Search Results (1,173)

Friction stir processing (FSP) is an advanced solid-state surface modification technique for biomedical titanium alloys. This study presents a computational investigation of FSP applied to Ti-6Al-4V alloy through three-dimensional finite element modeling and Taguchi-based statistical optimization. A Taguchi L9 orthogonal array evaluated rotational speed (400–1000 rpm), traverse speed (50–100 mm/min), shoulder diameter (6–18 mm), and pin diameter (2–6 mm), reducing the required simulations from 81 (full factorial) to nine (88.9% reduction). A calibrated friction model (μ = 0.35/0.25/0.20 for 400/800/1000 rpm, F = 6000 N) yielded maximum temperatures of 870–1384 °C; all predicted temperatures remained below the melting point of Ti-6Al-4V (1660 °C). These values are consistent with experimentally reported ranges for FSW/FSP of Ti-6Al-4V. Traverse speed is the dominant parameter (ANOVA contribution: 63.1%, F = 10.44), followed by rotational speed (26.7%) and shoulder diameter (4.1%). Simulation 3 (400 rpm, 100 mm/min, Ds = 18 mm, T_max = 870 °C) appears to be the most promising thermal condition for preserving the fine-grained α + β microstructure, as it remains below the β-transus temperature (980 °C) throughout the processed zone. Full article

Titanium alloys are among the most important biomaterials due to their good biocompatibility, high corrosion resistance and favourable mechanical properties. Particular interest is directed towards β-Ti alloys, whose properties can be tailored by adding β-stabilisers such as molybdenum and chromium, with the aim of developing materials suitable for biomedical applications. This paper investigates the influence of chemical composition on the phase composition, microstructure, microhardness and corrosion properties of experimental Ti-Mo-Cr alloys produced by casting. Phase composition was determined by X-ray diffraction analysis (XRD), while microstructural characteristics were analysed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results showed that increasing the molybdenum and chromium content contributes to the stabilisation of the β-phase and reduces the proportion of α and α″ martensite. Complete stabilisation of the β-phase was achieved in the Ti-10Mo-30Cr alloy, while the Ti-10Mo-10Cr alloy showed a dominant presence of α″ martensite. EDS analysis confirmed the segregation of alloying elements during solidification. Microhardness measurements showed an increase in hardness with increasing total alloying element content, with the highest hardness measured in the Ti-20Mo-20Cr alloy. Corrosion properties were tested using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and Tafel polarisation methods in 0.9% NaCl (sodium chloride) medium. Among the alloys investigated, Ti-20Mo-20Cr showed a favourable overall balance of electrochemical properties, while Ti-10Mo-30Cr exhibited the lowest corrosion rate. The results suggest that a balanced ratio of molybdenum and chromium plays a key role in optimising the microstructure, mechanical properties, and corrosion performance of Ti-Mo-Cr alloys. Full article

Glioblastoma (GBM), a highly aggressive brain tumor, is characterized by poor treatment outcomes and a strong tendency to recur after therapy. Therapy-induced senescence (TIS) of GBM cells has emerged as a key driver of GBM progression and relapse. Temozolomide (TMZ), which serves as the standard chemotherapeutic agent for GBM, is known to induce senescence; however, the molecular mechanisms underlying this process remain largely unknown. In this work, we found that interferon regulatory factor-1 (IRF1) was downregulated in TMZ-induced senescent GBM cells. Functionally, knockdown of IRF1 increased the activity of senescence-associated β-galactosidase (SA-β-gal), reduced protein expression of Lamin B1, inhibited cell division, and enhanced senescence-associated secretory phenotype (SASP) of GBM cells, indicating that downregulation of IRF1 promotes senescence of GBM cells. Conversely, overexpression of IRF1 partially reversed TMZ-induced senescence. Further exploration revealed that downregulation of IRF1 reduced the expression of 2′,5′-oligoadenylate synthetase 2 (OAS2), and overexpression of IRF1 increased the expression of OAS2. OAS2 was also downregulated in TMZ-induced senescent GBM cells, and knockdown of OAS2 induced senescence of GBM cells as well. Taken together, our study reveals that IRF1 inhibits TMZ-induced senescence of GBM cells through OAS2, highlighting a novel regulatory axis that may offer potential therapeutic targets for improving GBM treatment. Full article

