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Ti-6Al-4 V is an extensively used and highly versatile titanium alloy. It is renowned for its lightweight-to-strength ratio, excellent biocompatibility, and corrosion resistance. The pursuit of advanced materials with enhanced mechanical strength, and wear resistance has led to the exploration of high entropy alloys (HEA) as particle reinforcements. This study combines Ti-6Al-4 V with AlCoCrFeNi HEA at different weight compositions (0 %, 2 %, 4 %, 6 %, 8 %) to create novel composites with tailored properties. The composites were subjected to density, microhardness, tensile, and pin-on-disc tests to evaluate mechanical and tribological properties. Microstructural analysis revealed that microwave sintering has enhanced densification and resulted in uniform dispersion of HEA particles within the Ti-6Al-4 V matrix. The XRD and EBSD analysis revealed the presence of BCC structure in the composite. 8 wt%-AlCoCrFeNi/Ti-6Al-4 V sample exhibited an impressive 81.66 % increase in microhardness and 21.23 % in yield strength, compared to the base sample. Furthermore, noteworthy reductions of 45 % in wear rate and 40 % in coefficient of friction (COF) when subjected to tribological analysis. The worn surface revealed the presence of oxide layer formation at elevated sliding velocity and distance which resulted in reduced wear rate. [ABSTRACT FROM AUTHOR]

There is an increasing demand for durable metallic implants, particularly among elderly patients undergoing revision surgeries for degenerative bone diseases. Approximately 70–80% of the implants are made of metal. Despite their robustness, metallic implants exhibit a higher Young's modulus than bone, leading to a stress-shielding effect. Although porous structures in implants aim to mitigate this issue, their porosity compromises overall strength. The present study focuses on the design of porous gyroid Ti–6Al–4V specimens and their fabrication using laser powder bed fusion. Subsequently, hydroxyapatite (HAp) combined with polyamide binders was synthesized using the sol–gel method from precursors and infiltrated into porous specimens to enhance their bio-mechanical compatibility. The X-ray diffraction analysis confirmed the presence of both Ti–6Al–4V and HAp. The Tafel plots revealed that the corrosion rate of the porous specimen infiltrated with HAp was about 0.394 mm/year, which is very minimal considering the prolonged implant lifespan. Furthermore, the results from the compression testing revealed that the average Young's modulus and compressive strength of HAp-infiltrated specimens were found to be increased by 70% and 7.5% respectively when compared to the non-infiltrated porous gyroid Ti–6Al–4V samples. These findings confirm that the HAp not only enhances osseointegration and tissue growth but also enhances the compressive strength of the porous Ti–6Al–4V metallic implants. [ABSTRACT FROM AUTHOR]

Within the scope of these investigations, the feasibility of a material bond between Ti-6Al-4V and the magnesium alloy AZ91 is analyzed. Ti-6Al-4V is frequently used for implants due to its biocompatibility, corrosion resistance, and specific strength. However, depending on the surface quality, the attachment behavior of the bone to the implant varies. Magnesium implants promote the regeneration of bone tissue and biodegrade as the bone tissue heals. Combining the properties of both materials in one implant enables a reduced implant volume and increased stability. For this reason, this study aims to demonstrate the feasibility of creating a material bond between the materials Ti-6Al-4V and AZ91. For this purpose, Ti-6Al-4V truncated cones and AZ91 sleeves were produced using the additive manufacturing process of laser powder bed fusion (L-PBF). The as-built sleeves were then pressed onto machined truncated cones. Since zinc serves as a lubricant and has good diffusion properties with the materials used as a result of heat treatment, a comparison was made between zinc-coated and the as-built Ti-6Al-4V samples. This showed that a bond was created after hot isostatic pressing and that the push-out force could be increased by more than 4.5 times. Consequently, a proof of feasibility was demonstrated, and a high potential for applications in medical technology was shown. [ABSTRACT FROM AUTHOR]

Lattice structures have demonstrated the ability to provide secondary stability in orthopedic implants by promoting internal bone growth. In response to the growing prevalence of lattices in orthopedic design, we investigated the effects of porosity and unit cell geometry in additively manufactured Ti-6Al-4V biomimetic lattice structures on the osteogenesis of human MG-63 osteoblastic cell lines in vitro. We analyzed glucose consumption, alkaline phosphatase (ALP) concentration, and end-of-culture cell count as markers for osteogenic growth. Two different strut geometries were utilized (cubic and body-centered cubic), along with four different pore sizes (400, 500, 600, and 900 µm, representing 40–90% porosity in a 10 mm cube), in addition to a solid specimen. Structural characterization was performed using scanning electron microscopy. The results indicated that lattices with a 900 µm pore size exhibited the highest glucose consumption, the greatest change in ALP activity, and the highest cell count when compared to other pore sizes. Cubic 900 µm lattice structures outperformed other specimens in facilitating the maturation of viable MG-63 cells from the formation to the mineralization phase of bone remodeling, offering the most promise for osseointegration in additively manufactured titanium implants in the future. However, irrespective of a particular pore size or unit cell geometry, it was found that all the lattices were capable of promoting osteogenic growth due to surface roughness in the printed parts. [ABSTRACT FROM AUTHOR]

Additive manufacturing from metal powders using selective laser melting technology is gaining increasing interest in various industries. The purpose of this study was to determine the effect of changes in process parameter values on the relative density, microstructure and mechanical properties of Ti-6Al-4V and Ti-6Al-7Nb alloy samples. The experiment was conducted in response to a noticeable gap in the research on the manufacturability of the Ti-6Al-7Nb alloy in SLM technology. This topic is significant given the growing interest in this alloy for biomedical applications. The results of this study indicate that by properly selecting the volumetric energy density (VED), the relative density of the material produced and the surface roughness of the components can be effectively influenced. Microstructural analyses revealed similar patterns in both alloys manufactured under similar conditions, characterized by columnar β phase grains with needle-like α' phases. Increasing the VED increased the tensile strength of the fabricated Ti-6Al-4V alloy components, while the opposite effect was observed for components fabricated from Ti-6Al-7Nb alloy. At the same time, Ti-6Al-7Nb alloy parts featured higher elongation values, which is desirable from the perspective of biomedical applications. [ABSTRACT FROM AUTHOR]

This study focuses on the evolution of the fatigue strength of Laser Powder Bed Fusion (L‐PBF) produced Ti‐6Al‐4V as a function of the chemical etching finishing process. The aim is to identify the critical fatigue crack initiation mechanisms and the transitions between them in terms of the evolution of the surface micro‐geometry. This is done using three different geometries and six different surface states. The evolution of the crack initiation mechanisms is then used to explain the evolutions of the fatigue strength and the fatigue scatter. Chemical etching affects the fatigue life via a polishing effect, which directly influences both the finite and the high cycle fatigue domains. It is shown that chemical etching makes it possible to obtain fatigue strengths that are almost similar to those of the machined surface. However, it is also observed that etching cannot fully counteract the effects of large surface cavities caused by surface connected porosities. [ABSTRACT FROM AUTHOR]

