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Titanium alloy can be found in numerous applications, such as chemical, aerospace, and energy industries, among other sectors, due to its excellent performance. Nevertheless, the possible uses of a variety of titanium-based alloys have been greatly restricted by their low hardness and inadequate resistance to wear. Therefore, in this research work, WC–Cu composite electrode assisted electrical discharge coating (EDC) is used for improving microhardness (MH) and surface integrity of Ti–6Al–4V alloy. By utilizing powder composite electrode, the conductivity of the electrode can be increased, which provides controlled electric spark, resulting in uniform deposition. In order to increase the rate of deposition, the terminal of the EDM has been changed as WC–Cu composite electrode as anode and workpiece as cathode. Response surface methodology is used for studying the variables including compacting pressure (MPa), discharge current (I), pulse on time (Ton). In addition, microstructure, elemental analysis and coating interface of deposited Ti–6Al–4V alloy are investigated through scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The surface roughness of 8.86 µm was achieved at 400 MPa, 6 A, and 40 µs. The maximum MH of 988 HV was obtained at 400 MPa, 10 A, and 80 µs. The MH of the deposited layer is around 2–3 times harder than base material. Moreover, a greater adhesion strength coated layer was ∼118 N, which permits the alloy to have improved wear resistance. It was concluded that using a high-pressure electrode with lower settings resulted in an improved surface finish, while higher settings led to increased MH. [ABSTRACT FROM AUTHOR]

In this study, a nanofluid ultrasonic atomization minimum quantity lubrication (MQL) system was employed for grinding and processing titanium alloy (Ti-6Al-4V). Nanoparticles in the nanofluid were dispersed through the ultrasonic atomization MQL system to improve the lubrication efficiency. This system is a grinding manufacturing innovation on lubrication technology. First, a robust design method optimizes the grinding parameters of force ratio, temperature, and surface roughness of each quality characteristic. Surface integrity is considered a key component metric in grinding. Therefore, various images of the grinding surface quality were collected to establish a complete titanium alloy grinding image database. The convolutional neural network (CNN) technique was used to establish a model with high accuracy and automatic recognition of the surface quality after grinding, which is classified as Good, Plowing, Crushing pits, and Bad. This study employed VGG-19, GoogLeNet, ResNet-50, and AlexNet for modeling and testing comparison. Different hyperparameter configurations will affect each model's learning speed and performance. Therefore, their hyperparameter optimizations were performed before establishing our CNN model for classification. After optimization, the average accuracy of the four models can be improved by 3.75–12%, which can quickly improve the performance of the CNN model systematically. This study verified and validated our model. The findings show that this research method can be used by the industry in the actual grinding process monitoring and identification of the grinding quality of Ti-6Al-4V. [ABSTRACT FROM AUTHOR]

Direct Metal Laser Sintered (DMLSed) titanium grade 5 alloy (Ti-6Al-4V alloy) is one of the widely used 3D Printed alloy in structural aerospace components. In the present work, the effect of laser sintering on the microstructure and the mechanical and corrosion behavior of DMLSed Ti-6Al-4V alloy has been studied. The samples were printed by varying the laser power and scan speed over a wide range, one parameter at a time. The fabricated Ti-6Al-4V alloy predominantly showed the martensitic structure, which governs the overall performance of the printed alloy. The mechanism of martensitic laths formation in the microstructures is presented to understand their evolution and effect on the mechanical behavior. As a result, the tensile strength and hardness of the fabricated Ti-6Al-4V alloy increased by nearly 33 and 5%, respectively, when the laser power was increased from 150 to 300 W at a fixed scan speed of 1250 mm/s. An 8% increase in tensile strength and 1-2% increase in hardness was observed when the scan speed was increased from 500 to 1250 mm/s, at a fixed laser power of 150 W. The corrosion resistance of fabricated Ti-6Al-4V alloy improved with an increase in laser power but deteriorated with an increase in scan speed. This study led to new insights into the microstructural evolution of direct laser-sintered Ti-6Al-4V alloy, which is likely to assist in producing superior quality DMLS parts. [ABSTRACT FROM AUTHOR]

The effects of the secondary processes of Hot Isostatic Pressing (HIP) at 920 °C and Heat Treatment (HT) at 1000 °C of Electron Beam-Melted (EBM) Ti–6Al–4V alloy on the microstructure and hydrogen embrittlement (HE) after electrochemical hydrogen charging (EC) were investigated. Comprehensive characterization, including microstructural analysis, X-ray diffraction (XRD), thermal desorption analysis, and mechanical testing, was conducted. After HIP, the β-phase morphology changed from discontinuous Widmanstätten to a more continuous structure, 10 times and ~1.5 times larger in length and width, respectively. Following HT, the β-phase morphology changed to a continuous "web-like" structure, ~4.5 times larger in width. Despite similar mechanical behavior in their non-hydrogenated state, the post-treated alloys exhibit increased susceptibility to HE due to enhanced hydrogen penetration into the bulk. It is shown that hydrogen content in the samples' bulk is inversely dependent on surface hydride content. It is therefore concluded that the formed hydride surface layer is crucial for inhibiting further hydrogen penetration and adsorption into the bulk and thus for reducing HE susceptibility. The lack of a hydride surface layer in the samples subject to HIP and HT highlights the importance of choosing secondary treatment process parameters that will not increase the continuous β-phase morphology of EBM Ti–6Al–4V alloys in applications that involve electrochemical hydrogen environments. [ABSTRACT FROM AUTHOR]

The tailored thermal heat-treatment process for Ti-6Al-4V alloy manufactured by laser–arc hybrid additive manufacturing can achieve desired microstructures and excellent mechanical properties for components. The effects of different heat treatment regimens on the microstructure and mechanical properties of Ti-6Al-4V alloy manufactured by laser–arc hybrid additive manufacturing are investigated in this study. Utilizing optical microscopy and scanning electron microscopy, we analyze the variations in microstructure with changes in heat-treatment parameters and explore the reasons for the changes in mechanical properties under different solutions' treatment temperatures and cooling rates. The microstructure of Ti-6Al-4V alloy fabricated via laser–arc hybrid additive manufacturing was primarily composed of Widmanstätten α plate structures and a small amount of acicular martensite α′ within columnar β grains that grew outward from the substrate along the deposition direction. Following solution treatment and aging heat treatment, the microstructure transitioned to a typical high-performance net basket structure with significantly reduced α plate thickness, leading to noticeable enhancements in sample ductility and toughness. Specifically, when the solution treatment and aging treatment regimen was set at 950 °C for 1 h, followed by air cooling, and then aging at 540 °C for 6 h with subsequent air cooling, the average grain size decreased by a factor of two compared to the as-deposited samples, while the impact toughness increased by 66.7%. [ABSTRACT FROM AUTHOR]