Quaternary β-Ti-xTa-xZr-xNb (TTZN) alloys (x = 10, 20, and 30 wt%) were surface-modified by plasma electrolytic oxidation (PEO) to improve their surface properties. This treatment promotes the incorporation of bioactive ions, such as Ca and P, and favors the formation of a porous anodic surface resulting from the oxidation of the precursor metals. This study investigated how the addition of alloying elements (Zr, Ta, and Nb) influences oxide formation, PEO-induced pore morphology, wettability, and coating hardness. The surfaces were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), Vickers microhardness testing, and wettability analysis. XRD analysis revealed that the TTZN10 alloy exhibited crystalline TiO₂ phases in the form of anatase and rutile. In contrast, the TTZN20 and TTZN30 alloys exhibited only cubic ZrO₂ diffraction peaks, while no TiO₂ peaks were detected within the detection limits of the XRD technique. Micrographs showed micrometric pores on all alloy surfaces. The TTZN20 alloy exhibited the highest porosity (31.8%), which correlated with lower hydrophilicity (θ = 79°) and high surface free energy (67 mJ/m²). After PEO treatment, all surfaces exhibited high hardness values ranging from 491 to 561 HV. The highest hardness was observed for TTZN10, attributed to the mixed anatase/rutile TiO₂ phase composition. Full article

Titanium-doped diamond-like carbon (DLC:Ti) films were deposited by magnetron sputtering. The effects of Ti concentration on the microstructure, phase composition and piezoresistive properties of the films were systematically investigated. The surface morphology, crystal structure and chemical bonding states of the samples were characterized using SEM, XRD and XPS. The piezoresistive properties were then assessed by monitoring the resistance change in the thin films using a precision resistance meter under controlled external stimulation. The results demonstrate that the sp²/sp³ ratio of the DLC:Ti films increases with rising Ti concentration, and both Ti–C and Ti–Ti chemical bonds are formed within the films. An excessive β-Ti phase forms when the Ti concentration exceeds 39.7 at.%. The electrical resistance of DLC:Ti films decreases linearly as the applied normal stress increases from 0 to 35 MPa, with a maximum piezoresistive coefficient of −9.0 × 10⁻² GPa⁻¹ achieved for the film with a Ti doping concentration of 12.9 at.%. One hundred cyclic loading–unloading tests induce the structural transition from sp³ to sp², resulting in the graphitization of DLC:Ti films. In addition, external stress facilitates the fracture of Ti–C bonds and the relaxation of residual stress in the DLC:Ti films; the β- to α-Ti phase transformation induced by external loading is also observed in the films. Cyclic piezoresistive tests reveal that the piezoresistive stability of the DLC:Ti films is enhanced with increasing Ti concentration, which is attributed to the increased formation of Ti–C bonds in the films. Full article

Ti–6Al–4V is the primary titanium alloy for aerospace, biomedical, and additive manufacturing applications; however, the high cost of powders produced by atomization limits their widespread adoption. This study aims to develop a cost-effective method for producing chemically homogeneous pre-alloyed Ti–6Al–4V powders from titanium sponge. A combined process is proposed, involving the hydrogenation of titanium sponge, mechanical alloying of the hydride phase with Al and V powders, and subsequent vacuum dehydrogenation. The formation of the brittle δ-TiH₂ phase facilitated intensive material comminution and effective distribution of the alloying elements. According to laser diffraction data, the median particle size decreased from 450 to 30–35 µm. X-ray diffraction (XRD) analysis confirmed the sequential α-Ti → δ-TiH₂ transition and the formation of a stable α + β two-phase structure characteristic of Ti–6Al–4V following dehydrogenation. SEM observations demonstrated that the final powders predominantly consist of individual fractured particles with limited hard agglomeration, favorable for powder flowability and compaction behavior. EDS analysis indicated a relatively homogeneous microscale distribution of Al and V without observable large-scale segregation. The synthesized powders exhibited low impurity levels, with O < 0.07 wt.% and H < 0.02 wt.%. The developed approach represents a promising and economical alternative to expensive atomization techniques for powder metallurgy and additive manufacturing. Full article