This experimental study investigates the effect of the cutting parameters of the Electrical Discharge Machining (EDM) process of Ti-6Al-4V alloy material on surface roughness (Ra), cutting time (t) and Material Removal Rate (MRR) then solve the Multiple Objective Optimization Problem using separate Multi-Criteria Decision-Making (MCDM) methods namely Entropy-Weighted TOPSIS (E-TOPSIS), MOORA, SAW, VIKOR, and WPM. Focusing on nine 3-levels variants including Operating Voltage (OV), Pulse-On Time (Ton), Pulse-Off Time (Toff), Short-Circuit Off Time (AFF), Secondary Voltage (SV), Feed Rate (WF), Tension (WT), Water Pressure (WL) and Material Cutting Speed (F). Due to the large number of variants studied, the Taguchi L27 experimental design was chosen to reduce the number of experiments while still ensuring reliability in assessing the impact of technological parameters on responses in the study. The optimization results from the different methods indicated two distinct optimal outcomes. According to the E-TOPSIS, MOORA, and SAW, the optimal result is a Ra of 3.27 μm, a t of 7.37 min, and an MRR of 7.45 mm3/min. This result suggests a balanced and harmonious optimization among all criteria. On the other hand, the figures VIKOR and WPM methods are 2.87 μm, 9.57 min, and 5.74 mm3/min, respectively. These results indicate a higher priority for certain criteria, reflected in the lower Ra, longer cutting time, and a smaller MRR in comparison to the figures for the remaining MCDM methods. The different optimal results achieved by various methods highlight that each method is suited to and excels with different sets of values. Therefore, in each specific research or production process, comparing and choosing results calculated by different methods provides a comprehensive view, aiding in making appropriate decisions. [ABSTRACT FROM AUTHOR]

Studies have shown that the deformation of Ti alloys is due to the competition between hardening and softening effects under dynamic loading. However, there are limited indicators of this behaviour throughout the complete stress–strain process. This study aims to quantify the impact of strain rate and temperature on the hardening/softening behaviour of Ti-6Al-4V using a split-Hopkinson pressure bar system over a range of 2000 to 7000 s−1 strain rates and temperatures from 25 to 800°C. Firstly, this study proposes an evaluation index of material hardening/softening behaviour based on the complete stress–strain curve and energy evolution characteristic. Further, the dynamic mechanical properties of Ti-6Al-4V are investigated through the analysis of the stress–strain relationship and fracture morphology. Finally, the hardening/softening index is calculated and analysed. The findings revealed that the fracture surface of the impact specimen displayed dimple-like and smooth features, that are significantly influenced by both temperature and strain rate. The stress–strain curves demonstrated that Ti-6Al-4V exhibits remarkable strain-rate strengthening, plastic increasing, and strain work hardening behaviour. The hardening/softening index Br decreases with an increase in strain rate. For specific strain rates of 3000, 5000 and 7000 s−1, Br increases as the loading temperature rises from 25 to 400°C, but decreases when the loading temperature is increased to 600°C. At a strain rate of 2000 s−1, Br increases monotonically until the loading temperature reaches ∼ 800°C. These observations are found to be related to the microstructural evolution at varying temperatures and strain rates. [ABSTRACT FROM AUTHOR]

High-speed milling (HSM) of Ti-6Al-4V is subjected to complex thermo-mechanical loads, leading to alteration in metallurgical conditions within the cutting deformation zones, adversely impacting the mechanical performances of manufactured products. Hence, inclusive insight into microstructural alterations within the Adiabatic Shear Band (ASB) and the milled surface becomes essential for better service performance. This study first developed a Finite Element (FE) milling model to simulate the machining process of Ti-6Al-4V. The proposed FE model is validated through experimental results regarding cutting forces (CFs), cutting temperature (CT), and chip geometry, where the absolute relative error between simulations and experiments was less than 15 %. Secondly, Zenner-Holloman (Z-H) and Hall-Petch (H-P) equations were incorporated into a user-defined subroutine to simulate dynamic recrystallization (DRX) for grain size and microhardness prediction. Simulation results revealed that the grains became finer in the ASB than on the milled surface. In particular, when the cutting speed and feed rate were increased to 350 m/min and 0.30 mm/tooth, the grain size in the ASB decreased from 14 to 0.68 and 0.44 µm, while in the topmost milled surface, it reduced to 7.06 and 6.75 µm, respectively. Conversely, microhardness exhibited an inverse correlation with grain size and increased with cutting speed and feed rate. Furthermore, the impact of increased plastic strain and temperature on the grains during chip segmentation was also examined. Finally, the proposed FE model validity was established by comparing simulated results with experimental data using advanced characterization techniques. This research significantly contributes to a comprehensive understanding of microstructural evolution and its implications for the mechanical performance of machined titanium components. [ABSTRACT FROM AUTHOR]

Despite the many advantages that additive technologies have over subtractive ones, low porosity levels, good mechanical properties, and low residual stresses remain the most pressing issues that need further research. In particular, the latter can cause a mismatch between the desired geometry and the geometry that can be achieved. In this work, a process window for the Laser Powder Bed Fusion (LPBF) process of Ti-6Al-4V alloys, has been identified. The micro-warping phenomenon, which causes the deformation of the printed part during the printing job and the failure of the process, was taken into account together with the parts' strength, ductility, and porosity. The occurrence of micro-warping phenomena was assessed by the new Warping Alert (WA) parameter, which depends on the parameters P and v. It was found that, before balling, micro-warping limits the process window in the laser power (P) – laser velocity (v) plane. However, optimal mechanical performances can be found in the proximity of the micro-warping zone, thus making it extremely important to determine the WA threshold value to the process design. [ABSTRACT FROM AUTHOR]

Efficient and accurate segmentation of complex microstructures is a critical challenge in establishing process-structure-property (PSP) linkages of materials. Deep learning (DL)-based instance segmentation algorithms show potential in achieving this goal. However, to ensure prediction reliability, the current algorithms usually have complex structures and demand vast training data. To overcome the model complexity and its dependence on the amount of data, we developed an ingenious DL framework based on a simple method called dual-layer semantics. In the framework, a data standardization module was designed to remove extraneous microstructural noise and accentuate desired structural characteristics, while a post-processing module was employed to further improve segmentation accuracy. The framework was successfully applied in a small dataset of bimodal Ti-6Al-4V microstructures with only 112 samples. Compared with the ground truth, it realizes an 86.81% accuracy IoU for the globular α phase and a 94.70% average size distribution similarity for the colony structures. More importantly, only 36 s was taken to handle a 1024 × 1024 micrograph, which is much faster than the treatment of experienced experts (usually 900 s). The framework proved reliable, interpretable, and scalable, enabling its utilization in complex microstructures to deepen the understanding of PSP linkages. [ABSTRACT FROM AUTHOR]

Porous titanium scaffolds fabricated by powder bed fusion additive manufacturing techniques have been widely adopted for orthopedic and bone tissue engineering applications. Despite the many advantages of this approach, topological defects inherited from the fabrication process are well understood to negatively affect mechanical properties and pose a high risk if dislodged after implantation. Consequently, there is a need for further post‐process surface cleaning. Traditional techniques such as grinding or polishing are not suited to lattice structures, due to lack of a line of sight to internal features. Chemical etching is a promising alternative; however, it remains unclear if changes to surface properties associated with such protocols will influence how cells respond to the material surface. In this study, we explored the response of bone marrow derived mesenchymal stem/stromal cells (MSCs) to Ti‐6Al‐4V whose surface was exposed to different durations of chemical etching. Cell morphology was influenced by local topological features inherited from the SLM fabrication process. On the as‐built surface, topological nonhomogeneities such as partially adhered powder drove a stretched anisotropic cellular morphology, with large areas of the cell suspended across the nonhomogeneous powder interface. As the etching process was continued, surface defects were gradually removed, and cell morphology appeared more isotropic and was suggestive of MSC differentiation along an osteoblastic‐lineage. This was accompanied by more extensive mineralization, indicative of progression along an osteogenic pathway. These findings point to the benefit of post‐process chemical etching of additively manufactured Ti‐6Al‐4V biomaterials targeting orthopedic applications. [ABSTRACT FROM AUTHOR]

