Search

Highlights It is important to study damage evolution as well as failure of carbon fiber reinforced polymer (CFRP) plates bolted joints. Therefore, the quasi‐static tensile test on single‐lap and double‐lap CFRP plates bolted joints was conducted. Meanwhile, the tensile strength prediction model for titanium alloy bolted joint of CFRP plates was established based on the improved 3D Hashin failure criterion, then a theoretical model was proposed to accurately predict the load distributions and tilt angle of bolted joints. Thus, the load–displacement curves were divided into four stages, and load distributions at different stage points as well as the relationship between tilt angle of bolt and load variation were obtained. The damage evolution of single‐lap and double‐lap at different stage points was analyzed respectively, and failure mechanisms were revealed based on load distribution. The results show that the ultimate failure of single‐lap is caused by the intrusion of bolt head into CFRP plates, while double‐lap is caused by the compression deformation of central plate. The numerical simulation works are in high agreement with the experimental results. Calculate the load distribution at single‐lap and double‐lap bolted joints. Obtain the relationship between bolts tilt angle and load variation. Analysis of damage evolution in bolt‐hole wall of carbon fiber reinforced polymer (CFRP) plates. Using loads to reveal the failure mechanisms of single‐lap and double‐lap bolted joints of CFRP plates. [ABSTRACT FROM AUTHOR]

AbstractPolyetheretherketone (PEEK) implants have emerged as a clinically favored alternative to titanium alloy implants for cranial bone substitutes due to their excellent mechanical properties and biocompatibility. However, the biological inertness of PEEK has hindered its clinical application. To address this issue, we developed a dual-functional surface modification method aimed at enhancing both osteogenesis and antibacterial activity, which was achieved through the sustained release of chondroitin sulfate (CS) and levofloxacin (LVFX) from a biomimetic polydopamine (PDA) coating on the PEEK surface. CS was introduced to promote cell adhesion and osteogenic differentiation. Meanwhile, incorporation of antibiotic LVFX was essential to prevent infections, which are a critical concern in bone defect repairing. To our delight, experiment results demonstrated that the SPKD/CS-LVFX specimen exhibited enhanced hydrophilicity and sustained drug release profiles. Furthermore, in vitro experiments showed that cell growth and adhesion, cell viability, and osteogenic differentiation of mouse calvaria-derived osteoblast precursor (MC3T3-E1) cells were significantly improved on the SPKD/CS-LVFX coating. Antibacterial assays also confirmed that the SPKD/CS-LVFX specimen effectively inhibited the growth of Escherichia coli and Staphylococcus aureus, attributable to the antibiotic LVFX released from the PDA coating. To sum up, this dual-functional PEEK implant showed a promising potential for clinical application in bone defects repairing, providing excellent osteogenic and antibacterial properties through a synergistic approach. [ABSTRACT FROM AUTHOR]

In this work, we have used the full-potential linearized augmented plane wave (FP-LAPW) method implemented in the WIEN2k code combined with the generalized gradient approximation (GGA) of the density functional theory (DFT) to study the structural, elastic, mechanical, electronic, magnetic, and thermodynamic properties of the parent ternary inverse Heusler compounds based on Titanium and Cobalt Ti2CoGa, Ti2CoCu in the Hg2CuTi-type structure and their quaternary alloys Ti2CoGa 1 − x Cux (x = 0. 2 5 , 0.5, 0.75) for the chosen concentrations using a supercell with 16 atoms. We have calculated the structural properties, such as the lattice parameters, bulk modulus, and its first derivative, which are in good agreement with those that have been obtained based on other published theoretical methods. Also, we calculated the elastic constants of the studied Heusler alloys, and we found that these materials are elastically stable, ductile, and anisotropic. Therefore, the electronic and magnetic properties indicate that Ti2CoGa exhibits a half-metallic (HM) ferromagnetic behavior, while Ti2CoCu shows a metal and a non-magnetic (NM) character. Their quaternary alloys are found to be nearly HM ferromagnetic materials, with a magnetic moment mainly due to the atom Ti. Furthermore, the quasi-harmonic Debye model, which incorporates the lattice vibrations, was used to estimate the thermodynamic effects on some macroproperties of the Ti2CoGa 1 − x Cux alloys. Successful results were achieved for the variations of the primitive cell volume, bulk modulus, heat capacities, and Debye temperature with pressure and temperature, respectively, in the ranges of 0–30 GPa and 0–1400 K. To our knowledge, no analogous investigations on the mechanical and thermodynamic properties of the Ti2CoGa 1 − x Cux (x = 0. 2 5 , 0.5 and 0.75) alloys have been performed to date. As a result, it is predicted that Ti2CoGa 1 − x Cux Heusler alloys will be promising candidates for actual applications in spintronic devices. [ABSTRACT FROM AUTHOR]

