Search Results (2,927)

Titanium aluminides, particularly the Ti-48Al-2Cr-2Nb alloy, have drawn significant attention for their potential in high-temperature aerospace and automotive applications due to their exceptional performances and reduced density compared to nickel-based superalloys. However, their intermetallic nature poses challenges such as limited room-temperature ductility and fracture toughness, limiting their widespread application. Additive manufacturing, specifically Electron Beam Melting (EBM), has emerged as a promising method for producing complex-shaped components of titanium aluminides, overcoming challenges associated with conventional production methods. This work investigates the fracture behavior of Ti-48Al-2Cr-2Nb specimens with different microstructures, including duplex and equiaxed, under tensile and high-cycle fatigue at elevated temperatures. Fracture surfaces were analyzed to distinguish between static and dynamic fracture modes. A novel method, employing confocal microscopy acquisitions, is proposed to correlate surface roughness parameters with the causes of failure, offering new insights into the fracture mechanisms of titanium aluminides. The results reveal significant differences in roughness values between the propagation and fracture zones for all the temperatures and microstructure tested. At 650 °C, the crack propagation zone exhibits lower Sq values than the fracture zone, with the fracture zone showing more pronounced roughness, particularly for the equiaxed microstructure. However, at 760 °C, the difference in Sq values between the propagation and fracture zones becomes more pronounced, with a more substantial increase in Sq values in the fracture zone. These findings contribute to understanding fracture behavior in titanium aluminides and provide a predictive framework for assessing structural integrity based on surface characteristics. Full article

In this study, a titanium alloy torsional spring used in aviation was taken as the research subject. Aiming at the fatigue life prediction problem of this spring, the life analysis of the titanium alloy torsional spring was performed using a customized UMAT subroutine based on the theory of continuous damage mechanics. Several sets of life prediction models and tests were compared. The fatigue lives of the springs at 60, 80, 100, and 120 degrees were 45,070, 65,067, 99,677, and 181,322 cycles, respectively. Compared with other fatigue life prediction methods, the fatigue life calculated by the customized subroutine was the most consistent with the fatigue life of the titanium alloy torsion spring tests. The average relative error between the measured experimental life value and the predicted value was 2.04%, which is less than 5%, meeting engineering measurement requirements. The effectiveness and applicability of the proposed model and method were verified, and the time and economic cost caused by excessively long experimental cycles were reduced. This helps improve the accuracy of fatigue life prediction for this titanium alloy torsional spring and provides analysis support for subsequent structural optimization and improvement. Full article

The present study involved (TiB + TiC)/TC11 (Ti-6.5Al-3.5Mo-1.2Zr-0.3Si) + xFe titanium matrix composites (TMCs) reinforced by in situ TiB whiskers and TiC particles fabricated by hot isostatic pressing. Microstructure observation reveals a substantial distribution of in situ reinforcements, which form a network-reinforced structure at the prior particle boundaries of the TC11 matrix. The micro–nanoscale TiB whiskers and TiC particles within and surrounding this network serve as effective dislocation pinning. The enhancement of mechanical properties can be attributed to load-bearing strengthening, fine-grain strengthening, and dislocation strengthening. The hardness and compressive strengths were investigated through mechanical properties testing. The hardness increased by 19.4% (2 wt% B₄C-reinforced composites) compared with TC11 alloy. However, the addition of 2 wt% Fe at the same B₄C level (2 wt% B₄C + 2 wt% Fe-reinforced composites) resulted in a significant increase in hardness by 37.5% and 15.2% in compressive strengths of TMC and can be attributed to the solid solution strengthening effect and higher dislocation density provided by the addition of Fe. In addition, the optimal overall properties can be achieved by strictly regulating the addition ratio of 2 wt% Fe and 1 wt% B₄C, allowing for a compressive strength of 2301 MPa while still maintaining a compressive strain of 24.6%. Full article

The development of beta titanium alloys with biocompatible elements to replace Al and V is a subject of significant interest in the biomedical industry. This approach aims to enhance biocompatibility and mitigate potential cytotoxic effects associated with traditional alloying elements. In this work, Ti–xNb–ySi alloys were produced using powder metallurgy, with x of 35, 40, and 45 wt.%, and y of 0.10, 0.35, and 0.60% wt.%, using a $3^2$ experimental design. Milling was used to mix and disperse the powders, followed by cold pressing, sintering, and heat treatment. Nb was the main element used to stabilize the β phase, and Si was used to form Si precipitates, although Si also exhibits a β-stabilizing effect. It was found that an increase from 0.10 to 0.35 wt.% of Si improved relative density, with no benefits observed at 0.60 wt.% Si. Electron microscopy showed the presence of β phase grains, and grains with β + α intragranular structures and precipitates. Increasing Nb content resulted in a decrease in ultimate tensile strength while increasing Si content from 0.10% to 0.35 wt.% exhibited the opposite effect. Full article

