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。     

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.     

Ti6Al4V车削刀具磨损及切削力研究

Ti6Al4V是典型的难加工材料，切削效率低、刀具磨损严重严重，因此提高Ti6Al4V的加工效率和刀具寿命是急需解决的问题。作者对硬质合金刀具加工Ti6Al4V的切削力和磨损特性进行了实验研究。对三种不同刀具在干切削状态下车削Ti6Al4V切削力进行了试验，分析了切削力与切削速度、切削路程的关系，同时讨论了主偏角对TC4车削稳定性的影响。最后，对刀具的的磨损形态和磨损机理进行了研究。粘结、扩散、氧化是硬质合金刀具的主要磨损机理。     

电弧喷涂Ti6Al4V涂层组织与耐磨损性能

采用ZPGD-400型电弧喷涂机在Q235钢基体上喷涂Ti6Al4V涂层,并借助扫描电镜(SEM)、X射线衍射仪(XRD)、显微硬度计及滑动磨损试验机对喷涂涂层的显微组织、结合状态、硬度以及磨损表面进行分析.结果表明,Ti6Al4V涂层组织呈典型的层状特征,孔隙少,涂层与基体结合紧密,涂层平均显微硬度1013 HV0.2其耐磨损性能为Q235钢的20倍,磨损机制主要为剥层磨损和粘着磨损.     

外科植入物用Ti6Al4V(ELI)合金棒材的成分、组织和力学性能

对国内外外科植入物用Ti6Al4V(ELI)合金棒材的成分、组织和力学性能进行分析、比较,发现国内产品在一定程度上与国外产品相当,但存在成分、组织和性能等方面稳定性的差异.西安赛特金属材料开发有限公司通过近几年的生产实践,探索出有效控制该合金棒材成分、组织和性能的方法,为国内医疗器械行业提供一种高品质的棒材.     

Improving tribological and corrosion resistance of Ti6Al4V alloy by hybrid microarc oxidation/enameling treatments

A promising duplex coating was prepared by microarc oxidation(MAO) and enameling processes onto polished Ti6A14V alloy. The TiO_2 ceramic coating deposited by MAO was characterized and then combined with an enameling treatment in order to improve the tribological and corrosion resistance of Ti6A14V alloy. The morphology, phase composition, and hardness of MAO and MAO/enameling-coated Ti6A14V alloy were evaluated by scanning electron microscopy(SEM), X-ray diffraction(XRD), and Vickers microhardness tester, respectively.The tribological performance was investigated using a ballon-disk tribometer. The corrosion resistance was studied using immersion tests and potentiodynamic polarization.Wear tests show that the enamel coating on the MAOcoated surface causes a reduction in the friction coefficient.Immersion tests demonstrate that the duplex coating is more effective in improving the corrosion resistance of Ti6A14V than the MAO coating especially at high temperature(80 ℃). Potentiodynamic polarization curves reveal that the corrosion potential of the duplex coating increases by about 250 mV and the corrosion current density is slightly lower than that of the MAO coating. The duplex coating is superior to the stand-alone MAO coating in improving the tribological and corrosion behavior of Ti6A14V.     

Effect of thermal oxidation on the corrosion resistance of Ti6Al4V alloy in hydrochloric and nitric acid medium

The characteristics of Ti6Al4V alloy subjected to thermal oxidation in air atmosphere at 650 °C for 48 h and its corrosion behavior in 0.1 and 4 M HCl and HNO₃ medium are addressed. When compared to the naturally formed oxide layer (～4–6 nm), a relatively thicker oxide scale (～7 µm) is formed throughout the surface of Ti6Al4V alloy after thermal oxidation. XRD pattern disclose the formation of the rutile and oxygen‐diffused titanium as the predominant phases. A significant improvement in the hardness (from 324 ± 8 to 985 ± 40 HV_0.25) is observed due to the formation of hard oxide layer on the surface followed by the presence of an oxygen diffusion zone beneath it. Electrochemical studies reveal that the thermally oxidized Ti6Al4V alloy offers a better corrosion resistance than its untreated counterpart in both HCl and HNO₃ medium. The uniform surface coverage, compactness and thickness of the oxide layer provide an effective barrier towards corrosion of the Ti6Al4V alloy. The study concludes that thermal oxidation is an effective approach to engineer the surface of Ti6Al4V alloy to increase its corrosion resistance in HCl and HNO₃ medium.     