In this investigation, the factors were oil type ( O t ), powder type ( T p ), and powder concentration ( C p ) level, and the machining parameters were the voltage (V), capacitance (pf), pulse-on time ( T on ), and pulse-off time ( T off ). The output parameters were the material removal rate (MRR), and tool wear rate (TWR). Three types of oils and powders, along with their respective particle concentrations, were selected for this experiment. Neem, Karanja, and sesame oils were mixed with aluminum oxide (Al2O3), chromium (Cr), and nickel (Ni) powder at 4, 6, and 8 gm/l, respectively, using an overhead stirrer to investigate the conditions under which the green oil powder mixed mixture yielded a higher MRR and lower TWR during the micro-EDM process of titanium alloy (Ti-6Al-4V) using a 0.8 mm tungsten carbide (WC) tool with fixed machining parameters (240 V, 100 pf, 20 μ s T on , and 5 μ s T off ). All the powders used in this experiment had a 32-micron (450 mesh) size. The Taguchi L 2 7 orthogonal array and grey relational analysis methods were used to design and optimize the input process parameters for both responses. SEM, optical microscopic analysis, and EDS analysis were performed to examine the surface morphology, characteristics of the WC tool, and elemental composition of both the tool and the workpiece material. The optimum conditions for Karanja oil with a Cr powder mixture concentration of 4 g/l resulted in higher MRR and lower TWR. However, machining with neem and sesame oils resulted in higher TWR and lower MRR. [ABSTRACT FROM AUTHOR]

The present study considers the samples of an Ti-6Al-4V alloy obtained by selective laser melting with the addition of a 10% Cu-Al powder mixture. The microstructure, elemental composition and phase composition, as well as the physico-chemical properties, have been investigated by the methods of electron microscopy, X-ray phase analysis, and bending testing. The obtained samples have a relative density of 98.5 ± 0.1%. The addition of the Cu-Al powder mixture facilitates supercooling during crystallization and solidification, which allows decreasing the size and changing the shape of the initial β-Ti grains. The constant cooling rate of the alloy typical for the SLM technology has been shown to be able to prevent martensitic transformation. The formation of a structure that consists of β-Ti grains, a dispersed eutectoid mixture of α-Ti and Ti2Cu grains, and a solid solution of Al in Cu has been revealed. In the case of doping by the 10% Cu-Al mixture, the physico-mechanical properties are improved. The hardness of the samples amounts to 390 HRC, with the bending strength being 1550 ± 20 MPa and deformation of 3.5 ± 0.2%. The developed alloy can be recommended for applications in the production of parts of jet and car engines, implants for medicine, and corrosion-resistant parts for the chemical industry. [ABSTRACT FROM AUTHOR]

The inadequate fatigue performance of Laser Powder Bed Fusion (L-PBF) Ti-6Al-4V alloy, primarily due to intrinsic defects, poses a significant challenge for industrial applications. Internal defects often serve as initiation sites for fatigue cracks, significantly impacting the fatigue life of L-PBF Ti-6Al-4V components. Accurate evaluation of the role of internal defects in fatigue performance and quantitative analysis of influential parameters are crucial for guiding optimal L-PBF manufacturing design. This study aims to critically review recent notable contributions focusing on high-cycle fatigue (HCF) in these alloys, with many of the presented insights being easily transferred to other types of AM alloys. Efforts have been made to identify correlations between fatigue life at various stages and critical internal defects. Key aspects, including microstructure and post-processing treatments, and their effects on HCF have been thoroughly analyzed. The findings enhance the scientific understanding of fatigue performance of L-PBF Ti-6Al-4V alloy and open new avenues for future research. [ABSTRACT FROM AUTHOR]

Knowledge of the deformation behaviour of Ti-6Al-4V using single-point micro incremental forming (SPMIF) is very important to understand the physics behind the microstructural changes, and forming limit. In SPIF, shape changes in sheet metals up to ultra-thin sizes can be performed without using a die and punch (does not require any specific tooling as in the conventional forming process) and hence, this process is recommended for the fabrication of parts in the aerospace, automobile, and bio-medical industries. Furthermore, in SPIF, the components are manufactured using a hemispherical end tool moving along a predefined path with an enhanced forming limit. The present research work has focused on studying the formability, microstructure, mechanical properties and fracture mechanics of Ti–6Al–4V alloy foils during SPMIF. The importance of spindle speed on the forming limits of the Ti–6Al–4V alloy foil was studied and it was found that the maximum forming limits were achieved at higher spindle speeds (200 rpm) due to strengthening of basal texture and weakening of prismatic texture components. A forming limit strain (FLS) was drawn at different spindle speeds (100, 150, and 200 rpm). XRD, EBSD and TEM analyses were performed for the phase analysis, orientation and dislocation density respectively. The fracture behaviour was investigated and the void coalescence parameters were compared with respect to spindle speed. [ABSTRACT FROM AUTHOR]

This study presents a highly efficient chemical and magnetorheological fluid (C-MRF) hybrid polishing process established by using an eco-friendly slurry of malic acid, Fe3O4–SiO2 abrasive particles, and hydrogen peroxide (H2O2) as an oxidant, all mixed with purified water, highlighting its efficacy in a wide range of polishing applications. Herein, the polishing processes of Ti–6Al–4V alloy utilizing C-MRF with on Fe3O4–SiO2 abrasives are detailed, and the polishing performance is assessed by investigating the influence of oxidizing agent H2O2 and acid malic to the surface finish of the Ti–6Al–4V alloy. The linear variable magnetic field by improved Halbach array was proposed to improve the material removal rate and surface quality and create a polishing process with a highly efficient magnetic field source. Single-factor and orthogonal experimental analysis methods are applied to provide the technological parameters factors with varying influences on surface quality and material removal ability. [ABSTRACT FROM AUTHOR]

Herein, an anticorrosive and hydrophobic surface for Ti–6Al–4V was prepared through one-step anodic etching. The results showed that wettability was adjusted by current density and etching time. In particular, the maximum water contact angle (WCA) reached ~ 160.9° at a current density of 0.25 A cm−2 for 420 s. Energy dispersive spectroscopy and X-ray photoelectron spectroscopy showed the existence of spontaneous surface passivation, which was also verified by Tafel curves. In addition, Ecorr and icorr exhibited good anticorrosion properties on the surface of the Ti–6Al–4V after anodic etching. Furthermore, the change in surface adhesion was consistent with the change in the WCA after anodic etching. In conclusion, the one-step anodic etching can provide a convenient way to realize anticorrosion and superhydrophobic Ti–6Al–4V surface. Highlights: A superhydrophobic surface can be formed on Ti–6Al–4V substrate through one-step anodic etching. The maximum WCA of the surface reached ~ 160.9°. The change tendency of the adhesive force is contrary to that of the WCA. The large area and low-cost anticorrosive property of Ti–6Al–4V can be adjusted by current density. [ABSTRACT FROM AUTHOR]

