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This paper presents the results of research on the kinetics of transformations in the two-phase (α + β) Ti-6Al-4V alloy. The transformation start and end temperatures during heating at different rates were determined using a dilatometer. A modified dilatometer was employed, equipped with an acoustic emission measurement apparatus and software enabling the assessment of sample dimensional changes during heating and cooling. The results were obtained in the form of dilatometric curves. Additionally, the occurrence of the transformation was confirmed by acoustic emission signals. In the study of the Ti-6Al-4V alloy, acoustic emission refers to the application of this non-destructive technique to monitor the alloy's behavior during thermal processes. As the temperature increased, regardless of the heating rate, the α→β transformation was observed to occur after exceeding 900 °C. Within the transformation range, acoustic emission signals were recorded. Moreover, it was found that the applied research methods enabled the identification of signal components originating from the transformation. The application of acoustic methods in the analysis of phase transformations opens new possibilities for their use in industry. [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]

The finite element modeling method has been widely applied in the modeling of the cutting process to characterize the instantaneous and microscale deformation mechanism that was difficult to obtain using physical experiments. The lubrication and cooling conditions, such as minimum quantity lubrication and cryogenic liquid nitrogen, affect the thermo-mechanical behaviors and machined surface integrity in the cutting process. In this work, a grain-size-dependent constitutive model was used to model orthogonal cutting for Ti-6Al-4V alloy with MQL and LN2 conditions. The cutting forces and chip morphologies that were measured in the cutting experiments of Ti-6Al-4V alloy were used to validate the simulated forces. The relative errors between the measured and simulated principal forces were less than 8%, while the relative errors of thrust forces were less than 19%. The predicted chip morphologies and surface grain refinement agreed well with the experimental results under the conditions with different uncut chip thicknesses and edge radii. Additionally, the relationship between the plastic displacement and grain refinement, as well as the microhardness and residual stresses under MQL and cryogenic conditions, were discussed. This work provides an effective modeling method for the orthogonal cutting of Ti-6Al-4V alloy to understand the mechanism of the plastic deformation and machined surface integrity under the MQL and LN2 conditions. [ABSTRACT FROM AUTHOR]

In the present study, a hybrid machining process known as an electrochemical cut-off grinding (ECCG) is used for grinding of Inconel-718 material. The specimen (superalloy) contains nickel as major component. It cannot be machined conventionally due to its outstanding properties. During the electrochemical grinding of Inconel 718, the author examines the effects of input voltage (v), tool feed rate (mm/min), electrolytic concentrations (g/ltr), electrolytic flow rate (ltr/min), and grinding speed (rpm) on responses such as material removal rate (MRR) and surface roughness (Ra). The tests contains the bronze-bonded diamond abrasive grinding wheel. The MRR and surface roughness of Inconel 718 and titanium super alloy during the ECCG process are also compared in this research project. Based on the findings of the studies, it appears that the tool feed rate, the flow rate of the electrolyte, and the rotation of the grinding wheel are the maximum influential parameters for enhancing MRR and surface finish during electrochemical cut-off grinding of Inconel 718. Tool feed rates of 0.09 mm/min to 0.18 mm/min, electrolyte flow rates of 5 ltr/min to 8 ltr/min, and grinding wheel speeds of 800 rpm to 2000 rpm are the ideal influencing factors. The comparative analysis demonstrates that Ti-6Al-4 V alloy cannot match Inconel 718's machinability. Compared to Ti-6Al-4 V alloy, Inconel-718 has an average material removal rate that is up to 1.73 times higher and an average surface quality that is up to 3.16 times better. [ABSTRACT FROM AUTHOR]

This study investigates the effects of various surface modification techniques on the Ti-6Al-4V alloy for biomedical applications. Mechanical treatments (sandblasting, shot peening) and electrochemical corrosion using different electrolytes were employed to modify surface characteristics. Surface morphology, roughness, hardness, and chemical composition were analyzed using SEM, profilometry, and Raman spectroscopy. Cell attachment studies revealed that combined treatments, particularly shot peening followed by HF/HNO3 etching, significantly enhanced cell adhesion and distribution. The results demonstrate the potential for tailoring Ti-6Al-4V surfaces to optimize biocompatibility and osseointegration properties for dental and orthopedic implants. [ABSTRACT FROM AUTHOR]