Using polarization curve scanning, electrochemical impedance spectroscopy, macroscopic morphology observation, scanning electron microscope, X‐ray diffraction (XRD), and energy dispersive spectroscopy (EDS), the corrosion regulars of connectors were investigated. A galvanic corrosion simulation model of aluminum‐titanium rivets was established by electrochemical experimental parameters as boundary conditions. The results showed that the galvanic couple connection accelerated the corrosion significantly. XRD and EDS results show that the main corrosion products are Al2O3, Al(OH)3. The corrosion potential of riveted parts decreased from the riveting point to both sides, ranging from −0.664 to −0.655 V. The corrosion current density decreases along both sides, and the corrosion current density at the most edge is 0.0113 A/m2. The results of numerical simulation indicate that the model effectively predicted the galvanic corrosion behavior of aluminum‐titanium rivets. [ABSTRACT FROM AUTHOR]

Traditional metallic biomaterials including titanium and its alloys, stainless steel, cobalt‐chromium alloys, magnesium alloys are gold standards for load bearing hard tissue applications, because of adequate mechanical properties such as elastic modulus, ductility and strength for long term support and stability. However, metallic implants suffer from poor osteointegration and early degradation in host body, owing to an array of factors which include stress shieling effect, corrosion, metal toxicity, microbial contamination and low bioactivity. Therefore, to improve integration of implants with host tissue and overall mechanical and biological functions, metallic implants are coated with bioactive glasses (BG). BG are one of the most promising implant coating materials used for bone repair and reconstruction, mainly because of excellent angiogenic, osteoconductive, osteoinductive, corrosion resistance, resorbability, biocompatibility, bioactivity and anti‐microbial properties. Various BG compositions are employed for diverse biomedical applications ranging from wound healing, bone formation, corrosion resistance, drug delivery to scaffolds in tissue engineering and different methods are used for coating BG on implants to enhance stability and bond strength between implant and coating. This narrative review gives a detailed overview on metallic implants, issues of metal alloys when used in implants and how metallic implants are improved by various BG compositions and coating methods. This review provides an updated information on advantages of different BG compositions in implants fabrication in order to address challenges and tailor mechanical and biological properties of implants for future applications. [ABSTRACT FROM AUTHOR]

In modern industrial production, noise can reflect the cutting state of the workpiece and tool to a certain extent, and the noise collection method cannot interfere with the complex processing environment. To further improve the cutting performance of coated cemented carbide micro-textured tools, this paper builds a friction and wear test platform for micro-textured cemented carbide pins with AlSiTiN-AlCrN coating and titanium alloy discs. Based on the test noise signal, the relationship between friction and wear and the noise of the workpiece was studied by the Hilbert–Huang transform (HHT). Through the change of noise in different periods, the micro-texture and coating life of cemented carbide pin under other processing parameters were analyzed. Based on the influence of the interaction between processing parameters and micro-texture diameter on the test results, the test parameters were optimized. The results show that the change of noise signal during the test presents a "V" curve with the grinding process, which mainly affects the noise through the shift of pin-disc friction form and the anti-wear effect of micro-texture. The interaction mainly affects the test results by affecting the micro-texture diameter, laser energy concentration, and the roughness of the inner wall of the pit. The optimized micro-texture geometry and preparation parameters are as follows: scanning times is 8, micro-texture diameter is 50 μm, scanning speed is 1500 mm/s, micro-texture spacing is 170 μm, and laser power is 40 W. The research content of this paper provides a reference for improving the surface properties of cemented carbide. [ABSTRACT FROM AUTHOR]

The spatial orientation of α lamellae in a metastable β‐Ti matrix of Timetal LCB (Ti–6.8 Mo–4.5 Fe–1.5 Al in wt%) was examined and the orientation of the hexagonal close‐packed α lattice in the α lamella was determined. For this purpose, a combination of methods of small‐angle X‐ray scattering, scanning electron microscopy and electron backscatter diffraction was used. The habit planes of α laths are close to {111}β, which corresponds to (1320)α in the hexagonal coordinate system of the α phase. The longest α lamella direction lies approximately along one of the ⟨110⟩β directions which are parallel to the specific habit plane. Taking into account the average lattice parameters of the β and α phases in aged conditions in Timetal LCB, it was possible to index all main axes and faces of an α lath not only in the cubic coordinate system of the parent β phase but also in the hexagonal system of the α phase. [ABSTRACT FROM AUTHOR]

A good understanding of the interplay between the cutting tool edge radius, elastic recovery, friction, and contact pressure is essential for better modeling of ploughing forces during micro-scale cutting. This study conducts plunging tests on an ultra-precision CNC with engineered tungsten carbide cutting tools on commercially pure titanium alloy. The cutting tool edge radius is prepared to be around 3.5–4 μm, which resembles those cutting tools used in micro scale machining. During plunging tests, the micro cutting tool is given a sinusoidal movement with an amplitude close to edge radius of the tool as the work material is rotated at a constant speed. The residual depth profiles of the webs corresponding to the commanded depths were investigated in detail to identify elastic recovery rate. The cutting and thrust force measurements during plunging experiments together with identified elastic recovery rate was employed in an analytical model of micro scale machining to obtain the variations of contact pressure and coefficient of friction as a function of commanded depth. Due to the scale of the experiments that were performed, the effects of surface topography of the cutting tool and possible alignment errors are also considered in the analytical model. A linear relationship between the contact pressure and elastic recovery has been identified during ploughing-dominated machining conditions for the work material and the cutting tool pair considered in this study. The proposed experimental technique is shown to be promising in terms of modeling ploughing forces during micro-scale cutting. • Plunging tests reveal the influence of edge radius on elastic recovery. • A linear relationship between contact pressure and elastic recovery. • Coefficient of friction remains almost constant during ploughing. [ABSTRACT FROM AUTHOR]

