Titanium Base Metal Research Articles

The effect of vacuum brazing time on the microstructure and mechanical properties of Ti-6Al-4 V to 316 L dissimilar joint using BNi-2 filler metal

Due to the distinct differences in physical and metallurgical properties, it is hard to join titanium alloys to stainless steels directly via conventional welding processes. In this research, the grade 5 titanium alloy was subjected to brazing with austenitic stainless steel through the vacuum furnace, and the process was conducted above the β transition temperature (BTT). In order to reduce brittle intermetallic formation, a nickel base filler metal (Ni-6.6Cr-4.5Si-3B) was employed under a vacuum condition, and the effect of time on the microstructure and mechanical properties of the joints was investigated. The brazing temperature led to the thickening of the interface to 400 µm, toward the titanium alloy, and the FeTi formed adjacent to the diffusion affected zone (DAZ). Moreover, the isothermal solidified zone (ISZ) widened during the whole process, which, led to higher dissolution of the titanium base metal in the ISZ. Because of the widening of the interfaces, there were no Ni-rich compounds or residual filler metal in this region. SEM result showed that TiB strengthening borides, which were distributed after 45 min, and this evolution caused an increase in the shear strength of the joint up to 67 MPa. Fractography analyses and XRD results of the fractured surfaces revealed that the Ti2Ni phase, which formed in the athermaly solidified zone (ASZ) during a two-step solidification reaction, caused the brittle fracture in all joints.

High-Strength Dissimilar Welds Between a NiTi Shape Memory Alloy and Titanium Obtained by Intermixing Niobium Using Pulsed Laser Beam Welding

Joining of NiTi shape memory alloys with commercially pure titanium (Ti) is of great interest for manifold industrial applications. However, dissimilar fusion welding of these materials is associated with the formation of extremely brittle intermetallic compounds, e.g., Ti2Ni and TiNi3, which drastically limit the mechanical properties of NiTi/Ti joints. The present investigation seeks to improve both chemical compatibility and mechanical performance through intermixing of a niobium foil as filler material into a NiTi/Nb/Ti butt-joint configuration by means of pulsed laser beam welding. Different pulse durations are applied to tailor intermixing and evaluate the deviating chemical compositions of the weld metal. It is demonstrated that intermixing of niobium significantly increases the weldability of the material combination NiTi/Ti compared to autogenous welding. However, the proportion of intermixed filler material exerts a substantial impact on the microstructural evolution and mechanical properties. Ultimate tensile strengths of up to 679 MPa with fracture occurring in the titanium base metal at an elongation at break of 18.7 pct is obtained by a reduction of the pulse duration, which represents a major improvement over previous studies focusing on fusion welding of NiTi to titanium and its alloys.

Dissimilar tungsten inert gas welding between Inconel 718 and commercially pure titanium using a vanadium interlayer

A weight reduction of aero engines, in order to enhance their efficiency would be possible if the commercially pure titanium in the low-temperature region of the compressor could be welded with Inconel in the high-temperature portion. This joining of titanium/Inconel is challenging owing to the formation of hard TixNiy intermetallic compounds, the suppression of which is not possible using the conventional weld process optimization approach. In recent years, a number of approaches have been developed to reduce or eliminate these intermetallic compounds during welding and one approach is the use of an interlayer during the welding operation. The insertion of a V interlayer at the root side remarkably suppressed Ti and Ni diffusion across the interlayer. NiV3 and (Ti, V) solid solutions were present in the interfacial microstructure of V/Inconel 718 and V/commercially pure titanium, respectively, as characterized by scanning electron microscope and X-ray diffraction. The tensile strength of the weldment was 190 MPa (approx. 59% of the commercially pure titanium base metal) with an elastic modulus comparable with that of the base alloys. The joint exhibited brittle fracture at the Inconel 718 side near the V/Inconel 718 interface due to intermetallic compounds.