A SiC-SiO 2 nano-composite coating was prepared via a novel liquid-phase plasma-assisted particle deposition and sintering (LPDS) method to enhance the oxidation resistance of the Ti-6Al-4V alloy. For comparison, a conventional plasma electrolytic oxidation (PEO) ceramic coating is fabricated on the Ti-6Al-4V alloy. The microstructure and formation mechanisms of both ceramic coatings were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results indicated that the thickness of the SiC nano-composite coating (∼40 μm) increased significantly by 285 % compared to the PEO coating (∼14 μm). The microstructural evolution and isothermal oxidation performance of the PEO and SiC-SiO 2 nano-composite coating were comparatively investigated at 800 °C. After 100 h, the thickness gain of the SiC-SiO 2 nano-composite coating (∼14 μm) was lower than that of the PEO coating (∼26 μm). The improved oxidation performance is primarily attributed to the outermost layer containing abundant SiC nanoparticles, which transform into SiO 2 during the oxidation process and effectively inhibiting the inward penetration of oxygen. [ABSTRACT FROM AUTHOR]

Ti–6Al–4V and AZ31B alloy sheets were joined in lap joint configuration using cold metal transfer welding with a synergic power source. The torch angle was kept approximately 45° away from the top plate. Wire feed speeds (WFSs) have been varied from 3.0 m/min to 7.0 m/min. Cold metal transfer welding results in good deposition of weld metal at higher WFSs but at the cost of poor bonding and defects. Joints of the best qualities were fabricated at a WFS of 3.0 m/min and a welding speed of 0.6 m/min. The torch angle assisted in the proper deposition of AZ31B weld metal with a good bond between weld metal and Ti–6Al–4V base metal. Microstructural analysis confirms the joint interface integrity by revealing the absence of defects. Also, there is a significant variation among the grain morphology of weld region, transition zone and base metal. The presence of several oxides (MgO4, Al2O3, etc.) and intermetallics (Mg17Al12, Mg7Zn3, AlMg4Zn11, etc.) is indicated by metallurgical analyses. Tensile-shear tests revealed that the joints could sustain the maximum load of 1871 N. Fractography reveals the mixed mode of fracture containing majority brittle, and a ductile failure at a few locations. The unusual fracture at a few locations indicates the presence of oxides in these regions. [ABSTRACT FROM AUTHOR]

ABSTRACT The high cycle fatigue (HCF) behaviors of an additively manufactured (AM) Ti–6Al–4V alloy with fully lamellar microstructures processed electron beam powder bed fusion (EB‐PBF) and wire‐fed electron beam directed energy deposition (Sciaky) routes were compared. Ultrasonic fatigue (USF) testing at the stress ratio of R = −1 was applied to monitor the growth of small cracks initiated at surface micronotches. Crack growth rates lower than 10−8 (m/cycle) at ΔK = 6 MPa·m1/2 were measured in samples processed by both methods. The finer α lath thickness (~1 μm) of the Sciaky samples resulted in a slower fatigue crack growth rate than the EB‐PBF samples with coarser laths. The interaction of cracks with the lamellar microstructures was characterized by electron backscatter diffraction. Crack propagation largely followed the lath interfaces in the Sciaky samples, whereas cracks cut across colonies in the EB‐PBF samples. Different fatigue fracture surface characteristics were observed for the EB‐PBF and Sciaky samples. [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]

A coating of the CoCrCu base powder was prepared on the surface of Ti-6Al-4V alloy by laser cladding/remelting with a fibre laser. The effect of the different melt materials such as Tribaloy, Cu and Si3N4 on the microstructure and wear resistance of these laser clad coatings were investigated. The CoCrCu laser clad coating had a good metallurgical bond with a Ti-6Al-4V alloy substrate and consisted primarily of TiC, Cu4Ti3, (Co, Cr)2Ti. The microhardness and wear resistance of this laser clad coating was increased over the as-received Ti-6Al-4V alloy due to the Cu base and the other intermetallics leading to second phase/the fine grain strengthening. A fine microstructure was obtained due to the remelting effect. [ABSTRACT FROM AUTHOR]