A new Mg-4Zn X Ti-6Al-4V (TC4, of 0, 1, and 3 wt.%) alloy was successfully fabricated by a simple and low-cost gravity casting method and heat treatment at 150 °C for 24 h. The composite was examined by XRD, uniaxial tests, FESEM/EDS, potentiostat/EIS, and immersion tests for the material's microstructures, mechanical properties, electrochemical characteristics, and corrosion resistance. Experimental results indicate that heat treatment enables the precipitation of Zn along the Mg grain boundaries and drives the co-precipitation of Al around the TC4 particles and nearby grain boundaries. Uniaxial tensile tests reveal that TC4 reinforces the Mg-Zn matrix material with higher elastic modulus, ultimate tensile stress, and toughness. The heat treatment further enhanced these mechanical properties. Electrochemical tests show that 1 wt.% TC4 composite exhibits the highest open circuit potential among all tested samples, which implies the 1 wt.% TC4-added Mg-Zn is better resistant to the oxidation of the essential metals Mg, Zn, and Al. The immersion tests in the HBSS solution further show that the 1 wt.% TC4 composite has the lowest rise of pH values after 14 days, and EDS for the corroded surface signifies that Mg is the main element vulnerable to oxidation by corrosion. [ABSTRACT FROM AUTHOR]

In this work, a new use of mixed Ti-6Al-4V powder, consisting of the retained powder after screening for additive manufacturing and the recycled powder after multiple printing, has been exploited. The powder mixture has been hot-isostatically-pressed (HIPed) at 930 °C/120 MPa for 3 h to reach full density. The hot deformation behavior of the as-HIPed powder compacts were investigated through isothermal compression tests, kinetic analyses, and hot processing maps. Finally, the optimized hot working parameters were validated using upsetting tests. The results show that the as-HIPed Ti-6Al-4V alloy has a fine and homogeneous microstructure. The activation energies were calculated to be 359 kJ/mol in the α + β phase regime and 463 kJ/mol in the β phase regime, respectively. The optimal hot working parameters are a deformation temperature above 950 °C and strain rate higher than 0.1 s−1. The hot workability of as-HIPed powder compacts is better than the as-cast billets. The deformed microstructure can be finer than that of as-HIPed state, and the mechanical performance can be further improved by the optimal thermo-mechanical processing treatment. [ABSTRACT FROM AUTHOR]

The present work deals with heat treatment of tungsten inert gas (TIG)-welded Ti-6Al-4 V alloy plates. Four welded plates were taken under study. Three plates were heat-treated and one plate was kept in 'as welded' condition. The heating temperature was 1050°C for a holding time of 20 min. After heating, these three welded plates were cooled at three different media like water, sand and air. The tensile strength and hardness of the heat-treated samples and the 'as welded' sample were measured by using universal testing machine and Rockwell hardness tester, respectively. Also, the microstructures of all the samples were observed by using optical microscope. Three different types of microstructures of Ti alloy, Bi-modal, martensite and Widmanstätten, were observed in this study. Due to possessing Bi-modal structure, 'as welded' specimen showed a good combination of ultimate tensile strength (UTS), hardness and ductility. The martensitic structure had made the water-quenched specimen stronger and harder than 'as welded' specimen. The sand-cooled sample had both Widmanstätten and Bi-modal structure. It showed the least hardness among all samples. Air-cooled specimen had mainly contained Widmanstätten microstructure with high value of UTS and moderate hardness. [ABSTRACT FROM AUTHOR]

In the present study, the microstructural evolution alongside its microhardness evaluation has been emphasized for Ti-6Al-4V alloy sheets subjected to asymmetrical cryorolling, warm rolling, and hot rolling up to 50 and 75% thickness reductions. Cryorolling helps in achieving a unique combination of high strength and ductility after proper heat treatment procedures due to ultrafine grain refinement. Microstructural behaviors show that the average grain size is the lowest for Ti-6Al-4V sheet during cryorolling conditions when the average grain sizes recorded are 497, 369, and 216 nm after 50% thickness reduction, and 301, 253, and 106 nm after 75% thickness reduction due to asymmetrical hot rolling, warm rolling, and cryorolling, respectively. It is also observed that the samples subjected to 75% thickness reduction via cryorolling have the highest hardness (VHN395). Furthermore, phase analysis of the dual-phase Ti-(α + β) alloy has been accomplished which showed the effects of the presence of β-Ti phase and the balance alongside its α-Ti counterpart that dictate its mechanical properties. In conjunction with these studies, a simple FEM simulation has been shown for a conventional rolling process using ABAQUS 2019 software for its better understanding. [ABSTRACT FROM AUTHOR]

The isothermal constant strain rate compression test of Ti-6Al-4V alloy with a hydrogen content of 0.31 wt.% was carried out on a Gleeble-1500 thermomechanical simulator. The thermal deformation behavior at temperatures of 700-950 °C and strain rates of 0.001-10 s−1 was studied. The results show that the flow stress of the alloy is sensitive to the deformation temperature and strain rate. The flow stress decreases with increasing deformation temperature and increases with increasing strain rate. Using the Arrhenius hyperbolic sine function, the constitutive equations for the Ti-6Al-4V alloy with 0.31 wt.% hydrogen in the α + β two-phasic region as well as in the β single-phase region were derived. Processing maps were established by superimposing the instability map and the power dissipation map. Compared with the Ti-6Al-4V alloy without hydrogen, the flow stress of the alloy is reduced, and the microstructure becomes refined. The β grain size increases with increasing deformation temperature. The dynamic recrystallization rate decreases with decreasing strain rate. The instability phenomena often occur at low temperatures. The instability region grows steadily with increasing strain. The alloy should be avoided in thermal processing at high strain rates (> 0.01 s−1) and low temperatures (< 800 °C). [ABSTRACT FROM AUTHOR]

Ultrasonic vibration has considerable influence on the plastic deformation and resulting fracture responses of metallic alloys. This manuscript critically aims at quantification and assessment of two-dimensional ductile dimple geometry of Ti-6Al-4V alloy generated through the variation of ultrasonic vibration with different powers during tensile experiments. The analyzed dimple geometry statistics as a function of ultrasonic power are completely based on a published article. The alteration of microstructural states, leading to different dimple appearances after inducing different ultrasonic vibrations during tensile deformation, have been extensively quantified/assessed, compared and interpreted with respective mechanical responses of the alloy as a function of ultrasonic power. Moreover, the change in strain hardening path patterns through the variation of ultrasonic power has clearly reflected on the dimple statistics/dimensions on their respective tensile fractographs. This novel 'dimple geometry-ultrasonic power-tensile response' interpretation allows the use of two-dimensional ductile dimple fracture appearances in a quantitative way. The remarkable manifestation of ultrasonic vibration on tensile responses of Ti-6Al-4V alloy and hence the change in fracture appearances have been convincingly revealed. [ABSTRACT FROM AUTHOR]