Microstructural and Corrosion Properties of Ti-to-Zr Dissimilar Alloy Joints Brazed with a Zr-Ti-Cu-Ni Amorphous Filler Alloy

Titanium and Zircaloy-4 dissimilar alloys were brazed with a zirconium-titanium-copper-nickel amorphous filler alloy, and the resulting joint structures as well as their corrosion properties were examined. The microstructure of the brazed joints was investigated according to brazing holding time at 850 °C, and the corrosion property was analyzed by potentiodynamic polarization. During brazing, joints were produced by diffusion-induced isothermal solidification of the molten filler alloy. At a relatively brief brazing holding time of 5 min, a large segregation zone consisting of an active α-phase and a nobler intermetallic phase was generated in the joint center, which suffered from micro-galvanic corrosion. The presence of alloyed titanium deteriorated the nobility of the α-zirconium phase near the joint and induced galvanic coupling with cathodic base metals, resulting in massive localized corrosion. This localized corrosion caused the pitting behavior at the applied potential of −51.1~187.5 mV during anodic polarization. With a brazing holding time of 20 min, the concentration of the alloying elements was homogenized to eliminate the electrochemical potential difference and minimize the galvanic corrosion susceptibility of the joint region. This homogeneous joint resulted in a highly passive corrosion behavior comparable to that of the titanium base metal.

Research on fatigue crack growth behavior of commercial pure titanium base metal and weldment at different temperatures

In this paper, the effects of load ratio and temperature on fatigue crack growth (FCG) rates for commercial titanium alloy (CP-Ti) base metal and its weldment are investigated by experiments. Results show that the fatigue crack growth (FCG) rate of weldment is slower than that of base metal, which is mainly due to the difference of the microstructures between them. The microstructures at the weld are coarse grains and acicular martensite, which can reduce the FCG rate of weldment. The effect of load ratio on FCG rate will gradually weaken or even disappear with the increase of temperature. Also, the effect of temperature on FCG rate will gradually weaken or disappear with the increase of secondary cracks on the fracture surface. The results of finite element simulation show the FCG rate will be increased with the increase of plastic zone size and plastic strain, the increase of load ratio and temperature will reduce the FCG rate difference between weldment and base metal.

Influence of Beam Offset on Dissimilar Laser Welding of Molybdenum to Titanium.

Dissimilar joining of molybdenum (Mo) to titanium (Ti) is of great significance to the design and fabrication of high-temperature facilities. However, few reports were found about fusion joining of these two metals. The objective of this paper is to assess the feasibility of laser beam welding (LBW) of 2 mm-thick molybdenum and titanium. The effects of laser beam offset on the laser dissimilar joint of pure molybdenum to pure titanium were analyzed in terms of microstructure, chemical composition, microhardness, and tensile behavior. The results showed that the weld appearance improved with the increase of the offset. The fusion zone was strengthened because of the solid solution of these two elements. The mechanical properties of samples increased firstly and then decreased with the increasing of offset. When the laser beam irradiated on the titanium plate and the center of the laser spot was 0.5 mm away from the Mo/Ti interface, the joint performed the highest tensile strength, which was about 70% that of titanium base metal. LBW was demonstrated to be a promising method to join dissimilar Mo/Ti joint.

Influence of coping and veneer thickness on the color of zirconia-based restorations on different implant abutment backgrounds

Statement of problemThe effects of coping and veneer thickness on the color of zirconia-based restorations are unknown. PurposeThe purpose of this in vitro study was to evaluate the influence of coping and veneer thickness on the color of zirconia-based restorations on different implant abutment backgrounds and to define minimum coping and veneer thicknesses for the backgrounds investigated to achieve a target color. Material and methodsThirty zirconia disk specimens with thicknesses of 0.4, 0.6, and 0.8 mm and 30 veneering ceramic disk specimens with thicknesses of 0.8, 1.0, and 1.2 mm were fabricated. Three backgrounds were prepared: titanium alloy, zirconia ceramic, and base metal alloy. The zirconia specimens were placed on the backgrounds, and the veneering ceramic specimens were located on the zirconia specimens. Spectrophotometric measurements were made to determine CIELab values. Color difference (ΔE) values were calculated to measure color differences between the specimens and the A2 VITA classical shade tab. ΔE values were compared with a perceptibility threshold (ΔE=2.6). Repeated measures ANOVA, Bonferroni test, and 1-sample t test were used to analyze data (α=.05). ResultsMean ΔE values ranged from 2.0 to 9.8. Coping thickness, veneer thickness, and their combination significantly affected ΔE (P<.001). ConclusionsTo achieve the target color with zirconia-based restorations, regardless of the backgrounds tested, the minimum thickness of zirconia coping should be 0.6 mm, and the minimum thickness of veneering ceramic should be 1.2 mm.