This study investigates the impact of tightening torque (preload) and the friction coefficient on stress generation and fatigue resistance of a Ti-6Al-4V abutment screw with an internal hexagonal connection under dynamic multi-axial masticatory loads in high-cycle fatigue (HCF) conditions. A three-dimensional model of the implant–abutment assembly was simulated using ANSYS Workbench 16.2 computer aided engineering software with chewing forces ranging from 300 N to 1000 N, evaluated over 1.35 × 107 cycles, simulating 15 years of service. Results indicate that the healthy range of normal to maximal mastication forces (300–550 N) preserved the screw's structural integrity, while higher loads (≥800 N) exceeded the Ti-6Al-4V alloy's yield strength, indicating a risk of plastic deformation under extreme conditions. Stress peaked near the end of the occluding phase (206.5 ms), marking a critical temporal point for fatigue accumulation. Optimizing the friction coefficient (0.5 µ) and preload management improved stress distribution, minimized fatigue damage, and ensured joint stability. Masticatory forces up to 550 N were well within the abutment screw's capacity to sustain extended service life and maintain its elastic behavior. [ABSTRACT FROM AUTHOR]

Mastering the high strain characteristics at cryogenics and constructing an accurate constitutive model are critical for establishing a cryogenic cutting simulation of Ti-6Al-4V alloy. The traditional constitutive model is inadequate for accounting for high and cryogenic conditions. In this paper, cryogenic split Hopkinson pressure bar (SHPB) experiments are conducted, specifically for Ti-6Al-4V alloy, to develop a modified Johnson–Cook (J–C) constitutive model that incorporates the cryogenic effect. A coupled two-dimensional orthogonal finite element simulation involving temperature displacement was conducted for the cryogenic cutting of Ti-6Al-4V alloy. This simulation was performed using ABAQUS, based on a modified J–C constitutive model subroutine. It was observed that the smallest discrepancy between the simulation results and the data from ice-fixed milling experiments was just 2.12%. The modified J–C constitutive model is more adept at simulating the chip morphology under cryogenic conditions. It was also found that cryogenic machining enhances the distribution of temperature and stress within the chip. For every 5°C reduction in processing temperature, the tool temperature diminishes by more than 2%. [ABSTRACT FROM AUTHOR]

Fatigue indicator parameters (FIPs) can serve as a measure of fatigue crack initiation (FCI) in metals and alloys. FIPs are volume averaged over grains, bands, and sub bands in crystal plasticity (CP) simulation to investigate the influence of texture on FCI under low cycle fatigue. The equiaxed microstructure of Ti–6Al–4V was generated with three different textures: basal, basal/transverse and transverse. FIPs analysis shows that basal texture has the highest FCI resistance, basal/transverse texture has intermediate resistance, and transverse texture has the lowest resistance when tested along plate direction. All textures exhibit a lower FIP when deformed along rolling direction (RD) than that along transverse direction (TD). The interior of the alloys has a larger FCI resistance than the free surface. Further analysis shows a strong relationship between FIP distribution features and damage nucleation characteristics, with basal texture exhibiting the lowest and wider FIP distributions as a result of high resistance to damage and fatigue cracking; in contrast, the transverse texture exhibits intense and narrow FIP and damage nucleation along the grain boundaries (GBs), basal/transverse texture exhibits FIP and damage nucleation with mixed characteristics. The results can be used as a theatrical reference for the fatigue performance design of Ti alloy.

