采用氢化-脱氢（HDH）钛粉和氢化钛粉制备MIMTi-6Al-4V合金

以HDH钛粉制备MIM Ti-6Al-4V合金的过程为参照,对使用氢化钛粉为原料制备P/M模压钛合金以及MIM钛合金的工艺过程进行了探索.使用HDH钛粉制备的MIM Ti-6Al-4V合金抗拉强度为819 MPa,拉伸样延伸率为7%;使用氢化钛粉制备的P/M模压Ti-6Al-4V合金拉伸样抗拉性能高于850 MPa;使用氢化钛粉为原料制备MIM Ti-6Al-4V合金,顺利实现了脱氢-脱脂过程.     

Effect of HIP Treatment on Fatigue Notch Sensitivity of Ti-6Al-4V Alloy Fabricated by Electron Beam Melting

The effect of hot isostatic pressing(HIP)treatment on the fatigue notch sensitivity of Ti-6A1-4V alloy fabricated by electron beam melting(EBM)was investigated.The results indicate that the fatigue notch sensitivity of the as-fabricated samples is much lower than that of HIPed samples.The variation of α lamella thickness and the distribution of pore defects have an effect on the fatigue strength in smooth and notched EBM Ti-6A1-4V samples,resulting in the divergence of the as-fabricated and HIPed samples on fatigue notch sensitivity.     

Effect of Hypoeutectic Boron Additions on the Grain Size and Mechanical Properties of Ti-6Al-4V Manufactured with Powder Bed Electron Beam Additive Manufacturing

In additive manufacturing, microstructural control is feasible via processing parameter alteration. However, the window for parameter variation for certain materials, such as Ti-6Al-4V, is limited, and alternative methods must be employed to customize microstructures. Grain refinement and homogenization in cast titanium alloys has been demonstrated through the addition of hypoeutectic concentrations of boron. This work explores the influence of 0.00 wt.%, 0.25 wt.%, 0.50 wt.%, and 1.0 wt.% boron additions on the microstructure and bulk mechanical properties of Ti-6Al-4V samples fabricated in an Arcam A2 electron beam melting (EBM) system with commercial processing parameters for Ti-6Al-4V. Analyses of EBM fabricated Ti-6Al-4V + B indicate that the addition of 0.25–1.0 wt.% boron progressively refines the grain structure, and it improves hardness and elastic modulus. Despite a reduction in size, the β grain structure remained columnar as a result of directional heat transfer during EBM fabrication.     

Evaluation of titanium alloy fabricated using electron beam melting system for dental applications

In recently advanced rapid prototyping and manufacturing methods, one additional process is to use an electron beam to fabricate metal objects by the layer by layer sintering and/or melting metal powder. This method is often called electron beam melting (EBM). This study examined the mechanical properties, the grindability and corrosion resistance of Ti-6Al-4V ELI (extra low interstitial) specimens which were fabricated by the electron beam melting (EBM) process. Dumbbell-shaped specimens and two kinds of plate specimens were prepared using the Ti-6Al-4V ELI powder in the EBM system. The yield strength, tensile strength, modulus of elasticity and percent elongation at a crosshead speed of 0.25 mm/min were tested. The Vickers hardness in interior structures was determined. Grindability was evaluated as volume loss (mm³) when the specimen was abraded using a SiC wheel at 1250 m/min for 1 min. Lastly, corrosion behavior was examined using the dynamic potentiostatic polarization technique in an artificial saliva at 37 °C. As controls, cast and commercial wrought alloys of Ti-6Al-4V ELI and commercially pure titanium (CP Ti) were evaluated. Cast specimens were prepared in a centrifugal casting machine using a MgO based mold. For the cast specimens, all the mechanical properties, grindability and corrosion characteristics were tested. On the other hand, for wrought specimens, only grindability and corrosion properties were tested. The yield and tensile strength of the as-fabricated Ti-6Al-4V ELI specimens without any additional metallurgical treatments were found to be 735 MPa and 775 MPa, respectively. The elongation was 2.3%. These values are well within many of precious and non-precious dental casting alloys.     

The design and production of Ti-6Al-4V ELI customized dental implants

This paper addresses the production of customized Ti-6Al-4V ELI dental implants via electron beam melting (EBM). The melting of Ti-6Al-4V ELI powder produces implants with great biocompatibility, fi ne mechanical performance, and a high bone ingrowth potential. The EBM technology is used to produce one-component dental implants that mimic the exact shape of the patient’s tooth, replacing the traditional, three-component, “screw-like” standardized dental implants currently used. The new generation of implants provides the possibility of simplifying pre-insertion procedures leading to faster healing time, and the potential of better and stronger osseointegration, specifi cally through incorporating lattice structure design.     

