Dissimilar Titanium Alloys Research Articles

Effects of ultrasonic vibration on residual stress distribution and local mechanical properties of AA6061/Ti6Al4V dissimilar joints by resistance spot welding

The joining of dissimilar titanium and aluminum alloys has potential applications in railway and aerospace industries, owing to substantial weight reduction and better economic viability. In this study, the residual stress distribution and local mechanical performance of ultrasonic-assisted resistance spot welding (UaRSW) welds were investigated. The welding current, welding time, and electrode force of the RSW process were set as 9.0 kA, 350 ms, and 1.0 kN respectively, and the frequency and power of ultrasonic vibration were 20 kHz and 800 W. The residual stress was evaluated by X-ray diffraction (XRD) method and numerical simulation, and these methods showed a reasonable match. There was tensile residual stress distributed on RSW welds and UaRSW welds, but the value of residual stress was reduced by about 30% at welding nugget and 20% at heat affected zone (HAZ) with the ultrasonic vibration, the reduction of residual stress in UaRSW welds was attributed to the more uniform temperature distribution and lower plastic deformation resistant of AA6061. The welding peak temperature was decreased from 1673.4 °C to 1584.2 °C with the ultrasonic vibration, resulted from the modified Al/Ti contact surface and reduced contact resistance. The miniature tensile test results showed the improvement of mechanical performance by ultrasonic vibration. The maximum load of welding nugget region increased from 19.6 N to 22.3 N, and the elongation obtained 10% increase. This hybrid welding technique shows a potential to improve the quality of welds with ensured efficiency, which is also simple to realize automation in the manufacturing industry.

Interfacial microstructure evolution and mechanical response of TC19/Ti150 dissimilar joints obtained by diffusion bonding

The structure made by dissimilar titanium alloys can meet the differentiated requirements of performance for different parts, fully exerting their performance advantages during operation respectively, which holds significant technological and economic value. Here, we used diffusion bonding (DB) method to connect TC19 and Ti150 dissimilar titanium alloys in the temperature range of 810 °C–900 °C, and investigated the morphology, forming mechanism, deformation behavior and mechanical properties of the joints. The study showed that the interfacial voids disappeared with the increase of temperature, and the interfacial characteristics gradually evolved from the initial straight shape to a curved shape. The original bond line transformed into βTC19/αTi150 phase boundaries (PBs) and high-angle grain boundaries (HAGBs) formed by αTC19 and αTi150. No harmful intermetallic compounds were formed on the interface. The joint formation can be considered as a combination of three behaviors: plastic deformation, elemental diffusion and interfacial grain boundary migration (IGBM). In addition, it was observed that dislocation slip was the main deformation behavior of the joints. The dislocations generated in the both matrices were obviously accumulated at the interface during tensile deformation of the specimen, and the bonding interface hindered the dislocation transfer between two substrates. The room temperature uniaxial tensile results exhibited that the joints bonded at 810 °C and 840 °C were broken at the interface, showing poor mechanical properties caused by holes and straight interface. And yet the joints bonded at 870 °C and 900 °C occurred fracture on the Ti150 matrix. The strength of joints was comparable to that of the Ti150 matrix, indicating that the two dissimilar titanium alloys achieved a reliable bonding. This work provides valuable inspiration for the diffusion bonding process of titanium alloys with different microstructures.

High-cycle and low-cycle fatigue characteristics of multilayered dissimilar titanium alloys

Multilayered structures of dissimilar titanium alloys can achieve excellent fracture ductility and strength, while their fatigue characteristics especially dislocation networks and twin formation are rarely reported. Heterogeneous microstructures are observed in the multilayered TC4/TB8 alloys, including fine acicular α grains, continuous α layer at prior β grain boundaries (αGB) and β matrix on the TB8 layer, together with equiaxed α grains on the TC4 layer. High-cycle fatigue (HCF) and low-cycle fatigue (LCF) tests show that the initial fatigue damage appears at the αGB/β matrix interfaces on the TB8 layer instead of the boned TC4/TB8 interfaces. Since the stress concentration induced by dislocation pile-up is prone to micro-void formation and crack propagation at the αGB/β interfaces. For LCF, the αGB/β interfaces can not only act as impenetrable barriers and sources of lattice dislocations, but also allow the dislocations cross boundaries during cyclic tension and compression because of the high boundary energy. The formation characteristic of deformation twins that is beneficial for the plastic deformation of α grains in TC4 layer during cyclic strain is investigated. Furthermore, the hexagonal dislocation networks are also found within the equiaxed α grains of TC4 layer after LCF, and the role between interface barrier and slip direction in the formation mechanism is analyzed.

