Titanium Joints Research Articles

Effect of the surface morphology of 3D printed titanium substrates on the mode I fracture toughness of metal-metal and metal-composite bonded joints

Parts manufactured with Laser Powder Bed Fusion (LPBF) are drawing interest in the adhesive joints research because of their high surface roughness, which is usually associated with good adhesion. This work aims to assess the adhesion strength of the inherent surface morphology of LPBF manufactured titanium.Double Cantilever Beam (DCB) tests were carried out to determine the mode I fracture toughness of joints comprising as-printed titanium (Ti6Al4V) adherends, namely titanium-titanium secondary bonded and titanium-Carbon Fibre Reinforced Polymer (CFRP) co-bonded joints. The effect of high-temperature oxidation on the fracture toughness was also evaluated by testing a batch of joints in which the titanium underwent a post-printing thermal treatment. The as-printed specimens were compared to the same type of joints but with sandblasted titanium adherends to evaluate the effect of this surface pre-treatment on the value of fracture toughness.The results indicate that non-oxidised titanium joints with untreated adherends had an average of 11% higher fracture toughness than their sandblasted counterparts. On the other hand, sandblasting proved beneficial for oxidised joints, increasing the fracture toughness by 64% on average over the untreated samples.

Tribological and mechanical properties of FSW joints of untainted stainless steel and titanium: novel characterization of similar and dissimilar joints

Friction Stir Welding (FSW) is an emerging solid-state welding process that joins dissimilar or similar metals based on requirements. The additional material to make the joint is also a weight reduction factor deemed vital in weight-sensitive industries like aerospace and orthopedic applications. The similar and dissimilar Ti-6Al-3Nb-2Zr-1Mo (Ti6321) and stainless steel (SS 310) joints are performed through friction stir welding. This investigation aims to identify the effect of process parameters on the mechanical behavior and microstructural characteristics of the FSW joints. Five plates are chosen; three are FSW joints, and two are kept in the original base material. In all five plates, tensile, microhardness, and wear tests are performed, including an analysis of grain size. It is observed that the similar Ti6321 joint with a 6 mm pin diameter, 60 mm transverse speed, 900 mm rotational speed, and a constant axial force of 1 KN exhibits a maximum microhardness of 362 HV and a tensile strength of 927 MPa when compared to other joints. The tribological properties are identified as varying load (10–50 N), sliding speed (1–5 m s−1), and a constant sliding distance (1000 m) on pin-on-disc apparatus. It reveals that welding parameters and tool diameter influence tribological characteristics. The surface morphology carried out by FE-SEM revealed that the HAZ is composed of acicular α. The increase in microhardness is higher in WC than in BM due to the uniform distribution of particles. The chemical composition and phases are analyzed using XRD.

Stress Concentration Modelling on Resistance Spot Welding Lap Joint of Steel ASS316L and Titanium Ti-6Al-4V with Variable Weld Geometries

This research is a finite element simulation on resistance spot welding (RSW) process between dissimilar sheet metals consist of Titanium alloy, Ti-6Al-4V and Austenitic Stainless Steel (ASS) 316L. The problem statement was inability to visualize the stress concentration profile over weld nugget joint when Titanium alloy and steel welded with variable electrode geometry of circle, triangle, square and hexagon. To determine the best geometry for best weld with lowest maximum stress concentration. The methodology of simulation was tensile-shear test using SOLIDWORKS software. The tensile-stress load of 664.09 N was applied across all 4 different weld geometries. The result for the lowest magnitude of maximum stress 180.6 MPa was on circle weld geometry. Triangle geometry registered highest stress concentration of 219.6 MPa. This proves that most common weld geometry used in industry was circle. Even for dissimilar material joint the result supports that circle weld geometry as the best geometry. Keywords: Resistance spot welding (RSW), stress concentration, weld nugget, weld geometry.

