Titanium Alloy Ti Research Articles

Hot isostatic pressing of a near α-Ti alloy: Temperature optimization, microstructural evolution and mechanical performance evaluation

Hot isostatic pressing (HIP) shows distinct advantages in the manufacture of difficult-to-process materials into components with geometric complexity and high mechanical performance. In this work, a near-α titanium alloy Ti–6Al–2Zr–1Mo–1V (TA15) designed for service temperatures of ~500 °C in the aerospace industry was processed by HIP at three representative temperatures. A systematic study on the phase constitutions, microstructural evolution, and tensile properties measured at 20, 500, 600, and 700 °C was carried out for the assessment of HIP TA15 specimens. The relationships among HIP temperature, crystallographic characteristic, and mechanical performance of HIP TA15 were elucidated in detail. Spark plasma sintering (SPS) was selected to compare with the HIP technique regarding the fabrication of TA15 alloy. The tensile strength and ductility of the HIP specimens at 500 °C were 14.8% and 52.8% higher than those of the SPS counterparts. Furthermore, the high-temperature tensile properties of HIP TA15 specimens were comparable to those of the forged IMI 685 and even better than those of sintered Ti60 parts. These findings can serve as a guideline for the HIP process of TA15 alloy and the HIP parameter optimization for other near-α Ti alloys applied in harsh environments.

Experimental investigation on electric discharge drilling of titanium alloy (Ti–6Al–4V) with a gas-aided rotary tool

In this study, the authors tried to make holes in a titanium-based superalloy by a completely new machining method called electro-discharge drilling (EDD) using a gas-aided multi-hole rotating tool. Successful machining of the titanium work samples is extremely challenging due to its extreme hardness and stiffness. One of the key challenges facing the EDD operation is the elimination of spark-eroded matters from the electrodes gap. Arcing happens when the trash is collected in the working passage, which adversely affects the performance of the EDD. In this study, an effort has been made to explore an active flushing mechanism that can improve the flushing activity during the EDD process. Computational fluid dynamics analysis suggested that successful internal flushing by multi-hole rotating tools might result in the efficient removal of the molten material from the electrodes gap. In addition, in this study, a comparative assessment of the EDD with the gas-aided multi-hole rotary electrode and the EDD with the stationary solid tool was carried out taking into account significant EDD responses. Besides, it was observed from the investigation that increased material removal rate and reduced EWR as well as surface roughness were acquired in the EDD with a gas-aided multi-hole rotating electrode in comparison with the EDD with a conventional stationary solid electrode. Basic analysis of surface morphology indicates that the development of recast layers and surface cracks is not very likely to occur on specimens machined with a gas-aided multi-hole rotating electrode in comparison with a workpiece machined with a conventional stationary solid electrode. The results indicate that the use of pressured argon gas in EDD with a gas-assisted multi-hole rotating electrode has a beneficial effect on the execution of the procedure.

Influence of welding sequences on the microstructure and mechanical properties of dual-pass electron beam welded Ti60/V/Cu/GH3128 joints

Electron beam welding of Ti60 titanium alloy to GH3128 nickel-base superalloy was realized by using V/Cu composite interlayers, based on the element metallurgical compatibility. The effects of welding sequences on the microstructures and properties of the joints were analyzed. Microstructures and energy spectrum analysis shown that the reaction of Ti and Ni atoms to form brittle intermetallic compounds (IMC) can be effectively prevented by the interlayers. When the electron beam was first focused on the V foil, the copper foil was melted due to the high melting point of vanadium (1890 °C). Continuously distributed CuTi IMCs were produced near the Ti60 side. When the electron beam was first focused on the Cu foil, CuTi IMCs were replaced by the formation of (Ti,V) solid solutions at the interface of Ti60. A joint with a maximum tensile strength of 392 MPa, 49% of that of the GH3218 alloy was obtained. The fracture morphology proved that the fracture type belonged to brittle fracture.