An approach for the crystallographic mapping of two‐phase alloys on the nanoscale using a combination of scanned precession electron diffraction and open‐source python libraries is introduced in this paper. This method is demonstrated using the example of a two‐phase α/β titanium alloy. The data were recorded using a direct electron detector to collect the patterns, and recently developed algorithms to perform automated indexing and analyse the crystallography from the results. Very high‐quality mapping is achieved at a 3 nm step size. The results show the expected Burgers orientation relationships between the α laths and β matrix, as well as the expected misorientations between α laths. A minor issue was found that one area was affected by 180° ambiguities in indexing occur due to this area being aligned too close to a zone axis of the α with twofold projection symmetry (not present in 3D) in the zero‐order Laue Zone, and this should be avoided in data acquisition in the future. Nevertheless, this study demonstrates a good workflow for the analysis of nanocrystalline two‐ or multi‐phase materials, which will be of widespread use in analysing two‐phase titanium and other systems and how they evolve as a function of thermomechanical treatments. [ABSTRACT FROM AUTHOR]

This work presents the vibration and buckling analyses for a sandwich arch with Titanium alloy face sheets and a metal foam core via a new porosity-dependent model. Porous aluminum core consists of six layers so that each of them reinforce by graphene platelets (GPLs) with different values of porosity to achieve a piece-wise functionally graded media. The mathematical modelling is formulated to reveal nonlinear responses of the porous sandwich arch embedded in an elastic nonlinear medium. The higher-order equations of motion are achieved by taking Hamilton's principle within the framework of the von Kármán nonlinear hypothesis. Afterwards, the established nonlinear problems are solved analytically with the aid of a perturbation-based technique implementing the Galerkin procedure. The investigation results show effects of the weight fraction of GPLs, porosity distribution, geometrical characters and foundation stiffness on nonlinear vibration and buckling of the porous sandwich arch. [ABSTRACT FROM AUTHOR]

In recent years, laser cladding technology has been widely used in surface modification of titanium alloys. To improve the wear resistance of titanium alloys, ceramic-reinforced nickel-based composite coatings were prepared on a TC4 alloy substrateusing coaxial powder feeding laser cladding technology. Ti (C, N) ceramic was synthesized in situ by laser cladding by adding different contents (10%, 20%, 30%, and 40%) of TiN, pure Ti powder, graphite, and In625 powder. Thisestudy showed that small TiN particles were decomposed and directly formed the Ti (C, N) phase, while large TiN particles were not completely decomposed. The in situ synthetic TiCxN1−x phase was formed around the large TiN particles. With the increase in the proportion of powder addition, the wear volume of the coating shows a decreasing trend, and the wear resistance of the surface coating is improving. The friction coefficient of the sample with 40% TiN, pure Ti powder, and graphite powder is 0.829 times that of the substrate. The wear volume is 0.145 times that of the substrate. The reason for this is that with the increase in TiN, Ti, and graphite in the powder, there are more ceramic phases in the cladding layer, and the hard phases such as TiC, Ti(C, N) and Ti2Ni play the role in the structure of the "backbone", inhibit the damage caused by micro-cutting, and impede the movement of the tearing point of incision, so that the coating has a higher abrasion resistance. [ABSTRACT FROM AUTHOR]

Three titanium alloys with 0.5, 6, and 9 wt.% iron were investigated, and the samples were pre-annealed in three different regions of the Ti–Fe phase diagram, namely β, α+β, and α+FeTi. After annealing, five samples of different phases and structural compositions were studied. They were then subjected to the high-pressure torsion (HPT). The microstructure of the samples before and after HPT treatment was studied using transmission and scanning electron microscopy. The microstructure of the samples obtained during heat treatment before HPT treatment had a fundamental effect on the microstructure after HPT. Grain boundary layers and chains of particles formed during the annealing process made it difficult to mix the material during HPT, which led to the formation of areas with non-uniform mixing of components. Thus, the grain boundary layers of the α-phase formed in the Ti–6wt % Fe alloy after annealing at 670 °C significantly decreased the mixing of the components during HPT. Despite the fact that the microstructure and phase composition of Ti–6wt % Fe alloys pre-annealed in three different regions of the Ti–Fe phase diagram had significant differences, after HPT treatment, the phase compositions of the studied samples were quite similar. Moreover, the measured micro- and nanohardness as well as the Young's modulus of Ti–6wt % Fe alloy had similar values. It was shown that the microhardness of the studied samples increased with the iron content. The values of nanohardness and Young's modulus correlated well with the fractions of β- and ω-phases in the studied alloys. [ABSTRACT FROM AUTHOR]