粉末冶金Nb-35Ti-6Al-5Cr-8V合金组织演变及其力学行为

采用粉末冶金法对不同球磨时间的Nb-35Ti-6Al-5Cr-8V合金机械合金化粉末塑变行为,热压烧结材料的微观组织结构和力学行为进行了研究。研究结果表明：塑性良好的Nb-35Ti-6Al-5Cr-8V粉末随着球磨时间增加首先变形为大尺寸的片状、后经持续的加工硬化破碎成絮状;热压烧结能够制备微观组织可控晶粒细化的Nb-35Ti-6Al-5Cr-8V合金,合金由单一的Nbss相构成,Ti、Al、Cr、V元素固溶引起Nb晶格尺寸减小0.0685 ?;随着球磨时间增加合金晶粒明显细化进而显著提高了合金的维氏硬度和室温压缩强度,其变化符合材料硬度和强度的Hall-Petch规律。粉末冶金制备Nb-35Ti-6Al-5Cr-8V合金的各项力学性能明显优于熔铸法制备合金。     

Sintering properties of Ti-6Al-4V-xMo powder prepared by addition of Mo to Ti-6Al-4V scraps and subsequent pulverization

In this study, the sintering properties of Ti-6Al-4V-xMo powder prepared by an addition of Mo to Ti-6Al-4V scraps and subsequent pulverization were investigated. As the content of Mo added to Ti-6Al-4V scraps as a β stabilizer increased, the weight ratio of the α and β stabilizers in the Ti-6Al-4V-xMo changed and the original weight ratio of 6:4 varied to 5.71:8.57 when 5 wt% xMo was added. In order to compare the difference in properties of Ti-6Al-4V-xMo ingots with sintered bodies of the Ti-6Al-4V-xMo powder, we prepared sintered bodies from Ti-6Al-4V-xMo powder with an O content of about 5000 ppm and 325 mesh size. As a result, it was found that the sintered bodies of Ti-6Al-4V-xMo powder showed different properties of density and micro hardness compared to the Ti-6Al-4V-xMo ingots. These differences can be explained by the larger specific surface area of the sintered bodies, which formed a porous oxide layer on the surface due to the increase of Mo in the β zone of the Ti-6Al-4V alloys.     

The effects of gas nitriding on fatigue behavior in titanium and titanium alloys

Fatigue behavior has been studied on gas-nitrided smooth specimens of commercial pure titanium, an alpha/beta Ti-6Al-4V alloy, and a beta Ti-15Mo-5Zr-3Al alloy under rotating bending, and the obtained results were compared with the fatigue behavior of annealed or untreated specimens. It was found that the role of the nitrided layer on fatigue behavior depended on the strength of the materials. Fatigue strength was increased by nitriding in pure titanium, while it was decreased in the Ti-6Al-4V and Ti-15Mo-5Zr-3Al alloys. Based on detailed observations of fatigue crack initiation, growth, and fracture surfaces, the improvement and the reduction in fatigue strength by nitriding in pure titanium and both alloys were primarily attributed to enhanced crack initiation resistance and to premature crack initiation of the nitrided layer, respectively.     

Ti-6Al-4V合金的超高周疲劳行为

采用超声疲劳实验分别确定了双态和网篮两种组织的Ti-6Al-4V合金的疲劳寿命(S-N)曲线,并用SEM观察疲劳断口.结果表明,两种组织合金的S-N曲线均保持下降趋势,在105-109cyc间不出现水平段,不存在传统意义的疲劳极限,断口形貌分析表明,随着应力幅的降低,二者的裂纹萌生位置都发生了由试样表面到内部的转变.与加载频率为25 Hz时的疲劳实验结果进行比较后发现,超声疲劳加载条件下,疲劳强度提高,疲劳寿命延长,且频率对网篮组织合金疲劳性能的影响大于对双态组织的影响.     

The thermomechanical processing of titanium and Ti-6Al-4V thin gage sheet and plate

A new method for producing low-cost titanium powder, the Armstrong Process, has proven to be a scalable process. The process, which reduces TiCl₄ vapor in a molten stream of sodium to produce pure titanium and NaCl, can also be used to in-situ manufacture Ti-6Al-4V alloy powder. Armstrong Process titanium and Ti-6Al-4V powders were used to produce plate by vacuum hot pressing. Also, thin gage sheet was produced by cold rolling solid-phase sintered titanium and Ti-6Al-4V powder compacts. Chemical analysis and mechanical testing revealed that processed Armstrong titanium and Ti-6Al-4V sheet and plate had compositions and properties similar to those of grade 2 titanium and grade 5 Ti-6Al-4V. For more information, contact John D.K. Rivard, Strategic Analysis, 3811 N. Fairfax Drive Suite 700, Arlington VA 22202; e-mail jrivard@sainc.com.     