Cavitation erosion resistance of the titanium alloy Ti–6Al–4V manufactured through additive manufacturing with various peening methods

Additive manufacturing (AM) can produce parts with complex shapes quickly; therefore, it is applied in the manufacturing of impellers for pumps and screws for ships. However, cavitation erosion may occur in these fluid machine components. The fatigue strength and fatigue life of parts manufactured through AM are weaker than those of bulk metals, and the surfaces of these parts are rough owing to AM. Thus, the cavitation erosion resistance of the AM metal may be weaker than those of bulk metals. In this study, to investigate the cavitation erosion resistance of the AM metal, a cavitation erosion test was conducted by using a cavitating jet. The test specimens of titanium alloy Ti–6Al–4V manufactured through electron beam melting were treated using various peening methods that succeeded in improving the fatigue strength of the AM metal. The cavitation erosion resistance of the as-built AM metal without surface treatment was much lower than that of the bulk metal. When the results of the AM metal treated using various peening methods were compared with those of the as-built metal, the erosion rate was observed to have decreased by approximately 40% and 95% for cavitation peening and abrasive cavitation peening, respectively. Therefore, it was found that the cavitation erosion resistance of the AM metal can be improved through peening treatment.

Effect of the structural and phase state on the deformation behavior and mechanical properties of the ultrafine-grained titanium alloy (Ti–Al–V–Мо) at temperatures in the range of 293–973 K

The development of plastic deformation in an ultrafine-grained titanium alloy (Ti–Al–V–Mo; hereinafter VT16 alloy) under tension with a rate of 6.9·10−3 s−1 in the temperature range of 293–973 K is investigated depending on the structure and phase composition of the alloy. It has been established that the deviation of the phase composition from the equilibrium one toward the increasing β phase enhances the resistance of the UFG VT16 alloy to the localization of plastic deformation during tension at low temperatures (293–673 K). Under tension of the UFG VT16 alloy in the temperature range of the superplastic flow (823–973 K), the indicated deviation of the phase composition from the equilibrium one contributes to a greater elongation to failure.

Comparative Quality Control of Titanium Alloy Ti-6Al-4V, 17-4 PH Stainless Steel, and Aluminum Alloy 4047 Either Manufactured or Repaired by Laser Engineered Net Shaping (LENS).

Additive manufacturing attracts much interest for manufacturing and repair of structural parts for the aerospace industry. This paper presents comparative characterization of aircraft items made of Al 4047 alloy, Ti-6Al-4V alloy, and 17-4 precipitation hardened (PH) (AISI 630) stainless steel, either manufactured or repaired by laser engineered net shaping (LENS). Chemical analysis, density, and surface roughness measurements, X-ray micro-computed tomography (μ-CT) analysis, metallography, and micro-hardness testing were conducted. In all three materials, microstructures typical of rapid solidification were observed, along with high density, chemical composition, and hardness comparable to those of the counterpart wrought alloys (even in hard condition). High standard deviation in hardness values, anisotropic geometrical distortion, and overbuild at top edges were observed. The detected defects included partially melted and unmelted powder particles, porosity, and interlayer lack of fusion, in particular at the interface between the substrate plate and the build. There was a fairly good match between the density values measured by μ-CT and those measured by the Archimedes method; there was also good correlation between the type of defects detected by both techniques. Surface roughness, density of partially melted powder particles, and the content of bulk defects were significantly higher in Al 4047 than in 17-4 PH stainless steel and Ti-6Al-4V alloy. Optical gaging can be used reliably for surface roughness measurements. The implications of these findings are discussed.

