Search Results (364)

The conventional manufacturing of refractory complex concentrated alloys (RCCAs) for high-temperature applications is complicated, particularly when material costs and high melting points of the materials processed are considered. Additive manufacturing (AM) could provide an effective alternative. However, the extreme temperatures involved represent significant challenges for manufacturing defect-free alloys using this approach. To address this issue, we investigated the preparation of a CrNbTiZr quaternary complex concentrated alloy from an equimolar blend of elemental powders using commercially available powder-blown L-DED technology. Initially, the alloys exhibited some defects owing to the internal stress caused by the temperature gradients. This was subsequently resolved by optimizing the deposition strategy. SEM, XRD and EDS were used to analyze the alloy in the as-deposited condition, revealing a BCC phase and a secondary Laves phase. Furthermore, Vickers hardness testing demonstrated a correlation between the hardness and the volume fraction of the Laves phase. Finally, successfully performed compression tests confirmed that the prepared material exhibits high-temperature strength and therefore is promising for high-temperature application under extreme conditions. Full article

In this study, a Ag/ZrO₂ hybrid coating prepared by the sol–gel method on a β-type Ti45Nb alloy was applied by the spin coating technique, and the microstructural, mechanical, electrochemical, and tribological properties of the surface were evaluated in a multi-dimensional manner. The hybrid solution was prepared using zirconium propoxide and silver nitrate and stabilized through a low-temperature two-stage annealing protocol. The crystal structure of the coating was determined by XRD, and the presence of dense tetragonal ZrO₂ phase and crystalline Ag phases was confirmed. SEM-EDS analyses revealed a compact coating structure of approximately 1.8 µm thickness with homogeneously distributed Ag nanoparticles on the surface. As a result of the electrochemical corrosion tests, it was determined that the open circuit potential shifted to more noble values, the corrosion current density decreased, and the corrosion rate decreased by more than 70% on the surfaces where the Ag/ZrO₂ coating was applied. In the tribological tests, a decrease in the coefficient of friction, narrowing of wear marks, and significant reduction in surface damage were observed in dry and physiological (HBSS) environments. The findings revealed that the Ag/ZrO₂ hybrid coating significantly improved the surface performance of the Ti45Nb alloy both mechanically and electrochemically and offers high potential for biomedical implant applications. Full article

Medium-entropy alloys (MEAs) have attracted significant attention due to their unique structure–property relationships. In this study, we examine the effects of lattice distortion on the mechanical properties of Nb-Ti-V-Zr MEAs, focusing on two alloy series: Nb(Ti_1.5V)_xZr and Nb(TiV)_xZr (x = 1, 2, 3, 4 and 5). Experimental results show that the Nb(TiV)_xZr r alloys exhibit greater atomic size mismatches and increased lattice distortion compared to the Nb(Ti_1.5V)_xZr alloys, leading to higher yield strengths via enhanced solid-solution strengthening. However, excessive lattice distortion does not ensure an optimal strength–ductility balance, as the alloys with the highest distortion demonstrate limited plasticity. Thus, moderate reduction in lattice distortion proves beneficial in achieving an excellent compromise between strength and ductility. These findings offer valuable guidance for leveraging lattice distortion in the design of high-strength, high-ductility, body-centered cubic (BCC) MEAs for extreme environments. Full article