Conservation tillage plays an important role in improving sustainable land use and maintaining food production. Using survey data from 261 agricultural producers in Heilongjiang Province, China, this study examines how conservation tillage policy mixes affect agricultural green total factor productivity (AGTFP). The slack-based measure (SBM) model incorporating undesirable outputs is employed to estimate AGTFP. A Tobit model with interaction terms is applied to analyze the independent and combined effects of three policy instruments: subsidies, regulations, and supporting services, and a mediating effect model is used to verify how these instruments work. The results indicate that: (1) the mean AGTFP value stands at 0.37, reflecting a generally low level of performance, with the largest improvement requirements observed in seed inputs (66.25%), machinery inputs (65.53%), and nitrogen emissions (61.55%); (2) subsidies, regulations, and supporting services all improve AGTFP, while the combinations of subsidies and services, regulations and services, and the full three-policy mix generate significant positive synergistic effects; (3) policy mixes facilitate AGTFP enhancement by increasing agricultural producers’ perceived value of conservation tillage technologies and reducing perceived risks. In particular, the interaction between regulations and supporting services significantly increased perceived value (β = 1.129, p < 0.01) and reduced perceived risk (β = −0.810, p < 0.01); (4) the effects of policy mixes are stronger for producers pursuing green production goals and for small-scale farmers. Based on these findings, the following recommendations are proposed: policy efforts should strengthen the coordination of subsidies, regulations, and services, linking training and inspection results to subsidy eligibility; address efficiency bottlenecks in seeds, machinery, labor, and nitrogen emissions; design differentiated policy packages for various farm types; and build a training system that includes at least two mandatory sessions per season and ties training outcomes to subsequent subsidies. This study contributes a policy mix perspective to the evaluation of AGTFP and provides empirical evidence for coordinated conservation tillage policy design. Full article

We present the results of applications of ATLAS2.0 to experimental data in this final part of our series of publications. ATLAS2.0 retrieves particle microphysical parameters from multiwavelength Raman and high-spectral-resolution lidar measurements of backscatter (β) coefficients at three wavelengths, i.e., λ = 355, 532, and 1064 nm, extinction (α) coefficients at two wavelengths, i.e., 355 and 532 nm, and particle linear depolarization ratios (PLDR, δ) at three wavelengths, i.e., 355, 532, and 1064 nm, so-called 3β + 2α + 3δ datasets. The explicit use of PLDRs is a novel feature compared to all previously developed lidar data retrieval algorithms. For the tests of ATLAS2.0, we use data that were taken with NASA Langley Research Center’s airborne high-spectral-resolution lidar 2 (HSRL-2). We show the results of two case studies. We compare the particle microphysical parameters and single-scattering albedo (SSA) retrieved with ATLAS2.0 to results obtained with the first version of ATLAS, our Tikhonov regularization algorithm (TiARA), and in situ observations carried out aboard an aircraft that followed the airborne HSRL-2 instrument. The solutions converge within the retrieval uncertainties of these techniques. The discrepancy between the measured and backcalculated, i.e., retrieved 3β + 2α + 3δ data on average stays below 10%. The difference between the retrieved and measured PLDRs is, on average, even less. This comparably good convergence of the optical datasets (experimental versus backcalculated) of both measurement cases can only be achieved if the investigated aerosol particles are analyzed on the basis of a sphere-spheroid mixture. Full article