Residual Stress Measurement Using X-ray Diffraction in Friction Stir-Welded Dissimilar Titanium Alloys.

Surface residual stresses in welded specimens significantly influence properties such as fatigue resistance, fracture toughness, and the superplasticity of joints. In this study, we employed friction stir welding, a well-established joining method, to weld dissimilar titanium alloys. By combining two distinct titanium alloys, we aimed to harness their unique properties when subjected to cyclic loading, impact, or superplastic forming processes. Utilizing X-ray diffraction, macroscopic surface stresses were assessed in dissimilar titanium alloys (Ti-6242 standard grain (SG) and Ti-54M) welded via friction stir welding, assuming a linear lattice distortion. The study accounted for misalignment, significant distortion, and grain refinement in the stir zone. Macroscopic surface residual stresses were quantified on the weld surface and at a depth of 1.5 mm beneath it within a square cross-section (1 × 1 mm2) by oscillating the specimen in the (X-Y) direction. The sin2φ method, implemented through the LEPTOS® (v7.8) software, was employed for residual stress measurement. The analysis of the results was conducted with respect to different rotation and traverse speeds. It was noted that at the center (CEN) of the weld, commonly referred to as the weld nugget, approximately 50 MPa of tensile stress was observed under the lowest values of both tool rotation speed and traverse speed. Tensile residual stresses were evident at the boundaries and within the stir zone. No discernible pattern was observed at the specified locations. Notably, the resultant values of residual stress, influenced by rotation and traverse speeds, exhibited asymmetry.

Inertia radial friction welding of Ti60(near-α)/TC18(near-β) bimetallic components: Interfacial bonding mechanism, heterogenous microstructure and mechanical properties

Inertia friction welding has emerged as a promising technique for fabricating lightweight and high-strength components in aerospace industry. To achieve high-quality weldments between dissimilar titanium alloys, this present work systematically investigates Ti60 (near-α)/TC18 (near-β) bimetal components manufactured by inertia radial friction welding. The focus is on understanding the joint interface behavior, heterogenous grain structure, microstructural evolution and resulting mechanical properties, with a particular emphasis on dynamic recrystallization, phase transformation and atomic diffusion of elements in the welded zone and thermos-mechanical affected zone. The results revealed that the significant influence of thermo-physical property mismatch between the dissimilar workpieces (Ti60-Ring and TC18-Core) on the microstructure and tensile strength of the joints. This mismatch could be effectively controlled by setting different flywheel kinetic energy (Ek) before welding. The tensile strength of the Ti60/TC18 joints manufactured with levels of Ek ranging from 174.74 kJ to 207.95 kJ, were observed to be governed by the combined effect of mechanical interlocking, grain boundary strengthening, precipitation strengthening and hetero-deformation induced strengthening. The formation of heterogeneous grain structure and intergrowth grains on the Ti60 alloy side, and the dislocation tangles in the “forked” α phase of the TC18 alloy side are identified as key factors in achieving optimized bonding strength for dissimilar Ti60/TC18 bimetallic inertia radial friction welding.

Investigations into the Microstructure and Texture Evolution of Inertia-Friction-Welded Dissimilar Titanium Alloys

The welded joint of a dissimilar titanium alloy was obtained via inertial friction welding technology. The characteristics of the bonding interface and the microstructure of the welded joint were investigated via optical microscopy, scanning electron microscopy and electron backscattered diffraction. The results show that fine, equiaxed grains and interdiffusion bands of the elements Mo and Sn were formed in the weld zone under the high temperature and plastic deformation of the inertial friction welding. The weld zone and thermo-mechanically affected zone formed ⟨1¯21¯0⟩ α texture and ⟨111⟩ β texture, respectively.