Body-centered cubic (BCC) refractory high-entropy alloys (RHEAs) demonstrate significant potential as nuclear structural materials due to their exceptional mechanical properties and radiation tolerance. While Zr-containing RHEAs often develop multiphase structures through Zr-rich phase precipitation to enhance high-temperature mechanical performance, their irradiation response mechanisms remain poorly understood. This study investigated the microstructure evolution and radiation damage behavior in equiatomic MoNbTiVZr RHEA under Au-ion irradiation at fluences of 2 × 10¹⁵, 4 × 10¹⁵, and 1 × 10¹⁶ ions/cm². Microstructural characterization revealed that the annealed alloy primarily consisted of near-equiatomic BCC1 phase, Zr-rich BCC2 phase, (Mo,V)Zr Laves phase, and ordered Zr₂C phase. Post-irradiation analysis showed distinct defect evolution patterns: the BCC1 phase developed fine dislocation loops, while the Zr-rich BCC2 and Zr₂C phases exhibited dislocation clusters and dense dislocation networks, respectively. BCC1 phase exhibited the most pronounced irradiation hardening corresponding to its fine, dispersed dislocation loop characteristics. Phase separation induced by Zr precipitation reduced chemical complexity, accelerating irradiation defect evolution. These findings demonstrated that Zr-rich phase precipitation detrimentally impacted the radiation resistance of BCC-structured RHEAs, suggesting that single-phase stability should be prioritized in nuclear material design. Full article

In this work we revisit a vast amount of existing data on physical properties of Ti-Zr-Nb-(Cu,Ni,Co) glassy alloys over a broad range of concentrations (from the high-entropy range to that of conventional Cu-, Ni- or Co-rich alloys). By using our new approach based on the total content of late transition metal(s), we derive a number of physical parameters of a hypothetical amorphous TiZrNb alloy: lattice parameter $a=(3.42\pm 0.02)$ Å, Sommerfeld coefficient $\gamma =6.2\mathrm{mJ/mol}$${\mathrm{K}}^2$, density of states at $N\left(E_F\right)=2.6{\left(\mathrm{at}\mathrm{eV}\right)}^{-1}$, magnetic susceptibility $(2.00\pm 0.05)$mJ/${\mathrm{T}}^2$mol, superconducting transition temperature $T_c=(8\pm 1)$K, upper critical field ${\mathrm{\mu }}_0{H}_{c2}\left(0\right)=(20\pm 5)$T, and coherence length $\xi \left(0\right)=(40\pm 3)$Å. We show that our extrapolated results for the amorphous TiZrNb alloy would be similar to that of crystalline TiZrNb, except for superconducting properties (most notably the upper critical field $H_{c2}\left(0\right)$), which might be attributed to the strong topological disorder of the amorphous phase. Also, we offer an explanation of the discrepancy between the variations in $T_c$ with the average number of valency electrons in neighboring alloys of 4d transition metals and some high-entropy alloys. Overall, we find that our novel method of systematic analysis of results is rather general, as it can provide reliable estimates of the properties of any alloy which has not been prepared as yet. Full article

Based on their high mechanical strength, Ti-based high-entropy alloys (HEAs) are of great potential as materials for high-performance reduced-diameter dental implants. Despite previous studies demonstrating their corrosion resistance in various simulated body fluids, their resistance in simulated buccal conditions has yet to be confirmed. In this work, the corrosion behavior of two Ti-based HEAs, TiZrHfNb, and TiZrHfNbTa was evaluated in comparison to CP-Ti and Ti-6Al-4V in artificial saliva (AS) solution and in AS with fluoride ion content (ASF). A set of electrochemical tests (electrochemical impedance spectroscopy, cyclic polarization, and Mott–Schottky) was employed and complemented with surface characterization analyses (scanning electron microscopy and atomic force microscopy) to determine dissolution and passivation mechanisms of the alloys. In general, the HEAs exhibited a far superior corrosion resistance compared to CP-Ti and Ti-6Al-4V alloys in both solutions. In the AS solution, the TiZrHfNb exhibited the highest polarization resistance and pitting potential, indicating a high corrosion resistance due to the formation of a robust passive layer. Whilst in the ASF solution, the TiZrHfNbTa showed a greater corrosion resistance due to the synergistic effect of Nb and Ta oxides that enhanced passive film stability. This finding emphasizes the role of Ta in elevating the corrosion resistance of Ti-based HEAs in the presence of fluoride ions and confirms the importance of chemical composition optimization in the development of next-generation dental alloys. Based on its electrochemical corrosion behavior, TiZrHfNbTa HEAs are promising new materials for high-performance reduced-diameter dental implants. Full article

