES combined with X-ray diffraction. These layers promoted an excellent polarization resistance of the Ti6Al4V surfaces on impedance spectroscopy tests also. This better performance in these tests can be correlated with the formation of continuous nitride layer, which could retard chloride ions ingress into the substrate.     

模拟体液中纯钛及Ti6A14V合金的腐蚀行为

采用电化学测试技术研究了人体医用金属材料工业纯钛和Ti6A14V合金在人工模拟体液中的腐蚀行为,结果表明,阳极极化后两种合金均未发现点蚀,工业纯钛的维钝电流密度小于于Ti6A14V合金,前者的阳极极化性能优于后者,Ti6A14V合金缝隙试样在阳极电位超过＋2000mV(vsSCE)后,电流开始急剧增大,发生了缝隙腐蚀;通过电子探针分析发现,在缝隙内Al和V两种元素发生活性溶解。工业纯钛在电位达到＋4000mV/(vsSCE）时仍没有发生缝隙腐蚀。     

原位自生(TiC+TiB)/Ti6Al4V复合材料摩擦磨损性能研究

本文用原位反应法制备了不同TiC和TiB增强相含量的(TiC+TiB)/Ti6Al4V复合材料(简记为TMC),用HT-1000型摩擦磨损试验机研究了外加载荷对原位本文用原位反应法制备了不同TiC和TiB增强相含量的（TiC+TiB）/Ti6Al4V复合材料（简记为TMC）,用HT-1000型摩擦磨损试验机研究了外加载荷对原位（TiC+TiB）/Ti6Al4V复合材料干滑动摩擦磨损性能的影响,并利用扫描电镜及布鲁克三维形貌仪观察分析其磨损行为。结果显示,与Ti6Al4V基体相比,TiC+TiB增强相的生成提高了复合材料的耐磨性。对于含不同体积分数增强相的复合材料,随着外加载荷的增加,材料的磨损率和磨损深度增加,摩擦系数减小且在小范围内波动。在小负载下,磨损的表面覆盖有一些沟槽和少量磨屑;在大负载下,磨损的表面覆盖有一些浅沟槽和大量磨屑。磨损机制为磨粒磨损和氧化磨损。随着负荷增加,碎屑的尺寸增加,磨损加剧。     

Superplastic deformation mechanism in powder metallurgy magnesium alloys and composites

The parametric dependencies for superplastic flow in powder metallurgy (PM) magnesium alloys and composites were characterized so as to elucidate the deformation mechanism. The mechanism was proposed to be slip accommodated grain boundary sliding. However, the PM alloys and composites were strengthened at low temperatures below ∼550K. This was different from the case in ingot metallurgy (IM) magnesium alloys, that behaved identically over a wide range of temperatures. The critical strain rate, below which the effect of intragranular particle is lost, was developed by considering the dislocation–particle interaction during slip accommodation process. It was suggested that the diffusional relaxation around the intragranular oxide particles was not completed during the slip accommodation process at low temperatures, and this caused the dislocation pile-up at the intragranular particles. It was expected that the dislocation pile-up at the intragranular particles would contribute to the strengthening at low temperatures in PM alloys and PM composites.     

Creep behavior of ingot and powder metallurgy 6061Al

The creep behavior of 6061Al alloy obtained by ingot metallurgy and powder metallurgy, IM and PM, respectively, has been investigated in the context of published studies on this alloy. The behavior of the IM alloy in a given range of temperatures where the β, Mg₂Si, precipitates are formed, is dominated by dislocation climb-controlled creep and aluminum self-diffusion as rate controlling process. A dependence of the β inter-particle distance, λ, with the applied stress, σ, of the form is found when the creep data are analyzed in the context of the sub-structure invariant model. The superior creep resistance of the PM material can be explained if a threshold stress, σ₀, is brought into the creep equation. This term is the difference between the applied stresses needed to reach a given strain rate in the PM and the IM alloys, and correlates well with a particle–dislocation interaction mechanism according to the Artz–Wilkinson model.     

Wear behavior of Ti6Al4V biomedical alloys processed by selective laser melting,hot pressing and conventional casting

The aim of this work was to study the influence of the processing route on the microstructural constituents, hardness and tribological (wear and friction) behavior of Ti6Al4V biomedical alloy. In this sense, three different processing routes were studied: conventional casting, hot pressing and selective laser melting. A comprehensive metallurgical, mechanical and tribological characterization was performed by X-ray diffraction analysis, Vickers hardness tests and reciprocating ball-on-plate wear tests of Ti6Al4V/Al₂O₃ sliding pairs. The results showed a great influence of the processing route on the microstructural constituents and consequent differences on hardness and wear performance. The highest hardness and wear resistance were obtained for Ti6Al4V alloy produced by selective laser melting, due to a markedly different cooling rate that leads to significantly different microstructure when compared to hot pressing and casting. This study assesses and confirms that selective laser melting is potential to produce customized Ti6Al4V implants with improved wear performance.     

Effect of synovial fluid temperature on the corrosion resistance of Ti6Al4V,Ti6Al7Nb,and CoCrMo alloys

The frictional heat generated during the operation of the joint prosthesis in vivo could change the corrosion resistance of the prosthesis material. In this paper, the corrosion behavior of three medical alloys at different synovial fluid temperatures was analyzed using electrochemical measurement technology. Furthermore, the scanning electron microscope and energy-dispersive spectrometer were used to characterize the surface morphology and composition of the alloys after long-term immersion. The results show that increasing temperature causes the open-circuit potential of titanium alloy to shift negatively and the corrosion tendency to increase. The increasing temperature leads to the decrease of activation energy of titanium alloy, which in turn results in the increase of corrosion current density and accelerated corrosion. The results of Nyquist curves confirmed that the radius of the capacitive arc decreased with the increase of temperature, indicating the deterioration of corrosion resistance. The CoCrMo alloy shows the same regularity as the titanium alloy in 0.9% NaCl, though no obvious regularity in 25% newborn bovine serum; this may be related to the complexity of the corrosion system.     

The high-temperature deformation and tensile ductility of Al alloys

Tensile ductilities consistently in excess of 100 percent are produced at elevated temperatures in aluminum solid-solution alloys containing magnesium. The alloys that produce such enhanced ductility include commercially available 5XXX-series alloys and course-to fine-grained Al-Mg alloys. Eric M. Taleff earned his Ph.D. in mechanical engineering at Stanford University in 1995. He is currently an assistant professor of mechanical engineering at the University of Texas at Austin. Dr. Taleff is a member of TMS. Peter J. Nevland earned his B.S. in mechanical engineering at the University of Texas at Austin in 1997. He is currently an M.S. candidate in materials science and engineering at the University of Texas at Austin. Mr. Nevland is a student member of TMS.     

Microstructure and corrosion of Pd-modified Ti alloys produced by powder metallurgy

A method for the fabrication of titanium alloy parts with enhanced corrosion resistance by a powder metallurgy route is presented in this paper. Commercial purity titanium powders modified with Pd have been hot isostatically pressed (HIPped) and the microstructure and distribution of the noble metal characterised by optical and scanning electron microscopy. The electrochemistry of the HIPped alloy has been assessed and the effect of powder size fraction evaluated. Results show that the phase composition and electrochemistry of the HIPped Pd-modified alloy is equivalent to that of wrought grade 7 Ti.