Multi-scale analyses of phase transformation mechanisms and hardness in linear friction welded Ti17(α + β)/Ti17(β) dissimilar titanium alloy joint

The Ti17(α + β)-Ti17(β) dual alloy-dual property blisk produced using Linear Friction Welding (LFW) is considered as high-performance component in advanced aeroengine. However, up to now, microstructure evolution and relationship between microstructure and micro mechanical properties of LFWed Ti17(α + β)/Ti17(β) dissimilar joint have not been thoroughly revealed. In this work, complex analyses of the phase transformation mechanisms of the joint are conducted, and phase transformations in individual zones are correlated to their microhardness and nanohardness. Results reveal that α dissolution occurs under high temperatures encountered during LFW, which reduces microhardness of the joint to that of Ti17(α + β) and Ti17(β). In Thermo-Mechanically Affected Zone of Ti17(α + β) (TMAZ-(α + β)) side joint, a large number of nanocrystalline α phases form with different orientations. This microstructure strengthens significantly by fine grains which balances partial softening effect of α dissolution, and increases nanohardness of α phase and microhardness of TMAZ-(α + β). Superlattice metastable β phase precipitates from metastable β in Weld Zone (WZ) during quick cooling following welding, because of short-range diffusion migration of solute atoms, especially β stabilizing elements Mo and Cr. The precipitation of the superlattice metastable β phase results in precipitation strengthening, which in turn increases nanohardness of metastable β and microhardness in WZ.

Influence of Different Filler Metals on the Mechanical and Microstructural Characteristics of Arc-Welded Joints Made of Dissimilar Titanium Alloys

In the motorsport industry, the choice of material for manufacturing the heat resistant components often falls on titanium alloys. In most cases, the production flow for this kind of part involves CNC machining and subsequent assembly by welding process, to other parts obtained by cold plastic forming and possibly made using different titanium alloys. Hence, the alloying element-content in the joint area can be extremely heterogeneous and variable point-by-point. To investigate this topic further, dissimilar welding of the alpha/beta alloy Ti6Al4V and of the oxidation-resistant alpha alloy KS-Ti 1.2 ASN-EX was made by GTAW technology and using different filler metals. Chemical and mechanical properties of the welds were investigated by XRD, SEM-EDS, microhardness maps, and tensile and bending tests. Results show that, despite the different alloying elements present in the two filler wires investigated, static properties of the welds are similar. Results also show that the local V/Al content ratio affects the microhardness as it is responsible for the creation of supersaturated alpha phases during the cooling of the weld beads.

Dissimilar joining of titanium to aluminum using friction stir welding process and weld joint characterization

Abstract The present investigation studies the solid-state joining of difficult-to-weld aerospace materials such as titanium alloy (Ti6Al4V, ELI) and pure aluminum. Due to the wide difference in thermo-mechanical properties, it was a challenging task to establish a dissimilar metal joint. The friction stir welding process with a conically shaped tungsten carbide tool was used in the present investigation to join the dissimilar titanium alloy and aluminum in the lap joint configuration. After a series of pilot experiments, the optimum test conditions to produce the defect-free joint are spindle speed of 1200 rpm, feed rate of 40 mm min−1, tool tilt angle of 1°, and 1 mm tool offset towards the aluminum side. The results show that a good joint was achieved with a maximum joint strength of 89 MPa. The dissimilar joints are characterized by macrostructure, microstructure, microhardness, and scanning electron microscopic analysis.

Residual Stress Distributions in Dissimilar Titanium Alloy Diffusion Bonds Produced From Powder Using Field-Assisted Sintering Technology (FAST-DB)

The conventional approach when engineering components manufactured from titanium is to design the thermomechanical processing to develop an optimal microstructure in a single alloy. However, this conventional approach can lead to unnecessary over-engineering of components, particularly when only a specific subcomponent region is under demanding service stresses and environments. One approach being developed to join multiple alloys in a single component and enhance engineering performance and efficiency is FAST-DB—whereby multiple alloys in powder form are diffusion bonded (DB) using field-assisted sintering technology (FAST). But the joining of multiple alloys using conventional welding and joining techniques can generate high residual stress in the bond region that can affect the mechanical performance of the components. In this study, the residual stress distribution across dissimilar titanium alloy diffusion bonds, processed from powder using FAST, were measured using X-Ray diffraction and the Contour method. The measurements show low residual stress in the bulk material processed with FAST as well as in the diffusion bond region. In addition, FAST-DB preforms subsequently hot forged into different near-net shapes were also analyzed to understand how the residual stress in the bond region is affected by a subsequent processing. Overall, no sharp transitions in residual stress was observed between the dissimilar alloys. This study reinforces confidence in the solid-state FAST process for manufacturing next generation components from multiple titanium alloy powders.