Micro-electrical discharge machining (micro-EDM) stands out as a transformative methodology, offering substantial progress in both technical and economic efficiency through the integration of coated electrodes. This study meticulously analyzes various technological parameters in micro-EDM, focusing specifically on Ti-6Al-4V, a widely employed titanium alloy. The application of a titanium nitride (TiN) coating material on a tungsten carbide (WC) electrode is investigated using the Taguchi method of experimental design. This study employs an ANOVA and factorial design methodology to scrutinize the influence of key parameters, namely voltage (V), capacitance (C), and spindle rotation (in revolutions per minute) (RPM) on the tool wear rate (TWR), overcut (OVC), and Z coordinate (depth) within the micro-EDM process. The findings unveil a noteworthy increase in the TWR with an elevated V, C, and RPM, with capacitance exerting a pronounced influence while voltage exhibits the least impact. OVC exhibits notable variations, revealing an inverse relationship with RPM. The Z coordinate (depth) is significantly affected by capacitance, with voltage and RPM each having a relatively negligible impact. A surface quality analysis exposes similarities and numerous defects in both coated and uncoated electrodes, emphasizing the need for further exploration into the effectiveness of coated electrodes in enhancing post-micro-EDM machined surface layers. This study contributes valuable insights to optimize and advance micro-EDM processes, laying groundwork for future innovations in precision machining. [ABSTRACT FROM AUTHOR]

Laser surface quenching (LSQ) was employed to fabricate gradient microstructures in a Ti-6Al-4V alloy. The influence of the LSQ parameters on the surface morphology, the depth of the LSQ layer, gradient microstructure, and microhardness were investigated. The results showed that as the laser energy density increases, the surface roughness and thickness of the heat-affected zone (HAZ) increase. From the internal matrix to the surface, the microstructure in the HAZ changes from the equiaxed structure to the mixt structure, martensitic structure, Widmanstätten structure, and then the oxide layer. The size of the ß grains gradually decreases as the distance from the surface increases. The different microstructures and elemental distributions in the HAZ result in different microhardness values, which gradually decrease from the surface to the matrix. The laser energy density of 8.0 J/mm2 is recommended to obtain a HAZ with a thickness of 1200 µm and a peak microhardness of 393 ± 7.3 H V without surface remelting. The LSQ process may help to increase the longevity of Ti-6Al-4V alloy implants by hardening the surface. [ABSTRACT FROM AUTHOR]

Electrochemical machining (ECM) is an efficient technique for machining hard-to-cut metallic materials such as titanium alloys. Based on ECM, jet electrochemical machining (jet-ECM) in which electrolyte is continuously ejected from the cathode tool nozzle improves the mass transfer. In jet-ECM, the electrolyte usually forms a flow along the workpiece after the impacting, leading to a weak current density distribution which surrounds the machining region. In jet-ECM of titanium alloys, stray corrosion easily occurs on the un-machined surface around the machining region as a result of the susceptibility of titanium alloys to stray current. In this paper, a method for rapidly obtaining the ideal jet reflection shape by applying an ultra-high current density is proposed. This method effectively separates the reflected electrolyte from the workpiece, thus protecting the un-machined surface from stray corrosion. Simulations with multiple coupled physical fields are established to investigate the interactions among the electric field distribution, flow field distribution, and geometry deformation in jet-ECM. A series of observational experiments are carried out to verify the simulation results. To study the influence of the current density on the machining characteristics, the performance of jet-ECM using current densities from 200 to 600 A/cm2 was discussed in terms of the achievable groove dimensions, material removal rate, current efficiency, and energy efficiency. The results reveal that a proper jet reflection shape can be rapidly formed in jet-ECM by applying an ultra-high current density, and the grooves fabricated in this way are free from stray corrosion and possess shape edges. [ABSTRACT FROM AUTHOR]

In the application of Ti-6Al-4V to aerospace structural components, when welding thick plates similar of the thickness of the components, microstructure and hardness gradients emerge between the base material (BM) and the joint. This leads to the issue of significant stress concentration in the BM under tensile stress. To address this problem through post-welding heat treatment, this study conducted heat treatments at temperatures both below (mill annealing, MA) and above the beta-transus temperature (beta annealing, BA) on electron-beam weldments of 18 mm thickness Ti-6Al-4V plates. Subsequently, microstructures and hardness were analyzed at different depths from the upper surface and areas (fusion zone (FZ), heat-affected zone (HAZ), and BM), and tensile properties were measured at various depths. The results indicated that α′ observed in FZ and HAZ was resolved through both MA and BA. Particularly after BA, the microstructural gradient that persisted even after MA completely disappeared, resulting in the homogenization of widmanstätten α + β. Consequently, after BA, the hardness gradient in each zone also disappeared, and the tensile strength was higher than in just-welded and MA heat-treated plates. [ABSTRACT FROM AUTHOR]

A nanosecond laser is used to fabricate groove-patterned textures on the upper surface of Ti-6Al-4V alloys, and then molybdic sulfide solid lubricants are filled into the grooves. The treated titanium alloy is subjected to friction and wear tests. The tribological performances of Ti-6Al-4V alloys are evaluated, and the wearing mechanism is analyzed. The combination of solid lubricants and surface texturing can effectively reduce the frictional coefficient and reduce the adhesion of Ti-6Al-4V materials on the steel balls for friction. The main wearing mechanism is the adhesive wear of the Ti-6Al-4V alloy and the adhesion of Ti-6Al-4V alloy materials on the surface of the steel balls. During the friction process, solid lubricants are squeezed from the grooves and coated at the friction interface to form a solid lubrication layer. This is the important reason why the combination of surface texturing and solid lubricants can improve the friction properties of titanium alloys effectively. The combination of solid lubricants and laser surface texturing provides an effective alternative way to improve the tribological properties of titanium alloy materials. [ABSTRACT FROM AUTHOR]

The influence of gaseous hydrogen charging at 600 °C on the microstructure and mechanical behavior of wrought and Electron Beam Melted (EBM) Ti–6Al–4V alloys was investigated for hydrogen contents between 0.14 and 1.0 wt%. The small punch test (SPT) technique was used to characterize the mechanical behavior of all specimens. Both EBM and wrought alloys containing ∼6 wt% β and similar impurity levels showed similar phase content and mechanical property changes at all hydrogen contents, regardless of their original microstructural differences. This similarity can be explained by the high hydrogen diffusivity at the high temperature at which gaseous charging was carried out, and is in contrast to previous reports where EBM Ti–6Al–4V was found to be more sensitive to hydrogen embrittlement due to low-temperature electrochemical charging. After hydrogenation, α H and β H solid solutions were formed. The quantity of the α H phase reduced gradually with hydrogen content, while forming β H , α 2 , and hydrides. It was found that β H saturated at 0.27 wt% hydrogen content. Both alloys demonstrated relatively high strength and ductility up to hydrogen content of 0.2 wt%, i.e. below the β H saturation concentration. Above the β H saturation concentration, the mechanical properties of the maximum load (P max), deflection at maximum load (δ max), and absorbed energy (E) , degraded significantly due to hydride formation. [Display omitted] • The effects of gaseous hydrogenation on EBM and wrought Ti–6Al–4V were compared. • Both alloys had a similar phase and impurities content in the non-hydrogenated form. • Both alloys showed a similar mechanical behavior at any hydrogen content. • Above the β H saturation point, the mechanical properties degraded significantly. • Hydrogen-induced degradation is different after gaseous vs. electrochemical charging. [ABSTRACT FROM AUTHOR]