Improving tribological properties of Ti6Al4V alloy with duplex surface treatment

Ti-doped diamond like carbon films were deposited on both untreated and plasma nitrided Ti6Al4V alloy using Closed Field Unbalanced Magnetron Sputtering (CFUMBS) method and their tribological properties were evaluated by conducting sliding wear conditions. The influence of the nitrided layer on tribological behavior of Ti-DLC films was studied by means of XRD, SEM, scratch tester, microhardness tester and pin-on-disc tribotester. The microhardness results pointed out that the duplex treatment dramatically increased the surface hardness and reduced the plastic deformation of the alloy. Wear tests showed that Ti-DLC coatings on both untreated and nitrided surfaces caused a reduction in the coefficient of friction. The reason of the reduction in the coefficient of friction was found to be the formation of transfer film between the sliding surfaces. Wear rates demonstrated that wear resistance of duplex treated (Ti-DLC coating after nitriding) Ti6Al4V alloy was significantly improved.     

Characteristics and wear performance of borided Ti6Al4V alloy

In this study, a 10 µm thick uniform boride layer, composed of TiB₂ and TiB phases, was formed on the surface of a Ti6Al4V alloy using a pack boriding technique. The hardness of the boride layer was over 2000 HV. Beneath the boride layer, a boron diffusion zone (BDZ) appeared with a thickness of about 50 µm. The microstructure of the BDZ was composed of randomly oriented TiB whiskers mixed with the structure of the base metal. In the BDZ, hardness decreased gradually towards the base metal owing to the reduction of the TiB volume fraction. The borided alloy exhibited excellent wear resistance along with a lower coefficient of friction against sapphire ball under both dry and smear lubricated sliding conditions when compared to the as-received state.     

Diffusional transformation in Ti6Al4V alloy during isothermal compression

Thermodynamic calculation of the two-phase Ti alloy was completed using CompuTherm Pandat™ and Ti data base, followed by isothermal compression of Ti6Al4V (Grade 5), with an initial colony lamellar structure that was performed in the (α+β) and β-phase field. Microstructural evolution and phase transformation were investigated using X-ray diffraction, scanning and transmission electron microscopy. The presence of the Ti₃Al or α₂ (hcp), the phase stability and transition temperatures were predicted by the Gibbs free energy−temperature and phase fraction−temperature diagrams. The isothermal compression in the (α+β)-phase field is characterized by reorientation and localized kinking of α/β lamellae, and cracking at α/β interphase regions. While in the α→β-phase transformation area, deformation in β-phase and at α/β interphase boundaries, extensive transformation of α into β-phase, martensitic transformation and spheroidization of α-laths mainly characterize this isothermal compression. A complete transformation of α into β single phase occurs in the β-phase field. Ti₃Al or α₂ (hcp), β (bcc) and α (hcp)-phase, and additional hcp α' and orthorhombic α” phases in a deformed Ti6Al4V are revealed. The flow stress level, the dynamic recovery and dynamic globularization are affected by deformation temperature.     

Ag离子注入Ti6Al4V合金抗Hank’s溶液腐蚀性能研究

采用注入不同剂量5×1016, 1×1017, 5×1017和9×1017ions/cm2,加速电压30 kV对Ti6Al4V合金进行Ag离子注入表面改性。使用动电位极化曲线研究Ag离子注入前后Ti6Al4V合金抗Hank’s溶液腐蚀性能,利用小角掠射X射线衍射技术研究Ag离子注入前后Ti6Al4V合金表面物相组成,用X射线光电子能谱技术分析离子注入合金表面和腐蚀样品表面元素存在的化合态。结果表明,Ag离子注入提高了合金抗Hank’s溶液腐蚀性能,腐蚀电流密度随Ag离子注入剂量的增加稍有变化。离子注入Ti6Al4V合金表面的氧化物腐蚀阻挡层、离子注入表面合金层和表面生成的Ag和TiAg有利于合金抗Hank’s溶液腐蚀性能的改善     

Tribocorrosion behaviour of Ti6Al4V under various normal loads in phosphate buffered saline solution

Tribocorrosion tests were conducted on Ti6Al4V against alumina in phosphate buffered saline solution under normal loads of 3−30 N (corresponding to the maximum Hertzian contact pressures of 816−1758 MPa) using a ball-on-disk tribometer. Nano-hardness measurements revealed the formation of work-hardened layers on the pure wear and tribocorrosion surfaces. As the normal load increased from 15 to 30 N during the pure wear, the surface hardness was increased by about 100%. However, a lower generation of wear debris resulted in a lower wear rate under a normal load of 30 N. The presence of corrosion caused an increase in the wear rates by 28%−245% under various normal loads. The corrosion current density acquired from polarization curves was increased by three orders of magnitude and the open circuit potential (OCP) shifted to more negative potentials during tribocorrosion compared with the stagnant condition. The successive formation and removal of tribofilms, which consisted of oxygen and phosphorous compounds, resulted in peaks in the OCP trend and lower fluctuations in coefficient of friction under normal loads higher than 3 N.     