Background/Objectives: Periprosthetic joint infections (PJI) are difficult to treat due to biofilm formation on implant surfaces and the surrounding tissue, often requiring removal or exchange of prostheses along with long-lasting antibiotic treatment. Antiseptic irrigation during revision surgery might decrease bacterial biofilm load and thereby improve treatment success. This in vitro study investigated and compared the effect of five advanced wound irrigation solutions to reduce bacterial burden in the PJI microenvironment. Methods: We treated in vitro biofilms grown on titanium alloy implant discs with clinical bacterial strains isolated from patients with PJIs, as well as abscess communities in a plasma-supplemented collagen matrix. The biofilms were exposed for 1 min to the following wound irrigation solutions: Preventia^®, Prontosan^®, Granudacyn^®, ActiMaris^® forte (‘Actimaris’), and Octenilin^®. We measured the bacterial reduction of these irrigation solutions compared to Ringer–Lactate and to the strong bactericidal but not approved Betaseptic solution. Additionally, ex vivo free-floating bacteria isolated directly from clinical sonication fluids were treated in the same way, and regrowth or lack of regrowth was recorded as the outcome. Results: Irrigation solutions demonstrated variable efficacy. The mean CFU log₁₀ reduction was as follows: Octenilin, 3.07, Preventia, 1.17, Actimaris, 1.11, Prontosan, 1.03, and Granudacyn, 0.61. For SACs, the reduction was: Actimaris, 8.27, Octenilin, 0.58, Prontosan, 0.56, Preventia, 0.35, and Granudacyn, 0.24. Conclusions: All solutions achieved complete bacterial eradication in all tested ex vivo sonication fluids, except Granudacyn, which was ineffective in 33% of the samples (2 out of 6). Advanced wound irrigation solutions have the potential to reduce bacterial burden in the PJI microenvironment during revision surgery. However, their efficacy varies depending on bacterial species, growth state, and the composition of the irrigation solution. This underscores the importance of considering these factors when developing future PJI-specific irrigation solutions. Full article

Titanium potassium oxalate had been mixed into the electrolyte to improve the anti-corrosion property of the micro arc oxidation coating on the surface of the aluminium alloy. The surface and cross-section of the coating at different titanium potassium oxalate concentrations had been observed by scanning electron microscopy, showing that when the titanium potassium oxalate concentration was 10 g/L, the coating compactness was better. Additionally, the element content of the coating had been studied by the energy dispersive spectrometer, and results proved that the coating consisted of Al, O, Ti, Si, and P. The Ti increased with the increase in titanium potassium oxalate concentration. The X-ray diffractometer had been employed to analyze the crystalline structure of the coating. Then, it was found that after the micro arc oxidation, an alumina oxide coating was prepared on the surface of the aluminium alloy, and the Al₂O₃ and TiO₂ characteristic peak was observed. Furthermore, the electrochemical workstation was used to test the anti-corrosion of the coating. It was proved that when the titanium potassium oxalate concentration was 10 g/L, the open circuit voltage, corrosion current, corrosion potential, and impedance of the coating were improved, and the anti-corrosion property of the aluminium alloy had been strengthened. Full article

Silicon carbide-based titanium silicon carbide (SiC–Ti₃SiC₂) composites with low free alloy content and varying Ti₃SiC₂ contents are fabricated by two-step reactive melt infiltration (RMI) thorough complete reactions between carbon and TiSi₂ alloy in SiC-C preforms obtained. The densities of SiC-C preform are tailored by the carbon morphology and volumetric shrinkage of slurry during the gel-casting process, and pure composites with variable Ti₃SiC₂ volume contents are successfully fabricated with different carbon contents of the preforms. Due to the increased Ti₃SiC₂ content in the obtained composites, both electrical conductivity and electromagnetic interference (EMI) shielding effectiveness improved progressively, while skin depth exhibited decreased consistently. The improvement in the EMI shielding effectiveness of the composite is due to the free electrons being bound to move in the conductive network formed by the Ti₃SiC₂ phase, converting electrical energy into thermal energy and reducing the energy of electromagnetic waves. Notably, at a Ti₃SiC₂ content of 31 vol.%, the EMI shielding effectiveness of the SiC–Ti₃SiC₂ composites in the X-band reached an impressive 62.1 dB, confirming that SiC–Ti₃SiC₂ composites can be treated as high-performance EMI shielding materials with extensive application prospects. Full article