Tough bonding and low friction are required for the candidate artificial articular cartilage materials. Inspired by the soft-on-hard composite structure of natural cartilage, polyvinyl alcohol/polyacrylamide (PVA/PAAm) hydrogel-on-titanium alloy was prepared by a casting-drying method to combine the excellent lubrication of soft hydrogel and the high load-bearing capacity of rigid substrate. The influences of PVA: PAAm mass ratio and swelling on the interfacial toughness of PVA/PAAm hydrogel-on-titanium alloy were evaluated by the 90° peeling test, and the friction property was investigated as a function of PVA: PAAm mass ratio, lubricating medium, and load. The results show that the interfacial toughness of PVA/PAAm hydrogel-on-titanium alloy ranges from 150 N m−1 to 400 N m−1 in dry state, while the interfacial toughness decreases significantly after swelling in deionized water for 24 h. The friction coefficient of PVA/PAAm hydrogel-on-Ti6Al4V alloy is ~ 0.15 when PVA: PAAm mass ratio is 1:2 under fetal bovine serum lubricating. The polyvinyl alcohol/polyacrylamide (PVA/PAAm) hydrogel-on-titanium alloy configuration provide a new strategy for the design of soft-on-hard cartilage replacement with tough bonding and low friction. [ABSTRACT FROM AUTHOR]

Accurate fatigue life prediction of polycrystalline materials is crucial for many engineering applications. In polycrystalline materials, a significant portion of life is spent in the crack nucleation phase at the microstructural scale. Hence, the total fatigue life shows high sensitivity to the local microstructure. To predict fatigue life accurately, the microstructure models of polycrystalline material i.e., titanium alloy are virtually generated with the help of the Voronoi tessellation technique. These models incorporate critical microstructural features such as grain size, grain shape, and the volume fraction of different phases within the material. To efficiently predict microstructure sensitive fatigue life, the smooth finite element method (SFEM) is coupled with continuum damage mechanics (CDM). The SFEM provides flexibility in the meshing of complex microstructure geometries as it alleviates the need to use only triangular and quadrilateral elements. Moreover, there is no need of isoparametric mapping and explicit form of shape function derivatives in SFEM, hence it requires less computation time. To obtain the fatigue life (in number of cycles), jump in cycles algorithm is implemented using SFEM-CDM. The numerical results of fatigue life data obtained from simulations are compared with experimental data, which reveals the validity of the present approach. This approach is useful to find out the scatter in fatigue life data of polycrystalline materials along with the source of scatter. [ABSTRACT FROM AUTHOR]

Construction of the Kitagawa–Takahashi (K–T) diagram requires inputs of two material properties, namely, endurance limit and threshold stress intensity range, ΔKth. Both are sensitive to applied stress ratio. The effect of stress ratio on endurance limit is well known. Unfortunately, crack closure, associated with the nature of conventional testing practice obscures the effect of stress ratio on intrinsic, closure free ΔKth that would apply to natural crack like defects and short cracks. This study was made possible by the development of a new test method to characterize closure free threshold conditions under controlled near-tip residual stress conditions that essentially determine near-tip stress ratio at threshold. A procedure is described to construct the K–T diagram, using ΔKth values corrected for stress ratio and applicable to pre-existing defects and short cracks at notches that are unlikely to see closure. As a case study, a K–T diagram valid for different applied stress ratios is constructed for titanium alloy Ti-6Al-4V. [ABSTRACT FROM AUTHOR]

In this paper, a study was conducted on the electrochemical machining (ECM) of titanium-shaped grid holes. Firstly, the polarization characteristic curves of titanium alloy TC4 in different electrolytes were measured by an electrochemical workstation, and the mechanism of action was analyzed. The electrolyte formula was developed for 11%NaCl + 5%NaNO3 saturated ethylenediaminetetraacetic acid (EDTA). Secondly, the equal clearance method was used to design the cathode, gap flow field simulation was used to analyze five different structures of through-liquid slots, and the structural form and size of the through-liquid slots were preferred. The voltage range of ECM was determined to be 14 ~ 22 V by the multi-physical field coupling simulation analysis. Finally, through the process test, the Taguchi algorithm and gray correlation degree method were used to optimize the process objectives; to obtain the degree of influence of different factors on the experimental process objectives, machining voltage > feed velocity > duty ratio > inlet pressure; and to obtain the optimal combination of machining parameters, machining voltage of 20 V, duty ratio of 35%, inlet pressure of 0.7 MPa, and feed velocity of 0.55 mm/min. The titanium-shaped grid holes machined by the optimal process parameters have a dimension error of 0.14 mm and a surface roughness of 0.812 μm, which meet the actual production requirements. Using this process parameter for ECM of the more difficult shaped blind holes (hole depth of 10 mm), the dimension error and roughness meet the processing requirements, which further verifies the feasibility of the optimal parameters. The research results show the ECM can realize high-efficiency and high-quality processing of the titanium-shaped grid hole. It also provides process technology reference for the machining of other complex-shaped hole parts to promote the technical progress of the industry. [ABSTRACT FROM AUTHOR]