One of the most popular alloys for biomedical applications is TiAl6V4. Even though TiAl6V4 is widely used, it faces several challenges. Firstly, TiAl6V4 is prone to stress shielding caused by the difference in Young’s moduli of the alloy (110 GPa) and human bones (20–30 GPa). Secondly, there is the presence of cytotoxic elements, aluminum and vanadium. Researchers have proposed Ti-35Nb-7Zr-5Ta (TNZT) alloy to overcome these disadvantages, an excellent substitute for natural human bones. This alloy offers a lower elastic modulus (up to 81 GPa), much closer to human bones than TiAl6V4 alloy. Also, TNZT alloy contains no cytotoxic elements and has excellent biocompatibility and high corrosion resistance. Given the positive outcomes on powder-mixed micro electro-discharge machining (PM-μ-EDM) of Ti alloy using hydroxyapatite (HA) powder, we studied the machinability of TNZT alloy using HA powder mixed-μ-EDM by changing the HA powder concentration (0, 5, and 10 g/L), gap voltage (90, 100, and 110 V), and capacitance (10, 100, and 400 nF) according to the Taguchi L9 method. Machining performance metrics such as material removal rate (MRR), overcut, and circularity were examined using a tungsten carbide tool of 237 µm diameter. The results showed an overcut of 10.33 µm, circularity of 8.47 µm, and MRR of 6030.89 µm³/s for the lowest energy setup. Full article

As a promising candidate for next-generation aviation structural materials, lightweight refractory high entropy alloys (HEAs) exhibit high strength, low density, and excellent high-temperature performance. In this study, we investigated the influence of local chemical ordering on the properties of Ti–V–Zr–Nb–Al HEAs using Monte Carlo (MC) simulations based on density functional theory (DFT) calculations. We established that the chemical short-range ordering (SRO) in Ti–V–Zr–Nb–Al HEAs increases with the Al content, resulting in a gradual increase in stacking fault energy (SFE). This theoretical investigation suggests that SRO can be utilized to tailor the performance of HEAs, thereby providing guidance for the scientific design of macroscopic mechanical properties. Full article

This study investigates the role of Al alloying in tailoring the oxidation resistance of AlTiCrZrNbTa refractory high-entropy alloy (RHEA) coatings on Zry-4 substrates under high-temperature steam environments. Coatings with varying Al contents (0–25 at.%) were deposited via magnetron sputtering and subjected to oxidation tests at 1000–1100 °C. The results demonstrate that Al content critically governs oxidation kinetics and coating integrity. The optimal performance was achieved at 10 at.% Al, above which a dense, continuous composite oxide layer (Al₂O₃, TiO₂, Cr₂O₃) formed, effectively suppressing oxygen penetration and maintaining strong interfacial adhesion. Indentation tests confirmed enhanced mechanical integrity in Al-10 coatings, with minimal cracking post-oxidation. Excessive Al alloying (≥17 at.%) led to accelerated coating oxidation. This work establishes a critical Al threshold for balancing oxidation and interfacial bonding, providing a design strategy for developing accident-tolerant fuel cladding coatings. Full article

In this paper, a new TaMoNbTiZr multielement alloy has been designed, using chemical elements that exhibit extremely low bio-toxicity for the human body. The alloy was obtained by melting in vacuum arc remelting (VAR) equipment MRF ABJ 900 from high-purity chemical elements (99.5%) as mini-ingots having about 40 g weight each. The biocompatible alloys underwent changes in hardness after performing the annealing at 900 °C for 2 h, followed by cooling in water. The new alloy had an average hardness in the cast state of 545 HV0.5, and after heat treatment, it hardened to a value of 984 HV0.5, over 40% higher than that in the casting state, which ensures a longer working period. To use them as materials for medical instruments, their biocompatibility was highlighted through specific laboratory tests. For this, mesenchymal stem cells isolated from bone tissue and a human fibroblast cell line were cultured in vitro on the TaMoNbTiZr alloy’s surface. The biocompatibility of the alloy with the biological environment was evaluated by analyzing cell viability, adhesion, and proliferation, and in parallel, the cytolysis effects manifested by the increase in lactate dehydrogenase activity in the culture media were analyzed. Full article