An unfavourable combination of metallurgical factors and high stresses may result in the fracture of additively manufactured parts, especially in the case of high-strength alloys. Frequently in direct laser deposition (DLD) fabrication of large-scale parts, it is impossible to obtain desirable structural-phase composition and required mechanical properties of the depositing metal due to the low inter-pass temperature. Thereby, the stress and strain levels must be reduced to prevent fracture of the build part. The present work seeks to analyse the effectiveness of the proposed approaches for reducing residual stresses and strains by (i) local adjustment of the buildup geometry and (ii) addition of a ductile transition layer. The process conditions were close to those used to produce large-scale parts by the DLD method, resulting in the buildup having the same thermal history. The following cases are analysed: a single-wall buildup of Ti-6Al-4V alloy with flat-faced and concave fillets, and a single-wall buildup with a ductile transition layer of commercially pure titanium between the rigid substrate and rest buildup of the Ti-6Al-4V. A simulation procedure based on the implicit finite element method was adopted for the theoretical study of the stress-strain field evolution. It was found that the addition of flat-faced fillets has little effect on the magnitude of the accumulated plastic strain. On the other hand, concave fillets result in considerable plastic strain reduction compared to buildup without fillets by a factor of 2.8 for 14-mm fillet radius and 5.8 for 28-mm fillet radius. The addition of a transition layer of a less strong and more ductile alloy than the rest buildup causes non-uniform deformation of the buildup. The more brittle buildup part of the Ti-6Al-4V practically does not deform plastically and has a considerably lower peak stress than the buildup entirely composed of the Ti-6Al-4V. [ABSTRACT FROM AUTHOR]

Laser polishing, as a post-processing or in situ precision-smoothing technology, is a surface modification method aimed at improving the rough surface and properties of additive manufactured components. In this paper, the effect of in situ laser polishing on the surface modification of Ti-6Al-4V alloy prepared by selective laser melting (SLM) has been investigated. The optimum process parameters were selected for experiments in the range of high power and low power, respectively. The results showed that the surface roughness was reduced by 81.8% (from 6.38 to 1.16 µm Sa) after laser polishing, which significantly improved the surface quality of SLM parts. The number of pores in the polished layer and heat-affected zone was greatly reduced, and the depth of remelted layer was more than 400 µm, which made the microhardness and wear resistance of the laser polished parts obviously increased compared with the as-printed ones. In addition, the reduction of microdefects (adhesive particles, partially melted powders, and pores) on polished surface and the grain refinement made the laser polished parts exhibit stronger corrosion resistance. Because of these enhancements, in situ laser polishing represents a suitable method to improve surface properties of SLM parts, and provides the feasibility and possibility for the integrated processing of 3D printing and laser polishing. [ABSTRACT FROM AUTHOR]

For decades many models of orthogonal cutting have been developed with limited practical application. In the scope of Industry 4.0, a need is felt to develop models of practical machining operations, like turning, milling, and drilling. This research work contributes for the development of reliable 3D models of practical machining operations by proposing a model of turning using a constitutive model considering the effects of the state of stress and strain-rate on the elasto-viscoplastic and damage behaviors of Ti-6Al-4V alloy. The accuracy of the 3D turning model was evaluated by comparing the predicted machining outcomes (forces, chip thickness, residual stresses, and thickness of strain-hardened layer) with those obtained experimentally. The model can predict quite well the cutting force but underestimate the feed force. The predicted residual stresses match reasonably well the experimental ones in both circumferential and axial direction, and the simulated thicknesses of strain hardened layer were close to the experimental ones. ANOVA permitted to investigate the influence of the cutting conditions on the thermomechanical phenomena and surface integrity. Suggestions to improve 3D models of practical machining operations are proposed. [ABSTRACT FROM AUTHOR]

This manuscript describes the study of density, porosity, microstructure, formation of phases, elemental distribution, tensile properties, fractography, microhardness, fracture toughness, and abrasion resistance of multi-layer deposition Ti-6Al-4V-5Ni alloy developed by μ-plasma metal additive manufacturing (μ-PBMAM) process for high temperature and high strength applications. It also presents comparison of these aspects with multi-layer depositions of Ti-6Al-4V alloy. Thermo-calc simulated phase diagram was used to decide at.% of Ni to be added to aerospace grade Ti-6Al-4V alloy. It found that adding 5% of Ni promotes grain refinement without forming C14 Laves phase and increasing the β-transus temperature. Optimum values of μ-plasma power and μ-plasma torch travel speed were identified by manufacturing single-layer depositions of Ti-6Al-4V-5Ni alloy thorough diluted depth, aspect ratio, deposition quality, deposition geometry, and deposition efficiency as the criteria to manufacture its multi-layer deposition. Results reveal that inclusion of nickel to Ti-6Al-4V alloy increased the volumetric percentage of β-Ti phase from 13 to 27% and refined grains of α-Ti and β-Ti phases which improved yield and ultimate tensile strength of Ti-6Al-4V-5Ni alloy by 13.4% and 17.8% respectively and reduced % elongation by 36% as compared to Ti-6Al-4V alloy. It changed fractured pattern from ductile to combined ductile and brittle fracture consisting of cleavage facets, voids, and larger size dimples. It increased % porosity, microhardness, fracture toughness, and abrasion resistance thus imparting Ti-6Al-4V-5Ni alloy more resistance to crack initiation and more restriction to movement of the dislocations. Vanadium and nickel contents in β-Ti phase of Ti-6Al-4V-5Ni alloy are 3 to 5 times and 21 to 25 times more than that its α-Ti phase, respectively. Findings of this work demonstrate that μ-PBMAM developed Ti-6Al-4V-5Ni alloy is useful for high temperature, high strength, and light weight applications in aerospace, space, automobile, and dies and mold industries due to promotion and grain refinement of β-Ti phase, improvement in microstructure, microhardness, yield and tensile strength, fracture toughness, abrasion resistance. [ABSTRACT FROM AUTHOR]

One of the most recent methods for fabricating titanium-based products is metal injection molding (MIM). However, there have been few systematic studies on the definition and generation mechanism of surface porosity of MIM Ti–6Al–4V and its relationship with powder, process, and mechanical performances so far. In this article, MIM was selected to produce Ti–6Al–4V, and the investigation aimed to determine the impact of the sintering and subsequent hot isostatic pressing (HIP) process on its microstructure and mechanical performances. The results indicate that Ti–6Al–4V alloy formed a dense layer after sintering because of the temperature gradient from surface to core. The thickness of dense layer, grain size, grain morphology, and grain orientation are the key factors that determine Ti–6Al–4V alloy's mechanical performances. Under the condition of sintering at 1000 ℃ with HIP process, Ti–6Al–4V alloy formed a dense layer with a thickness of 290 µm, equiaxed grains with an average grain size of 16 µm, and a significant number of high-angle grain boundaries (88.9%). The optimized microstructure of Ti–6Al–4V led to outstanding mechanical performances, exhibiting tensile strength of 1067 MPa, yield strength of 997 MPa, and elongation of 17.5%. Other MIM materials can also be guided by this approach. [ABSTRACT FROM AUTHOR]