Transient liquid phase (TLP) bonding of Ti-6Al-4 V/UN32750 joint with a composite interlayer of Cu-0.5 wt.% CNT and a pure Cu interlayer has been investigated. TLP process was performed in a vacuum furnace at three different temperatures (900, 950, and 1000 °C) with a constant holding time (60 min). Microstructure and mechanical properties of all joints were studied using scanning electron and optical microscopes, microhardness, and shear tests. The x-ray diffraction (XRD) test was done on all fracture surfaces to do phase analysis at the interface. Results showed that the increase in the thickness of the TLP layer is associated with CNT addition, inferring that CNT enhances the diffusion of alloying elements across the interface. All joints experienced a reduction in the strength after CNT addition, with the highest strength obtained at 950 °C. The microhardness of the CNT-containing joints is higher than that of CNT-free samples due to the formation of plate-shaped Al-based phases and solid solution strengthening. All joints showed brittle fracture features. CNTs improved the brittle fracture to some extent, especially at 1000 °C. [ABSTRACT FROM AUTHOR]

Binder jetting 3D printing is an additive manufacturing technique based on the creation of a part through the selective bonding of powder with an adhesive, followed by a sintering process at high temperature to densify the material and produce parts with acceptable properties. Due to the high initial porosity in the material after sintering, which is typically around 5%, post-sintering treatments are often required to increase the material density and enhance the mechanical and fatigue properties of the final component. This paper focuses on the study of the benefits of hot isostatic pressing (HIP) after sintering on the mechanical and fatigue properties of a binder jetting Ti-6Al-4V alloy. Two different HIP processes were considered in this study: one at 920 °C/100 MPa for 4 h, and a second at a higher pressure but lower temperature (HIP-HPLT) at 850 °C/200 MPa for 2 h. The effects of the HIP on the densification, microstructure, mechanical behavior, and fatigue properties were investigated. The results show that the HIP-HPLT process produced a significant increase in the mechanical and fatigue properties of the material compared with the as-sintered parts and even with the conventional HIP process. However, the fatigue and fracture micromechanisms suggest that the oxygen content, which resulted from the decomposition of the binder during the sintering process, played a critical role in the final mechanical properties. Oxygen could reduce the ductility and fatigue life, which deviated from the behavior observed in other additive manufacturing techniques, such as powder bed fusion (PBF). [ABSTRACT FROM AUTHOR]

This study investigates the influence of processing parameters, specifically laser power and scan speed, on the melt pool characteristics of Ti-6Al-4V alloy during Powder Bed Fusion–Laser Beam (PBF-LB) printing. The objective is to provide a deeper understanding of the melt pool based on in-process melt pool monitoring data obtained from a production scale PBF-LB system (RenAM 500 S), experimental melt pool characterisation from single line print studies, and numerical modelling studies using Computational Fluid Dynamics (CFD). The findings demonstrate that laser power has a more pronounced effect on melt pool depth compared to scan speed, for a given line scan energy. This is due to an increased dwell time at elevated temperatures and reduced local cooling rates. A direct correlation is established between melt pool depth, increased emission intensity from in situ monitoring system, and the temperature-time profile derived from numerical modelling. Additionally, melt pool fluid flow based on numerical modelling reveals the presence of intense thermocapillary flow at higher laser power conditions, leading to the retention of porosity along the track. This observation was supported through experimental validation, as evidenced by the increased levels of porosity observed in line scan samples printed at higher laser powers. [ABSTRACT FROM AUTHOR]

Thin-walled parts with low stiffness and poor machinability are prone to chatter during milling. Chatter can adversely affect machined surface quality and workpiece performance. Most existing chatter monitoring models require training and test data from workpieces with the same stiffness as well as large amounts of training data. In this paper, force signals from workpieces with different stiffnesses are obtained through a series of experiments as source and target domain data. Autoencoders are utilized for feature extraction and support vector machines for chatter recognition. Model-agnostic meta-learning (MAML) optimizes the global model parameters, and transfer learning reduces the demand for target domain samples. The model can monitor the chatter of two types of workpieces at the same time through one training. Compared with common transfer learning models visual geometry group network-16 (VGG-16), this paper decomposes force signals using ensemble empirical mode decomposition (EEMD) and extracts intrinsic mode function (IMF) components as features. VGG-16 model is optimized by adding fully-connected layers, dropout, L2 regularization for chatter recognition. The proposed method achieves 99% accuracy on source domain and 98% on target domain. The target domain accuracy is 6% higher than without using MAML optimization, and 8% higher than the VGG-16 method. [ABSTRACT FROM AUTHOR]

The precision machining of Ti-6Al-4V (TC4) micro-channels remains a challenge due to the poor surface integrity and limited tool life. Ultrasonic vibration-assisted grinding (UVAG) is a promising technique that is being employed to enhance the achieved quality of Ti-6Al-4V micro-channels. Taking the wheel's wear and the springback of the workpiece into consideration, a new kinematic simulation model for the 3D surface generation process is first developed, and the material removal mechanism under different ultrasonic parameters during UVAG of Ti-6Al-4V is investigated based on the calculated grit-cutting trajectory and ground surface topography. Comparing the simulated and experimental results, it is found that the built surface topography prediction model can successfully capture the obtained surface characteristics of Ti-6Al-4V by CG and UVAG process. The condition for intermittent machining in UVAG is obtained by establishing the mathematical relation between grinding and ultrasonic parameters. Therefore, the model developed in this paper can be applied to predict surface roughness and optimize the UVAG process of Ti-6Al-4V. [ABSTRACT FROM AUTHOR]

Laser-based powder bed fusion of metals (PBF-LB/M) is the most used additive manufacturing (AM) technology for metal parts. Nevertheless, challenges persist in effectively managing metal powder, particularly in blending methodologies in the choice of blenders as well as in the verification of blend results. In this study, a bespoke laboratory-scale AM blender is developed, tailored to address these challenges, prioritizing low-impact blending to mitigate powder degradation. As a blending type, a V-shape tumbling geometry meeting the requirements for laboratory AM usage is chosen based on a literature assessment. The implementation of thermal oxidation as a powder marking technique enables particle tracing. Blending validation is achieved using light microscopy for area measurement based on binary image processing. The powder size and shape remain unaffected after marking and blending. Only a small narrowing of the particle size distribution is detected after 180 min of blending. The V-shape tumbling blender efficiently yields a completely random state in under 10 min for rotational speeds of 20, 40, and 60 rounds per minute. In conclusion, this research underscores the critical role of blender selection in AM and advocates for continued exploration to refine powder blending practices, with the aim of advancing the capabilities and competitiveness of AM technologies. [ABSTRACT FROM AUTHOR]