Ti6Al4V钛合金的变形组织及织构

在温度850~930°C、应变速率0.01~1 s-1的条件下,对初始组织为等轴组织的Ti6Al4V钛合金进行变形程度为70%的热压缩变形实验,研究合金的变形组织及织构。结果表明,当温度低于900°C、应变速率高于0.1 s-1时,合金的组织主要是拉长的α晶粒;而在高于900°C以及低应变速率下,则会发生动态再结晶。电子背散射衍射（EBSD）结果显示,合金在再结晶过程中亚晶界吸收位错,最终形成大角晶界。在930°C时动态再结晶已基本完成,水冷至室温时形成针状α相。与原始组织相比,合金在930°C变形时织构得到增强,低于930°C变形时织构变弱。     

Ti6Al4V合金显微组织对超声声速的影响

通过对Ti6Al4V合金棒材在β相区、α+β两相区热处理后的显微组织观察和纵向超声声速值测量、分析,研究了合金显微组织对超声声速的影响。结果表明,Ti6Al4V合金在相变点以上加热,随着冷速的降低,次生α析出长大为粗大片层状,声速值也随之提高;在相变点以下加热,组织中的初生α相含量对超声声速值的影响不明显,次生相的形貌对超声波声速起决定作用,其中规则片层次生α 相的析出有利于超声声速值的提高。     

Ti6Al4V表面激光熔覆NiCrBSi+B4C涂层的组织结构

选用NiCrBSi及2％民C混粉在Ti6Al4V合金表面进行激光熔覆处理，使基体中的Ti和B4C发生化学反应原位生成TiC、TiB2硬质增强相，制备出TiC与TiB2等增强相增强钛基复合材料涂层。综合运用XRD、SEM、EPMA和TEM等分析手段研究了优化熔覆工艺条件下的NiCrBSi＋B4C激光熔覆层的组织结构与相组成，并对复合涂层进行了硬度测试，结果表明：NiCrBSi＋2％B4C熔覆层的微观组织是在γ—Ni和Ni3Ti＋Ni3B共晶的基体上均匀分布着TiB2、TiC、CrB等相的多元组织，激光熔覆层的硬度比Ti6Al4V基体硬度提高到3～4倍。     

Ti6Al4V合金表面热浸镀Ti-Al镀层相组成

采用热浸镀方法在Ti6Al4V合金表面制备Ti-Al镀层,并在1100 ℃高温下进行热扩散处理。结果表明,TC4合金热浸镀铝后在1100 ℃保温,形成了表面氧化层、过渡层及基体,表面氧化层和过渡层厚度随扩散时间延长而增加,表面氧化层主要由Al₂O₃和TiO₂构成,过渡层主要相为TiAl₃、Ti₂Al₅和Ti₁₉Al₆金属间化合物。     

多束流电子束焊接对Ti6Al4V钛合金薄板变形的影响

多束流电子束焊是一种能够同时产生多个电子束流作为焊接热源的电子束焊接新技术,能够有效的减小焊接应力和变形。为了减小Ti6Al4V钛合金薄板焊接变形,本文提出了一种新型的多束流电子束焊接技术,除了熔化金属的主束流外,还包括两个对称分布的辅助束流用来焊后加热。分别用传统电子束焊和多束流电子束焊对1 mm厚的Ti6Al4V钛合金薄板进行焊接试验,试验表明,通过调节两个辅助束流的位置和能量分布,多束流电子束焊能够有效减小钛合金薄板的焊接变形。     

The effect of nitric acid surface treatment on CaP deposition of Ti6Al4V open-cell foams in SBF solution

The effect of nitric acid surface treatment on CaP deposition of an open-cell Ti6Al4V foam (60% porous and 300-500 ?m in pore size), prepared by means of the space holder method using 94 and 66 μm average particle size powders, was investigated in a simulated body fluid (SBF) solution up to 14 days. Although, nitric acid surface treatment did not change the foam flat surface roughness values significantly, it increased surface area difference greatly by introducing nano scale undulations on the surface. The increased surface area difference was found to be more pronounced in smaller particle size foam samples. A continuous relatively thin CaP coating layer formed after 5 and 14 days of SBF immersion in nitric acid surface treated small and larger average particle size foam specimens, respectively. Whereas, the cells of untreated foam specimen were observed to be filled with CaP precipitates and a continuous CaP layer development was found after 14 days of SBF immersion. These results were also confirmed with the grazing incidence XRD and FTIR analysis of SBF immersed specimens.