In the presented work, the formation of anodic oxide film on Ti-6Al-4V ELI (Extra Low Interstitial) alloy in 0.02 M trisodium phosphate (Na3PO4) electrolyte solution using various voltages were investigated. The color produced by the anodizing, the intensity of TiO2 content, the thickness of the oxide layer, and the corrosion rate were examined. It was obtained that the color appearance of Ti-6Al-4V ELI could be changed easily by altering the applied voltages. The higher the voltage applied in the anodizing process, the thicker the titanium oxide layer formed. The corrosion resistance analysis in a Simulated Body Fluid revealed that the non-anodized specimen showed a higher corrosion rate compared to the anodized specimen. The increase of oxide layer thickness leads to a significant decrease in corrosion rate and consequently increases the corrosion resistance. In addition, the anodized sample achieved the highest corrosion resistance at 15 V. [ABSTRACT FROM AUTHOR]

Welding and joining Titanium and its alloys are always challenging because getting a contamination-free joint is difficult with arc welding. For this concern, an attempt was made with and without shielding arrangements using the Gas Tungsten Arc Welding (GTAW) process on the Ti-6Al-4V alloy sheet. To study the presence of oxygen and other elements with respect to surface colourization at the weld zone, an Energy-dispersive X-ray spectroscopy (EDX) analysis is carried out. Based on the EDX analysis, post-flow and pre-flow shielding gases are also included in the operation window. Bead on Plate (BoP) trials are performed using the shielding arrangement setup and selected parameters on the thin sheets (2 mm) of Ti-6Al-4V. After examining the BoP trails, defect-free joins in a 2 mm sheet are fabricated using the optimal welding parameters. The microstructure of the joint is captured and compared with the simulation work. Compared to the base metal, coarse and enormous grains are identified at the weld zone. Due to the proper shielding, no cracks appeared in the joint subjected to the three-point bend test. The considerable heat input during the GTAW process resulted in the nucleation of (ά) in FZ, as spotted in the TEM images. The microhardness value at FZ for base metal is 373 HV and 332 HV, respectively. It is confirmed that the suggested shielding setup could prevent contamination in welds resulting in better mechanical properties. [ABSTRACT FROM AUTHOR]

Ti1-xAlxN coating is formed by replacing some Ti atoms in TiN with Al atoms, and their properties are closely related to Al content (0 < x < 1). Recently, Ti1-xAlxN-coated tools have been widely used in the machining of Ti-6Al-4V alloy. In this paper, the hard-to-machine material Ti-6Al-4V alloy is used as the study material. Ti1-xAlxN-coated tools are used for milling experiments. The evolution of the wear form and the wear mechanism of Ti1-xAlxN-coated tools are studied, and the influence of Al content (x = 0.52, 0.62) and cutting speed on tool wear are analyzed. The results show that the wear on the rake face changes from the initial adhesion and micro-chipping to coating delamination and chipping. Wear on the flank face varies from the initial adhesion and grooves to boundary wear, build-up layer, and ablation. The main wear mechanisms of Ti1-xAlxN-coated tools are dominated by adhesion, diffusion, and oxidation wear. Ti0.48Al0.52N coating protects the tool well and extends its service life. [ABSTRACT FROM AUTHOR]

Here, we investigated the microstructure and mechanical properties of dissimilar joints between grade 2 commercially pure titanium (CPTi-2) and Ti6Al4V alloy welded via friction welding. Accordingly, specimens with 15mm diameter and 50mm length were prepared, and friction welding was performed at a constant rotation speed (1600 rpm) and different upset lengths: 1, 2, and 3 mm. Electron backscattered diffraction (EBSD) method was introduced to systematically analyze grain boundary characteristic distributions (GBCDs), such as grain size, grain orientation, phase distribution, and misorientation angle distribution. In addition, mechanical properties of dissimilar joints were evaluated using the micro-Vickers hardness and tensile test machine. The microstructures at both sides of the CP-Ti-2 and Ti6Al4V alloy were refined materials, compared with each base material. These grain refinements were determined via dynamic recrystallization accompanied by frictional heat and severe plastic deformation. In addition, the increase in the upset length distinctively affected the change trend of the grain size of the CP-Ti-2 and Ti6Al4V alloy. The hardness values in regions around the weld interface were higher than those of base materials. Furthermore, yield and tensile strengths were maintained at a similar level to those of CP-Ti-2, and the tensile specimens were fractured at the base material zone of CP-Ti-2, not at the weld interface and its periphery. Consequently, friction welding to dissimilar joints between the CP-Ti-2 and Ti6Al4V alloy was successfully conducted and sound welded materials without welding defects were obtained. [ABSTRACT FROM AUTHOR]

In this work, the micro-laser metal wire deposition (μLMWD) with ms-pulsed wave emission and low duty cycles was utilized to build the Ti-6Al-4V thin walls. The work first investigated the influence of the process parameters on single track stability and geometry. With the developed processing conditions thin walls with multiple layers were produced. The μLMWD produced thin walls were characterized by fine grain size expected to be due to the columnar to equiaxed transition (CET) in the produced wall. Fine columnar grains formed in the bottom region of wall due to the restriction of melt pool size and large cooling speed, while equiaxed grain formation and further refinement were achieved in the middle region, attributed to the intermittent stirring force that broke dendritic arms and increased nucleation events before solid–liquid interface. From the bottom to top region microstructures transferred from acicular α′ to short α lamella constituting basketweave structure, and the periodic heating and cooling generating by pulsed laser reduced the acicular α′ at higher cooling rate and decreased α size. The forming of equiaxed grain and fine grain and microstructure increased the wall microhardness. [ABSTRACT FROM AUTHOR]

In this research, hydroxyapatite powder particles were coated on a Ti-6Al-4V alloy substrate by the plasma spraying method to create bone implants by benefitting from titanium's mechanical properties and hydroxyapatite's biological properties. Hydroxyapatite prepared by the plasma spraying method suffers from decomposition, formation of other calcium phosphate phases, weak adhesion to the substrate, and microcrack formation in the coating due to residual stresses initiated by the high temperature of the coating process. To improve the hydroxyapatite coating properties, the Ti-6Al-4V alloy was preheated, and then hydroxyapatite coating took place. The results showed that residual stress in the interface decreased, and adhesion improved by preheating the substrate. However, formation of an amorphous phase on coating was observed, resulting in a higher dissolution rate in the biological environment and weak mechanical properties compared to crystalline hydroxyapatite. Experimental results showed that heat treatment after the coating process decreased the amount of this amorphous phase and heightened the crystallinity of the coating by up to more than 60%. [ABSTRACT FROM AUTHOR]