Evolution of Mechanical Properties of Ti–6Al–4V Alloy in the Temperature Range of 20 to − 196 °C

Cryogenic cooling is becoming an attractive method for machining difficult-to-cut materials to extend their machinability. However, it’s a challenging task to analyze the effect of cryogenic cooling on the machining. In order to better understand the various physical phenomena in the cryogenic cutting process, cryogenic impact test, and tensile test of titanium alloy Ti–6Al–4V were undertaken in this work. The impact and tensile properties of Ti–6Al–4V alloy in the temperature range of 20 to − 196 °C were investigated. Later on, the macroscopic and microscopic morphology of the produced fractures were analyzed. Findings have depicted a decreasing impact toughness and an increase of tensile and yield strength of Ti–6Al–4V alloy in the temperature range from 20 to − 196 °C. The impact fracture appeared as a tendency of becoming material brittle. Meanwhile, three kinds of zones of shear-lip, fiber, and radiation were found on the fracture morphology. Those zones correspond to the shear fracture zone, crack initiation zone, and crack extension zone, respectively. With the temperature decrease, the proportion of fiber zone was decreased, while a gradual increase in the radiation zone was observed. Besides, the fiber zone was observed for the macroscopic morphology of the fracture under the temperature of − 196 °C. Some dimples were found in the tensile fracture at − 196 °C indicating the ability of Ti–6Al–4V alloy to deform plastically under such low temperature. This work is a fundamental support to analyze the behavior of Ti–6Al–4V alloy under cryogenic cooling conditions.

Crack initiation mechanism and fatigue life of titanium alloy Ti–6Al–2Sn–2Zr–3Mo-X: Effects of stress ratio and loading frequency

In this paper, the fatigue behavior of Ti–6Al–2Sn–2Zr–3Mo-X alloy with basketweave microstructure is investigated at stress ratios R = −1, −0.5, 0.1 and 0.3 and loading frequencies f = 0.4 Hz, 4 Hz and 35 Hz. It is shown that the Ti–6Al–2Sn–2Zr–3Mo-X alloy presents two different crack initiation mechanisms. One is due to the cleavage of α grains and the other is due to the microstructure inhomogeneity and deformation incompatibility. For the former case, the fracture surface exhibits facet feature in the crack initiation region. For the latter case, the crack nucleates and initiates at α grains or interfaces and the fracture surface presents no facet feature in the crack initiation region. The higher stress ratio and the lower frequency tend to induce the higher probability for the occurrence of multiple crack initiation mode. Moreover, the paper indicates that the effect of stress ratio on fatigue life could be expressed as Nf = A [(1–R)/2]lσma,R, where A, l and m are material parameters. The scatter of fatigue life is related to both the stress amplitude and the loading frequency. For relative higher stress amplitude, the fatigue life and the frequency at R = −1 could be correlated by a linear relation in log-log scale.

Influence of welding parameters on microstructure and mechanical properties of electron beam welded Ti60 to GH3128 joint with a Cu interlayer

Effects of welding parameters on the microstructure and mechanical properties of Ti/Cu/Ni joint welded by electron beam were investigated. High welding heat input increased the melting quantity of Ti60 titanium alloy and promoted the formation of Ti–Cu intermetallic compounds (IMC) such as Ti2Cu and Ti3Cu4, increasing the brittleness of the joints. Low welding heat input was not conducive to the complete melting of the copper interlayer, and the unmelted copper reduced the performance of the joints. Under the optimal welding parameters, Ti–Ni IMCs in the weld would be replaced by (Cu, Ni) solid solutions ((Cu, Ni)ss). However, Ti–Cu IMC layers cannot be eliminated entirely by changing the welding parameters. The maximum tensile strength of the joints was 201 MPa. The fracture of the joints occurred at the Ti–Cu IMC layer, which was a typical brittle fracture.