Performance of additively manufactured Ti6Al4V ELI finger joints: biomechanical testing and evaluation for arthritis management

Abstract Approximately 24 out of every 100 adults in the United States, or 58.5 million people, have arthritis, which refers to a condition that causes pain and inflammation in a joint according to US National Center for Chronic Disease Prevention and Health Promotion. Osteoarthritis is the most common type of arthritis, and it may damage almost any joint but mainly occur in hands, hips and knees. While there are several joint replacement options for hips and knees, there are only limited options for finger joints. In this paper, we report on several aspects of testing of novel finger joints: testing apparatus design, cadaveric performance test and material testing results of titanium joints using 3D-printed Ti6Al4V extra low interstitial (ELI). Soft cadaveric hands with finger joints were surgically replaced by additively manufactured titanium joints following the exact same anatomy of the cadavers. These small joints were engineered to mimic the biological and natural movements of fingers. The apparatus, methodology and results of biomechanical tests were deployed to evaluate and validate the joints particularly those of titanium joints manufactured via laser powder bed fusion methods (PBF-L/M).

The Impact of Al2O3 Particles from Grit-Blasted Ti6Al7Nb (Alloy) Implant Surfaces on Biocompatibility, Aseptic Loosening, and Infection.

For the improvement of surface roughness, titanium joint arthroplasty (TJA) components are grit-blasted with Al2O3 (corundum) particles during manufacturing. There is an acute concern, particularly with uncemented implants, about polymeric, metallic, and corundum debris generation and accumulation in TJA, and its association with osteolysis and implant loosening. The surface morphology, chemistry, phase analysis, and surface chemistry of retrieved and new Al2O3 grit-blasted titanium alloy were determined with scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and confocal laser fluorescence microscopy, respectively. Peri-prosthetic soft tissue was studied with histopathology. Blasted retrieved and new stems were exposed to human mesenchymal stromal stem cells (BMSCs) for 7 days to test biocompatibility and cytotoxicity. We found metallic particles in the peri-prosthetic soft tissue. Ti6Al7Nb with the residual Al2O3 particles exhibited a low cytotoxic effect while polished titanium and ceramic disks exhibited no cytotoxic effect. None of the tested materials caused cell death or even a zone of inhibition. Our results indicate a possible biological effect of the blasting debris; however, we found no significant toxicity with these materials. Further studies on the optimal size and properties of the blasting particles are indicated for minimizing their adverse biological effects.

Investigations on the diffusion bonding of titanium alloy and aluminum alloy using copper at low bonding pressure

This research investigates the diffusion bonding of hybrid aluminum (Al)–titanium (Ti) joints using a copper (Cu) interlayer in a vacuum environment. At 610 °C and 1 MPa pressure, partial melting of Al caused deformation and misalignment, while 520 °C showed no melting of Al–Cu at the interface. A rod-shaped precipitate with primarily Al was observed at 550 °C, and grain coarsening occurred at 580 °C at the interface, accompanied by increased Cu diffusion within the Al matrix for a bonding time of 45 min. A Ti–Al-based intermetallic layer formed on the Ti side, but voids and cracks were present in the Al–Cu diffusion region at 580 °C. Hardness variation resulted from microstructural changes due to bonding temperature, particularly near the bond line due to hard intermetallic compounds. Shear strength averaged 41 MPa at 550 °C and decreased to 33 MPa at 580 °C due to grain growth, voids, and crack propagation, causing brittle joint failure at the interface. X-ray diffraction on the fracture surfaces revealed that the failure of diffusion-bonded joints is attributed to fractures through the Ti–Al-based intermetallic compounds at the interface and unbonded region.

Investigation on Performance of Hydraulically Expanded Joint of Titanium-Steel Clad Tubesheet.

The performance of a hydraulically expanded joint between tubesheet and titanium tube was analyzed using a finite element numerical calculation. The connection strength of Q345R tubesheet and TA2-Q345R clad tubesheet was studied using a tight expansion method. The results proved that the residual contact pressure and pullout force of the tight expansion joint of TA2-Q345R clad tubesheet were greater than those of the Q345R tubesheet. However, the residual contact pressure of the expanded joint without a groove for the TA2-Q345R tubesheet and the pullout force failed to meet the requirement of connection strength. Hence, the groove was employed on the contact surface. The influences of groove position and groove width on the connection strength of the expanded joint with grooves in tubesheet hole were studied. The results show that the residual contact pressure of the clad tubesheet of grooving in the cladding layer was higher than that of grooving in the base layer. The effect of the position of groove in the cladding layer and base layer on the residual contact pressure could be neglected. A wider groove led to a higher residual contact pressure, which increased significantly when the groove width was 4 mm.