$\mathrm{T}{\mathrm{i}}_{70}\mathrm{Z}{\mathrm{r}}_{20}\mathrm{T}{\mathrm{a}}_{10}$ alloy is a $\beta$-titanium based shape memory alloy with a high martensitic transformation temperature and large recoverable strain. It is thought to be to develop into a new generation of high-performance high-temperature shape memory alloy materials. By partially replacing the Ta element in the $\mathrm{T}{\mathrm{i}}_{70}\mathrm{Z}{\mathrm{r}}_{20}\mathrm{T}{\mathrm{a}}_{10}$ alloy with Al, Ti-Zr-Ta-Al alloys with different Al contents were prepared. In this study, isothermal oxidation tests at 900 °C were conducted on Ti-Zr-Ta-Al alloys with different Al contents to investigate the effect of Al content on the high-temperature oxidation behavior of the $\mathrm{T}{\mathrm{i}}_{70}\mathrm{Z}{\mathrm{r}}_{20}\mathrm{T}{\mathrm{a}}_{10}$ alloy. The results show that the isothermal oxidation kinetics curves of $\mathrm{T}{\mathrm{i}}_{70}\mathrm{Z}{\mathrm{r}}_{20}\mathrm{T}{\mathrm{a}}_{10-\mathrm{x}}\mathrm{A}{\mathrm{l}}_{\mathrm{x}}$ (x = 0, 0.5, 1, 3 at.%) at 900 °C all follow a parabolic law. The oxide films formed on the alloy surface are mainly composed of $\mathrm{Ti}{\mathrm{O}}_2$, $\mathrm{T}{\mathrm{a}}_2{\mathrm{O}}_5$ and $(\mathrm{Ti},\mathrm{Zr}){\mathrm{O}}_2$. However, the surface of the oxide films is relatively rough. The films are not dense and there are pores and cracks, leading to spallation during the oxidation process. After the addition of Al, the high-temperature oxidation resistance of the Ti-Zr-Ta alloy is improved. When the Al content is 1 at.%, $\mathrm{T}{\mathrm{i}}_{70}\mathrm{Z}{\mathrm{r}}_{20}\mathrm{T}{\mathrm{a}}_9\mathrm{A}{\mathrm{l}}_1$ exhibits the best high-temperature oxidation resistance. Full article

The microstructural characteristics and precipitate features of titanium matrix composites (TMCs) are critical to tribological performance. In this study, TiCp/TA15 composites were fabricated via laser powder bed fusion (LPBF). The as-built composite was then heat-treated at 750 °C for 2 h to obtain a uniform duplex (α + β) microstructure with enhanced TiC precipitation, which was labeled as HT-750. The influence of the microstructural evolution on the tribological performance was systematically investigated. Compared to the as-built composite, the HT-750 composite exhibited a microhardness increase from 360.2 ± 6.4 HV to 459.2 ± 3.1 HV, a reduction in the friction coefficient from 0.649 ± 0.167 to 0.581 ± 0.111, and a decrease in the wear rate from 8.24 ± 0.44 × 10⁻⁴ mm³/(N·m) to 4.81 ± 0.39 × 10⁻⁴ mm³/(N·m), indicating a significant enhancement in wear resistance. This improvement is primarily attributed to the synergistic strengthening effect of the duplex matrix and TiC particles, which enhanced the load-bearing capability and suppressed surface plastic deformation. During the friction process, the dominant wear mechanisms of as-built and HT-750 composites evolved over time but exhibited distinct differences. The as-built composites were prone to continuous plastic deformation and damage accumulation, resulting in severe delamination, oxidative, and abrasive wear. Conversely, the HT-750 composites demonstrated higher resistance to plastic deformation and crack propagation, effectively mitigating interfacial shear and inhibiting damage evolution, with the wear mechanism being dominated by oxidative wear accompanied by abrasive wear and minor delamination. This work provides deep insights into the wear mechanisms of additively manufactured TMCs. Full article