The present study demonstrates laser bending which is a flexible and (external) tool-free method for bending and shaping of metallic components. The numerical and experimental analysis of the bending behaviors of Ti-6Al-4V titanium alloy sheets has been done under the constant line energy concept. Numerical simulations using Abaqus examine the transient temperature fields, thermal stress, strain, and deformation characteristics. To validate the numerical calculations and observe the effects of process parameters such as laser powers and scanning speeds on the bending capability, the experimental analysis has been conducted and compared with the numerical simulations. In addition, the influence of laser irradiation on the surface morphology of the laser-scanned specimens has been observed by scanning electron microscope (SEM). The findings show that higher line energy causes significant enhancement in bending deformation. The maximum numerical and experimental bending angles of 0.91° and 0.88° have been observed at the line energy of 15 J/mm, respectively. The average percentage deviation of 5.24% has been observed between the numerical and experimental results at the line energy of 15 J/mm. Moreover, melting, thermal oxidation, and crack propagations have been observed during the SEM analysis at high laser power. The numerical simulation and experimental outcomes are helpful for the selection of optimum process conditions in the laser bending method of Ti-6Al-4V sheets. [ABSTRACT FROM AUTHOR]

Recent publications indicate that the order of electrochemical anodization (before or after the laser processing step) plays an important role for the response of bone‐forming osteoblasts—an effect that can be utilized for improving permanent dental or removable bone implants. For exploring these different surface functionalities, multimethod morphological, structural, and chemical characterizations are performed in combination with electrochemical pre‐ and postanodization for two different characteristic microspikes covered by nanometric laser‐induced periodic surface structures on Ti–6Al–4V upon irradiation with near‐infrared ps‐laser pulses (1030 nm wavelength, ≈1 ps pulse duration, 67 and 80 kHz pulse repetition frequency) at two distinct sets of laser fluence and beam scanning parameters. This work involves morphological and topographical investigations by scanning electron microscopy and white light interference microscopy, structural material examinations via X‐ray diffraction, and micro‐Raman spectroscopy, as well as near‐surface chemical analyses by X‐ray photoelectron spectroscopy and hard X‐ray photoelectron spectroscopy. The results allow to qualify the mean laser ablation depth, assess the spike geometry and surface roughness parameters, and provide new detailed insights into the near‐surface oxidation that may affect the different cell growth behavior for pre‐ or postanodized medical implants. [ABSTRACT FROM AUTHOR]

Herein, the detailed corrosion behavior of ultrafast laser‐surface structured Ti6Al4V (using a Ti: Sapphire laser processed under optimum parameters) is carried out in simulated body fluid using electrochemical impedance spectroscopy and correlated with surface characteristics. Laser structuring leads to a topographically modified surface consisting of periodic surface patterns (nanoripples, nanodots) in the presence of a thin oxide layer. Surface processing introduces strain on the surface up to a depth of 150 μm, with the grains aligned along the (101¯0)$\left(\right. 10 \bar{1} 0 \left.\right)$ and (21¯1¯0)$\left(\right. 2 \bar{1} \bar{1} 0 \left.\right)$ planes. The detailed electrochemical impedance spectroscopic studies show the formation of stable passive layers in surface‐structured Ti6Al4V as compared to as‐received Ti6Al4V. [ABSTRACT FROM AUTHOR]

Titanium and its alloys are known to allow the straightforward laser‐based manufacturing of ordered surface nanostructures, so‐called high spatial frequency laser‐induced periodic surface structures (HSFL). These structures exhibit sub‐100 nm spatial periods – far below the optical diffraction limit. The resulting surface functionalities are usually enabled by both, topographic and chemical alterations of the nanostructured surfaces. For exploring these effects, multi‐method characterizations were performed here for HSFL processed on Ti–6Al–4V alloy upon irradiation with near‐infrared ps‐laser pulses (1030 nm, ≈1 ps pulse duration, 1–400 kHz) under different laser scan processing conditions, i.e., by systematically varying the pulse repetition frequency and the number of laser irradiation passes. The sample characterization involved morphological and topographical investigations by scanning electron microscopy (SEM), atomic force microscopy (AFM), tactile stylus profilometry, as well as near‐surface chemical analyses hard X‐ray photoelectron spectroscopy (HAXPES) and depth‐profiling time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). This provides a quantification of the laser ablation depth, the geometrical HSFL characteristics and enables new insights into the depth extent and the nature of the non‐ablative laser‐induced near‐surface oxidation accompanying these nanostructures. This allows to answer the questions how the processing of HSFL can be industrially scaled up, and whether the latter is limited by heat‐accumulation effects. [ABSTRACT FROM AUTHOR]