Features of Permanent Joints of Titanium (α+β)-Alloys Obtained by Friction Stir Welding Using a Nickel Superalloy Tool

Titanium alloys are widely used in industry, especially (α+β)-alloys, among which Ti-6Al-4V alloy is the most popular one. Another common alloy that often appears in patents for titanium products is Ti-4Al-3Mo-1V. Here, we investigate welded joints of (α+β)-alloy Ti-4Al-3Mo-1V obtained by friction stir welding (FSW) using a working tool made of nickel-based heat-resistant alloy ZhS6U. In addition, welded joints of Ti-6Al-4V and Ti-4Al-3Mo-1V alloys with similar mechanical characteristics were considered. Mechanical tests showed that the obtained joints had a tensile strength greater than that of the base metal. This result was achieved in the welding mode where the axial load was varied during the welding process. X-ray diffraction analysis revealed a change in the phase structure of the welded joint.

Effects of silver interlayer thickness on the microstructure and properties of electron beam welded joints of TC4 titanium and 4J29 Kovar alloys

Abstract Electron beam welding of TC4 titanium alloy and 4J29 Kovar alloy was performed by using different thicknesses of silver interlayers. The microstructure and the composition of welded joints were characterized by scanning electron microscopy, X-ray diffraction, and energy-dipersive spectrometry. The mechanical properties of welded joints were evaluated by tensile strength tests. The results indicated that Ag thickness has great effects on the weld appearance, microstructure, and mechanical properties of electron beam-welded joints. In case of 0.3 and 0.4 mm thickness of Ag interlayers, a considerable part of 4J29 and TC4 melts and a large amount of Fe, Ti, and Ni elements diffuse into the molten pool forming intermetallic compounds (IMCs) such as TiFe2, NiTi, and FeTi. In case of 0.6 mm thickness of Ag interlayer, the welded joint exhibits brazing characteristics with little IMCs near the fusion line of 4J29 Kovar alloy side. When the thickness of the Ag interlayer increases to 0.8 mm, the diffusion of Ti and Fe elements is completely inhibited by Ag. As the thickness of the Ag interlayer increases from 0.3 to 0.8 mm, the tensile strength of the welded sample shows a phenomenon that first rises and then falls, and the largest tensile strength is 243 MPa.

Narrow-gap laser welding with beam wobbling and filler wire and microstructural performance of joints of thick TC4 titanium alloy plates

How to control poor fusion of sidewall and interlayer in narrow-gap laser welding with filler wire of thick plates is an unsolved problem. When the groove width changes in the direction of the plate thickness (for example, V-shaped narrow-gap grooves or preset inverse deformation to offset angular distortion caused by welding), incomplete fusion is more difficult to control, resulting in low yield. Laser welding with beam wobbling and filler wire (LWBWFW) was carried out on narrow-gap butt joints of thick TC4 titanium (Ti) alloy plates with V-shaped grooves. On this basis, the relationship between welding conditions and incomplete fusion under four widths of the groove bottom (4, 6, 8 and 10 mm) was studied. It is found that the key to eliminating incomplete fusion is shown as follows: on the one hand, the beam wobbling amplitude should be appropriate. On the other hand, the ratio of the welding line energy to the wire feed amount should be proper. The former mainly affects incomplete sidewall fusion, while the latter mainly influences incomplete interlayer fusion. Following the above principles, this research obtained well-formed joints of TC4 alloy with the thickness of 30 mm welded by LWBWFW (hereinafter referred to as LWBWFW joints) and the tensile strength of the joints can reach 99.6% that of base metal (BM).