Dehydrogenation of Hydrogenated Ti-6Al-4V Alloy

对未置氢及置氢Ti-6Al-4V合金进行了TG/DSC试验,研究了置氢钛合金的除氢行为。结果表明,当温度超过600℃时,置氢钛合金的失重规律与未置氢钛合金具有较大的差别。当加热温度在600~900℃之间时,置氢钛合金的失重随着氢含量的增加而增加。这是由于置氢合金中的亚稳相发生了分解。不考虑合金氧化的影响,置氢钛合金的最大失重与合金中的氢含量一致。置氢钛合金的最佳除氢温度为750℃。对于不同氢含量的置氢钛合金,其除氢工艺是相同的。     

Investigation of fatigue crack initiation in Ti-6Al-4V during tensile-tensile fatigue

Fatigue crack initiation in Ti-6Al-4V has been investigated in high cycle fatigue (HCF) and low cycle fatigue (LCF) regimes at stress ratio R=0.1 using the replication technique. In all four tested α/β microstructures, the crack was initiated by fracture of equiaxed alpha grain. Fractured alpha grains are seen on the fracture surface as flat facets with features characteristics of cleavage fracture. In the regime of low stress amplitudes and in the absence of reverse loading, cleavage fracture contributes to crack initiation and early stages of crack growth in Ti-6Al-4V. This mechanism is discussed in relation to the anomalous mean stress fatigue behavior exhibited by this alloy.     

Microstructure,Mechanical Properties,and Flatness of SEBM Ti-6Al-4V Sheet in As-Built and Hot Isostatically Pressed Conditions

Sheet (0.41–4.80 mm thick) or thin plate structures commonly exist in additively manufactured Ti-6Al-4V components for load-bearing applications. A batch of 64 Ti-6Al-4V sheet samples with dimensions of 210/180 mm × 42 mm × 3 mm have been additively manufactured by selective electron beam melting (SEBM). A comprehensive assessment was then made of their density, surface flatness, microstructure, and mechanical properties in both as-built and hot isostatically pressed conditions, including the influence of the hot isostatic pressing (HIP) temperature. In particular, standard long tensile (156 mm long, 2 mm thick) and fatigue (206 mm long, 2 mm thick) test sheet samples were used for assessment. As-built SEBM Ti-6Al-4V sheet samples with machined surfaces fully satisfied the minimum tensile property requirements for mill-annealed TIMETAL Ti-6Al-4V sheet products, whereas HIP-processed samples (2 mm thick) with machined surfaces achieved a high cycle fatigue (HCF) strength of 625 MPa (R = 0.06, 10⁷ cycles), similar to mill-annealed Ti-6Al-4V (500–700 MPa). The unflatness was limited to 0.2 mm in both the as-built and HIP-processed conditions. A range of other revealing observations was discussed for the additive manufacturing of the Ti-6Al-4V sheet structures.     

机械合金化制备纳米晶Ti-6Al-4V合金

采用机械合金化制备Ti-6Al-4V粉末。结果表明:采用机械合金化可以制备纳米晶Ti-6Al-4V合金粉,其反应机理以扩散为主,该固态反应是缺陷能和碰撞能共同作用的结果;随球磨时间延长,部分V固溶于Ti中形成置换固溶体Ti(V),球磨过程中没有中间相生成。球磨40 h后都能获得纳米晶,60 h的粉末为纳米晶和非晶的混合物,晶粒尺寸小于60 nm;60 h后晶粒尺寸变化缓慢。球磨后Ti、Al、V的原子比近似为90:6:4,与Ti-6Al-4V元素成分一致。     

Synchrotron-Based X-ray Microtomography Characterization of the Effect of Processing Variables on Porosity Formation in Laser Power-Bed Additive Manufacturing of Ti-6Al-4V

The porosity observed in additively manufactured (AM) parts is a potential concern for components intended to undergo high-cycle fatigue without post-processing to remove such defects. The morphology of pores can help identify their cause: irregularly shaped lack of fusion or key-holing pores can usually be linked to incorrect processing parameters, while spherical pores suggest trapped gas. Synchrotron-based x-ray microtomography was performed on laser powder-bed AM Ti-6Al-4V samples over a range of processing conditions to investigate the effects of processing parameters on porosity. The process mapping technique was used to control melt pool size. Tomography was also performed on the powder to measure porosity within the powder that may transfer to the parts. As observed previously in experiments with electron beam powder-bed fabrication, significant variations in porosity were found as a function of the processing parameters. A clear connection between processing parameters and resulting porosity formation mechanism was observed in that inadequate melt pool overlap resulted in lack-of-fusion pores whereas excess power density produced keyhole pores.     