Electrochemical synthesis and characterization of erbium oxide

Erbium oxide (Er2O3) has been used in a variety of microelectronic, optoelectronic, thermophotovoltaic, and biomedical applications, and especially in nuclear reactor systems. Electrochemical synthesis of rare earth oxides has conventionally been based upon base generation under the application of anodic or cathodic potential and subsequent sintering of as-deposited rare earth hydroxides. In this study, we investigated a direct, room-temperature electrochemical synthesis of Er2O3 onto titanium base metal by applying cathodic potentials. Iminodiacetate (IDA) ligand was added to form Er(IDA)2− complexes with Er3+ in a neutral electrolyte. A cathodic reaction for the direct deposition of Er2O3 from Er(IDA)2− was suggested as the mechanism of Er2O3 synthesis. The formation of cubic Er2O3 phase at all applied potentials was verified by means of X-ray diffractometry and X-ray photoelectron spectroscopy. The relationship between the diffusion characteristics of the reacting ions and the resulting microstructures of Er2O3 deposits was also studied as a function of applied potential.

Analysis and Characterization of the Role of Ni Interlayer in the Friction Welding of Titanium and 304 Austenitic Stainless Steel

Joining of commercially pure Ti to 304 stainless steel by fusion welding processes possesses problems due to the formation of brittle intermetallic compounds in the weld metal, which degrade the mechanical properties of the joints. Solid-state welding processes are contemplated to overcome these problems. However, intermetallic compounds are likely to form even in Ti-SS joints produced with solid-state welding processes such as friction welding process. Therefore, interlayers are employed to prevent the direct contact between two base metals and thereby mainly to suppress the formation of brittle Ti-Fe intermetallic compounds. In the present study, friction-welded joints between commercially pure titanium and 304 stainless steel were obtained using a thin nickel interlayer. Then, the joints were characterized by optical microscopy, scanning electron microscopy, energy dispersive spectrometry, and X-ray diffractometry. The mechanical properties of the joints were evaluated by microhardness survey and tensile tests. Although the results showed that the tensile strength of the joints is even lower than titanium base metal, it is higher than that of the joints which were produced without nickel interlayer. The highest hardness value was observed at the interface between titanium and nickel interlayers indicating the formation of Ni-Ti intermetallic compounds. Formation these compounds was validated by XRD patterns. Moreover, in tensile tests, fracture of the joints occurred along this interface which is related to its brittle nature.

Interfacial Microstructural Characterization of Ti/Al Joints by Gas Tungsten Arc Welding

Ti/Al dissimilar materials were welded by gas tungsten arc welding with filler wires. Microstructure in the Ti/Al joint was studied with optical microscope, scanning electron microscope, energy-dispersive spectrometer, etc. Results show that various Ti–Al intermetallic compounds are formed along the interface. According to the degree of Ti alloy melted, interface is divided into different reaction layers. Under the effect of martensite transformation, microhardness in heat-affected zone is higher than it in titanium base metal. Element silicon enriched in the interface. The dispersive distribution of precipitated phase improved joint strength.

