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。     

Fretting wear of micro-arc oxidation coating prepared on Ti6Al4V alloy

Micro-arc oxidation(MAO)coating was prepared on Ti6Al4V alloy surface and its characterizations were detected by Vickers hardness tester,profilometer,scanning electric microscope(SEM),energy dispersive X-ray spectrometer(EDX)and X-ray diffractometer(XRD).Fretting wear behaviors of the coating and its substrate were comparatively tested without lubrication under varied displacement amplitudes(D)in a range of 3-40μm,constant normal load(Fn)of 300 N and frequency of 5 Hz.The results showed that the MAO coating,presenting rough and porous surface and high hardness,mainly consisted of rutile and anatase TiO2 phases.Compared with the substrate,the MAO coating could shift the mixed fretting regime(MFR)and slip regime(SR)to a direction of smaller displacement amplitude.In the partial slip regime(PSR),lower friction coefficients and slight damage appeared due to the coordination of elastic deformation of contact zones.In the MFR,the friction coefficient of the coating was lower than that of the substrate as a result of the prevention of plastic deformation by the hard ceramic surface.With the increase of the displacement amplitude,the degradation of the MAO coating and the substrate increased extremely.The fretting wear mechanisms of the coating were abrasive wear and delamination with some material transfer of specimen.In addition,the coating presented a better property for alleviating fretting wear.     

Ti6Al4V合金表面激光熔覆钛基复合涂层的显微组织研究

在Ti6Al4V合金表面预置Ti和Cr3C2混合粉末,采用横流CO2激光进行熔覆试验,制备出了原位自生的TiC颗粒增强的钛基复合涂层.利用SEM、XRD等手段对激光熔覆层的组织、成分、物相进行了分析,测试了激光熔覆层的显微硬度.结果表明,熔覆层不同位置,组织形态不同,TiC在熔覆层表层以树枝晶形态存在,而在熔覆层底部为近球状颗粒.熔覆层与基材之间形成良好的冶金结合.熔覆层显微硬度在600～800 HV0.5之间,约为基材硬度的2～3倍.     

Ti6Al4V合金激光熔覆Ni基自润滑涂层的组织和性能

利用光纤激光器在Ti6Al4V合金基体表面制备了Ni25为基体和Ni包MoS2为润滑剂的Ni基自润滑涂层,通过FESEM、XRD、硬度测试仪和摩擦磨损试验机研究了熔覆层的显微组织、物相组成和摩擦性能.结果表明,熔覆层表面主要以花瓣状组织以及少量的树枝晶组成,界面处的组织主要是以树枝晶为主,还有少量的等轴晶粒.熔覆层...     

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。     

Surface characterization of plasma sprayed pure and reinforced hydroxyapatite coating on Ti6Al4V alloy

Hydroxyapatite coatings suffer from poor mechanical properties like fretting fatigue, toughness and abrasive wear resistance. These properties can be enhanced by incorporation of secondary ceramic and metallic reinforcements in HA. An attempt has been made to deposit HA and HA reinforced with 10 wt.% (80Al₂O₃-20TiO₂) by plasma spray process on Ti6Al4V substrate. These coatings have been characterized using SEM/EDAX, XRD and FTIR spectroscopy. Corrosion studies have been done in SBF solution. Bio compatibility study is not included in this work. Reinforcement has enhanced the tensile strength. There is marginal improvement in microhardness and surface roughness with reinforcement. Both pure and reinforced coatings show superior resistance against corrosion in simulated body fluid.     

生物医用Ti6Al4V合金表面Nb涂层的耐磨性和耐腐蚀性

为了提高生物医用Ti6Al4V合金的耐磨性和耐腐性能,采用双辉光等离子体表面冶金技术在其表面制备了均匀致密的Nb涂层.结果表明:Nb涂层主要由Nb和金属间化合物AlNbTi2和AlNb2组成.相比Ti6Al4V基材,Nb涂层的显微硬度是其的2倍,Nb涂层的平均摩擦系数和磨损率分别下降了 14％和95.4％,Nb涂层的主要的磨损机制为粘着磨损.Nb涂层的腐蚀电位(Ecorr)和极化电阻(Rp)较高,腐蚀电流密度(Icorr)较低,表明具有优良的耐腐蚀性,且具有Nb涂层的Ti6A14V合金的孔隙率仅为3.1％,大大降低了侵蚀性介质与基材接触的可能性.     

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。     

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.     

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.     

Formation of adherent polypyrrole coatings on Ti and Ti–6Al–4V alloy

Highly adherent polypyrrole coatings were electrodeposited at etched Ti and Ti–6Al–4V from 0.2 M oxalic acid and 0.2 M pyrrole at a constant applied potential of 0.8 V versus SCE. The substrates were etched in an alkaline peroxide solution at ambient temperature for a 10 min period prior to the electropolymerization reactions. Chemical etching of the substrate gave rise to an increase in the hydrophilicity of the surface, the formation of a micro-etched surface and the formation of a semiconducting titanium oxide film. There was a considerable increase in the density of nucleation sites for polypyrrole growth at the micro-etched surface. Growth of the polypyrrole proceeded slowly from a high number of nucleation sites at the etched surface to give rise to a highly adherent polypyrrole coating. Adhesion of the polypyrrole coating was attributed to micro-etching of the substrate and the conductivity of the oxide film generated during the chemical etching process.     