In the realm of additive manufacturing, powder bed fusion (PBF) is recognized as an innovative and highly effective technique for manufacturing titanium-based materials. With an understanding of and regulation for the complex microstructural evolution that occurs during the PBF process, several previous studies have been conducted to enhance the reliability, efficiency, and performance of the PBF through investigation and optimization of microstructure evolution in PBF. These studies have examined various aspects, including feedstock materials, process parameters, and post-processing techniques, in order to gain a comprehensive understanding and control over the progression of microstructure in the PBF. Process parameters are widely acknowledged as critical determinants in the PBF process for titanium-based materials, significantly influencing the quality in 3D printed components. Previous studies have provided an in-depth discussion of the effects of process parameters, such as laser power, scanning speed, and hatching space, on the microstructure evolution of Ti-based materials. The primary objective of this review paper is, therefore, to provide a comprehensive and clear explanation of recent efforts, with a particular focus on investigating the complex evolution of microstructures in Ti-based materials during the PBF process. This thorough discussion is devoted to providing a comprehensive understanding of the effects of process parameters on the evolution of microstructures in Ti-based materials. [ABSTRACT FROM AUTHOR]

Titanium alloys are encouraging materials as bone implantations in medical operations due to their interesting performances. However, wear debris engendered by wear was found to be the biggest handicap in terms of implant longevity. On the other hand, the biological environment has been considered to impact the tribological response. In this context, this work investigated the effect of the lubrication on the tribological response of the TiAl6V4/TiAl6V4 couple using a pin-on-disk tribometer. Thus, four various bio-lubricants were used: the physiological solution (NaCl 0.9%), nigella and sesame natural oils and Hyalgan® (sodium hyaluronate) used for the treatment of osteoarthritis (OA). The results displayed an enhancement in the friction and wear behaviors of the TiAl6V4/TiAl6V4 pair in the presence of natural oils. The analyses of the chemical structure of natural oils in terms of the unsaturations number (UN) suggest the existence of a dependency between the oil chemical structure and the wear resistance. The wear mechanism of the titanium alloys is governed by the continuous wear process of the formed and re-formed thin oxide layer on the metallic surface. It is found that the change of wear mechanism with the use of oils is mainly linked to their structure. In fact, natural oils have the ability to generate a dense lubricating layer on the metallic surface which will reduce wear. [ABSTRACT FROM AUTHOR]

Titanium alloys are difficult to machine and have poor tribological properties. Nanoparticles have good cooling and lubricating properties, which can be used in metal cutting fluid. The lubrication characteristics of the two-dimensional materials Ti3C2TX MXene and graphene oxide in water-based fluid for titanium alloys were comparatively investigated in this paper. Graphene oxide had smaller friction coefficients and wear volume than Ti3C2TX MXene nanofluid. As to the mechanism, MXene easily formed TiO2 for the tribo-chemical reaction, which accelerated wear. Moreover, GO nanofluid can form a more uniform and stable friction layer between the frictional interface, which reduces the friction coefficient and decreases the adhesive wear. The effects of different surfactants on the lubricating properties of MXene were further investigated. It was found that the cationic surfactant Hexadecyl trimethyl ammonium chloride (1631) had the lowest friction coefficient and anti-wear properties for the strong electrostatic attraction with MXene nanoparticles. The results of this study indicate that 2D nanoparticles, especially graphene oxide, could improve the lubricating properties of titanium alloys. It provides insight into the application of water-based nanofluids for difficult-to-machine materials to enhance surface quality and cutting efficiency. The developed nanofluid, which can lubricate titanium alloys, effectively has very broad applications in prospect. [ABSTRACT FROM AUTHOR]

The passivation characteristics of titanium alloys in electrolytes are often the main reason that impede the electrochemical reaction process. Hence, maintaining uniform electrochemical dissolution is a prerequisite for stable electrochemical machining (ECM) of titanium alloys. In this study, a novel cathode structure with built-in insulator is proposed, whichimproves machining stability of titanium alloys in ECM. Flow dynamics simulation results show that the cathodes with built-in insulator 1 or insulator 3 demonstrate more uniform flow effect. ECM experiments reveal that the optimized cathode can reduce the time of current from transition section to balance section, presenting a optimal transition time of 180 s. Compared with the original cathode, the sample surface machined using the optimized cathode is smooth without defects. Additionally, the optimal width of the non-processing stray corrosion area decreases from 603.47 μm to 214.54 μm, and 1010.47 μm to 349.25 μm. The optimal machining taper angle is 9.85°. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ti600/TC18 dissimilar titanium alloy joints were prepared by inertia friction welding and then underwent stress-relief annealing and three-stage annealing. The microstructure and corrosion resistance of the joints were characterized through scanning electron microscopy and X-ray diffractometry, and were tested by electrochemical measurements and static immersion corrosion experiments in HCl solution with different concentrations. The results show that the microstructure becomes more refined with more grain boundaries after stress-relief annealing, while the secondary α phase is coarsened and the α phase in the grain boundaries is formed on the microstructure after three-stage annealing with fewer grain boundaries. The specimen treated by stress-relief annealing has excellent corrosion resistance due to the denser and stabler passivation film formed on the grain boundaries. When the stress-relief annealing process is defined as 650°C, 3 h, and air cooling, more grain boundaries appeared on the joint, and, as a result, it provides more nucleation sites for the formation of the passivation film, so it is endowed with a good ability to resistant corrosion. [ABSTRACT FROM AUTHOR]