Additively manufactured (AM) Ti-6Al-4V devices are implanted with increasing frequency. While registry data report short-term success, a gap persists in our understanding of long-term AM Ti-6Al-4V corrosion behavior. Retrieval studies document β phase selective dissolution on conventionally manufactured Ti-6Al-4V devices. Researchers reproduce this damage in vitro by combining negative potentials (cathodic activation) and inflammatory simulating solutions (H2O2-phosphate buffered saline). In this study, we investigate the effects of these adverse electrochemical conditions on AM Ti-6Al-4V impedance and selective dissolution. We hypothesize that cathodic activation and H2O2 solution will degrade the oxide, promoting corrosion. First, we characterized AM Ti-6Al-4V samples before and after a 48 h -0.4 V hold in 0.1 M H2O2/phosphate buffered saline. Next, we acquired nearfield electrochemical impedance spectroscopy (EIS) data. Finally, we captured micrographs and EIS during dissolution. Throughout, we used AM Ti-29Nb-21Zr as a comparison. After 48 h, AM Ti-6Al-4V selectively dissolved. Ti-29Nb-21Zr visually corroded less. Structural changes at the AM Ti-6Al-4V oxide interface manifested as property changes to the impedance. After dissolution, the log-adjusted constant phase element (CPE) parameter, Q, significantly increased from -4.75 to -3.84 (Scm-2 (s)α ) (p = .000). The CPE exponent, α, significantly decreased from .90 to .84 (p = .000). Next, we documented a systematic decrease in oxide polarization resistance before pit nucleation and growth. Last, using k-means clustering, we established a structure–property relationship between impedance and the surface's dissolution state. These results suggest that AM Ti-6Al-4V may be susceptible to in vivo crevice corrosion within modular taper junctions. [ABSTRACT FROM AUTHOR]

Minimizing the drilling-induced damage on the walls and sub-surfaces of the drilled holes is a challenging but demanding task, especially on hard-to-machine materials such as CFRP/Ti-6Al-4 V stacks. In general, these stacks are highly preferred in aerospace structural applications. This paper analyzes the surface integrity of the drilled CFRP holes when they are stacked above the Ti-6Al-4 V alloy, by incorporating the laser-based marking of micro-textures on the flank and rake faces of the drill, which enables the micro-pool lubrication between the cutting-edges and work material. Comparative experimentations were conducted under MQL conditions. Considering the flank face micro-grooved drill, consistently lower thrust forces were observed across the entire range of cutting speeds and feeds, achieving reductions of up to 17 to 20%. Furthermore, the tool life study was performed, which reveals a substantial 26% enhancement in tool life with the flank face grooved drill, emphasizing its significant advantages for enhanced machining performance. [ABSTRACT FROM AUTHOR]

Geometrically complex objects are more and more often produced with the help of the so-called additive manufacturing commonly referred to as 3D printing. This technology proves itself to be effective in the field of medical industry due to processing potential of titanium alloys. Nonetheless 3D printing also has its drawbacks, the most severe being high roughness of printed elements’ area as well as the need to remove support structures created following the printing. Mechanical processing is commonly used for said parameters being enhanced. The completion of that process, however, takes a lot of time and prevents hard-to-reach elements from being reached. The task of this article is to provide a new method of firming the print’s surface and removing load-bearing structures. To achieve this, selective laser melting (SLM) technology will be used along with bathing prints in HF/HNO3 solution, all of which are supported by ultrasound.

Ti-6Al-4 V is an extensively used and highly versatile titanium alloy. It is renowned for its lightweight-to-strength ratio, excellent biocompatibility, and corrosion resistance. The pursuit of advanced materials with enhanced mechanical strength, and wear resistance has led to the exploration of high entropy alloys (HEA) as particle reinforcements. This study combines Ti-6Al-4 V with AlCoCrFeNi HEA at different weight compositions (0 %, 2 %, 4 %, 6 %, 8 %) to create novel composites with tailored properties. The composites were subjected to density, microhardness, tensile, and pin-on-disc tests to evaluate mechanical and tribological properties. Microstructural analysis revealed that microwave sintering has enhanced densification and resulted in uniform dispersion of HEA particles within the Ti-6Al-4 V matrix. The XRD and EBSD analysis revealed the presence of BCC structure in the composite. 8 wt%-AlCoCrFeNi/Ti-6Al-4 V sample exhibited an impressive 81.66 % increase in microhardness and 21.23 % in yield strength, compared to the base sample. Furthermore, noteworthy reductions of 45 % in wear rate and 40 % in coefficient of friction (COF) when subjected to tribological analysis. The worn surface revealed the presence of oxide layer formation at elevated sliding velocity and distance which resulted in reduced wear rate.

The effect of coating thickness (CT) on the microstructures, hardness, and wear of cold sprayed Ti-6Al-4V (CS-Ti64) coatings was systematically investigated since the prolonged high pressure CS deposition could change their microstructures and porosity levels. In addition, the CT was relatively important for their durability, performance, and service life. Therefore, the CS-Ti64 coatings with different CT of 100-3000 µm were prepared on commercially available Ti64 (CA-Ti64) substrates via high pressure CS processes. The CS-Ti64 coatings had low porosity levels wherewith severely deformed Ti64 particles with a crescent-shape could be seen in their cross-sectional microstructures. The hardness of the CS-Ti64 coatings increased with increased CT probably due to their lowered bulk porosity levels associated with longer high pressure CS deposition. As a result, the increased CT from 100 to 3000 µm resulted in a 9.8% decrease in the wear of the CS-Ti64 coatings. The wear of the CS-Ti64 coating with 3000 µm was 16.8% lower than that of the CA-Ti64 as all the CS-Ti64 coatings had lower wear than the CA-Ti64. It could be concluded that the prolonged high pressure CS deposition for the thick CS-Ti64 coatings had an influence on their porosity, hardness, and wear.

Additively manufactured, Electron Beam Melted (EBM) specimens of the titanium alloy, Ti–6Al–4V, have been produced using a process window determined through a normalised energy density method. Two batches were manufactured and compared using identical energy density values with differing beam current, power, and beam velocity. A stable process window has been demonstrated with a Vickers hardness range of 360–395 VHN resulting from α lath coarsening from 0.7 μm up to 3 μm. A range of macro morphologies have been reported and relate to the hatch overlap and beam velocity parameters. Base plate position does not appear to influence microstructure or micro-hardness. Prior-β columnar and colony size increases with α lath width resulting from increased energy input; however, each grain type appears to respond differently to either beam velocity or hatch space variation. Average α lath width values show greater correlation to energy density, which demonstrates the dependence of grain formation on hatch overlap.

The addition of growth restricting elements in additive manufacturing of Ti and Ti-based alloys can result in the formation of equiaxed structures. However, an excessive incorporation of these elements frequently impairs the mechanical properties. Obtaining the minimum necessary amount of addition is crucial to achieve the transition from columnar to equiaxed microstructure. This ensures that the desired equiaxed structure is obtained while minimizing any potential negative effects on the material's properties. Here manganese was taken as the potential grain refiner in Ti alloy. Then, evolutions of grain morphologies and microstructures as well as the mechanical properties various of Ti-6Al-4V alloy in laser wire deposition additive manufacturing with the growth restriction factors of 26, 32, 39 were explored respectively. And the average hardness of the deposits were 495 HV, 512 HV, and 530 HV, respectively, showing an increase of approximately 15%, 19% and 23%. When the growth restricting factor value reached 39, the columnar prior β grains underwent a complete transformation into equiaxed grains. Mn elements promoted the decomposition of β→α+Mn2Ti during the multi-pass deposition and the microhardness of the deposits were significantly increased. Additionally, Mn elements were expelled outwards during the β→α transition. Nevertheless, the diffusion rate of Mn elements was low and thereby there was a low growth rate of α phases, thus refining α phases.