In this research, as-built Ti–6Al–4V anatomical plates were successfully fabricated using laser powder bed fusion (LPBF). This study thoroughly examines the microstructural evolution and its role in enhancing the mechanical properties of clavicle bone plates under sub-β-transus heat treatment for medical application. Scanning electron microscope (SEM) images of the as-built specimens reveal a dense formation of a hard α’ hcp martensite structure, which decomposes during annealing at 650 °C and ultimately transforms into an α + β lamellar structure at 950 °C. Additionally, coarse grains resulting from recrystallization and reduced dislocation density were observed through electron backscatter diffraction (EBSD) following heat treatment. Due to these microstructural evolutions, the desired mechanical properties of as-built Ti64 parts for surgical applications were achieved. Heat treatment of the anatomical plates at 950 °C demonstrated an excellent strength–ductility synergy under tensile deformation and the highest energy absorption capability under bending deformation, indicating sufficient durability for medical implantation applications. Full article

In this paper, the issue of an aging process’s influence on power LEDs’ properties is considered. Some measured DC characteristics of these devices and their thermal and optical parameters obtained are presented after considering different values of the aging process’ duration. Components soldered using different metal–ceramic composite pastes, e.g., with TiO₂, were tested. The tested devices and the used measurement setup are described. The measurement procedure is described in detail. The obtained measurement results are discussed. It is shown that after the aging process at elevated temperatures, worse properties were observed for the power LEDs soldered using classical SACX0307 alloy. Most of the samples soldered with reference alloy (not composite) were damaged during the test. The best properties were obtained for the samples soldered with solder paste with the addition of titanium oxide. Full article

In recent years, the excellent mechanical properties and lightweight characteristics of multi-layer hollow components have led to a surge in research focused on their forming processes. This growing interest has greatly advanced technological progress in aerospace and other related fields. In this paper, the metal flow behavior of TA15 titanium alloy at different temperatures from 840 °C to 940 °C and different strain rates from 0.001 s⁻¹ to 0.1 s⁻¹ was studied. Utilizing the finite element method, this study examined the local stress concentration, total strain distribution, thickness thinning characteristics, and pressure loading control during the superplastic forming process of the component. The integrated solid/hollow four-layer grid lightweight structural parts were successfully fabricated using the superplastic forming/diffusion bonding (SPF/DB) process. The quality of the components was evaluated using X-ray and ultrasonic C-scan detection methods. The results show that the maximum elongation of the alloy is 1340% at 900 °C/0.001 s⁻¹. When the temperature is too high, the grain size increases remarkably, and the elongation decreases. Based on the finite element simulation results, 900 °C is the best superplastic forming temperature. Under this temperature parameter, the maximum thinning rate of the core sheet is 39.7%, the SPF time is 10,000 s, the maximum thinning rate of the face sheet is 9.8%, and the SPF time is 2400 s. In addition, the solid block has a minimal effect on the thinning of the core sheet. The grid exhibits obvious stress concentration and thinning at its rounded corners, while the thickness distribution in other areas remains relatively uniform. The nondestructive testing results confirmed that the ribs of the component are fully formed, with no missing or broken ribs. The grid exhibits good geometry and high-quality diffusion bonding. The average thickness at key positions of the component is 1.84 mm, with the minimum thickness being 1.7 mm. As the size of the grid cavity decreases, the thickness of the component tends to increase gradually. The maximum error between the simulated and measured values is 4.47%, indicating good accuracy in the simulation. Additionally, the thickness distribution of the component is relatively uniform. Full article