Comparison of process behavior, microstructure and mechanical properties of ultrasound enhanced friction stir welded titanium/titanium joints

AbstractTitanium as a high-performance material offers great potential for a wide range of applications with different aspects like lightweight-constructions, biocompatibility as well as design and is used in various industrial areas like the transportation sector or in medical and sports engineering. To exploit the full potential of titanium, there is still a need for innovative and efficient joining techniques compared to conventional methods. The process of friction stir welding as a solid-state joining method is able to produce high-quality similar joints of titanium. Nevertheless, there are still some challenging aspects when friction stir welding titanium like the formation of oxide layers that affect the mechanical properties especially in the field of fatigue negatively. The superposition of power ultrasound on the friction stir welding process can address this issue. Therefore, the hybrid process of ultrasound enhanced friction stir welding was applied on similar Ti6Al4V/Ti6Al4V joints in a butt joint configuration to reduce the amount of oxide layers and improve the fatigue lifetime of the joints. For the joint configuration, a positive impact of the power ultrasound could be identified by the breakup of oxide layers and an increase in the tensile strength of 16%. Also stepwise load increase tests revealed a higher estimated fatigue strength for ultrasound enhanced friction stir welded specimen in this butt joint configuration.

Weld Quality and Microstructure Development in Ultrasonically Welded Titanium Joints

Weld Quality and Microstructure Development in Ultrasonically Welded Titanium Joints

NDT studies and microstructure investigation on dissimilar materials joining by using FSW method

Recent research work is carried the joining of different materials of hardened steel, aluminum and titanium interface. The unique or comparable joining strategies are giving better execution of materials strength. High rotational speed and High manufacturing joining method is given good bonding contacts. The most extreme temperatures are Titanium and hardened steel materials range around 1600 °C. High-tension, Temperature and great speed locales are needed for the welding system. Titanium and tempered steels are covered 300 °C reaches to applied aluminum shower covering with steady tension. The reason for covering aluminum is great holding strength of titanium and hardened steel. Non Destructive testing results are checked and examined with the assistance of frictional joints. This exploratory work finishes four distinct trials of hardened steel, aluminum and titanium joints through various paces with constant manufacturing pressure. Hardened for titanium and tempered steel relations of 2100 °C and 60 MPa producing pressure, rubbing time 5 sec and grinding tension of 70 MPa. Rubbing welding tests are finished the materials surfaces and evaluated the assistance of contact behaviors.

Ultrasonic-Assisted Brazing of Titanium Joints Using Modified Al-Si-Cu Based Fillers: Brazing at Liquid—Semisolid States under Load

Brazing joints of Ti/Ti under ultrasonic vibration (USV) and compression load were investigated using optimized and modified filler alloys of Al-Si-Cu-(Ni)-(Sr) group prepared in the lab. Preliminary trails at semisolid to liquid states were conducted using the ready Al-Si-Cu-(Mg) alloy as a filler, then the brazing cycle was redesigned and enhanced according to the microstructural observations of the produced joints. USV assisted brazing at the semisolid state of low solid fraction was able to produce joints with round silicon morphology and granular α−Al, while at a high solid fraction, USV was only able to affect the silicon and intermetallic particles. Applying a compression load after ultrasonic vibration, at a designed solid fraction, was proved to be a successful technique for improving the quality of the joints by reducing the porosity, enhancing the soundness of the joint, and the diffusion at the interface. Based on alloy composition and the improved brazing cycle, joints of thin intermetallic layer and high shear strength (of 93 MPa average value) were achieved. The microstructures and the mechanical behavior were discussed based on the filler compositions and brazing parameters.

Study of the welded joint of VT1-0 titanium with 1.3343 steel

The work describes a method for obtaining a composite structure of small plates. The resulting plates are a layered structure consisting of a substrate (1.3343 steel) and a titanium coating (VT1-0). A method of resistance welding in the open air was applied to form a layered structure. The resulting titanium-steel compound was tensile tested. The maximum force at break of the welded joint varied in the range from 1.05 to 2.17 kN.

