Search Results (1,496)

Titanium alloys, particularly Ti-6Al-4V, are widely used in many industries due to their high strength, low density, and corrosion resistance. However, machining these materials is challenging due to high strength at elevated temperatures, low thermal conductivity, and high chemical reactivity. This study investigates Recurrence Plot (RP) and Recurrence Quantification Analysis (RQA) to analyze tool wear during the finish turning of Ti-6Al-4V. The tests were conducted under Minimum Quantity Lubrication (MQL). Three inserts (two coated, one uncoated) were tested, and tool life was evaluated based on material removal volume. The issue of tool exploitation and process reliability is crucial, as it directly impacts machining performance. Results show that the uncoated insert outperformed the coated ones. RQA parameters indicated a stable-to-unstable transition in coated inserts but not in the uncoated insert. This suggests that recurrence analysis can monitor cutting dynamics in coated insert machining, but further research is needed for uncoated tools. This paper’s novelty lies in applying RP and RQA to diagnose tool wear in titanium alloy machining under MQL conditions, a method not previously explored in this context. Full article

Due to their excellent mechanical properties and corrosion resistance, high-entropy alloys (HEAs) have the potential to be used as new engineering structures and functional materials. In this study, an FeCo_1.5CrNi_1.5Ti_0.5HEA coating was prepared on the surface of a 1Cr18Ni9Ti alloy by laser cladding technology. Phase structure and microstructure were characterized by XRD and using an SEM. The corrosion resistance was evaluated by an electrochemical workstation, and the polarization curves were obtained in simulated seawater and 3.5 wt.% NaCl and 5% HCl solutions. The corrosion morphology of the Fe-based HEA coating was further characterized using the SEM, super depth of field observation, and 3D topological images. The results showed that the Fe-based HEA coating had a single-phase FCC structure with a grain size of about 10.7 ± 0.25 μM. Electrochemical analysis results showed that the corrosion resistance of the current Fe-based HEA coating was poor in HCl solutions. However, it exhibited good corrosion properties in simulated seawater and 3.5 wt.% NaCl solutions. Further analysis of the corrosion morphology revealed that in simulated seawater and the 3.5 wt.% NaCl solution, the surface of the current Fe-based HEA coating exhibited a preferential corrosion tendency between dendrites, while in the 5% HCl solution, it exhibited more obvious pitting characteristics. The results indicate that the current Fe-based HEA coating exhibits good comprehensive performance, especially in an acidic Cl⁻ corrosion environment. These findings provide a reference for the application of laser cladding prepared Fe HEA coatings. Full article

The deformation behavior and microstructure changes of electron-beam cold-hearth-melted (EBCHM) Ti-6Al-4V alloy were investigated. The stress–strain curves of the alloy were obtained, the constitutive model was established based on the Arrhenius equation, and the hot processing map was drawn. The results showed that the stress of the alloy decreases with increasing temperature and decreasing strain rate. In the β phase field, there are more recrystallized grains when the strain rate is slow, and the recrystallization of the β phase does not have enough time to occur when the strain rate is fast. There are obvious shear bands in the microstructure at the strain rate of 10 s⁻¹. In the α + β field, the morphology and crystallographic orientation of the microstructure changed simultaneously. Globularization is a typical microstructure evolution characteristic. The prismatic slip is easier to activate than basal and pyramidal slips. Moreover, globularization of the lamellar α phase is not synchronously crystallographic and morphological. Full article

The present study assessed the compression performance of four strut lattices manufactured via laser powder bed fusion (LPBF), namely selective laser melting (SLM) from Inconel 625 and Ti-6Al-4V. Static finite element analysis and mechanical testing were performed, and it was concluded that the experimentally determined performance trend was in good agreement with that obtained by numerical methods. The cell type greatly influences the compressive performance of the lattices, regardless of the material used for manufacturing. The best compressive performances were recorded for the octet lattice, followed by the truncated octahedron, Kelvin, and re-entrant lattices. Regarding material performance, for the first maximum compressive strength, similar results were recorded for both materials; a difference was recorded in the case of yield strength, with higher values were recorded for Ti-6Al-4V compared to Inconel 625. The average first maximum compressive strength for the Ti-6Al-4V lattice was between 30.39 and 290.17 MPa, and it was within a range of 16.22–258.71 MPa for Inconel 625. The elastic modulus was between 1.74 and 4.72 GPa for Ti-6Al-4V, and 1.13 and 4.46 GPa for Inconel 625. A more ductile behavior was registered for the nickel-based superalloy than for the titanium alloy; the Inconel 625 specimens were characterized by a bending-dominant damage mode, and Ti-6Al-4V specimens were characterized more by a stretch-dominant damage mode. Full article