A powder-bed-based additive manufacturing process called electron beam melting (EBM) is defined by high temperature gradients during solidification, which produces an extremely fine microstructure compared to the traditional cast material. However, porosity and segregation defects are still present on a smaller scale which may lead to a reduction in mechanical properties. It is important to have a better knowledge of the influence of post-fabrication treatments on the microstructure and mechanical characteristics before the use of additive manufacturing parts in specific applications. In this study, the effects of solution heat treatment (SHT) and hot isostatic pressing (HIP) on the microstructure and mechanical properties of Ti-6Al-4V alloy fabricated by the EBM process have been investigated. The SHT and HIP treatments can significantly improve the ductility of EBM Ti-6Al-4V due to the coarsening of α laths and the formation of β grains.

In this study, post-heat treatments were applied to Ti–6Al–4V (TC4) alloy fabricated by selective laser melting (SLM) to investigate the effects of annealing temperature (750–950 °C in 50 °C intervals) on the alloy's microstructure, residual stress and mechanical properties. The initial microstructure of as-SLMed TC4 alloy was dominated by needle-like α′ martensite with a high density of dislocations and minor β phase, resulting in high strength (1190 MPa) but limited ductility (2.2% elongation). Annealing led to the transformation of α′ martensite into α phase, with the β phase content remaining relatively stable. Increasing the annealing temperature caused the acicular martensite to evolve into bundles of coarse α laths, forming a basket-weave microstructure. Annealing at 750 °C for 2 h reduced the yield strength to 1040 MPa and improved elongation to 8.3%. Interestingly, both the strength and ductility decreased with further increases in annealing temperature. This unusual phenomenon was rarely mentioned in current literature and was considered to be associated with the abnormal variations in the Schmid factor of (0001) [11-20] slip system and the reduction of mobile dislocations within the coarsened α martensite. Additionally, annealing combined with air cooling effectively alleviated residual tensile stresses in the SLM-formed TC4 alloy.

In this study, lattice sandwich structures of Ti–6Al–4V alloy with simple cubic (SC) and rhombic dodecahedron (RD) unit cells were prepared by electron beam powder bed fusion (EB-PBF) technique. Through a combination of finite element simulation and experimental investigation, the effect of lattice cell shape and heat treatment on the bending fatigue performance of these lattice sandwich structures was studied. The results show that the underlying fatigue mechanism of the RD lattice sandwich structure is primarily dominated by cyclic ratcheting of the lattice. In contrast, for the SC lattice sandwich structure, the fatigue mechanism involves an interaction of cyclic ratcheting and fatigue crack initiation and propagation of the lattice. During the cyclic deformation process, the struts of the lattice unit cells in the SC lattice sandwich structure mainly undergo buckling deformation. Under the same bending deformation strain, the struts experience much higher stress in the SC lattice sandwich structure, making them more susceptible to crack initiation and resulting in a quick fatigue failure. Therefore, the fatigue performance of the RD lattice sandwich structure is significantly superior to that of the SC lattice sandwich structure. Heat treatment result in the enhanced plasticity of parent materials of the lattice sandwich structure, leading to improved resistance to cyclic strain accumulation during fatigue processes and an increase in fatigue strength.

The anisotropic creep response in both the XY and XZ planes of Ti–6Al–4V ELI manufactured by powder bed fusion (PBF) was examined under nanoindentation creep loading at room temperature, ranging from nm to μm scales. The stress exponent values of 4.06–4.30, rationalised through threshold stress, indicate that the creep behaviour is primarily dominated by dislocation gliding. Creep displacement results show that the anisotropic creep behaviour in the XY and XZ planes of the as-built, and heat treatment enhances the creep resistance of the XZ plane, while there is no significant difference in creep displacement between the as-built and heat-treated XY planes. Due to the higher dislocation density and compressive residual stress in the XY plane compared to the XZ plane, the creep resistance is higher in the XY plane for the as-built. It is highlighted that compressive residual stress is more relieved in the XY plane than in the XZ plane through heat treatment. The heat treatment results in improved creep resistance due to the formation of the Widmanstätten structure and β precipitates, which can impede dislocation movement under creep loading. The combination of residual stress and microstructural effects leads to anisotropic creep behaviour, suggesting that the anisotropy is inherited from the additive manufacturing process at micron scales.

In this study, we propose an innovative approach that enhances the performance of the backpropagation (BP) neural network in predicting the low‐cycle fatigue life of Ti‐6Al‐4V alloy by improving the dung beetle optimization (DBO) algorithm with the maximin Latin hypercube design (MLHD) strategy. To address the challenges posed by complex geometric components under different temperature conditions, this research employs finite element simulation to expand the limited experimental dataset and utilizes these data to further guide and optimize the MLHD_DBO_BP model. Test results indicate that the proposed MLHD_DBO_BP model significantly outperforms the traditional finite element method (FEM) and other neural network models in terms of fatigue life prediction performance. This research demonstrates the effectiveness of machine learning models that combine experimental and simulation data in predicting the low‐cycle fatigue life of Ti‐6Al‐4V alloy. Highlights: Maximin Latin hypercube design enhances dung beetle optimization for neural network tuning.Improved dung beetle algorithm outperforms finite element method in predicting fatigue life.High‐precision fatigue life predictions for complex geometries are achieved.Dung beetle‐optimized neural network validated across various engineering structures. [ABSTRACT FROM AUTHOR]

The corrosion behavior of the TiN monolayer and CrN/TiN multilayer coatings deposited via cathodic arc evaporation physical vapor deposition (CAE‐PVD) on the Ti–6Al–4V substrates were evaluated in Ringer's and Hank's physiological saline electrolytes. XRD (x‐ray diffractometry) and scanning electron microscopy (SEM) analysis were used to characterize the coatings. The corrosion behavior of coatings was assessed by impedance spectroscopy and potentiodynamic polarization techniques. The results showed that the corrosion resistance of coatings was increased in the order of TiN‐Ringer's < TiN‐Hank's < CrN/TiN‐Ringer's < CrN/TiN‐Hank's. Therefore, it can be concluded that the CrN/TiN coating, due to having a large number of interfaces and a smoother surface with fewer macroparticles and pinholes, is more efficient in raising the corrosion resistance properties of titanium than TiN monolayer coating. Moreover, it was observed that Ringer's solution is a more severe environment than Hank's solution. Both coatings, because of the precipitation of a protective corrosion products layer on their surface, showed an enhancement in corrosion resistance with increasing the immersion time from 1 to 14 days in Hank's. The results suggest TiN monolayer and CrN/TiN multilayer coatings as promising candidates for biomedical applications. [ABSTRACT FROM AUTHOR]

Electron beam melting is a powder bed fusion process capable of manufacturing parts from a variety of high-temperature alloys. Given that the process relies on feedstock recycling for process economics, understanding process-part quality relationships is critical. This work investigates process-part quality relationships in terms of the internal and external defects and component microstructure relative to a feedstock subjected to 33 build cycles without replacement. To accomplish this, a volume of fluid mesoscale model consisting of three different powder distributions were considered: (1) Monomodal; (2) As-measured; and (3) Irregular. Particle morphology was characterized using shape factors examined via optical microscopy. To approximate the particle shapes in three-dimensions, a method is presented that utilizes a binarized domain to define low frequency, macroscale particle "base" shapes implicitly and is thus not restricted to starlike particles. The discrete element method was also used to investigate velocity distributions and packing densities of the as-measured and irregular particles with respect to deviations in the nominal layer thickness of 50 μm. In general, beam power and scan speed were found to have an appreciable effect on microstructure formation and surface roughness. Finally, correlations were found between specific classifications of irregular particles and lack of fusion defect formation. [ABSTRACT FROM AUTHOR]