Friction Welding of Type 304 Stainless Steel to CP Titanium Using Nickel Interlayer

Dissimilar metal joints of stainless steel to titanium find extensive industrial applications especially in the nuclear industry. However, it is well known that fusion welding of stainless steel to titanium is difficult because of the formation of brittle intermetallic compounds and the associated problems. To avoid this, welding processes or techniques with high reliability and productivity for these dissimilar materials are demanded. In the present work, joints comprising of 304 stainless steel and commercially pure titanium were produced by friction welding using nickel as interlayer. Investigation on the mechanical properties of the joints shows the occurrence of highest hardness value at the interface of titanium and nickel interlayer. X-ray diffraction studies confirmed the presence of various types of intermetallic compounds at the interface of the welded joint. The tensile strength of the joint varies with the thickness of nickel interlayer used. Joints having maximum strength equals to 72% of that of titanium base metal could be produced. In all the joints, tensile failure occurred at Ti-Ni interface due to the presence of the intermetallic compounds at this interface. Fracture surface analysis reveals that the tensile fracture path is along the intermixing zone of titanium and nickel interlayer.

A comparison of the marginal adaptation of cathode-arc vapor-deposited titanium and cast base metal copings

A new fabrication process where a titanium coping, with a gold colored titanium nitride outer layer, can be reliably fused to porcelain; however, the marginal adaptation characteristics are undetermined. The purpose of the study was to compare the clinically acceptable marginal adaptation (CAMA - defined as a marginal gap mean of ≤ 60 μm) rates of cathode-arc vapor-deposited titanium and cast base metal copings to determine whether the titanium copings would produce a higher CAMA rate than the cast base metal copings. Thirty-seven cathode-arc vapor-deposited titanium copings and 40 cast base metal copings were evaluated using an optical microscope. Fifty vertical marginal gap measurements were made of each coping, and the mean of these measurements was used to form the gap score. A 1-tailed t test was used to compare the CAMA rates, and the Satterthwaite t-score was used to analyze the consistency of the coping adaptation (α =.05). CAMA was achieved by 24 of the 37 (64.86%) titanium copings compared to 19 of the 40 (47.50%) base metal copings. A 1-tailed t test produced a Z-score of 1.533 (1-tailed P=.063), which allowed acceptance of the study hypothesis with only a modest risk of a Type I error. Cathode-arc vapor-deposited titanium copings exhibited a higher rate of CAMA compared to base metal copings.

Surface roughness changes caused by the galvanic corrosion between a titanium abutment and base metal alloy

연구 목적: 이 연구의 목적은 티타늄 지대주와 비귀금속 보철물이 접촉한 경우를 가정하여 이종 금속간 접촉에 의한 갈바닉 부식으로 인해 발생하는 표면 거칠기 변화를 비교, 평가하고자 하였다. 연구 재료 및 방법: 성분과 조성이 다른 3종의 Ni-Cr합금 (T3, Bella bond plus, Tilite)과 cp 티타늄 Grade 2를 이용하여 $13{\times}13{\times}1.5\;mm$ 의 크기로 시편을 각 군당 6개씩 제작하였다. 연마과정 후 절연 테이프로 직경 6 mm만을 노출시켜 potentiostat (Parastat 2273A)를 이용하여 동전위 분극 시험과 갈바닉 부식 시험을 시행하였으며, 표면 거칠기 측정기(Surftester SV-3000)를 이용하여 부식 전 후 거칠기를 평가하였다. 측정값을 paired t-test와 One-way ANOVA로 분석하였다. 결과: 티타늄과 접촉한 모든 Ni-Cr 시편의 표면 거칠기는 통계적으로 유의하게 증가하였다. 증가량은 베릴륨을 포함한 T3합금 ( $0.016{\pm}.007\;{\mu}m$ )이 가장 컸으며, 베릴륨을 포함하지 않은 Bella bond plus ( $0.012{\pm}.003\;{\mu}m$ ), 티타늄을 첨가한 Tilite ( $0.012{\pm}.002\;{\mu}m$ )는 큰 차이를 보이지 않았다. 금속 종류에 따른 거칠기 증가는 유의한 차이를 보이지 않았다. 결론: 티타늄과 접촉한 비귀금속 합금은 갈바닉 부식에 의해 표면 거칠기가 증가하였다. 【Purpose: The purpose of this study was to evaluate the level of electro-chemical corrosion and surface roughness change for the cases of Ti abutment connected to restoration made of base metal alloys. Materials and methods: It was hypothesized that Ni-Cr alloys in different compositions possess different corrosion resistances, and thus the specimens ( $13{\times}13{\times}1.5\;mm$ ) in this study were fabricated with 3 different types of metal alloys, commonly used for metal ceramic restorations. The electrochemical characteristics were evaluated with potentiostat (Parstat 2273A) and the level of surface roughness change was observed with surface roughness tester. Paired t-test was used to compare mean average surface roughness (Ra) changes of each specimen group. Results: All specimens made of nickel-chromium based alloys, average surface roughness was increased significantly (P $0.016{\pm}.007\;{\mu}m$ ) had the largest change of roughness followed by Ni-Cr ( $0.012{\pm}.003\;{\mu}m$ ) and Ni-Cr-Ti ( $0.012{\pm}.002\;{\mu}m$ ) alloy. There was no significant changes in surface roughness between each metal alloys after corrosion. Conclusion: In the case of galvanic couples of Ti in contact with all specimens made of nickel-chromium based alloys, average surface roughness was increased.】