Titanium is a metal with excellent physical and chemical properties. Although it is highly abundant in the earth's crust, the difficulty of its extraction makes it expensive and restrict its application on a large scale. It has become a world problem to develop a titanium smelting method with low cost and short process. In this research, TiH1.924 powder with a low oxygen content was produced by hydrogen-assisted magnesiothermic reduction at 650 °C for 2 hours. By optimizing the thermodynamic calculation method of Ti–O–H solid solution, the thermodynamic data of Ti–O, Ti–H, and Ti–O–H with different oxygen contents have been calculated. The results showed that the hydrogen in Ti–O–H has destabilizing effect on the oxygen in Ti–O lattice. Therefore, under hydrogen atmosphere, Mg can break the thermodynamic limit of deoxidation of Ti–O solid solution, obtaining a low oxygen content reduction product. In order to further reduce the oxygen content in the product, the mechanism of secondary oxidation of the titanium hydride product was investigated, leading to the conclusion that higher hydrogen content in titanium hydride can obviously enhance its anti-oxidation property. The research can provide theoretical support for the deep reduction of TiO2 using low-cost Mg powder to obtain titanium powder with a low oxygen content. [ABSTRACT FROM AUTHOR]

The long-term safety of pressure-resistant structures used in deep-sea equipment may be threatened by creep deformation. The creep deformation behavior of a pressure-resistant structure made of different titanium alloys, Ti-6Al-4V and Ti-4Al-2V, at room temperature is investigated in this research. The kinetics and mechanisms underlying creep deformation in these materials is explained by proposing an improved constitutive model considering the effects of stress level, loading rate and environmental temperature field, offering crucial information for optimizing design parameters and guaranteeing the lifespan of the structure. Model parameters are determined for the two types of titanium alloys based on tensile creep testing results and validated through a simulation of the experimental process. In this study, a material creep model was used to predict the long-term deformation of large pressure-resistant titanium structures to ensure safe long-term operation. The safety factor used in the model is 1.5. Finite element analyses are conducted for the creep behavior of the pressure-resistant structure under real operating circumstances based on the creep constitutive model. The simulation predicts stress distribution, strain evolution, and deformation size over long periods of time by integrating complicated geometries, boundary conditions, and material characteristics. The present research can provide basic information for the local impacts of creep deformation on the inside of facilities, which helps refine design strategies to reduce possible damage risks. [ABSTRACT FROM AUTHOR]

We performed a gas nitriding and quenching process (GNQP) on Ti–18 mass% Nb alloy to obtain a high damping capacity and wear resistance. GNQP was performed at temperatures of 1023, 1123, and 1223 K. The outermost surface of the GNQP specimen obtained at 1023 K mainly comprised TiO2, whereas that at 1223 K mainly comprised TiN. The surface and interior of the specimens exhibited higher hardness at 1223 K than that at 1023 K. Compared to the specimen obtained by solution–quenching (AQ), the unit volume of the α" martensite phase at a depth of 320 μm of the GNQP specimen obtained at 1023 K was similar, and that at 1223 K was higher. Such a difference can be related to the difference in the core hardness of the specimens. The wear amounts of all GNQP specimens were lower than those of the AQ specimen. The coefficient of friction of the GNQP specimen obtained at 1023 K was lower than that obtained at 1223 K. The surface constituent phase and surface roughness exhibited a strong influence on the wear at a load of 500 g. Meanwhile, the nitride layer and damping capacity were considered to be related to the wear at a load of 3000 g. [ABSTRACT FROM AUTHOR]

In recent years, micro-cutting has been employed to obtain components that are more detailed and/or have great surface quality, regardless of dimensions, like dental implants. In the manufacturing of medical/dental components, titanium and its alloys are biomaterials of great notability. Like in conventional machining, sustainability is a delicate issue because it does not only depend on environmental aspects. One simple solution would be to perform dry machining. However, in the machining of difficult-to-cut materials, like titanium and its alloys, the use of cutting fluids is generally recommended to avoid the high temperature causing damage to the tool and/or machined surface. Concerned with the quality surface that is required for dental components, this work investigates the use of cutting fluid in the micro-cutting of commercially pure titanium. Orthogonal micro-cutting experiments were carried out under dry and wet conditions, using cutting fluid at room and cooled temperatures. To evaluate the lubri-cooling performance, cutting efforts, the friction coefficient, specific cutting energy, and chip formation analysis were compared. The outcomes indicated that, under the test conditions, the use of dry cutting and high feed levels had a positive effect on micro-cutting performance. [ABSTRACT FROM AUTHOR]