Evaluation of electron beam wire-fed deposition technology for titanium compressor blade repair

In this research, two Ti‐8Al‐1V‐1Mo compressor blades with approximately 20,000 h of service were repaired using electron beam wire-feed (EB-WF) additive manufacturing (AM) technology. Ti‐6Al‐4V wire was used as the feedstock to fabricate layer-by-layer a thin-walled structure on the worn blade. The repaired compressor blades were inspected to examine the residual stresses, distortion, microstructure, chemistry, and mechanical properties with special attention given to characterize the interfacial zone between the dissimilar titanium alloys. The distortion after the repair was limited to ± 0.1 mm on the leading edge just adjacent to the interface, which shows the good potential of the developed method for repair applications. The different microstructural regions, consisting of transient, steady-state, dilution, and heat affected zones, were thoroughly characterized using optical microscopy and correlated with the microhardness. The average Vickers hardness in the blade and repair were measured as 338 ± 6 Hv and 312 ± 7 Hv, respectively. To characterize the tensile properties, miniature tensile test specimens were extracted from the repair interface. The yield strength, ultimate tensile strength, and elongation at break of the tested miniature specimens ranged between 869 and 906 MPa, 925–956 MPa, and 10–11 %, respectively. The tensile results were compared to similar literature studies and related standards. All specimens met the minimum requirement of AMS 4911 P wrought specifications, indicating the sound mechanical integrity of the repair. Fractography analysis showed that failure occurred in the repair section, which carries a high potential for maximizing the service life of the blade by allowing periodic repair and overhaul.

Microstructure and deformation mechanism of dissimilar titanium alloy Ti600/Ti22Al25Nb weld joints strengthened by isothermal forging

With the rapid development of the aerospace and civil fields, there are often different performance requirements for different parts of one component. In this paper, we jointed traditional titanium Ti600 and Ti-based intermetallic compound Ti22Al25Nb by vacuum electron beam welding. To improve the weld properties, isothermal forging was performed to strengthen the weld joints. The microstructure after welding and that after isothermal forging were compared, and the mechanism of microstructure evolution was analyzed. The deformation behaviors of the weld joints after isothermal forging were analyzed by the in situ tensile method, and the fracture characteristics were investigated. The results showed that the fusion zone of Ti600/Ti22Al25Nb vacuum electron beam weld joints was a typical dendrite structure, that postwelding heat treatment cannot refine grains, and that the improvement in mechanical properties was limited. During isothermal forging, dynamic recrystallization of grains occurred, and the second phase α2 in the grains was effectively broken. The plasticity and strength of the samples were significantly improved after isothermal forging.

Texture characteristics and fracture mechanism of linear friction welded joints of dissimilar titanium alloys after annealing

In the paper, we discussed the effect of annealing on the microstructure, crystal texture, and toughness of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si (TC11) and Ti–4Mo–4Cr–5Al–2Sn–2Zr (TC17) linear friction welding (LFW) joint. The results reveal that the microstructure difference on both welded zone (WZ) decreases. The TC11 WZ consists of supersaturated solid solution α′ phase and β phase, the coarse α grains disappear and the orthorhombic martensite α″ phases transform into lamellar α+α′ phases on the TC17 WZ after the double furnace annealing. Two β textures (shear and annealing textures) and two α textures (D and E textures) exist at the original joint, and both of them transform into new β textures (brass and copper textures) and α textures (F and G textures) after the double furnace annealing. The dislocation density of the TC17 WZ is significantly higher than that of the TC11 WZ at the original joint. After the double furnace annealing, dislocation density, grain type, and Schmid factor (SF) distribute uniformly throughout the entire WZ. The average dislocation density decreases slightly and the low SF (μ<0.25) almost disappears. The microhardness value of the entire joint is more uniform and stable, and the fracture toughness is 137% higher than that of the original joint, approximately reaching 91% of the TC11 fracture toughness. The research provides a theoretical basis for preparing high-toughness joints of dissimilar titanium alloys.

Effect of Heat Treatment on the Microstructure and Properties of Ti600/TC18 Joints by Inertia Friction Welding

The Ti600/TC18 dissimilar titanium alloy joints were prepared by inertia friction welding (IFW). Then, stress-relief annealing and two-stage annealing were performed to optimize the microstructure and properties of the original joints, the purpose of them is to improve the structure and performance of the joints. Then, the microstructure, phase composition, tensile properties, microhardness, and fracture morphology of the joints after heat treatments were investigated. The results showed that after stress-relief annealing, the microstructure of the joints was almost similar to that of the specimen before annealing; the weld zone (WZ) of the joints was composed of fine recrystallized grains and α', and the more β phases underwent a martensitic transformation. The shapes and sizes of αp phases were increased after two-stage annealing; its percentage content was decreased. The tensile properties and the microhardness values of the joints undergoing stress-relief annealing were relatively higher than that of the joints undergoing two-stage annealing; there was no obvious change in the plasticity of the joints. It was confirmed that the stress-relief annealing microstructure was composed of α' and β phases, which were beneficial to the properties of the joints. However, the αs phases were coarsened after two-stage annealing, and the properties of the joints were reduced.