Implant surface optimization aims to reduce osteointegration process time and prevent failures. Here, we report a novel laser-assisted approach for incorporating hydroxyapatite into titanium implant surfaces and evaluate the resulting biological response. Titanium discs were fabricated by Nd:YVO4 laser texturing and coated with hydroxyapatite using either conventional or laser sintering, according to seven study groups: flat titanium (TiL), laser-textured titanium with 0.25 and 0.8 mm patterns (TiT025 and TiT08), and laser-textured titanium with 0.25 and 0.8 mm patterns plus bioactive coating using conventional sintering (TiT025CS and TiT08CS) or laser sintering (TiT025LS and TiT08LS). Human gingival fibroblasts (HGF hTERT) were cultured on discs to assess adhesion, morphology, viability, and cytokine secretion. Surface texturing alone did not significantly affect fibroblast viability over 7 days (p > 0.05). Hydroxyapatite coatings significantly reduced viability on both patterns when conventionally sintered (p < 0.05), whereas laser-sintered coatings did not cause a significant decrease; overall viability was higher in LS than in CS samples (p < 0.05). Scanning electron microscopy after 24 h showed adherent cells on all surfaces. IL-1β secretion was consistently lower than IL-10 secretion during the 3-day study period. When normalized to cell viability, these findings remained consistent. At day 1, IL-1β/viability and IL-10/viability ratios were similar across groups. By day 3, the IL-1β/viability ratio decreased in all groups, with TiT08 showing significantly lower values than TiT08CS (p < 0.05). In contrast, the IL-10/viability ratio increased in coated patterned samples (TiT025, TiT025CS, TiT025LS, TiT08, TiT08CS, and TiT08LS). In conclusion, the 0.25 mm laser-textured pattern combined with optimized hydroxyapatite sintering elicited a more favorable cytokine secretion profile compared to the 0.8 mm pattern, suggesting a reduced pro-inflammatory response. Full article

TC2 titanium alloy (Ti-4Al-1.5Mn, wt.%) is a near-α titanium alloy with promising aerospace and biomedical applications, but its limited room temperature ductility and strong texture sensitivity hinder the fabrication of high-performance sheets. In this study, the effects of hot rolling at 830 °C and 930 °C on the microstructure, macro-texture, mechanical properties, and fracture behavior of TC2 alloy were investigated. Compared with the 830 °C rolled sample, the 930 °C rolled sample exhibited finer primary α grains, a higher volume fraction of fine and dispersed secondary α_s phase, and more uniform Mn distribution, while both samples retained an α + β phase constitution. Texture and ODF (orientation distribution function) analyses revealed that increasing the rolling temperature reduced the maximum intensity of the (0001) pole figure from 6.68 to 5.23 m.r.d. (multiples of a random distribution) and increased that of the (10-10) pole figure to 9.62 m.r.d., indicating weakened basal texture, enhanced prismatic texture, and more dispersed orientation distribution. Consequently, although the tensile strength slightly decreased to approximately 730 MPa, the elongation increased from approximately 24% to 28%. The finer and denser dimples observed after 930 °C rolling further confirmed improved plastic deformation coordination. Full article

Achieving a favorable synergy of strength, ductility, and toughness is a critical challenge for expanding the engineering applications of titanium alloys. In this work, a medium-strength and high-toughness novel Ti-Al-Mo-V-Cr-Sn-Zr (named Ti62F) titanium alloy in the form of a Φ400 mm bar was adopted to systematically investigate the regulation behavior of double annealing on its microstructure and mechanical properties, and quantitative correlations between microstructural parameters and macroscopic properties were established. Increasing the cooling rate during the first annealing stage (air cooling, force air cooling and water quenching) significantly refined the secondary α (α_s) phase and reduced the volume fraction and size of the primary α (α_p) phase, leading to an increase in the ultimate tensile strength of the alloy from 1077 MPa to 1229 MPa. However, the impact-absorbed energy decreased from 51.5 J to 23.3 J. When the second annealing temperature was varied within the range of 625–675 °C, the ultimate tensile strength fluctuated slightly and the impact toughness increased moderately. Equiaxed α_p phase and relatively thick α_s can induce multiple crack deflections, prolong the crack propagation path and enhance energy absorption. Dislocations are mainly piled up at α/β phase boundaries, triggering void nucleation and growth, which dominate the ductility and toughness levels. Tensile twinning acts only as an auxiliary deformation mechanism and contributes limitedly to toughness. After heat treatment under the optimized schedule of 880 °C/2 h/AC + 650 °C/4 h/AC, the Ti62F alloy exhibits a superior strength–toughness balance compared with conventional medium-strength titanium alloys such as TA15, TC4, and TC4-DT. The findings can provide a heat treatment basis for microstructural regulation of large-size Ti62F bars and their engineering applications in aerospace structural components. Full article