This review paper provides a comprehensive synthesis of the current advancements in investigations of different titanium-based alloys, including pure titanium, commercially available Ti6Al4V, and modified alloys, such as Ti-Nb-Zr-Fe alloys, for biomedical applications. Several researchers have explored the effects of alloying elements and processing techniques on enhancing the mechanical, chemical, and biological properties of these materials. Ti-Nb-Zr-Fe alloys are of particular interest due to their potential to address critical requirements in medical applications, including reduced Young’s modulus, superior corrosion resistance, biocompatibility, and mechanical strength. Despite substantial progress, the detailed mechanisms for optimizing these properties remain underexplored in the current literature. The main objective of the present review paper is to emphasize the importance of ongoing investigations aimed at overcoming challenges such as biocompatibility concerns, fatigue resistance, and wear under biological conditions. By critically analyzing existing data, this study highlights gaps in knowledge and identifies opportunities for advancing research on these alloys. Specifically, this review paper highlights the need for targeted studies to reduce the Young’s modulus and improve other critical characteristics of Ti-Nb-Zr-Fe alloys to better meet the demands of orthopedic implants, dental prosthetics, and cardiovascular devices. Even if the current scientific literature is ample on this topic, we consider that through this review we can positively contribute to the collective effort in this field trying to fill some gaps, including some updates on the topic, time frames, advantages, and limitations, and pave the way for further advancements that could revolutionize biomedical implant technology. The review encompasses studies performed over the last 5 decades, specifically from 1975 to 2025, to ensure the inclusion of the most relevant and up-to-date research. This approach aims to highlight the significant progress made while situating the findings within the broader context of ongoing investigations. Full article

The in situ electrochemical behaviors of Ti-39Nb-6Zr alloy were investigated in 2.3 ppm Li⁺ and 1500 ppm B³⁺ solution at 300 °C and 14 MPa. The activation energy is 12.84 kJ/mol, and the oxidation of titanium is controlled by oxygen ions diffusion in the liquid phases. The morphology, phase structure, and composition of the oxide film after 700 h exposure time in 300 °C and 14 MPa solution were characterized. The oxide film mainly included anatase TiO₂ phases, ZrO₂, Nb₂O₅, and a slight B₂O₃. The morphology of the film is shown by many nanocrystalline grains and the thickness is about 5 μm. The passivation film on the alloy substrate transforms from a single-layer film structure to a double-layer film structure. The impedance of the passivation decreases with the increase in temperature, which is related to the enhanced ion conductivity of the passivation film at high temperatures. The impedance of the dense layer inside the passivation film is much greater than that of the loose layer outside, and the dense layer inside plays a crucial role in the corrosion resistance of the Ti-39Nb-6Zr alloy. During the insulation process, the impedance of the dense layer inside the passivation film first increases and then slowly decreases, and the corrosion resistance of the passivation film first increases and decreases. Full article

Refractory high-entropy alloys (RHEAs) have drawn much attention in the field of materials science for their unique properties and wide compositional design space. The Nb₃₅Zr₂₆Ti₁₉Hf₁₅Mo₅ alloy is important for exploring RHEAs’ potential in high-temperature applications. It can break through existing material limitations and bring benefits to related fields, especially in the aerospace field. This paper focuses on Nb₃₅Zr₂₆Ti₁₉Hf₁₅Mo₅ RHEAs and studies the effects of cold rolling and heat treatment on its microstructure and mechanical properties. The alloy has a single-phase BCC structure. As rolling reduction rises from 20% to 80%, the alloy’s strength increases notably while plasticity drops. At 80% rolling reduction, the tensile strength reaches 1408 MPa, and the elongation is 10.5%. During rolling, grains deform along the rolling direction, the number of low-angle grain boundaries grows, and dislocation and solid solution strengthening effects are enhanced. With the increase in annealing temperature, recrystallized grains increase, and the change in grain-boundary structure weakens the strengthening effect, leading to a strength decrease and a plasticity increase. After annealing at 800 °C, the elongation reaches 17%, and the dislocation density in the alloy decreases with a recrystallization degree of 49%. Full article