TC17 titanium alloy is widely used in the aviation industry for dual-performance blades, and linear friction welding (LFW) is a key technology for its manufacturing and repair. However, accurate evaluation of the mechanical properties of TC17−LFW joints and research on their joint fracture behavior are still not clear. Therefore, this paper used the finite element numerical simulation method (FEM) to investigate the mechanical behavior of the TC17−LFW joint with a complex micro−structure during the tensile processing, and predicted its mechanical properties and fracture behavior. The results indicate that the simulated elastic modulus of the joint is 108.5 GPa, the yield strength is 1023.2 MPa, the tensile strength is 1067.5 MPa, and the elongation is 1.98%. The deviations from measured results between simulated results are less than 2%. The stress and strain field studies during the processing show that the material located at the upper and lower edges of the joint in the WZ experiences stress and strain concentration, followed by the extending of the stress and strain concentration zone toward the center of the WZ. And finally, the strain concentration zone covered the entire WZ. The fracture behavior studies show that the material necking occurs in the TMAZ of TC17(α + β) and WZ, while cracks first appear in the WZ. Subsequently, joint cracks propagate along the TC17(α + β) side of the WZ until fracture occurs. There are obvious tearing edges formed by the partial tearing of the WZ structure in the simulated fracture surface, and there are fracture surfaces with different height differences at the center of the joint crack, indicating that the joint has mixed fracture characteristics. Full article

MoS₂ coating is a newly developed method to prevent bolt corrosion and the seizure of bolts used in equipment in sea areas. It is of great significance to investigate the evolution of the tensile properties and intact coatings for the maintenance of coated bolts. To evaluate the tensile properties of MoS₂-coated titanium alloy bolts, titanium alloy bolts coated with MoS₂ (TC4+MoS₂) and bolts treated with a composite treatment of anodizing oxidation and MoS₂ coating (TC4+AO+MoS₂) were corroded in salt spray tests for 4300 h. The MoS₂ coating significantly enhanced the bolts’ corrosion resistance, demonstrating exceptional protective performance by only experiencing minor peeling due to oxidation-induced cracking of the coating during the extensive 4300 h salt spray test. The tensile strengths of the TC4+MoS₂ and TC4+AO+MoS₂ bolts both decreased as compared with the original bolts. The bolts pretreated with anodic oxidation revealed lighter coating peeling and maintained a higher tensile strength after corrosion. Therefore, it can be concluded that the coatings provided excellent corrosion resistance, leading to a minor impact on the bolts’ tensile strength and fracture behavior under the synergistic damage of sea water corrosion and preloading. Full article

Taking the titanium alloy wing–body connection joint at the rear beam of a certain type of aircraft as the research object, this study analyzed the failure mechanism and verified the structural safety of the wing–body connection joint under actual flight loads. Firstly, this study verified the validity of the loading system and the measuring system in the test system through the pre-test, and the repeatability of the test was analyzed for error to ensure the accuracy of the experimental data. Then, the test piece was subjected to 400,000 random load tests of flight takeoffs and landings, 100,000 Class A load tests, and ground–air–ground load tests, and the test piece fractured under the ground–air–ground load tests. Lastly, the mechanism analysis and structural safety verification of the fatigue fracture of the joints were carried out by using a stereo microscope and scanning electron microscope. The results show that fretting fatigue is the main driving force for crack initiation, and the crack shows significant fatigue damage characteristics in the stable growth stage and follows Paris’ law. Entering the final fracture region, the joint mainly experienced ductile fracture, with typical plastic deformation features such as dimples and tear ridges before fracture. The fatigue crack growth behavior of the joint was quantitatively analyzed using Paris’ law, and the calculated crack growth period life was 207,374 loadings. This result proves that the crack initiation life accounts for 95.19% of the full life cycle, which is much higher than the design requirement of 400,000 landings and takeoffs, indicating that the structural design of this test piece is on the conservative side and meets the requirements of aircraft operational safety. This research is of great significance in improving the safety and reliability of aircraft structures. Full article

Wear resistance and optical properties are the key point for the application of titanium alloys as structural materials in the aerospace field. To enhance the wear resistance and optical properties of titanium alloys, a black plasma electrolytic oxidation (PEO) coating incorporating MoSi₂ nanoparticles was fabricated on the TC4 alloy via the PEO process, with the MoSi₂ nanoparticles being in situ doped into the coating. The doping of MoSi₂ nano-particles can effectively reduce the pore size of the PEO layer. The nPEO coating exhibited lower surface roughness than that of the PEO layer. The surface hardness of the nPEO coating increased to 42.5 HRC, significantly enhancing the wear resistance of the PEO layer (40.7 HRC). Furthermore, the PEO coatings exhibited better optical property compared to TC alloy, and the incorporation of MoSi₂ particles further improved the performance in most wavelength ranges. The infrared emissivity of the nPEO coating was 0.87, a dramatic increase from the 0.38 value of the TC4 alloy. This coating strategy effectively enhances the wear resistance and optical performance of TC4 alloy, which is critical for the surface design of titanium alloys used in aerospace applications. Full article

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