In this study, we present a microstructural and mechanical analysis of Ti–6Al–4V alloys processed by low-temperature multi-directional forging at 900 °C, achieving near-theoretical density (99.9%), with a tensile strength of 1070 MPa and elongation of 14.9%. The microstructure is defined by both continuous and discontinuous dynamic recrystallization occurring simultaneously, related to an increase in dislocation density. Significantly, this study reveals the interaction between crystallographic orientation and spheroidization during the forging process. Specifically, changes in crystallographic orientation include the asynchronous formation of new subgrains/grains, the disruption of the Burgers orientation relationship, and rotation around the axis, which not only increases the orientation differences between α lamellae but also enhances the spheroidization process. Moreover, our findings demonstrate that during deformation, the activation of basal and pyramidal slip systems is favored over prismatic slip, indicating that the forging process has enhanced slip activity. The average misorientation angle and the fraction of high-angle grain boundaries are quantified, providing a detailed characterization of the evolved microstructure. This study adopts a new perspective to examine the microstructural evolution during the multidirectional forging process in powder metallurgy, presenting findings that elucidate how multidirectional forging effectively controls.

This study explores the dynamic interaction between environmentally sustainable plasma enhancer and quencher agents during the incorporation of SiO2 into a TiO2 layer, with the primary objective of simultaneously augmenting protective and bioactive attributes. This enhancement is realized through the synergistic utilization of Tetraethyl orthosilicate (TE) and Stevia (ST) within a plasma-assisted oxidation process. To achieve this goal, Ti–6Al–4V alloy underwent oxidation in an electrolyte solution containing acetate-glycerophosphate, with the addition of TE and ST separately and in combination. TE, as a silicon oxide (SiO2) precursor, facilitates the creation of a calcium-rich, rough, porous layer by undergoing hydrolysis to generate silanol groups (Si–OH), which subsequently condense into silicon-oxygen-silicon (Si–O–Si) bonds, resulting in SiO2 formation. In contrast, ST acts as a plasma quencher, absorbing highly reactive plasma species during the oxidation process, reducing energy levels, and diminishing sparking intensity. The combination of TE and ST results in moderate sparking, balancing Stevia's quenching effect and TE's sparking influence. As a result, this coating exhibits enhanced corrosion resistance and bioactivity compared to using either ST or TE alone. The study highlights the potential of this synergistic approach for advanced TiO2-based coatings.

AbstractTitanium 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]

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A high temperature-dependent wear setup was employed to examine the Ti-6Al-4V (an α+β titanium alloy) tribological properties under vacuum environments. The components of Ti-6Al-4V alloys used in aerospace and space environments are subjected to relative motion which results in the occurrence of tribo phenomenon. In this study, Ti6Al4V pin slid against SS316L disc under vacuum conditions at high temperature. The analysis of the wear debris clearly shows the effect of wear morphology of the worn surface which was analyzed by Field emission scanning electron microscope (FE-SEM) equipped with Energy-Dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The fine particles were observed at room temperature under vacuum conditions where Adiabatic Shear Band (ASB)-effects of plastic deformations and Mechanically Mixed Layer (MML) are observed at 137.3 N and 0.01ms−1. The tribological tests were carried out employing a pin on disc configurations at high temperatures (up to 400∘C). Further, its influence on wear debris under (137.3 N) high load and 0.01ms−1 was also tested. The experimental results showed that various types of debris exhibited decreasing wear rates with increases in temperatures. [ABSTRACT FROM AUTHOR]