Fractography, Fracture Toughness and Structural Turbulence Under Low-Temperature Shock Loading of a Nonequilibrium Titanium Alloy Ti–6Al–4V

The titanium alloy Ti–6Al–4V with strongly nonequilibrium α- and β-phases has been studied for the first time. For this, it was subjected to cross-helical rolling (CHR) at T = 1000°C (above the polymorphic transformation temperature), and then quenched in water in order to partially preserve vanadium in the α-phase, and aluminum in the β-phase. Under active uniaxial tension, the non-equilibrium VT6 alloy was deformed in the absence of strain hardening at room temperature. Alloys treated with CHR below the polymorphic transformation temperature showed traditional parabolic hardening. The non-equilibrium of the VT6 alloy caused a strong increase in its impact toughness at low temperatures down to T = –70°C. The fatigue life of a nonequilibrium alloy has doubled. If the initial alloy has ductile-brittle fracture at low negative temperatures, then the nonequilibrium alloy deforms viscously with all signs of structural turbulence. Structural turbulence in a nonequilibrium alloy manifests itself in the temperature range from 20 to –70°C, during deformation of 3D-printed samples, under conditions of shock separation of diffusion-sintered multilayer VT6 alloy packets.

In-situ investigation on tensile deformation and fracture behaviors of a new metastable β titanium alloy

The tensile deformation and fracture behaviors of a new metastable β titanium alloy (Ti–5Cr–4Al–4Zr–3Mo–2W-0.8Fe) with single β phase are investigated by in-situ tensile test under scanning electron microscopy. With the increase of deformation degree, in addition to the transition from single slip to multiple slip, the stress induced martensite (SIM) and mechanical twins will also occur to coordinate the overall deformation of the alloy, leading to further work hardening. The slip system activation, slip transfer and grain rotation are closely related to the crystallographic orientation, which can be evaluated by Schmid factor, geometric compatibility factor and misorientation. The dislocation pile-up leads to serious stress concentration and inhomogeneous deformation appeared in the areas near grain boundary, dislocation line and shear band, and the microvoids are easy to nucleate and grow in the above areas and then coalescence into microcracks. The primary crack formed by microcrack extension propagates along the activated slip system in the grain, and deflects as it passes through the grain boundary to coordinate the slip system in the adjacent grain, resulting in the overall crack propagation path being zigzag. Considering the damage prone location and crack propagation path, it can be concluded that the fracture mechanism of the alloy belongs to the intergranular and transgranular mixture.

A study on the machinability of advanced arc PVD AlCrN-coated tungsten carbide tools in drilling of CFRP/titanium alloy stacks

This study aims to investigate the effect of an aluminum chromium nitride (AlCrN) coating on tool wear and hole quality in the conventional drilling process of carbon fiber-reinforced plastic (CFRP) composites, titanium alloy (Ti), and CFRP–Ti stack workpieces popular in the aerospace industry. The advanced arc plasma acceleration (APA) method of physical vapor deposition (PVD) was used for all AlCrN coatings. The drilling experiments were conducted with uncoated drills as well as AlCrN-coated drills. When drilling CFRP only, the AlCrN coating was removed at the drill cutting edges and the margin area, which suggests the carbon fibers abraded the coatings. When drilling Ti only, the AlCrN-coated drill mitigated the Ti adhesion formation, which resulted in less tool wear. In addition, hole quality for both CFRP and Ti was improved when the coating was used versus the uncoated tool. The machinability of CFRP–Ti stacks in the drilling process was improved by utilizing the advanced AlCrN coating on the WC tool in terms of drilling forces and hole quality parameters such as average hole size, average hole roundness, hole surface roughness, and Ti exit burr height.

Tensile deformation behavior of coarse-grained Ti-55 titanium alloy with different hydrogen additions

The effect of hydrogen addition on the deformation behavior of coarse-grained Ti-55 alloys (~ 20 μm) was studied by uniaxial tension tests at high temperature. The elongation of hydrogenated Ti-55 titanium alloy firstly increases and then decreases with hydrogen content increasing at 875 °C. The highest elongation of 243.8% is obtained in the hydrogenated alloy with 0.1 wt% H, and the peak stress reaches a minimum value of 29.0 MPa in the hydrogenated alloy with 0.3 wt% H. Compared with that of the unhydrogenated alloy, the elongation of the hydrogenated alloy with 0.1 wt% H increases by 41.3% and its peak stress decreases by 40.6% at 875 °C. Hydrogen addition can promote the transformation of β phase and the dislocation movement. Appropriate hydrogen content can evidently improve the deformation properties of coarse-grained Ti-55 titanium alloy.