Hip joint implants are among the most prevalent types of medical implants utilized for the replacement of damaged joints. The utilization of modern implant materials, such as cobalt–chromium alloys, stainless steel, titanium, and other titanium alloys, is accompanied by challenges, including the toxicity of certain elements (e.g., aluminum, vanadium, nickel) and excessive Young’s modulus, which adversely impact biomechanical compatibility. A mismatch between the stiffness of the implant material and the bone tissue, known as stress shielding, can lead to adverse outcomes such as bone resorption and implant loosening. Recent studies have shifted the focus to β-titanium alloys due to their exceptional biocompatibility, corrosion resistance, and low Young’s modulus, which is close to the Young’s modulus of bone tissue (10–30 GPa). In this study, the microstructure, mechanical properties, and phase stability of the Ti-38Zr-11Nb alloy were investigated. Energy dispersion spectrometry was employed to confirm the homogeneous distribution of Ti, Zr, and Nb in the alloy. A subsequent microstructural analysis revealed the presence of elongated β-grains subsequent to rolling and quenching. Furthermore, grinding contributed to the process of recrystallization and the formation of subgrains. X-ray diffraction analysis confirmed the presence of a stable β-phase under any heat treatment conditions, which can be explained by the use of Nb as a β-stabilizer and Zr as a neutral element with a weak β-stabilizing effect in the presence of other β-stabilizers. Furthermore, the modulus of elasticity, as determined by tensile testing, exhibited a decline from 85 GPa to 81 GPa after annealing. Mechanical tests demonstrated a substantial enhancement in tensile strength (from 529 MPa to 628 MPa) concurrent with a 32% reduction in elongation to fracture of the samples. These alterations are attributed to microstructural transformations, including the formation of subgrains and the rearrangement of dislocations. This study’s findings suggest that the Ti-38Zr-11Nb alloy has potential as a material of choice due to its lower Young’s modulus compared to traditional materials and its stable β-phase, which enhances the implant’s durability and reduces the risk of brittle phases forming over time. This study demonstrates that the corrosion resistance of titanium grade 2 and Ti-38Zr-11Nb is comparable. The material in question exhibited no evidence of cytotoxic activity in the context of mammalian cells. Full article

Due to the huge component space of refractory high-entropy alloy, the traditional, experimental “trial and error method” can not meet the design requirements. In order to improve the “trial and error method”, guidance is provided for the prediction and design of refractory high-entropy alloys. Based on the literature data, a comprehensive dataset was constructed, including the composition, phase composition, and strength data of various high-entropy alloys. On this basis, nine regression models were established for strength prediction. By comparison, the XGBoost (XGB) model achieves better prediction performance in the test set; the root mean square error (RMSE) is 195.53 MPa, and the coefficient of determination (R²) is 0.87. By using Shapley additive interpretation (SHAP) to analyze the explainability of the model, it was found that the key characteristics affecting the mechanical properties of the high-entropy alloy were mixed entropy and electronegativity. In order to further evaluate the precision of the model, through the vacuum arc melting preparation, Ti27.5Zr26.5Nb25.5Ta8.5Al12 high-entropy alloys were experimentally verified. The alloy experiments’ yield strength was 1356 MPa, predicting strength was 1304.71 MPa, external validation error was 3.81%, and the average accuracy of the model was 87.38%. Full article