The fatigue performance of laser powder bed fusion-fabricated Ti-6Al-4V alloy was investigated using four-point bending testing. Specifically, the effects of keyhole and lack-of-fusion porosities along with various surface roughness parameters, were evaluated in the context of pore circularity and size using 2D optical metallography. Surface roughness of Sa = 15 to 7 microns was examined by SEM, and the corresponding fatigue performance was found to vary by 102 cycles to failure. The S–N curves for the various defects were also correlated with process window examination in laser beam power–velocity (P–V) space. Basquin's stress-life relation was well fitted to the experimental S–N curves for various process parameters except keyhole porosity, indicating reduced importance for LPBF-fabricated Ti-6Al-4V alloy components. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the influence of combined plasma immersion ion implantation (PIII) and shot peening (SP) treatments on the axial fatigue strength of the Ti-6Al-4V alloy. The specimens were superficially treated with SP and PIII separately and in a combined way. The tensile–tensile fatigue behavior was investigated based on microstructural analysis, residual stress measurements, profilometry, Vickers microhardness, scanning electron microscopy, and transmission electron microscopy. Axial fatigue tests at room temperature were performed for the Ti-6Al-4V base material, PIII at 500 and 800 °C, SP process and the combination of both surface treatments. The residual stress measurements indicated that PIII treatment at 500 °C induced tensile residual stresses of 189 MPa on the material surface. The PIII treatment at 500 °C maintained the fatigue resistance of the Ti-6Al-4V alloy in the low-cycle fatigue region, while the PIII treatment at 800 °C reduced the fatigue life at all stress levels, from 32 to 96% reduction in lifetime. The combination of SP pretreatment and PIII treatment at 500 °C decreased the tensile residual stress value at the surface from 189 to 23 MPa, resulting in an improvement of the fatigue strength compared to only PIII treatment, for N = 106, the fatigue strength doubled in value. The analysis and tests presented in this work showed the potential of combining PIII and SP treatments to promote the surface protection without the substantial fatigue strength loss frequently associated to surface treatments. [ABSTRACT FROM AUTHOR]

For the application of Ti-6Al-4V alloys in urban air mobility, safety is very important, so achieving excellent strength and toughness is essential to prevent fractures. Regarding toughness, which is a combination of strength and ductility, it is necessary to derive the optimal heat treatment conditions for this combination of Ti-6Al-4V alloy and further understand its microstructure and fracture characteristics. For this purpose, this study investigated the microstructure in terms of grain size, plate thickness, and element distribution, as well as mechanical properties, including phase hardness and tensile properties, of Ti-6Al-4V alloy subjected to solution treatment and aging (STA) heat treatment under various aging conditions. As a result, this study suggests that solution treatment followed by aging at 630 °C for 480 min can achieve approximately 26% higher toughness than the just-solution treatment process. This is because there is little difference in hardness between the equiaxed α and basketweave structures, and β plates, which contain an excessive V between α plates, function like fibers and delay fracture. [ABSTRACT FROM AUTHOR]

In this paper, hip implants made of Ti-6Al-4V titanium alloy are analyzed numerically using Extended Finite Element Method XFEM. The combined effect of corrosion and fatigue was considered here since this is a common cause of failure of hip implants. Experimental testing of Ti-6Al-4V alloy was performed to determine its mechanical properties under different working environments, including normal, salty, and humid conditions. The integrity and life of the hip implant were assessed using the Linear Elastic Fracture Mechanics (LEFM) approach. For this purpose, the conditional fracture toughness Kq using CT specimens from all three groups (normal, humid, salty conditions) were determined. This provided insight into how different aggressive environments affect the behavior of Ti-6Al-4V alloy; i.e., how much its resistance to crack growth would degrade depending on conditions corresponding to the real exploitation of hip implants. Next, analytical and XFEM analyses of fatigue behavior in terms of the number of cycles were performed for all three groups, and the obtained results showed good agreement, confirming the validity of the integrity assessment approach shown in this work, which also represented a novel approach since fatigue and corrosion effects were investigated simultaneously. [ABSTRACT FROM AUTHOR]

This study investigates the optimization of cutting conditions for machining titanium alloy (Ti-6Al-4V) using Response Surface Methodology (RSM), with the goal of minimizing tool-chip interface temperature and surface roughness. The research focuses on key cutting parameters to investigate the most effective combinations for enhancing surface finish and reducing thermal impact during machining. The present study deals with the dry turning of Ti-6Al-4V alloy with carbide alloy inserts in a way to utilize the Analysis of Variance (ANOVA) to develop predictive models for minimum surface roughness and optimum temperature. The findings reveal that both cutting speed and depth of cut are critical in determining machining outcomes. Specifically, a low cutting speed of 88 m/min coupled with a high depth of cut of 0.20 mm was found to elevate the cutting temperature to approximately 835 °C, resulting a surface roughness of 0.59 μm. Conversely, increasing the cutting speed to 120 m/min while reducing the depth of cut to 0.10 mm significantly lowered the temperature to around 607 °C, resulting a surface roughness of 0.19 μm; thus, thereby improving surface finish and reducing thermal stress on the tool. Additionally, a 27 % reduction in cutting temperature and a minimum surface roughness of 0.19 μm were achieved with optimal settings of 120 m/min cutting speed, 0.08 mm/rev feed rate, and 0.10 mm depth of cut. The study demonstrates the effectiveness of RSM in optimizing machining parameters for optimum temperature and better surface finish in the titanium alloy machining.