Production and bond strength of similar-titanium ultrasonic welded joints

The joinability of unalloyed titanium and the bond strength of similar titanium welded joints by ultrasonic welding were investigated. It turned out that sound welded joints of similar titanium were obtained by using the jig for fixing both base metals. In the case of non-fixing and fixing the lower base metal, sound welded joints were not usually obtained due to the slip between the two base metals. Producing welded joints having sufficient bond strength required a certain threshold value of the ultrasonic energy. When the ultrasonic welding was carried out under the condition where the ultrasonic energy was higher than a threshold value (approximately 2000 W s), the welded joints were fractured within the titanium base metal but not at the interface. The values of the bond strength were associated with the fixing method and the surface roughness of the base metals. The bond interface was joined metallurgically for the most part, although some small voids were observed on the bond interface by SEM and EPMA observation.

Production and Bond Strength of Similar-Titanium Ultrasonic Welded Joints

The joinability of unalloyed titanium and the bond strength of similar-titanium welded joints by ultrasonic welding were investigated. It turned out that sound welded joints of similar-titanium were obtained by using the jig for fixing both base metals. In the case of non-fixing and fixing the lower base metal, sound welded joints weren't usually obtained due to the slip between the two base metals. Producing welded joints having sufficient bond strength required a certain threshold value of the ultrasonic energy. When the ultrasonic welding was carried out under the condition where the ultrasonic energy was higher than a threshold value (approximately 2000 W•s), the welded joints were fractured within the titanium base metal but not at the interface. The values of the bond strength were associated with the fixing method and the surface roughness of the base metals. The bond interface was joined metallurgically for the most part, although some small voids were observed on the bond interface by SEM and EPMA observation.

Corrosion in titanium dental implants: literature review

The corrosion of dental biomaterials is a pertinent clinical issue. In spite of the recent innovative metallurgical and technological advances and remarkable progress in the design and development of surgical and dental materials, failures do occur. The present article describes the problem of corrosion in titanium dental implants. The clinical significance of the dental implant corrosion is highlighted and the most common form of corrosion i.e. galvanic corrosion is emphasized both in vitro and in vivo conditions. The article is presented keeping in view of carrying out different studies for indigenous titanium dental implant and indigenous alloys. The Department of Dental Research at Institute of Nuclear Medicine & Allied Sciences has developed indigenous Titanium Dental Implants and Base metal Alloys. The studies carried out have proven their biocompatibility and suitability to be used for oral defects. The aim of the study is to evaluate galvanic corrosion current around indigenously developed Titanium Dental Implant when coupled to a Base metal Alloy.

タングステンとチタンとの拡散接合

We investigated the influences of bonding parameters on joint strengths of diffusion bonds between swaged tungsten and titanium (case A), and between rolled tungsten and titanium (case B). In case of A, joints bonded at temperatures of 1073 K and 1473 K for a bonding time of 1.8 ks showed the tensile strengths of 120 MPa. The joint strength obtained at a bonding temperature of 1073 K increased with increase of bonding times, and for a bonding time of 30 ks reached about 240 MPa, which was 88% of the tensile strength of the tungsten base metal. In the case of B, joint strength obtained at a bonding temperature of 1173 K was 16 MPa, when fracture occurred along grain boundaries. In the both case, the voids were formed in titanium base metal away from the W/Ti interface. It is therefore seemed that the existence of voids give no effect on the joint strength.