In this experimental study, the initial phase involved preparing composite structures with various mix ratios using the Ti‐6Al‐4V alloy, widely used in clinical applications, in conjunction with ZrO2 and hydroxyapatite (HA) synthesized via the precipitation method, employing powder metallurgy techniques. Subsequently, the microstructures of the resultant hybrid composite materials were imaged, and x‐ray diffraction (XRD) phase analyses were conducted. In the final phase of the experimental work, tests were performed to determine the biocompatibility properties of the hybrid composites. For this purpose, cytotoxicity and genotoxicity assays were carried out. The tests and examinations revealed that structures compatible both morphologically and elementally were obtained with no phase transformations that could disrupt the structure. The incorporation of ZrO2 into the Ti‐6Al‐4V alloy was observed to enhance cell viability values. The value of 98.25 ± 0.42 obtained by adding 20% ZrO2 gave the highest cell viability result. The addition of HA into the hybrid structures further increased the cell viability values by approximately 10%. All viability values for both HA‐added and HA‐free groups were obtained above the 70% viability level defined in the standard. According to the genotoxicity test results, the highest cytokinesis‐block proliferation index values were obtained as 1.666 and 0.620 in structures containing 20% ZrO2 and 10% ZrO2 + 10% HA, respectively. Remarkably, all fabricated composite and hybrid composite materials surpassed established biocompatibility standards and exhibited nontoxic and nongenotoxic properties. This comprehensive study contributes vital insights for future biomechanical and other in vitro and in vivo experiments, as it meticulously addresses fundamental characterization parameters crucial for medical device development. Research Highlights: Support of optimum doping rates ions on hybrid composites and concentrations.Development of uniform surface appearance and distributions/orientations of microcrystals on ceramic compoundsImprovement of cell viability and desired increase in biocompatibility with the doping of HA. [ABSTRACT FROM AUTHOR]

3D printing technology proves itself to be effective in the field of medical industry due to processing potential of titanium alloys. Nonetheless it also has its drawbacks, the most severe being high roughness of printed elements’ area as well as the need to remove support structures created following the printing. Mechanical processing is commonly used for said parameters being enhanced. The completion of that process, however, takes a lot of time and prevents hard-to-reach elements from being reached. The task of this article is to provide a new method of firming the print’s surface and removing load-bearing structures. To achieve this, selective laser melting (SLM) technology will be used along with bathing prints in HF/HNO3 solution, all of which are supported by ultrasound. This process will enhance the material fatigue processing while reducing the postprocessing time and complexity. [ABSTRACT FROM AUTHOR]

Fatigue crack initiation sites would transfer from surface to subsurface of metal specimens through shot peening (SP) or laser shock surface strengthening. This phenomenon is typically attributed to the introduction of compressive residual stress on the surface of the specimen during the surface strengthening process. In this study, Ti–6Al–4V specimens featuring a high-density twinned structure on their surfaces, which eliminated compressive residual stress, were fabricated. Fatigue test result revealed that fatigue crack initiation sites in specimens with twinned structures were predominantly located in the subsurface, near the junction area between the twinned structure and the matrix. This phenomenon was accompanied by an increase in fatigue life. The microstructural features in the fatigue crack source were analyzed using focused ion beam (FIB) coupled with electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). It was observed that primary crack formed in badly oriented grains that are difficult to initiate dislocation slip according to the Schmid factor (SF). Nonetheless, TEM observations revealed the activation of basal dislocations in these grains, potentially leading to crack nucleation along basal slip bands and subsequent propagation along the basal plane. Our results suggest that a high-density twin structure on the surface can enhance the fatigue strength of Ti–6Al–4V by transferring the fatigue crack source to the subsurface.

Wire and arc additive manufacturing (WAAM) technique has introduced a novel approach for producing complex Ti–6Al–4V parts with metric dimensions. However, the produced part leads to the development of a strong texture and anisotropic mechanical properties due to the formation of large columnar β grains. To resolve this issue, the plastic deformation of each deposited track through hammer peening was developed as a means to refine these large β grains. In this study, we have investigated an innovative approach to further enhance the efficiency of β grain refinement by minimizing the arc heat input associated with previous deposited layer, which is achieved by employing a C-type filler wire. Our findings reveal a notable enhancement in grain refinement efficiency through the utilization of a C-type filler wire with peening process, as compared to available conventional commercial round shape filler wire. Specifically, the employment of the C-type filler wire results in a reduced melt pool penetration depth of WAAM Ti–6Al–4V (3.3 mm), compared to the commercially available round shape (R-Type) filler wire (4.48 mm). Within the plastically deformed region by peening, fine and randomly oriented β grains are observed, extending to a depth of deformation reaching 844 ± 32.65 μm. Peening WAAM Ti–6Al–4V with the C-type filler wire leads to the development of isotropic mechanical properties in both horizontal and vertical directions, offering high strength due to the presence of small equiaxed β grains and thin α laths (0.56 ± 0.18 μm), in contrast to the use of conventional commercial round shape filler wire.

Additive Manufacturing (AM) is receiving widespread attention from both industry and academia who are looking to benefit from the numerous advantageous possibilities that AM processes have to offer, such as the potential to design and produce highly complex bespoke geometries with minimal material wastage. Yet, despite this, AM also has some drawbacks. Some of the most significant include the presence of process-induced defects and the inherent surface roughness of an AM built component, both of which can have a considerable influence on the mechanical properties of the final product. This research will investigate the role of an as-built surface on the fatigue properties of AM Ti–6Al–4V manufactured by electron beam melting (EBM), laser powder bed fusion (L-PBF) and laser metal deposition with wire (LMD-w). Fatigue results have been generated alongside advanced surface profilometry, microstructural, defect and fractographic analyses that have revealed that whilst the surface roughness in the majority of instances is the primary factor impacting the fatigue performance on AM material, it cannot be considered alone. It was found that the inherent as-built (AB) surface finish was significantly different across the various AM processes, inducing a range of effective stress concentrations and thus, a contrasting impact on the resulting fatigue performance. Results from each variant have been compared against a machined and polished equivalent, to provide a further consideration as to whether the as-built surface would be suffice from a time and economical viewpoint. Statistical analysis of the generated results also allowed for an extrapolation of predicted fatigue lives in the very high cycle regime for the alternative AM Ti–6Al–4V variants.

Introduction: The aluminum and vanadium contents of the titanium-aluminum-vanadium alloy (Ti-6Al-4V) surface are known to have cytotoxic effect, the use of laser grooving was thought to produce dental implants-controlled surface roughness and a better surface chemical composition. Aims: The aim of the current work was to test the titanium alloy machined and laser grooves surface content of the aluminum and vanadium, and their effect on cellular viability. Materials and Methods: Threaded titanium dental implants were designed, milled and micro-grooved using the Avia coherent pulsed ultraviolet laser and produced 10 µm grooves on their machined surface. The scanning electron microscope was used to evaluate the produced micro-grooves, and the X-ray diffraction to study the surface composition of the titanium alloy before and after laser grooving. And the MC3T3-E1 mouse osteoblasts were cultured on such surfaces to test their cytotoxic effect. Results and Discussion: The laser grooving significantly reduced the alloy surface content of the aluminum and vanadium as proved by the significantly better viability of the cells cultured on it as compared to the machined surface. Conclusion: The laser grooving reduced the Ti-6Al-4V alloy surface content of the cytotoxic elements.