Thermal-strain-induced dynamic recrystallization and elements partitioning at heterogeneous bonding interfaces of titanium alloys

• Fine recrystallization grains are formed at the heterogeneous bonding interface. • The original bonding interfaces transform into different curved grain boundaries. • Elements partitioning occurs across the bonding interface with Mo and Nb diffusion. • No harmful heterogeneous precipitates formed around the bonding interface. The laminated bonding interfaces of Ti6Al3Nb2Zr1Mo (Ti-6321) and Ti6Al4V (TC4) form an interfacial transition zone during plastic deformation bonding. The interfacial dynamic recrystallization by lattice and subgrain rotation occurs around the bonding interface, inducing the formation of fine grains at the interface. The original bonding interface transforms into curved low or high-angle grain boundaries, suggesting that the bonding interface of dissimilar titanium alloys achieves complete metallurgical bonding. Moreover, elements partitioning occurs across the bonding interface with Mo and Nb in the α phase of Ti-6321 diffusing into the β phase of the TC4 side adjacent to the bonding interface.

Evaluation of welded joints of dissimilar titanium alloy Ti-5Al-2.5Sn and stainless-steel 304 at different multi-interlayer modes

Products manufactured by joining titanium and stainless steel are of great attention to the modern-day industries (aerospace and nuclear) due to their several benefits like high strength, low cost, and corrosion resistance. However, it is difficult to join these alloys owing to the formation of TiFe, Ti2Fe, and TiFe2 compounds which damage their mechanical properties. This study aims to evaluate the microstructural and mechanical properties of titanium alloy Ti-5Al-2.5Sn and stainless steel 304 joints. Joining was performed through pulse–gas tungsten arc welding (P-GTAW) by inserting the Nb-Cu multi-interlayer. The effects of welding speed, two multi-interlayer application modes, and arc offset on the microstructure and mechanical properties such as tensile strength and microhardness were investigated. The mechanical properties were evaluated through tensile and hardness tests while microstructural analysis using scanning electron microscopy (SEM) supported by electron dispersive spectroscopy (EDS). The results revealed that sound and high-quality welds were achieved using a multi-interlayer, which inhibited the formation of TiFe, Ti2Fe, and TiFe2 brittle intermetallic compounds (IMCs). Maximum joint strength of 327 MPa was achieved at a welding speed of 200 mm min−1, mode of multi-interlayer (Nb used as a foil and Cu as a wire) at no arc offsetting, whereas a low joint strength was obtained in the multi-interlayer mode (Nb and Cu both as foils), and arc offset towards SS. The SEM and EDS results revealed that a Cu solid solution was obtained in the fusion zone, which improved the tensile strength. Joint fracture surface analysis indicated that ductile fracture was obtained for high-strength and brittle fracture for the low-strength weld. It is evident that high hardness (400 HV) was obtained at a low welding speed (150 mm min−1) and an arc offset to the stainless steel side owing to the formation of TiCu and Ti2Cu phases, as revealed by the x-ray diffraction phase analysis.

Investigation of microstructure evolution and mechanical properties of gas tungsten arc welded dissimilar titanium (CP-Ti/Ti–6Al–4V) alloys

Economical welding of dissimilar titanium alloys has always been a challenge for the aerospace and nuclear industries, where these alloys are extensively used because of their high strength-to-weight ratio. The present investigation deals with the development of a novel shielding setup for the successful welding of commercially pure titanium (α-phase) to Ti–6Al–4V ((α + β)-phase) without any atmospheric contamination using gas tungsten arc welding. Commercially pure titanium (CP-Ti) and Ti–6Al–4V sheets of 3 mm thickness were butt-welded autogenously and using CP-Ti filler metal. Metallographic studies, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, microhardness measurements, tensile testing, and fractography were carried out to understand the evolution of the microstructure and characterize the welds. Grain coarsening in heat-affected zone and weld, and variation in the distribution of phases were observed from the optical micrographs and energy-dispersive X-ray spectroscopy spectrum of different zones. An unsymmetrical variation of hardness was observed in the weld region, and a 15% reduction in hardness value (280 HV0.2) was obtained at the weld center of using filler metal weld than autogenous weld. Comparable strengths with little drop from as-received CP-Ti (307 MPa) were observed for welded specimens. Welds produced using CP-Ti filler metal (272 MPa) had higher strength than autogenous welds (214 MPa). As-received tensile specimens fractured nearly from the center of gauge length, but welded tensile specimens fractured near the base/heat-affected zone boundary of the CP-Ti side.