チタンとニッケルのろう付過程における反応機構

A commercially pure titanium has been liquid phase diffusion bonded to pure nickel by using amorphous alloy filler metal.The dissolution phenomenon of the base metals into the liquid filler metal and the isothermal solidification process during bonding was investigated. Main experimental results obtained in this reserch are as follows;(1) The dissolution phenomenon of the base metals into the liquid filler metal was completed rapidly, its time was about 60 sec at 1125 and 1150 K, and about 120 sec at 1200 K.(2) The dissolution of titanium base metal shown a value three times as much the dissolution of nickel base metal into the liquid filler metal. The maximum dissolution width of the base metals were related to the boning temperature by the following equations.WDTi=(1.78×10-6×T)-(1.99×10-3), WDNi=(4.85×10-7×T)-(5.37×10-4)(3) The relation between dissolution parameter P of the base metals and bonding time dose not shown by the straight line relation, the dissolution process was divided into three stage according to the dissolution rate constant K. therefor, the dissolution phenomenon does not conformed to the Nernst-Brunner's theory.(4) The concentration of each elements were distributed itself uninformly throughout the bonded interlayer after the dissolution phenomenon of the base metals was completed.(5) The maximum width of the bonded interlayer was related to the boning temperature by the following equation.WBImax=(2.32×10-6×T)-(2.55×10-3)(6) The Ti-Cu and Ti-Ni system intermetallic compound layers formed on the interface of titanium base metal to the bonded interlayer. The Ti-Ni system intermetallic compound layer formed on the interface of nickel base metal to the bonded interlaver.

Preparation of oxygen evolving electrodes with long service life under extreme conditions

Among the numerous base metals tested for DSA® type electrodes (e.g., titanium and its alloys, zirconium, niobium etc.), tantalum is a potentially excellent substrate owing to its good electrical conductivity and corrosion resistance, and the favourable dielectric properties of its oxide. Nevertheless, a DSA® type electrode fabricated on a tantalum substrate would be very expensive due to the high cost of the metal. To prepare an anode combining the excellent properties of tantalum at reasonable price, a new material has been developed in our laboratory. This consists of a common base metal (e.g., Cu) covered with a thin tantalum coating. This tantalum layer was obtained by molten salt electroplating in a LiF–NaF–K2TaF7 melt at 800°C. Thus, an anode of the type Metal/Ta/Ta2O5–IrO2 with a surface load of 22gm-2 IrO2, submitted to the severe test conditions used in this work, exhibits a standardized lifetime tenfold greater than one made with ASTM grade 4 titanium base metal. Thus, this type of electrode might be advantageously employed as an oxygen evolution anode in acidic solutions.

Effect of coating thickness and surface treatment of titanium on the properties of IrO2-Ta2O5 anodes

The effect of coating thickness and the effect of surface treatment of the titanium base metal on the surface morphology and electrochemical properties of IrO2-Ta2O5 anodes were investigated. It was observed that for an iridium content of 0.45–1.2 mg cm−2 the service life is proportional to the iridium content in the coating. During etching of titanium in 5% HF at 25 °C a surface with macroroughness is formed, while during etching in HCl at 30, 50 and 80°C a microrough surface with visible pitting is formed. The morphology of the IrO2-Ta2O5 active layer (0.32–0.39 mg Ir cm−2) depends strongly on the pretreatment of the titanium base metal. After etching of titanium in HF, the resulting IrO2-Ta2O5 layer is adherent to the macrorough surface of the titanium base metal. After etching of titanium in HCl the resulting surface of the IrO2-Ta2O5 layer is microrough with partly filled pitting holes. The service life of IrO2-Ta2O5 coating with different roughness does not differ and has a value of 1500 ± 400 h (0.5 M H2SO4, 25 °C and j = 2 A cm−2).