This work aims to describe the effect of the surface modification of TiO2 nanotube (TNT) layers on Ti-6Al-4V (TiAlV) alloy by ultrathin TiO2 coatings prepared via Atomic Layer Deposition (ALD) on the growth of MG-63 osteoblastic cells. The TNT layers with two distinctly different inner diameters, namely ∼15 nm and ∼50 nm, were prepared via anodic oxidation of the TiAlV alloy. Flat, i.e., non-anodized, TiAlV alloy foils were used as reference substrates. Additionally, a part of the TNT layers and alloy foils was coated with ultrathin coatings of TiO2 by ALD. The number of TiO2 ALD cycles used was 1 and 5 leading to a nominal TiO2 thickness of ∼0.055 and ∼0.3 nm, respectively. The ultrathin TiO2 coating by ALD enabled to optimize the surface hydrophilicity for optimal cell growth. In addition, coatings shaded impurities of V- and F-based species (stemming from the alloy and the anodization electrolyte) that affect the biocompatibility of the tested materials while preserving the original structure and morphology. The evaluation of the biocompatibility before and after TiO2 ALD coating on TiAlV flat surfaces and TNT layers was carried out using MG-63 osteoblastic cells and compared after incubation for up to 96 h. The cell growth, adhesion, and proliferation of the MG-63 on TiAlV foils and TNT layers showed significant enhancement after the surface modification by TiO2 ALD.

The ultra-fine grain Ti–6Al–4V alloy sheet was successfully achieved by friction stir processing (FSP). The low-temperature superplastic deformation mechanism of Ti–6Al–4V alloy under the strain rate of 3 × 10−4 s−1 at 600 °C was studied by scanning electron microscope, electron backscatter diffraction and superplastic tensile test. It is found that the grain size of Ti–6Al–4V alloy by FSP is refined from 7.48 μm to 0.82 μm, and there is no preferential crystallographic orientation of the uniform grain. After FSP, the β phase of the base material (BM) in the grain boundary is refined and homogenized. During the superplastic tensile processing, with the increase of strain, the grain is refined continuously, and the α→β phase transition is induced by the dislocations pile-up at the β grain boundary, and the content of β phase increases. The grain near the fracture was refined to 0.35 μm, and the stress concentration led to the formation of cavities near the β phase, which eventually caused the fracture. The dynamic recrystallization in superplastic tensile processing is mainly geometric dynamic recrystallization and discontinuous dynamic recrystallization. The elongation of superplastic tensile (1033%) is 19.7 times higher than that of BM (50%). The order of superplastic deformation mechanism in the low-temperature superplastic deformation of the ultra-fine grain Ti–6Al–4V alloy sheet is as follows: intragranular dislocation slip and diffusion, grain boundary sliding, and phase boundary sliding. Phase boundary sliding is the main deformation mechanism for low-temperature superplastic deformation.

Texture is inevitably generated during the rolling process of titanium alloys, which has a significant impact on mechanical properties. The relationship between microstructure, texture and mechanical properties of the rolled Ti–6Al–4V alloy plate with large thickness was systematically investigated in this study. The texture type varied with the thickness of the plate. The basal pole concentrated in the transverse direction (TD) at the surface of the plate and tilted from TD towards the rolling direction (RD) at the quarter thickness of the plate. For the center of the plate, the basal pole had peaks concentrated close to both TD and RD. Tensile tests indicated that TD samples not only have high strength but also maintain good plasticity compared with RD and the normal direction (ND) samples. The yield anisotropy could be explained by the difficulty of prismatic and basal dislocation slip. The cold creep behavior of the thick plate depended on both Schmid factor of dislocation slip and grain size. Moreover, the strain hardening exponent was positively correlated with cold creep strain. Abundant prismatic and pyramidal dislocations were activated, and slip transfer and cross-slip made the dislocation slip distance longer, which contributed to creep strain and thus reduced the creep resistance of ND sample.