Microstructure evolution during linear friction welding of dissimilar titanium alloys TC4 and TC17

Microstructure evolution during linear friction welding of dissimilar titanium alloys TC4 and TC17

Microstructure transition gradients in titanium dissimilar alloy (Ti-5Al-5V-5Mo-3Cr/Ti-6Al-4V) tailored wire-arc additively manufactured components

The nature of the chemical mixing and microstructure gradients that occur across the interface transition, when manufacturing tailored components with the two high-performance dissimilar titanium alloys (Ti-6Al-4V (Ti-64) and Ti-5Al-5V-5Mo-3Cr (Ti-5553)) by the wire-arc additive manufacturing (WAAM) process, are reported. It has been shown that a relatively long-range chemical gradient occurs during the transition between layers produced with the two different titanium alloys, due to convective mixing in the melt pool between the substrate layers and new alloy wire. This resulted in a stepwise exponential decay composition profile normal to the layers, the width of which can be described by a simple dilution law, with steep local composition gradients seen within the boundary layers at the fusion boundary of each individual layer. The alloy-alloy composition gradients had little effect on the β-grain structure. However, they strongly influenced the transformation microstructure, due to their effect on the parent β-phase stability and the β → α transformation kinetics and reaction sequence. The microstructure gradient seen on transitioning from Ti-64 → Ti-5553 was significantly more abrupt, compared to when depositing the two alloys in the reverse order. Under WAAM thermal conditions, Ti-64 appears to be more sensitive to the effect of adding β-stabilising elements than when Ti-5553 is diluted by Ti-64, because at high cooling rates, stabilisation of the β phase readily suppresses α nucleation when cooling through the β transus, and the normal Ti-64 lamellar transformation microstructure is abruptly replaced by finer scale α laths generated by precipitation during subsequent reheating cycles.

Microstructural response at the interface and its effect on the fatigue fracture behavior of rotary friction welded dissimilar titanium alloys: Ti–5Al–2Sn–2Zr–4Mo–4Cr (Ti17) and Ti–6Al–2Sn–4Zr–2Mo (Ti6242)

Ti17 and Ti6242 tubes were subjected to rotary friction welding to fully understand the microstructural response and its effect on the fatigue fracture behavior of the dissimilar joint. Experiment was conducted using friction linear speed 1 m s−1, friction pressure 80 MPa, burn-off length 5 mm and forging pressure 120 MPa as welding parameters. Electron backscattered diffraction was utilized to systematically examine the microstructures and microtextures across the Ti17/Ti6242 friction welded interface. Thereafter, two fatigue tests were conducted to characterize the fatigue performance of Ti17/Ti6242 joint, one of which is used to identify the fatigue fracture location of the joint and another one to analyze the fatigue fracture behavior. Results clinched that the formation of joint exhibited 600 μm thick weld interface comprises of thermal-mechanical affected zone (TMAZ), heat affected zone (HAZ) and welding zone (WZ) with varying thicknesses (i.e. 100 μm to 200 μm). It was also observed that Ti17 WZ is occupied by equiaxed β grains (mean size of 10 μm) with only one texture which was closely similar to {110} < 111 >. Whereas, Ti6242 WZ contained acicular α’ laths (1 μm) with two types of α texture. Ti17 HAZ + TMAZ were consisted of acicular α’ laths within refined equiaxed β grains and three types of texture of α and β, were respectively found in Ti17 HAZ + TMAZ zone. Whereas, Ti6242 HAZ + TMAZ zone was developed by elongated equiaxed α, acicular α’ laths and few β phases and only two types of texture of α and one type texture of β were found in this zone. The microstructural response across the joint concentrates plastic deformation in Ti6242 HAZ + TMAZ during fatigue cycle, which causes the fatigue fracture occurs at a radial distance of 150μm from the boundary between the Ti6242 TMAZ + HAZ and Ti6242 base metal.