During the additive manufacturing (AM) of Ti-6Al-4V alloy components, the coarse columnar primary β grain structure is more likely to form due to the low nucleation rate of titanium alloys, rapid solidification, and a high-temperature gradient. However, the effect of the size and morphology of the primary β grains on α phase is not well understood. To eliminate large coarse columnar grains in Ti-6Al-4V alloy, a dual ultrasonic vibration (UV) method was proposed and implemented in laser and wire AM to fabricate thin-walled parts. The mechanisms of microstructure evolution and the effects of ultrasound under dual UV were simulated using electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and COMSOL software. It was observed that coarse columnar primary β grains were transformed into equiaxed primary β grains (CET),with the average grain size decreasing from 1678.4 μm to 467.9 μm after the simultaneous application of dual UV on the top and the bottom of the deposited layer. The α phase showed an obvious radial growth pattern attributed to the uniform energy field produced by the dual ultrasound. Compared with the samples without the UV treatment, the ultimate tensile strength (UTS), yield strength (YS), and elongation of the Ti-6Al-4V alloy subjected to dual UV treatment increased by 26.7 %, 24.7 %, and 104 %, respectively. Furthermore, the ultrasonic mechanism associated with the Ti-6Al-4V alloy was discussed. [ABSTRACT FROM AUTHOR]

In the aeronautical industry, many components are subjected to abrasive machining processes to ensure surface integrity. However, many of these components are manufactured from titanium alloys, such as the Ti-6Al-4V alloy, which is considered a difficult material to machine due to its low thermal conductivity, high mechanical strength, and chemical reactivity with ceramic materials. As dressing one of major factors governing grinding, the proper selection of dressing parameters for the abrasive wheel is crucial for the surface quality of difficult-to-machine materials as well as the loading of the abrasive wheel. In this sense, the present work aimed to evaluate the effects of different dressing conditions of a SiC grinding wheel on the surface integrity of the Ti-6Al-4V alloy. A fliesen dresser, two different overlap ratio values (Ud = 3 and Ud = 12), and two depth of dressing cuts (ad = 20 µm and ad = 40 µm) were employed in the experiments. From the analysis of the results, it was verified that the change in the grinding wheel conditioning from an aggressive dressing (Ud = 3 and ad = 40 µm) to a soft dressing condition (Ud = 12 and ad = 20 µm) generated a drop of 53.74% in the roughness values, oriented grooves on the ground surface, reduction in thermal dams below the grinding interface, and an increase of 65.93% in the G ratio. Therefore, the results showed that the change in the conditioning of the SiC grinding wheel through the dressing can improve Ti-6Al-4V alloy grindability. [ABSTRACT FROM AUTHOR]

BACKGROUND: Full crowns have variable shapes and sizes, and are used for tooth restoration. This type of thin-walled parts usually requires high precision, light weight and thin wall thickness, but it is easy to deform during forming and reduce the accuracy of the workpiece. OBJECTIVE: To explore the influence of different energy densities on the deformation of titanium alloy full crowns, and obtain the optimal combination of process parameters for forming titanium alloy full crowns. METHODS: The full crown of Ti-6Al-4V titanium alloy was formed by selective laser melting. The influence of energy densities (77.38, 48.15, 32.83, 71.76, 46.97, 61.51, 68.18, 85.71, 55.56 J/mm3 ) on deformation was studied. The process parameters were optimized, and the parts printed after parameter optimization were heat treated. RESULTS AND CONCLUSION: Deformation experiments showed that a reasonable combination of process parameters could reduce the degree of deformation of the formed parts. When the energy density was 68.18 J/mm3 (laser power, scanning speed, and scanning distance were 180 W, 800 mm/s, 0.11 mm, respectively), the average value of deformation of the specimen formed at this energy density was 1.594 mm, which was smaller than the deformation of the cantilever beam at other energy densities. Under the optimized combined process parameters, the average amount of deformation after heat treatment was 0.355 mm; the average roughness was 8.306 μm; the average hardness was 345 HV, in line with industry standards. The research results provide experimental data and theoretical basis for forming high-quality thin-walled parts. [ABSTRACT FROM AUTHOR]

Lanthanum oxide powder was added to improve the microstructure and properties of a Ti-6Al-4V alloy part during cold metal transfer (CMT) based on wire arc additive manufacturing (WAAM). The macrostructure, microstructure and properties of the part were studied by using an optical microscope (OM), scanning electron microscope (SEM), electron backscatter(ed) diffraction (EBSD), microhardness evaluation and a tensile test. The results showed that the β grain size and martensite (α) size were reduced by adding lanthanum oxide powder. The texture intensity of the part also decreased due to the change in microstructure. Accordingly, the microhardness and tensile properties of the part obtained by adding lanthanum oxide were improved. In addition, based on the interdependence theory model, adding La2O3 particles in the molten pool as heterogeneous nucleation points could reduce the distance of XSD, so fine equiaxed β grains can be formed in the deposition layer. [ABSTRACT FROM AUTHOR]

In this work, the experimental investigation of the surface integrity and biomechanical properties of the superficial layer obtained by wire electrical discharge machining (W-EDM) of Ti-6Al-4V alloy for biomedical application has been carried out. The surface morphology and elemental composition of the superficial layer have been investigated by field-emission scanning electron microscope (FE-SEM) and energy dispersive X-ray spectroscopy (EDS) techniques. The micro-mechanical behavior in terms of compressive strength and surface hardness was studied using the micro-pillar and nano-indentation technique. The corrosion resistance and in vitro bioactivity have been investigated using electrochemical and immersion test. Morphological analysis showed that surface morphology and superficial layer thickness were affected by peak current, pulse-duration and pulse-interval. The niobium (Nb)-rich layer was developed in superficial layer zone. The low peak current (3–6 A), low pulse-duration (5–10 μ s) and high pulse-interval (> 4 5 μ s) have been recommended for better surface morphology and thin superficial layer (ranging from 4–6 μ m) free from surface defects. The micro-pillar and nano-indentation results showed that the superficial layer comprised of a brittle structure that improved the mechanical properties of the layer and the compressive strength was measured to be 1198 MPa. The corrosion resistance analysis revealed that the Nb-rich layer in the superficial layer improved the corrosion resistance and bioactivity. Excellent apatite growth has been found in the W-EDM-processed zone. The W-EDM can be used for the biomedical industry as a potential surface engineering technique. [ABSTRACT FROM AUTHOR]

It is a novel promising technology that the advantages of vibration are applied to the plastic forming process. This study is prompted by the effect of the number of blows and dwell time on the forming properties of forgings when hammer forging impact is considered as vibration excitation. Taking Ti-6Al-4V alloy as the research object, this study investigates the forging quality and strength-toughness through hammer forging experiments. Then, a numerical model is established and verified by experiments. The results show that increasing the number of blows at constant total dwell time can obviously decrease the cumulative damage, stress concentration and residual stress in forgings, while improving the uniformity of forging deformation, average grain size and residual stress distribution. In addition, the proportion of fine grains in the forging is also increased. The adjustment of hammer forging impact parameters from the perspective of vibration excitation is effective in improving the performance of forgings, which can provide a theoretical basis for the future development of advanced hammer forging technology. [ABSTRACT FROM AUTHOR]