We present a novel algorithm for the retrieval of non-spherical particle microphysical parameters (PMP) from 3β + 2α + 3δ optical data taken with multiwavelength lidar. The 3β + 2α + 3δ optical datasets describe particle backscatter coefficients (β) at three wavelengths, λ = 355, 532, and 1064 nm, particle extinction coefficients (α) at two wavelengths, λ = 355 and 532 nm, and particle linear depolarization ratios (PLDR, δ) at three wavelengths, λ = 355, 532, and 1064 nm. The algorithm can be used for retrieving bimodal particle size distributions (PSDs). The PSDs can comprise mixtures of spheres and spheroids (SS). One or both modes can comprise spheroid-shaped particles or spherically shaped particles. The spheroids are used for approximating an arbitrary ensemble of non-spherical particles. The algorithm works on the basis of a combination of direct and analytical inversion methods. The algorithm uses the spheroid reference look-up table (RLUT) we developed and presented in part 1 of our research work. The algorithm uses constraints regarding the particle complex refractive index (CRI) and information on relative humidity (RH) in the atmosphere (in the case of aerosol lidar observation) for suppressing retrieval uncertainties. We carried out a numerical simulation study to evaluate the algorithm’s performance. In these numerical simulations, we considered perturbed synthetic 3β + 2α + 3δ optical data that mimic different organic carbon (OC)–dust (D) mixtures. Such mixtures are suitable examples for describing bimodal PSDs that consist of a fine mode of spherical particles and a coarse mode of non-spherical particles. The results of the numerical simulation show that (1) the PMPs of each mode of these particle mixtures can be found separately, (2) the mean retrieval errors of the effective radius, number, surface-area, and volume concentrations of these mixtures are 25%, 52%, 9%, and 28%, respectively, and (3) the mean retrieval error of single-scattering albedo (SSA) at 355 nm of these mixtures is as low as ±0.02. SSA retrieval accuracies at 532 and 1064 nm degrade because the complex refractive index (CRI) of OC and D particles depends on the measurement wavelength. In future studies, we will upgrade the algorithm such that it takes into account a spectrally dependent CRI. We also compare the results of our novel algorithm with our TiARA2.1 algorithm. The errors obtained from the TiARA2.1 algorithm are approximately three times larger compared to the errors we obtain with our novel ATLAS algorithm for the case of the OC-D mixtures considered in the present study. We explain the higher accuracy of the PMP retrievals by the use of three PLDRs and the extra constraints placed on CRI and RH. Full article

To elucidate the corrosion behavior of Ti-based metallic glass composites in chloride-containing environments, this study investigates the corrosion resistance of an in situ dendritic Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅ metallic glass composite across varying NaCl concentrations and temperatures. The microstructure, surface film composition, and corrosion characteristics were characterized using XRD, SEM, TEM, EDS, XPS, and electrochemical measurements. Results indicate that the alloy consists of a β-Ti(Zr, Nb) dendritic phase embedded in an amorphous matrix. Both increasing NaCl concentration and rising temperature lead to an increase in corrosion current density and a reduction in the capacitive loop radius, signaling a decline in corrosion resistance. The degradation is primarily characterized by localized corrosion and the selective dissolution of the amorphous matrix, which leaves the dendritic phase increasingly prominent. Following polarization, a multi-component oxide film, dominated by TiO₂, ZrO₂, and Nb₂O₅, develops as a protective layer on the alloy surface. However, higher Cl⁻ concentrations and temperatures destabilize this passive film, accelerating matrix dissolution and compromising the material’s overall protective performance. Full article