This study demonstrates the application of a new experimental technique for laboratory-scale simulation of the open-die forging process, known as cogging, an intermediate hot-working process necessary to design an optimised microstructure in the advanced engineering titanium alloy Ti-6Al-4V. Small test-bars of Ti-6Al-4V alloy were subjected to multi-directional cogging operations at elevated temperatures (950–1050 °C). The as-received material, prior to forging, underwent heat treatments to coarsen the initial grain structure, to better simulate the industrial-scale intermediate microstructure (i.e., β recrystallised) and to help prove the capability of the set-up to achieve microstructure modification via globularisation (below β-transus), and recrystallisation (dynamic and static) and recovery mechanisms (above β-transus) within the cogged material. The influences of hot working parameters on deformation localisation, width of α platelets, and globularisation within the resulting microstructure variation have been investigated using light microscopy (LM), Vickers hardness (HV) testing, and electron backscatter diffraction (EBSD). The cogged Ti-6Al-4V alloy specimens underwent various microstructural evolution stages after hot forging, thus indicating successful application of the designed miniaturised open-die forging apparatus for high temperature experimentation and characterisation studies. This will be suitable for low-cost small-scale trials to determine the key process parameters affecting the onset of microstructure evolution during open-die forging (e.g., ingot-to-billet conversion) of the Ti-6Al-4V alloy, prior to large-scale trials which are rather more expensive.

Ti–6Al–4V, an alloy of titanium has recently gained focus of research to overcome its machinability challenges. Miniaturization in devices has forced a shift towards micro and meso-scale machining. Sustainability and green manufacturing concepts have shifted focus in machining from cutting fluids towards modern cooling approaches to minimize or eliminate them. In present research, cutting forces & tool wear in Ultrasonic Vibrations Assisted End Milling of Ti–6Al–4V at meso-scale under Dry, Flooded, Minimum Quantity Lubrication & Cryogenic cooling have been analyzed to develop optimum machining parameters. Taguchi L16 orthogonal array was designed to perform experiments keeping Cutting Speed, Feed per tooth, Depth of cut, Ultrasonic vibrations amplitude & Cooling environment as inputs. ANOVA was used to analyze contribution ratios by these parameters towards cutting forces & tool wear. Results indicated that machining conditions, cooling environment and Ultrasonic Vibrations influence cutting forces & tool wear. Depth of cut had the highest influence with 63.41% contribution towards cutting forces while cutting speed remained the highest influencing factor with 39.86% contribution towards tool wear. Cutting forces were reduced by 33.49%, 16.93% and 4.91% while tool wear was reduced by 26.43%, 9.48% and 5.17% under Minimum Quantity Lubrication environment compared to dry, flooded and cryogenic cooling respectively. Cutting forces and tool wear under ultrasonic vibrations were reduced by 24.52% and 13.16% respectively as compared to Conventional Machining (CM). For optimum results, Minimum Quantity Lubrication with low Cutting Speed, Depth of cut, Feed per tooth and high amplitude of ultrasonic vibrations is recommended to machine Ti–6Al–4V.

Ti-6Al-4V alloy is widely used in aerospace and chemical equipment manufacturing due to its good strength, plasticity, toughness, corrosion resistance and weldability, but its hardness and abrasion resistance are not high enough to limit its service life under frictional wear conditions to some extent. Ti-6Al-4V alloy homogeneous cermet cladding layer with TiC-added phase was additively prepared based on the optimized process method of laser cladding, and the strengthening effect of TiC enhancement with respect to the cladding layer microstructure as well as the basic mechanical properties was characterized and verified. The results show that the main phases of the cladding layer include α-Ti, β-Ti and TiC, of which TiC is supersaturated and precipitated within the cladding layer. Due to the difference in the supercooling degree at different locations of the cladding layer, the precipitated TiC is mainly in the form of fine particles at the top of the cladding layer, while it is mainly in the form of dendrites and petals in the middle of the cladding layer. The bottom of the cladding has a new wheat spikes precipitation shape, while no significant TiC precipitation is seen in the dilution zone. The average microhardness of the cladding layer is 530HV0.5, which is 61% higher than that of the substrate; the average friction coefficient of the cladding layer is 0.3583 at 35 N load, which is 11% lower than that of the substrate, and the volume wear rate is about 87% that of the substrate, and the wear is in the form of adhesive wear and abrasive wear.

The parameters used in the production process in laser powder bed fusion (L-PBF) technology, one of the additive manufacturing methods, have a critical effect on the mechanical behavior and density properties of the product and can change the properties of the product. Therefore, this study examined the influence of laser power, scanning speed, hatch spacing and beam rotation angle on the tensile strength, impact energy, surface roughness, and porosity levels of Ti–6Al–4V produced through the L-PBF method. It was observed that the tensile strength changes directly proportional to the laser power. In addition, the tensile strength decreases significantly with a value of 645 MPa obtained at lowest 0.07 mm hatch spacing, 190 W laser power and 900 mm scanning speed. The lowest value of impact energy, with a value of 8.7 J, was reached at a rotation angle of 180°. It has been determined that surface roughness decreases significantly with increasing laser power, while it demonstrates an increase with higher scanning speeds. Surface roughness values of 8.9 μm parallel and 8.35 μm perpendicular to the building direction were achieved at a laser power level of 220 W. Laser power was identified as the most influential factor in determining the porosity ratio, with a high porosity rate 0.48% occurring at 160 W laser power. Furthermore, an increase in scanning speed resulted in a corresponding increase in the porosity rate.

Considering the anisotropy of microstructure of additive manufactured metal materials, quantitative assessment of the anisotropy of fatigue crack growth (FCG) behavior is necessary for structural damage tolerance design and evaluation. This study conducted an experimental and mechanistic investigation of the FCG behavior of the laser metal deposited (LMD) Ti–6Al–4V alloy, focusing on the anisotropy of FCG and the effect of overload on FCG. Both the FCG experiments with constant amplitude loading (CAL) and with a single overload (OL) were performed in different directions. Under CAL, the FCG rate exhibits a bilinear correlation with the stress intensity factor. Before the transition point (ΔKT = 16.9 MPa√m), since the grain boundaries are sparser along the columnar crystal growth direction, the FCG rate in the XY specimen is higher than that in the other directions. When the FCG rate further increases, the hindrance effect of grain boundaries on FCG weakens, and the anisotropy of FCG rates disappears. An interesting new finding is that when an overload is applied after ΔKT, the FCG rates in the XZ and ZX directions become different, and the overload-induced anisotropy increases with the overload ratio (OLR). The difference in FCG rates between the two directions exceeds 23.2% when OLR is 2.5. Based on microscopic and theoretical analysis, it was demonstrated that the overload induces residual strain in front of the crack-tip and enhances FCG resistance. The FCG resistance is positively related to the size of the plastic zone and negatively related to the yield strength in the loading direction.