Thermophysical properties of the Ti-6Al-4V titanium alloy make it difficult to process with electro discharge machining (EDM) process. The aim of this experimental work was to investigate manufacturing of micro-holes in titanium alloy by means of EDM. Further investigation the accuracy of drilled holes was performed in order to improve the EDM drilling method in this alloy. As a part of the research, the impact of four EDM process parameters on performance factors such as: material removal rate (MMR), linear tool wear (LTW) was verified in parallel to accuracy metrics of the micro-hole: radial overcut (ROC), cylindricity (CYL), recast layer thickness (RLT). The analysis of the obtained relationships showed that the properties of the Ti-6Al-4V alloy, such as low thermal conductivity, and low electrical conductivity significantly affect the EDM process efficiency. It is clearly visible through increased electrode wear, as well as the accuracy and quality reduction of the drilled holes. When analyzing the accuracy of the hollow micro-holes, it was observed that the highest current amplitude resulted in a smaller amount of microcracks in the layer around the hole entrance. The optimal process parameters to obtain a satisfactory geometry of micro-holes have been found such as: current amplitude 3.33-4.65 A, pulse time duration 550-1000 µs, open voltage 100 V, and tool rotation speed 300 rpm. [ABSTRACT FROM AUTHOR]

The kerf taper angle is one of the most significant parameters for AWJ cutting. Choosing the best cutting parameters is critical to reducing the kerf taper. Therefore, the aim of this work is to demonstrate on to implement RSM in conjunction with the Rat swarm optimizer algorithm to optimize the kerf taper angle of a Titanium alloy. Thirty-two number of experiments were conducted according to CCD considering five process parameters namely jet traverse rate, water jet pressure, abrasive flow rate, stand-off distance and diameter of focusing nozzle to achieve kerf taper angle. A second-order full quadratic model is used for mathematical modeling. The result demonstrates that the model is sufficiently adequate and acceptable. A recent Rat Swarm Optimization (RSO) algorithm is considered for finding out the global optimal solution. It is observed that after optimizing the process that the jet traverse rate of 1.952 mm/sec, water jet pressure of 250.548 MPa, abrasive flow rate of 0.554 kg/min, stand-off distance of 3.75 mm and diameter of focusing nozzle of 2.0 mm gives minimized with 0.754 degree of kerf taper angle. A series of verification tests are carried out to ensure that the optimization technique is accurate in determining the best levels of process. [ABSTRACT FROM AUTHOR]

Titanium alloy is a key supporting material in the field of engineering technology and high-tech, and also an extremely important national defense strategic metal material. However, the high cost limits its wider application. Direct rolling of titanium alloy melted by electron beam cold hearth melting (EBCHM) technology is considered to be an important low-cost plate production process. The rolling process has a considerable influence on the microstructure and mechanical properties of the alloy. Therefore, Ti-6Al-4V alloy melted by EBCHM technology was investigated in this study. The effects of different rolling processes on the microstructural evolution and mechanical properties of titanium alloy plates were evaluated. The results show that with the increase of deformation amount and rolling temperature, the more obvious the disintegration of lamella α and the higher the degree of equiaxation when the deformation is below the β transus. However, only dynamic recovery occurs when rolling temperature above the β transus, and lamella α does not undergo disintegration and equiaxation. With ultimate tensile strength (UTS) of 1076 MPa and elongation (EI) of 11%, the plate with 90% deformation at 950 °C has good strength and plasticity. [ABSTRACT FROM AUTHOR]

In this work, the external longitudinal magnetic field hybrid metal inert gas welding (M-MIG) additive manufacturing method is employed to produce the Ti-6Al-4V alloy part. The effect of process parameters on the droplet transfer formation and microstructure of the part was studied by a high-speed camera, optical microscope, and electron backscattered diffraction. The results showed that a typical short-circuiting transfer was obtained with the wire feeding speed of 2 m/min–4 m/min. An external longitudinal magnetic field had an obvious effect on the arc shape. The uniform formation of the deposition layer was obtained with the wire feeding speed of 4 m/min. The width of M-MIG deposition layer was greater than that of the MIG, and the width of M-MIG deposition layer was increased with the increase of the magnetic excitation current. The microstructure of the deposition layer was mainly comprised of acicular martensite α' and massive martensite αm. In addition, the β grain size in the M-MIG was less than that of the MIG. The average microhardness of the MIG deposition layer was 281.6 HV, which was less than that of M-MIG. [ABSTRACT FROM AUTHOR]

In the present work, a novel process called vacuum-encapsulated slurry method is used to form the silicon-modified aluminide coating on Ti-6Al-4V alloy. In this research, the microstructure and high temperature oxidation resistance of such a coating have been investigated. The obtained coating had a triple layer structure. The inner layer was TiAl2, the middle layer contained very thin Ti5Si3 lamellae within the TiAl3 matrix, and was ultimately the outermost layer of Ti(Al,Si)3 into which the Ti7Al5Si12 particles were distributed. The evaluation of isothermal oxidation at 700 °C for 400 h revealed that the formation of silicon-modified aluminide coating is able to improve the high temperature oxidation resistance of the uncoated Ti-6Al-4V alloy. It should be noted that the remarkable improvement in the high temperature oxidation resistance of the sample coated with the silicon-modified aluminide coating produced by the vacuum-encapsulated slurry method is due to the fact that the protective Al2O3 + SiO2 mixed oxide scale along with the continuous, compact and uniform layers of Ti(Al,Si)3 and Ti5Si3 act as a barrier against oxygen diffusion toward the Ti-6Al-4V substrate surface during the high temperature oxidation. [ABSTRACT FROM AUTHOR]

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Ti-6Al-4V (an α + β titanium alloy) pins were slid against the SS316L disc in a pin-on-disc apparatus at different temperatures under vacuum and ambient conditions. Tribological characterization was performed using a field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDAX) analysis and X-ray diffraction. The worn pin surfaces of Ti-6Al-4V were investigated in order to identify the effect of frictional heating at the interface of tribo-pair. To investigate the effects of frictional heating on mechanically mixed layer (MML), experiments were performed under vacuum conditions (2 × 1 0 − 4 Torr) by varying the temperature from 25°C to 400°C at a constant sliding speed of 0.01 ms − 1 and at constant normal load of 137 N. The material was found to transfer from the counter-face to the worn pin surface of alloy where an MML and tribo-oxide (TO) layer were observed to developed on the worn pin surfaces under both the experimental environments. Moreover, a new mechanism, called the "debris burial mechanism" during the formation of the MML at different temperatures was obtained at the interface. The rate of wear was observed to decreased with the increase in frictional heating at the interface resulting to the progressive formation of thicker MML over the worn pin surface. The wear resistances in Ti–6Al–4V alloy decrease rapidly due to loosening the generated MML on the sliding surface. [ABSTRACT FROM AUTHOR]