In competitive industry, economical and environmentally friendly production techniques are essential. In this sense, cleaner and more sustainable machining techniques are the industry’s focus. In addition to green methods, effective parametric control is necessary for hard-to-cut materials, particularly titanium Ti-6Al-4V, which is extensively used in a diversity of industries, including aerospace, medical, and military applications. Therefore, the current study aims to improve the machining performance of Ti-6Al-4V alloy using sustainable lubrication conditions. The effect of Al₂O₃ nanoparticles based on the minimum quantity lubrication (N-MQL) condition on surface quality and productivity are compared with minimum quantity lubrication (MQL). The performance measures, including surface roughness (Ra), material removal rate (MRR), and temperature, are evaluated at three machining variables, i.e., cutting speed (V_c), feed rate (f), and depth of cut (a_p). These performance measures are further assessed by tool wear and surface morphology analysis. a_p, f, and V_c are the most influencing parameters for Ra, MRR, and temperature, regardless of lubrication mode. The optimized values of RA of 0.728443 µm, MRR of 2443.77 m³/min, and temperature of 337 °C are achieved at N-MQL. For the N-MQL state, the optimized values of Ra of 0.55 µm, MRR of 2579.5 m³/min, and temperature of 323.554 °C are attained through a multi-response optimization desirability approach. Surface morphology analysis reveals a smooth machined surface with no obvious surface flaws, such as feed marks and adhesion, under N-MQL conditions, which significantly enhances the surface finish of the parts. The machining performance under the N-MQL condition has been enhanced considerably in terms of an improvements in surface finish of 32.96% and MRR of 11.56%, along with a decrease in temperature (17.22%) and higher tool life (326 s) than MQL. Furthermore, Al₂O₃ is advised over MQL because it uses less energy and has reduced tool wear and improved surface quality, and it is a cost-effective and sustainable fluid. Full article

This article compares the properties of the diamond-like carbon (DLC) coating with those of ZrN and (Zr,Hf)N coatings deposited on the Ti-6Al-4V titanium alloy substrate. To improve substrate adhesion during the deposition of the DLC coating, preliminary etching with chromium ions was conducted, ensuring the formation of a chromium-saturated diffusion surface layer in the substrate. A Si-DLC layer followed by a pure DLC layer was then deposited. The hardness of the coatings, their surface morphology, fracture strength in the scratch test, and tribological properties and wear resistance in the pin-on-disk test in contact with Al₂O₃ and steel indenters were investigated. The structure of the DLC coating was studied using transmission electron microscopy, and its corrosion resistance in an environment simulating blood plasma was also investigated. In the pin-on-disk test in contact with Al₂O₃ and AISI 52100 indenters, the DLC-coated sample demonstrates a much lower friction coefficient and significantly better wear resistance compared to the nitride-coated and uncoated samples. Both nitride coatings—(Zr,Hf)N and ZrN—and the DLC coating slow down the corrosive dissolution of the base compared to the uncoated sample. The corrosion currents of the (Zr,Hf)N-coated samples are 37.01 nA/cm², 20% higher than those of the ZrN-coated samples. The application of (Zr,Hf)N, ZrN, and DLC coatings on the Ti-6Al-4V alloy significantly inhibits dissolution currents (by 30–40%) and increases polarization resistance 1.5–2.0-fold compared to the uncoated alloy in 0.9% NaCl at 40 °C. Thus, the DLC coating of the described structure simultaneously provides effective wear and corrosion resistance in an environment simulating blood plasma. This coating can be considered in the manufacture of medical products (in particular, implants) from titanium alloys, including those functioning in the human body and subject to mechanical wear (e.g., knee joint endoprostheses). Full article

This paper investigates the use of machine learning methods to predict the loading frequency of shape memory alloys (SMAs) based on experimental data. SMAs, in particular nickel-titanium (NiTi) alloys, have unique properties that restore the original shape after significant deformation. The frequency of loading significantly affects the functional characteristics of SMAs. Experimental data were obtained from cyclic tensile tests of a 1.5 mm diameter Ni_55.8Ti_44.2 wire at different loading frequencies (0.1, 0.5, 1.0, and 5.0 Hz). Various machine learning methods were used to predict the loading frequency f (Hz) based on input parameters such as stress σ (MPa), number of cycles N, strain ε (%), and loading–unloading stage: boosted trees, random forest, support vector machines, k-nearest neighbors, and artificial neural networks of the MLP type. Experimental data of 100–140 load–unload cycles for four load frequencies were used for training. The dataset contained 13,365 elements. The results showed that the MLP neural network model demonstrated the highest accuracy in load frequency classification. The boosted trees and random forest models also performed well, although slightly below MLP. The SVM method also performed quite well. The KNN method showed the worst results among all models. Additional testing of the MLP model on cycles that were not included in the training data (200th, 300th, and 1035th cycles) showed that the model retains high efficiency in predicting load frequency, although the accuracy gradually decreases on later cycles due to the accumulation of structural changes in the material. Full article