Corrosion resistance of selective laser melted Ti–6Al–4V alloy in salt fog environment

In this study the corrosion resistance of an additively manufactured (AM) titanium alloy Ti–6Al–4V (Ti64) in a simulated marine environment was investigated. Selective laser melting (SLM) process was used to fabricate Ti64 coupons that were tested in a simulated marine environment using a salt fog chamber. The corroded specimens were characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. The AM printed Ti64 was determined to form a protective oxide layer that develops after approximately 400 ​h of exposure in a salt fog chamber, after which mass change plateaued. The protective oxide formed was determined to be a mixed oxide primarily consisting of TiO2and Al2O3.

High speed machining of titanium Ti 6Al4V alloy components: study and optimisation of cutting parameters using RSM

ABSTRACT Titanium alloy Ti 6Al4V alloys are widely used in aerospace industries due to attractive characteristics of the material for its highest formability characteristics also offers a combination of high strength, light weight and corrosion resistance which have made it a world standard in aerospace applications. The new challenge in machining is to use high cutting speed in order to increase the productivity but for rapid tool wear. The titanium and its alloys are difficult to machine due its low thermal conductivity, wherein 80% of the heat generated in the cutting region goes to the cutting tool and causes wear. High speed finish machining of highly reactive material like titanium and its alloys is still uncertain. A detailed optimisation study of machining parameters with different cutting speeds before advancing to high speed machining. This research paper presents the influence of machining parameters like coolant flow rate, cutting speed, feed rate, depth of cut on tool life of PVD coated inserts used for machining of Titanium alloy.

Corrosion-Resistant Functional Diamond Coatings for Reliable Interfacing of Liquid Metals with Solid Metals.

Gallium-based liquid metals (GLMs) exist as atypical liquid-phase metals at and near room temperature while being electrically and thermally conductive, enabling copious applications in soft electronics and thermal management systems. Yet, solid metals are affected by interfacing with GLMs, resulting in liquid metal embrittlement and device failure. To avert this issue, mechanically durable and electrically tunable diffusion barriers for long-term reliable liquid metal-solid metal interfacing based on the deposition of various diamond coatings are designed and synthesized, as they feature high chemical inertness and extraordinary mechanical resistance. The diamond coatings show superlyophobicity (GLM contact angle ≥ 155°) and are nonstick toward GLMs, thereby achieving high mobility of GLM droplets (sliding angle 8-12°). The excellent barrier and anti-adhesion performance of the diamond coatings are proven in long-term experiments (3 weeks) of coated titanium alloy (Ti) samples in contact with GLMs. The electrical performance of the conductive diamond coating deposited on Ti is reliable and stable over a period of 50 h. As proof-of-concept applications a switch and a thermal management device based on liquid metals are demonstrated, signifying that coating diamond films on metals is a potent means to achieve stable integration of solid metals with GLMs.

Enhanced extra-long life fatigue resistance of a bimodal titanium alloy by laser shock peening

Ultrasonic fatigue tests were performed on notched specimens to investigate high and very high cycle fatigue behaviors in the laser shock peened region of a compressor blade titanium alloy (Ti–8Al–1Mo–1V). The plastic deformation and compressive residual stress, induced by the laser shock peening (LSP), present gradient distributions along the depth direction. High-angle grain boundaries (HAGB, >15°) are increased by deformation twins, which are introduced into primary α phases during the plastic deformation. The enhancement in fatigue resistance is ascribed to the comprehensive retardation effects of the compressive residual stress, high-density dislocations, and HAGBs.