The joining of thin sheet Ti-6Al-4V alloy has potential application as an encapsulation of miniature components. However, it is quite challenging to achieve a defect-free joint in a fusion welding process since the complexity increases many folds with reduced thickness of the materials. In the present investigation, thin sheet Ti-6Al-4V alloy is welded under different process parameters (26, 45, and 74 J/mm), using a controlled and regulated pulse laser welding technique. The weld joints are further analysed using an experimental and numerical approach to explore the interplay of thermal-microstructural and mechanical characteristics. The outcome of the present investigation reveals better surface quality, desirable microstructural changes, and enhanced joint strength for the joints fabricated under the least heat input condition (26 J/mm). Such overall improvement in the joint characteristics is associated with the high value of cooling rate (2834 K/s), leading to the formation of fine needle-shaped α'-martensite, which corresponds to maximum joint efficiency of 90%. Surface finish is another crucial factor that is affected by the amount of heat input. Joints fabricated under low heat input conditions (26 J/mm) exhibits a lower roughness value (Ra~5.67 µm) as compared to joints fabricated under high heat input conditions (74 J/mm). [ABSTRACT FROM AUTHOR]

This work thoroughly investigated the microstructure of laser powder bed fusion (LPBF) Ti64 alloy induced by electropulsing (ECP) with different current densities. The results show that as the electric current density increases, the small-sized (<10 μm) α′ martensites increase and the large-sized (>10 μm) α′ martensites decrease, resulting in a typical grading microstructure treated by the ECP treatment. The thermodynamic barrier was found to decrease as the electric current passed, recrystallization occurred, and the percentage of small-sized α′ martensites increased. At the same time, the unique electrothermal coupling effect of ECP treatment acted on the needle-like α′ martensites, causing an energy concentration on the tip to break the adjacent α′ martensite and the percentage of large-sized α′ martensites to decrease. When the current density of ECP treatment was 48.37 A/mm2, the grading phenomenon of acicular α′ martensites was the most obvious and its size distribution changed significantly, which simultaneously improved the strength and elongation of LPBF-Ti64 alloy. Thus, the typical grading phenomenon of the α′ martensites plays a decisive role in improving the mechanical properties of the LPBF-Ti64 samples induced by the ECP treatment. The present results provide new information on the ECP processing additive manufacturing metallic materials. [ABSTRACT FROM AUTHOR]

Titanium alloy is a typical difficult-to-machine material with features of superhigh strength and hardness, and low elastic modulus. It is difficult to guarantee the processing quality and efficiency due to the high cutting force and tool wear in conventional cutting. Elliptical vibration cutting (EVC) as an effective method can improve the machinability of titanium alloys. In this paper, the finite element method (FEM) was adopted to study the cutting force and residual stress of 3D EVC in machining of Ti6Al4V. The Johnson-Cook constitutive model was utilized to illustrate the plastic behavior of Ti6Al4V alloy. The kinematics of the 3D EVC was described, and then the influence of various cutting speeds, vibration amplitudes, vibration frequencies and depths of cut on cutting force and residual stress were carried out and analyzed. The simulation results show that the cutting speed, vibration amplitude a, vibration frequency and depth of cut have larger effect on principal force. In addition, the compressive stress layer can be easily obtained near the machined surface by using 3D EVC, which is helpful to improve the working performance of workpiece. [ABSTRACT FROM AUTHOR]

3D printing (or more formally called additive manufacturing) has the potential to revolutionize the way objects are manufactured, ranging from critical applications such as aerospace components to medical devices, making the materials stronger, lighter and more durable than those manufactured via conventional methods. While the mechanical properties of Ti-6Al-4V parts manufactured with two major 3D printing techniques: selective laser melting (SLM) and electron beam melting (EBM), have been reported, it is unknown if the corrosion resistance of the 3D-printed parts is comparable to that of the alloy made with isothermal forging (ISF). The aim of this study was to identify the corrosion resistance and mechanisms of Ti-6Al-4V alloy manufactured by SLM, EBM and ISF via electrochemical corrosion tests in 3.5% NaCl solution, focusing on the effect of microstructures. It was observed that the equiaxed α + β microstructure in the ISF-manufactured Ti-6Al-4V alloy had a superior corrosion resistance to the acicular martensitic α′ + β and lamellar α + β microstructures of the 3D-printed samples via SLM and EBM, respectively. This was mainly due to the fact that (1) a higher amount of β phase was present in the ISF-manufactured sample, and (2) the fraction of phase interfaces was lower in the equiaxed α + β microstructure than in the acicular α′ + β and lamellar α + β microstructures, leading to fewer microgalvanic cells. The lower corrosion resistance of SLM-manufactured sample was also related to the higher strain energy and lower electrochemical potential induced by the presence of martensitic twins, resulting in faster anodic dissolution and higher corrosion rate. [ABSTRACT FROM AUTHOR]

In the present work, the microstructure and mechanical properties of Ti-6Al-4V alloy during multidirectional isothermal forging (MDIF) were systematically investigated. The evolution of the microstructure and texture of Ti-6Al-4V alloy during MDIF was studied using TEM and electron backscattered diffraction (EBSD). The experiment results showed that the grain size decreased with the increase in cumulative strain, especially in the easy deformation zone. After four deformation cycles, a homogeneous equiaxed grained microstructure with an average grain size of 0.14 μm was achieved. The texture changes of the alloy were studied in detail. After one cycle of MDIF, the texture was mainly composed of (0002) [0 1   1 0], and the Euler angles were (8°, 30°, 30°). The density of texture decreased with the increase in loading cycle, but the dispersion of texture increased. After four cycles of MDIF, the non-basal texture (1 010) <11 0 2> texture was observed, and the Euler angles were (82°, 33°, 0°). The highest achieved mechanical properties for Ti-6Al-4V alloy in the MDIF condition were a yield strength 900 MPa, ultimate tensile strength of 921 MPa, and an elongation of 12.1% at room temperature. The increase in MDIF cycles improved the hardness of the alloy. The significant improvement in mechanical properties was attributed to the ultrafine-grained microstructure. [ABSTRACT FROM AUTHOR]

Ti–6Al–4V fine-grained plates were manufactured using a rolling method and then subjected to superplastic tensile tests at varying temperatures and strain rates on an AG 250KNE electronic tensile testing machine. The superplastic behaviours of the plates were also tested. A cavity-growth model was established and the changing laws of energy during cavity growth and microstructure evolution of superplastic deformation were predicted. The Ti–6Al–4V alloy possessed the maximum elongation rate of 886% at 840°C and a strain rate of 5 × 10−4 s−1. The strain-rate sensitivity index m for this alloy was 0.54. The mechanism of superplastic deformation was established to be strain-induced grain-boundary slip, and the mechanism of cavity growth to be plasticity-controlled cavity coalescence and growth. [ABSTRACT FROM AUTHOR]