The use of the minimum quantity lubrication (MQL) method during machining leads to the reduced consumption of cooling and lubricating liquids, thus contributing to sustainable machining. To improve the properties of liquids used under MQL conditions, they are enriched with various types of micro- and nanoparticles. The purpose of this study was to investigate the effect of the addition of graphite micropowder (GMP) on tool life, cutting force components, and selected surface roughness parameters during the finish turning of the Ti-6Al-4V titanium alloy under MQL conditions. The addition of 0.6 wt% of GMP to the base liquid in machining under MQL conditions leads to an extension of tool life by 7% and 96% compared to machining with a liquid without the addition of GMP and dry machining, respectively. Mathematical models of the cutting force components and surface roughness parameters were developed, taking into account the change in cutting speed and feed. It was found that the use of a liquid with the addition of GMP extends the range of cutting parameters for which the shape of chips obtained is acceptable in terms of work safety. The novelty of this study lies in the use of a cutting fluid composed of bis(2-ethylhexyl) adipate and diester, enriched with graphite micropowder, which has not been extensively investigated for machining titanium alloys under MQL conditions. Full article

This study explores the fatigue behavior and fracture mechanisms of TC11 titanium alloy formed by laser metal deposition (LMD) and subjected to double annealing. The research focuses on how the alloy’s unique microstructure, consisting of alternating equiaxed and columnar crystals, influences its fatigue performance. The microstructure’s basket-like α’ phase, made up of both plate-shaped and needle-like structures, leads to variations in crack growth behavior, as shown in the relationship between the crack growth rate and the stress intensity. An analysis of slip patterns reveals that equiaxed crystals undergo more frequent deformation, accelerating crack propagation compared to the more evenly distributed deformation in columnar crystals. These findings suggest a new approach for improving the fatigue resistance of 3D-printed titanium alloys by optimizing their microstructure. This study provides valuable insights for enhancing material toughness and extending the lifespan of titanium alloys in applications such as aerospace and biomedical engineering. Full article

Good oral hygiene is crucial during treatment with fixed appliances, emphasising the need for additional or alternative oral health methods during orthodontic treatment. This study investigates the effect of essential oil (EO)-based preparations on biofilm adhesion to orthodontic archwires. Five identical-sized orthodontic archwires of different materials were tested using therapeutic and preventive applications of essential oils. This study also used molecular docking to explore how essential oil compounds interact with key proteins of common oral pathogens like Staphylococcus aureus and Streptococcus mutans. We found that the constituent materials heavily influence the antimicrobial effects of essential oils on different orthodontic archwires. Stainless steel-based orthodontic archwires demonstrated the highest efficacy in antimicrobial protection against S. mutans strains (maximum BIP = 28.82% on the epoxy-coated SS). Conversely, inhibition effects in preventive applications against S. aureus were observed exclusively with titanium–molybdenum alloy orthodontic archwires across all tested emulsions (maximum BIP = 29.44%). CuNiTi alloys showed ineffectiveness in preventive treatments, as none of the EO mixtures inhibited biofilm development on this material. After biofilm contamination with S. mutans and S. aureuss strains, the ternary emulsion was most effective for four out of five orthodontic archwires. Computational analysis revealed strong binding interactions between essential oil compounds and key proteins of S. aureus and S. mutans, highlighting specific amino acid residues that are critical for these interactions. Based on the results, stainless steel with epoxy coating or TMA archwires, combined with BEO/CEO/OEO ternary mixture, are recommended for optimal antibacterial protection against biofilm formation on orthodontic archwires. Full article

Superelastic metastable β-Ti-Nb alloys are attractive low-modulus materials for use in biomedical implants. The antibacterial properties of silver and its ability to lower the modulus of Ti-Nb-based transforming alloys make it an appealing ternary addition, but the Ti-Nb-Ag system is poorly characterised at present. This study elucidates the microstructure, equilibrium phases, and mechanical behaviour of a systematic series of Ti–24Nb–XAg (X = 0, 2, 6) (at.%) alloys. The mutual solubility of Nb and Ag in Ti overcame the immiscibility of Nb and Ag and produced an alloy with a single-phase β microstructure for low Ag concentrations. However, at silver concentrations above approximately 5 at.%, the solubility limit was reached and precipitates began to form. These precipitates were found to form quickly during recrystallisation, refining the grain size by Zener pinning, and persisted even after a 500 h heat treatment at 1100 °C. All three alloys showed non-linear-elastic behaviour typical of transforming alloys. The addition of up to 2 at.% Ag to Ti–24Nb was found to decrease the elastic modulus, suppress formation of the ω phase, and cause the critical transformation stress to decrease, though the transformation stress increased above that of Ti–24Nb when 6 at.% Ag is added. These results indicate that Ti-Nb-Ag alloys are a promising candidate for developing new low-modulus implants. Full article