Ultrasonic-Assisted Brazing of Titanium Joints Using Al-Si Based Fillers: Numerical and Experimental Process Design

The ultrasonic-assisted brazing process was studied both numerically and experimentally. The ultrasonic brazing system was modeled by considering the actual brazing conditions. The numerical model showed the distribution of acoustic pressure within the filler and its variations according to the gap distance at different brazing temperatures. In the experimental part, brazing joints were studied and evaluated under multiple conditions and parameters. Although either the initial compression load or the ultrasonic vibration (USV) can initiate the interaction at the interface, the combined effect of both helped to produce joints of a higher quality with a relatively short brazing time, which can be further optimized in terms of their mechanical strength. The effect of the Si content on the joint interface, and the effect of the brazing conditions on the microstructures were studied and discussed.

Erratum to: Studying the Laser Welding of Porous Metals with the Application of Compact Inserts and Nanopowders

The effect of thermal regimes and some technological methods (the application of intermediate compact metal inserts and nanomodifying additives) on the quality of laser-welded permanent joints of porous titanium or stainless steel plates has been experimentally studied in this work. It has been established that the formation of a high-quality defectless seam requires the use of an intermediate compact (nonporous) metal insert placed butt to butt between the edges of welded plates. In this case, the position of a focal spot should be installed at a depth equal to the thickness of a plate, i.e., on its lower surface. To form a bead joint or a joint flush to the plates to be welded together, the height of an insert must exceed the thickness of the plates. The application of nanomodifying titanium nitride based additives increases the structural dispersity and uniformity of a seam, thus producing a positive effect on the mechanical characteristics of a welded joint.

Microstructural analysis and mechanical behavior of TC4 titanium alloy and 304 stainless steel by friction stir lap welding

The optimization of welding parameters of the welded joints of TC4 titanium alloys/304 stainless steel (TC4/304 SS) by friction stir lap welding (FSLW) based on orthogonal test was researched. The results show that under low heat input (low rotating speed and high traversing speed), there was a damaging defect in stir zone (SZ) and cracks started from the defect under the tension. Under high heat input (high rotating speed and low traversing speed), the intermetallic compounds were barely formed, and the cracks formed from 304 SS blocks existed in thermal mechanically affected zone of TC4 titanium alloys (TMAZTC4), eventually obtaining the highest fracturing load. However, under middle heat input (middle rotating speed and low traversing speed), the intermetallic compounds and the maximum hardness were found at the interface, and cracks started from these compounds under the tension, getting a middle fracture load. In conclusion, the joints with good properties can be obtained with high rotating speed and low traversing speed.

INFLUENCE OF HIGH-VELOCITY IMPACT PARAMETERS ON THE STRUCTURE AND PROPERTIES OF THE VT1-0 + AMG5 JOINT

The paper presents the results of studying the joints of VT1-0 titanium with the aluminum-magnesium alloy AMg5, obtained by explosion welding in different modes of impact. The analysis of microstructures showed that, depending on the conditions of collision, the boundary of the joint zone can have both a wave and a waveless profile. Areas of melted metal are formed even with minimal energy input, but until a certain point they do not significantly affect the strength of the joint. At relatively low values of the energy W, titanium weakly dissolves in aluminum and is present in the melted areas in the form of crushed particles. A further increase in the modes of explosion welding leads to an increase in the degree of dissolution of titanium in melts, which is accompanied by the appearance of cracks. The results of the performed mechanical tests showed that the values of the peel strength of the layers are noticeably higher and reach an equal-strength joint in comparison with the method of welding through an intermediate layer of pure aluminum. In the investigated range of welding modes, the strength of the joint increases in the energy range W = 0,85...1,1 MJ/m, and at W = 1,1 MJ/m it reaches a maximum. With a further increase in the modes of explosion welding, the strength of the joint decreases, which is associated with a change in the structure of the melted regions with the formation of brittle intermetallics in them.

Fatigue Resistance of Welded Titanium Joints

The paper presents the results of studies of the structural state, changes in mechanical characteristics during static and cyclic loading of welded joints from technically pure titanium during thermal cycling. Based on the change in the relative deflection of the sample, a quantitative assessment of the fatigue damage accumulation at the stage of cyclic deformation up to the moment of opening and propagation of the main crack depending on the number of cycles of thermal cycling treatment is provided.