The ultra-precision Ti–6Al–4V alloy parts are growing used in medical and aerospace industries, and which always work in the extreme working conditions such as high temperature, high pressure, and variable load. Thus, the requirements for machining accuracy and surface quality of parts are getting higher and higher. The ultrasonic elliptical vibration assisted cutting (UEVC) technology has been proved to be an effective method for the ultra-precision machining of Ti–6Al–4V alloy. However, in the UEVC process, the evolution mechanism of microstructure and microhardness, which directly affect the service performance and life, is unrevealed. In this paper, the comprehensive investigations of microstructural plastic deformation, grain refinement, phase transformation and microhardness of machined surface layer under conventional cutting (CC) and UEVC processes are carried out. The experimental results indicated that, due to the effects of UEVC technology, the plastic deformation area show obvious compression deformation, the depth of plastic deformation is less than 10 μm, there is no obvious phase transformation on the machined surface layer material, and the hardening rate of machined surface is more than 20%. These findings show the UEVC technology has a unique influence on the microstructure and microhardness of Ti–6Al–4V alloy, which have important implications for the cutting parameter design of ultra-precision Ti–6Al–4V alloy parts.

Aseptic loosening and inadequate osseointegration are significant issues associated with titanium alloy implants in complex body fluid environments. Surface coatings techniques are often employed to enhance the bioactivity and osseointegration capabilities. In this research, biocomposite coatings were fabricated on Ti-6Al-4V alloy employing micro-arc oxidation (MAO) and the integration of micro-arc oxidation/electrophoretic deposition (MAO/EPD) technology. Microstructure, bioactivity, and corrosion resistance of the coatings were studied. To investigate the effect of the coatings on the stress corrosion cracking (SCC) behavior of Ti-6Al-4V alloy, slow strain rate tension (SSRT) tests were conducted in simulated body fluid (SBF). Results show that the adhesive strength of the MAO/EPD composite coatings is around 28.41N, with an average contact angle of 19.05 °, indicating excellent wettability and biocompatibility. The corrosion rate of biocomposite coatings is 3.43 μm·a−1 and the biocomposite coatings exhibit excellent SCC resistance, with a SCC sensitivity of 9.21%, which is significantly lower than the 18.39% of Ti-6Al-4V alloy. This can be attributed to the lower porosity of the coatings, which can provide excellent protection for the alloy. [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]

One of the biggest advantages in metal additive manufacturing using laser powder bed fusion is low powder usage compared to traditional manufacturing methods. The process can be made more efficient by enabling metal powder to be reused. Recycling promotes environmental sustainability by minimizing material wastage and decreasing the demand for raw materials, making the metal additive manufacturing process more resource efficient.In this study, Ti6Al4V powder was recycled and reused up to 50 times. In order to understand the effects of reusing powder, the study included a detailed examination of both the powder and the processing method. The microstructure and characteristics of the recycled powder were examined in extensive detail.

Sub-atmospheric pressure environment and oscillation laser are both excellent ways to improve welded joint quality. However, the differences in their effects and mechanisms are unclear. Therefore, the differences between sub-atmospheric pressure and oscillating laser in weld formation, porosity suppression and grain size refinement were analyzed in this study. The results revealed that penetration depth of welded joint was increased to 6.09 mm under sub-atmospheric pressure environment while it was decreased to 3.3 mm under oscillation laser. Furthermore, reducing fluctuating vapor pressure and suppressing vortex formation were the main means to improve the keyhole stability and promote the escape of bubbles in a sub-atmospheric pressure environment. The improvement of the oscillating laser in these two aspects was attributed to enlarging keyhole area, shortening escape path and oscillation keyhole absorption. Additionally, the average grain size in the upper weld was reduced from 134.6 μm to 118.6 μm and 114.1 μm under the sub-atmospheric pressure environment and laser oscillation, respectively. The reduction of the temperature gradient led to former grain refinement while the increase of heterogeneous nucleation rate was responsible for latter grain refinement. Correspondingly, the mechanical properties of welded joints were improved. The study offered valuable insights for the application of laser welding with oscillation laser and sub-atmospheric pressure in industrial production.