The effects of hydrogen on fatigue crack growth behaviour of Ti-6Al-4V and Ti-4.5Al-3V-2Mo-2Fe alloys

The fatigue crack growth rates (FCGRs) of Ti-6Al-4V and Ti-4.5Al-3V-2Mo-2Fe alloys were determined in gaseous hydrogen, air, and a soft vacuum. In hydrogen and at a stress ratio of 0.1, the deflected crack path associated with the localized brittle fracture of the α-phase could account for the reduced FCGR of Ti-6Al-4V. At a higher stress ratio of 0.5, hydrogen embrittlement enhanced cracking and alleviated the effect of crack deflections in Ti-6Al-4V specimens, resulting in the FCGR in hydrogen similar to that in air. In contrast, the FCGR of Ti-4.5Al-3V-2Mo-2Fe was insensitive to both the environment and stress ratio.     

Ti-6Al-4V合金的轧制与组织性能

采用光学显微镜、透射电镜和拉伸试验等手段,研究了多道次两向轧制和单向轧制对不同原始状态(热轧态、水淬态和空冷态)Ti-6Al-4V合金显微组织和力学性能的影响。结果表明,热轧态Ti-6Al-4V合金的组织为片状α相+β相+少量等轴α相,水淬态Ti-6Al-4V合金形成了针状马氏体组织,空冷态Ti-6Al-4V合金形成了网状组织。Ti-6Al-4V合金适宜的两向轧制温度为700 ℃,此时合金中可见颗粒状β相弥散分布在α基体上。两向轧制Ti-6Al-4V合金的抗拉强度和屈服强度从高至低顺序为:水淬态>热轧态>空冷态,且轧向强度要高于横向;相较于单向轧制,两向轧制明显降低了Ti-6Al-4V合金板材拉伸性能的各向异性,且水淬态Ti-6Al-4V合金的轧向和横向强度差异最小,700 ℃轧制Ti-6Al-4V合金的主要细化机制为位错细化。     

两种3D打印用雾化Ti-6Al-4V粉末的对比研究

本研究分别利用水冷铜坩埚真空感应熔炼气雾化(VIGA-CC)和等离子旋转电极(PREP)两种技术制备出球形Ti-6Al-4V合金粉末,作者利用SEM、同步辐射CT扫描-三维重建和氩气含量测试等分析手段对不同粒径的Ti-6Al-4V合金粉末的孔洞缺陷和氩气含量、硬度值进行了表征。实验结果表明, VIGA-CC粉末粒度分布宽,细粉收得率较多,粉末粒度分布在40~180 μm之间, PREP粉末的粒度分布较窄,主要集中在110~180 μm之间；金属粉末内部的孔隙率、气体含量和孔尺寸随着粉末粒度的增大而增大,且同一粒径范围内VIGA-CC粉末的气孔概率多于PREP粉末；随着粉末粒径减小,粉末截面组织逐渐细化,其硬度值逐渐升高,整体上VIGA-CC粉末硬度值高于PREP粉末。     

Ambient and High-Temperature Bulk Characterization of Additively Manufactured Ti-6Al-4V Using Neutron Diffraction

Characterization of the bulk microstructure using neutron diffraction has been applied to investigate the phase fractions and textures of α- and β-phases in Ti-6Al-4V fabricated by additive manufacturing. The microstructure of a specimen cut from a fan structure, built by either electron beam melting (EBM) or selective laser melting, indicated that predominantly the build direction and not the fan angle determines the microstructure. In situ heating experiments of specimens from a rod built using EBM provided insight into the lattice strain, phase fraction, and texture evolution, providing a rich picture of the microstructure changes during heat treatment of additively manufactured Ti-6Al-4V. A remarkably low weight fraction of β-phase at lower temperatures, deviations from thermal expansion behavior attributed to vanadium repartitioning, as well as texture strengthening were observed.     

置氢Ti-6Al-4V钛合金的热压缩变形行为研究

通过热模拟压缩实验,研究了氢对Ti-6Al-4V钛合金热变形行为的影响。结果表明,置氢可以显著降低Ti-6Al-4V钛合金高温压缩时的流动应力,提高Ti-6Al-4V钛合金的热加工变形速率一个数量级以上,并且明显降低了Ti-6Al-4V钛合金的变形温度。在变形温度760℃~800℃范围内,置氢量为0.4wt%的Ti-6Al-4V钛合金的流动应力最小;在变形温度840℃~920℃范围内,置氢量0.2wt%的Ti-6Al-4V钛合金的流动应力最小。同时,置氢前后Ti-6Al-4V钛合金的变形激活能计算结果表明,置氢量为0.4wt%的Ti-6Al-4V钛合金在α+β两相区的变形激活能为208.3kJ/mol,与未置氢Ti-6Al-4V钛合金相比降低了316kJ/mol。