Effect of machined surface texture on fretting crack nucleation under radial loading in conformal contact

This paper presented the influence of machined surface texture on fretting cracks behaviors of Titanium alloy Ti–6Al–4V under radial loading in conformal contact. The contacted holes of specimen were machined with combined helical and flank milling before fretting fatigue tests, and a special fretting fatigue test apparatus was proposed to focus on conformal contact fretting fatigue (CCFF) test under radial loading. The test results showed that all the specimens failed at the contact area where characterizes an inner obtuse angle between the material flow direction (or cutting direction) and the direction of the tangential component of the contact force. The area with higher surface skewness and kurtosis values was also prone to nucleate fretting fatigue crack. These results suggested that the corresponding machining conditions in hole-making and surface strengthen processes should be adjusted to guide the production of surface texture properties, in terms of obtaining desirable lower skewness and kurtosis features to relieve nucleation of fretting cracks. Additionally, the debris in conformal contact tended to aggregate towards the partial slip zone (PSZ) due to the conformal geometry and form a compacted layer in the gross slip zone (GSZ) subjected to radial loading. These characteristics exacerbated and alleviated fretting damage in the PSZ and GSZ, respectively. In this research, a set of suitable milling parameters for the hole flank milling process in terms of prolonging fretting fatigue life were also defined.

Compressive deformation of a metastable β titanium alloy undergoing a stress-induced martensitic transformation: The role of β grain size

Compressive deformation of a metastable β titanium alloy (Ti–10V–2Fe–3Al) with different β grain sizes ranging from 109 μm to 494 μm was systematically investigated by using X-ray diffraction, electron backscatter diffraction and transmission electron microscopy techniques. As β grain size increases, the triggering stress of stress-induced martensitic transformation (β→α″) in Ti–10V–2Fe–3Al alloys gradually increases, while the amount of α″ martensite decreases, along with the gradual disappearance of double yield behavior in compressive stress-strain curves and three-stage behavior of work hardening rate and exponent. Deformation mechanisms of Ti–10V–2Fe–3Al alloy with different β grain sizes change from stress-induced martensitic transformation at small strains to stress-induced martensitic transformation, together with widening and merging of α″ martensite at large strains. Besides, {111}α″ type I internal twinning and {112}α″ type I deformation twinning are observed at Ti–10V–2Fe–3Al alloy with an average β grain size of 494 μm. During the compressive deformation, β matrix was repeatedly consumed and cut by α″ laths, leading to the formation of nano-sized α″ blocks and β blocks. This dynamic grain refinement contributes to a higher work hardening rate and enhanced compressive mechanical properties in the metastable β titanium alloy.

DESIGN, ANALYSIS AND COMPARISON OF VARIOUS MATERIALS FOR CONNECTING ROD

Connecting rod is engine component which transmits motion from piston to the crankshaft and serves as lever arm. The function of connecting rod is to convert piston’s reciprocal movement into rotary motion of the crankshaft. Connecting rod generally made from Carbon steel and Aluminium alloys have been used in recent days and some different materials are finding it’s application. The performance connecting rod in automobile engine is influenced by it’s design and weight for production of durable, cheaper and light connecting rod, hence optimization and analysis of connecting rod. The 3D model of connecting rod is designed and developed using CATIA V5. In proposed approach different materials compared like Aluminium alloy 7075, Magnesium alloy, Titanium alloys (Ti -3Al- 2.5V) and beryllium alloy (25) are taken for the analysis of connecting rod and factors like Stress, Strain and Deformation were obtained. The purpose of this study is identify best materials for connecting rod, after analysing at ANSYS APDL 15.0. KEYWORDS : Connecting rod, CATIA V5, ANSYS APDL15.0, Aluminium alloy 7075, Magnesium alloy, Titanium alloy (Ti-3Al-2.5V) and Beryllium Alloy (25).