High-temperature structural materials face severe degradation challenges due to oxidation and corrosion, leading to reduced long-term stability and performance. This review comprehensively examines the interfacial migration mechanisms of reactive elements (REs) such as Ti, Al, and Cr in Ni/Fe-based alloys, emphasizing their role in forming and stabilizing protective oxide layers. We discuss how these oxide layers impede ion migration and mitigate environmental degradation. Key findings highlight the importance of selective oxidation, oxide layer healing, and the integration of novel alloying elements to enhance resistance under ultra-supercritical conditions. Advanced insights into grain boundary engineering, alloy design strategies, and quantum approaches to understanding charge transport at passive interfaces are also presented. These findings provide a foundation for developing next-generation high-temperature alloys with improved degradation resistance tailored to withstand extreme environmental conditions. Full article

The machining of titanium alloys, particularly Ti6Al4V, presents a significant challenge in manufacturing engineering. Its high strength, low thermal conductivity and high chemical reactivity make Ti6Al4V a hard-to-machine material. However, the machining process is critical for aerospace and biomedical industries. The rapid wear and short lifetime of cutting tools are the main limitations in Ti6Al4V machining, leading to a large increase in manufacturing costs and compromising the surface quality of machined components. Faced with this problem, the texturing of cutting tools, especially through laser-based techniques, has gained considerable attention in the last decade due to improvement of the tribological properties of textured surfaces. Laser Surface Texturing (LST) has emerged as a promising technique to improve the tribological performance of cutting tools by enabling the creation of precise surface structures. Building on prior research, this review provides a comprehensive overview of the most recent research on this topic, summarizing key findings and outcomes from various investigations. Full article

Laser cladding, as an advanced surface modification technology, has the advantages of a high energy density, controlled dilution rate and good metallurgical bonding between the coating and the substrate. Its rapid heating and cooling properties help to form a dense and fine coating structure on the surface of the substrate, thus enhancing wear and corrosion resistance. In recent years, the in situ generation of carbide-reinforced iron-based composite coatings has gradually become a research hotspot because it combines the high hardness values of carbide with the high toughness values of iron-based alloys, which significantly improves the comprehensive performance of the coatings. This paper reviews the research progress of laser cladding in situ carbide-reinforced iron-based alloy coatings and explores the role of different types of in situ synthesized carbides (TiC, NbC, WC, etc.) in the coatings and their effects on their wear resistance and mechanical properties. The distribution of carbides in the coatings and their morphological characteristics are also discussed, and the effects of laser power, scanning speed and auxiliary treatments (ultrasonic vibration, induction heating, etc.) on the microstructure and properties of the coatings are analyzed. Finally, the problems and future directions of development in this field are envisioned. Full article

Background: Flatfoot deformity is a common condition in children and teenagers that may increase the risk of knee, hip, and back pain. Most of the insoles suggested to treat flatfoot symptoms are not designed to adapt to foot temperature during walking, and they are either too soft to provide support or hard enough to be uncomfortable. Purpose: This study aims to develop an advanced solution to diagnose and treat flexible flatfoot (FFT) using infrared thermography measurements and a hybrid insole reinforced by nitinol (NiTiCu) smart-memory-alloy wires (SMAWs), this super-elastic alloy can return back to its pre-deformed shape when heated, which helps to reduce the local high-temperature points caused by the uneven pressure of FFT. This approach achieves a more uniform thermal distribution across the foot, which makes the hybrid insole more comfortable. Methods: The study involved 16 subjects, divided into two groups of eight flat-footed and eight normal. The procedure includes two parts, namely, designing a prototype insole with SMAW properties based on thermography measurement by using SolidWorks, and evaluating this design using Ansys. Second, a hybrid insole reinforced with SMAWs is customized for flatfoot subjects. The thermography measurement differences between the medial and lateral sides of the metatarsophalangeal line are compared for the normal and flatfoot groups before and after wearing the suggested design. Results: The results show that our approach safely diagnosed FFT and significantly improved the thermal distribution in FFT subjects by more than 80% after wearing the suggested design. A paired t-test reported significant (p-value > 0.001) thermal decreases in the high-temperature points after using the SMAW insole, which was closely approximated to the normal subjects. Conclusions: the SMAW-reinforced insole is comfortable and suitable for treating FFT deformity, and infrared thermography is an effective tool to evaluate FFT deformity. Full article