The high-temperature wear resistance plays an important role for Ti–6Al–4V alloy components working in extreme environments, especially vital for avoiding unexpected failure. However, the reasonable method of surface modification should meet the requirement of improving in wear resistance and less decreasing in mechanical properties simultaneously, which brings a great challenge. In the present research, the laser shock peening (LSP) technique was applied to optimize the superficial layer of Ti–6Al–4V alloy by different processing. The microstructure, elastic modulus, nano-hardness and high-temperature tribology properties of the LSP processed Ti–6Al–4V were investigated to reveal the improving effect. The results demonstrate the LSP processing transforms the dual-size grain structure to relative homogeneous grain structure and forms the gradient nano-structure in superficial layer. With the increasing of LSP processing numbers, the density of geometrically necessary dislocation (GND) decreases obviously, but the density of statistically stored dislocation (SSD) rises significantly, which promotes the increase of total dislocation density compared with the as-received (AR) alloy. Due to the crystal evolution, the Ti–6Al–4V alloy with three-times LSP processing has the lowest wear rate which is less than half of the as-received state. The observations on worn surface and adjacent cross-sectional microstructure reveal the severe scratching and many inner microcracks in the AR sample but the slight scraping and few inner microcracks in the three-times LSP processed sample. Considering the elevated nano-hardness and elastic modulus, the improved tribological properties should be mainly attributed to the optimized microstructure and dislocation state by LSP processing. The present research provides a more reasonable method to improve the high-temperature wear properties of Ti–6Al–4V alloy.

Powder metallurgy (PM) technology is expected to provide a promising strategy for the cost-effective and highly efficient utilization of spherical Ti–6Al–4V powders with particles size of large than 150 μm to reduce material waste. However, how to overcome the problem of low sinterability and poor ductility of coarse lamellar microstructures of large-diameter spherical powders are still remains a significant challenge. In this study, Ti–6Al–4V alloys were prepared by spark plasma sintering (SPS) at different sintering temperatures with plasma rotating electrode process (PREP) large-diameter spherical powders (∼156 μm). The microstructure evolution, grain structure, mechanical properties and fracture mechanisms were systematically investigated. Results demonstrate that the acicular martensite structure inside the unmelted particles changed to a uniform and fine α/β lamellar microstructure with the increased sintering temperature. Consequently, the Ti–6Al–4V alloys exhibit excellent strength-ductility at 925 °C. (ultimate tensile strength of 881 MPa and elongation up to 14.8 %). Fundamentally, the excellent strength-ductility was attributed to the uniform and dense fine α/β lamellar structure that enhanced the effective bearing area during deformation. The stacked dislocations at the α/β phase interface provided high strength. In addition, the high-density α/β phase interface in the matrix reduced the mean free path of the dislocation, which resulted in a high strain hardening rate of the high-density geometrically necessary dislocations (GNDs) and delayed the premature fracture. The intergranular brittle fracture mode of the alloys changed to the ductile fracture mode. These findings have important implications for recycling super-large diameter spherical powders.

This study investigates the effects of various surface modification techniques on the Ti-6Al-4V alloy for biomedical applications. Mechanical treatments (sandblasting, shot peening) and electrochemical corrosion using different electrolytes were employed to modify surface characteristics. Surface morphology, roughness, hardness, and chemical composition were analyzed using SEM, profilometry, and Raman spectroscopy. Cell attachment studies revealed that combined treatments, particularly shot peening followed by HF/HNO3 etching, significantly enhanced cell adhesion and distribution. The results demonstrate the potential for tailoring Ti-6Al-4V surfaces to optimize biocompatibility and osseointegration properties for dental and orthopedic implants.