Pressure–composition isotherms and reversible hydrogen-induced phase transformations in Ti–6Al–4V

Reversible stepwise phase transformations induced by the addition and removal of hydrogen in pure Ti and Ti–6Al–4V (Ti64) were examined by means of pressure–composition (P–C) isotherm measurement from 550 to 700 °C. Both Ti–H and Ti64–H systems exhibit two pressure plateaus in the P–C isotherms which indicate phase transformations. Phase transformations take place at lower hydrogen content and higher hydrogen pressure in Ti64 than in Ti due to the effect of substitutional elements Al and V. Upon hydrogenation, the Ti–H system exhibits the sequence of phase transformation α ↔ α_H ↔ α_H + β_H ↔ β_H ↔ β_H + δ ↔ δ, whereas the Ti64–H system shows a sequence of α + β ↔ α_H + β_H ↔ β_H ↔ β_H + δ ↔ δ because of the presence of the original β phase. Partial phase diagrams for Ti–H and Ti64–H were established based on their P–C isotherms. Modification of microstructure of Ti64 occurs after cyclic hydrogenation. This can be ascribed to hydrogen-induced atomic migration during the sequential phase transformations.     

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.     

石墨添加剂对Ti6Al4V合金微弧氧化陶瓷层性能的影响

在硅酸盐体系电解液中,采用微弧氧化技术在钛合金表面制备含C元素陶瓷层,通过扫描电镜、能谱、显微硬度计、粗糙度仪及摩擦磨损试验机检测分析了陶瓷层的性能,并对电解液进行了电导率测量。结果表明,石墨会增强电解液的导电率,降低了微弧氧化过程中的起弧电压,制备的陶瓷层孔洞细小,均匀分布;并且发现石墨进入了陶瓷层,提高了膜层表面硬度及耐磨性。     

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。     

置氢质量分数0.15%Ti6Al4V合金扩散连接

采用真空扩散连接技术对置氢质量分数0.15%Ti6Al4V合金进行了焊接.利用扫描电镜、电子探针、X射线衍射分析手段研究了置氢质量分数0.15%Ti6Al4V合金母材焊接前后的相组成、接头界面结构及连接工艺参数对界面扩散孔隙的影响.结果表明,焊前母材组织为长条状α 片层状(α βH),焊后母材组织为等轴α 粗片层状(α β) β相上α'马氏体,在扩散连接过程中,α相中V元素扩散到βH相中,βH相中Al元素扩散到α相中.随着连接温度的升高,连接时间的延长和连接压力的增大,界面的扩散孔隙逐渐减少,当连接温度达到850 ℃,压力为12 MPa,连接时间为60 min时,扩散孔隙消失,接头抗剪强度高达543 MPa.     

氟化物ATIG焊接Ti6Al4V的焊缝成形和组织

试验选用MF型氟盐(LiF,NaF,KF)、MF2型氟盐(MgF2,CaF2,BaF2)和KN型钾盐(KF,KCl,KBr)对Ti6Al4V进行ATIG焊接,焊后研究了焊缝的成形、熔深和组织.结果表明,除MgF2焊道成形稍有曲折外,其它活性剂ATIG焊接接头均成形良好、无缺陷;氟化物能起到阻止熔池金属氧化的作用;KF和MF2型氟盐可显著减小焊缝熔宽;同阳离子的氟化物相比其氯化物和溴化物可显著增加Ti6Al4V焊缝熔深;MF型氟盐中KF活性剂获得的焊缝熔深最大,MF2型氟盐中MgF2活性剂获得的焊缝熔深最大,且熔深MgF2>KF;TIG和ATIG的焊缝组织均为粗大的柱状晶,活性剂ATIG焊可细化焊缝晶粒尺寸,但不会对焊缝的相结构组成造成影响.     

Antifouling properties of micro arc oxidation coatings containing Cu2O/ZnO nanoparticles on Ti6Al4V

Micro arc oxidation (MAO), as a new special surface treatment method, has been introduced to the marine antifouling field for titanium alloys because of the anatase and rutile TiO₂ with antibacterial effects obtained during the oxidation process. Despite this, metallic oxide antifouling additives have been added into MAO coatings to improve the antibacterial and antifouling abilities of titanium alloy. In this study, MAO coatings containing nanometer particles were obtained by adding nano Cu₂O and nano ZnO into the electrolyte. Structure, morphology, phase constitution and chemical composition of the MAO coating film were studied by SEM, XRD and EDS. The antibacterial properties of the film were evaluated by exposing the specimens to Escherichia coli and comparing the Ti-MAO and Ti-bared controls. The results showed that the MAO process on Ti6Al4V has an outstanding antibacterial property which can be further enhanced by nano Cu₂O and nano ZnO. The Ti-MAO–Cu₂O group had the best antibacterial ability. These findings indicate that by means of this process adding nanometer metallic oxide into an MAO coating film via an electrolyte is useful for enhancing the antibacterial and antifouling abilities of titanium.     

Ti6Al4V合金表面离子铌合金化及其耐磨性能研究

采用双辉离子渗技术对Ti6Al4V钛合金表面渗Nb,利用扫描电子显微镜、X射线衍射仪、显微硬度计、磨损试验机、电化学测试系统研究钛合金表面离子渗Nb合金化层的形态、结构、力学性能、摩擦学性能和电化学腐蚀性能,并探讨渗Nb改性处理对钛合金在3.5%NaCl溶液中腐蚀磨损行为的影响.结果表明,渗Nb工艺参数对合金化层的形态、结构和性能影响显著,高浓度渗Nb合金化改性层表现出良好的强化效果,显著地改善了Ti6Al4V合金的抗大气环境和抗NaCl溶液腐蚀磨损性能.Ti6Al4V合金基材和渗Nb层的耐磨性能在NaCl溶液中优于大气环境,其原因归于溶液的润滑作用和试样的良好耐腐蚀性能.