Titanium-based dental prostheses are essential for prosthodontics and can now be 3D printed using powder bed fusion (PBF) technology with different densities by controlling the process parameters. This study aimed to assess the surface topography and bonding strength of dental resins made of 3D-printed titanium alloys with varying densities and growth directions. Three groups of titanium alloy (Ti6Al4V) specimens differentiated by density (low, medium, and high) were produced using laser-melting 3D printing technology (N = 8). Each group included specimen surfaces with vertical and horizontal growths. Vickers microhardness, surface profilometry, wettability, and shear bond strength (SBS) of the titanium samples were measured for all groups. Scanning electron microscopy (SEM) was performed. Statistical analyses were conducted using a two-way ANOVA and Fisher's multiple test. Higher-density specimens exhibited greater microhardness (p < 0.05), and those with horizontal growth directions were harder (p < 0.05) than their vertical counterparts within the same density category. Additionally, low-density specimens in both growth directions had the highest surface roughness values (p < 0.05) compared to the other groups. The wettability values were similar (p > 0.05) among the groups in the vertical direction, but not in the horizontal direction (p < 0.05). However, the density type did not significantly (p > 0.05) influence the bonding strength of 3D-printed titanium. This study revealed significant variations in surface roughness, contact angle, and microhardness based on density and growth direction. [ABSTRACT FROM AUTHOR]

Because of its superior strength, low elastic modulus, and exceptional resistance to corrosion, titanium alloy is commonly used as a replacement for carbon steel in the construction of oil well pipes. This paper starts with the application of titanium alloy in oil well pipes in the petroleum industry, summarizes the research progress of its mechanical properties and corrosion properties in titanium alloy drill pipes and oil casing, and compares the fatigue life of several common carbon steel materials and titanium alloy in the petroleum industry. At the same time, the influence of adding metal elements and optimizing the manufacturing process on the corrosion resistance of titanium alloy is discussed. Finally, the problems that titanium alloys may face in the actual production and application process are put forward. [ABSTRACT FROM AUTHOR]

The conventional practice of heat-resistant nickel-alloys' brazing involves the utilization of industrial Ni-Cr-(B, Si)-based filler metals. However, employing filler metals within this system results in the formation of brittle compounds, specifically, silicides and borides of nickel, chromium, and other elements. These brittle phases have the potential to diminish the mechanical characteristics of brazed assemblies. This study investigates the feasibility of developing multicomponent high-entropy filler metals for brazing Nibased alloys (specifically, heat-resistant ones) without including boron and silicon in their composition. Utilizing computational methods and the updated Hume-Rothery rules, we identified a promising NiCoCrAl-(Ti, Nb) system. Various thermodynamic parameters are computed, and corresponding dependences on the alloying-components' content are established. The alloying limits of experimental alloys are determined, aligning with the criteria established for high-entropy alloys (HEA). Melting temperatures are calculated, and the liquidus-surface area of the NiCoCrAl-(Ti, Nb) system is delineated. Based on the research findings, it is determined that this alloy possesses a dendritic structure with some amount of eutectic component, and its melting temperature below 1220°C makes it suitable for brazing heatresistant nickel alloys. [ABSTRACT FROM AUTHOR]

In the single-pass multilayer deposition process of laser wire additive manufacturing, variations in process parameters significantly influence the morphology of the deposited layer. This study experimentally investigates how the main process parameters (laser power, scanning speed, and wire feeding speed) affect the morphology of the deposited layer. It was found that each parameter has distinct effects on the geometrical morphology of deposition. Simultaneously, aiming to enhance the surface topography of the deposited layer and its bonding with the substrate, three optimization objectives are defined. An optimization model is then constructed using experimental data to refine the process parameters. The optimal parameters are determined through experimentation, resulting in significant enhancement of the deposited layer's topography. [ABSTRACT FROM AUTHOR]

Laser-arc hybrid additive manufacturing (LAHAM) based on the synergistic interaction of laser and arc has vast potential applications due to the advantages of high precision and fast manufacturing speed. Titanium alloy is a kind of indispensable material in the aerospace and marine industries because of its superior performance. This study primarily investigates the effect of laser power on formability, microstructure evolution, and mechanical properties of Ti-6Al-4V, a titanium alloy fabricated by LAHAM. The results indicate that the material utilization of the Ti-6Al-4V wire first increases and then decreases with the increasing laser power, reaching a maximum value of 95.48% at a power of 1500 W. As laser power increases, the acicular martensite α′ content in the LAHAM samples decreases, while the α phase increases and exhibits a coarsening phenomenon. Tensile strength increases with the rise in laser power, reaching a maximum horizontal tensile strength of 1080 MPa and a maximum vertical tensile strength of 1100 MPa. However, elongation decreases with increasing laser power. Microhardness decreases with the rise in laser power. The increase in laser power enhances the bonding between deposition layers, significantly improving the tensile strength of the specimens. [ABSTRACT FROM AUTHOR]

Titanium alloys (Ti−6Al−4V) are being used in many biomedical applications due to their unique properties of bioactivity, excellent mechanical properties, low toxicity, biocompatibility, and long‐term implant application for their satisfactory corrosion resistance. We have developed a new two‐step fabrication process of zirconium oxide (ZrO2) and Chitosan/Mg−Zn−HAP (Chitosan/M−HAP) bilayer layer coating on Ti alloy for biomedical applications. Flower‐structured bilayers were coated by the electrochemical deposition method. Electrochemically deposited bilayer‐coated Ti alloy specimens were characterized by various analytical techniques like field‐emission scanning electron microscope (FE‐SEM), X‐ray diffraction (XRD), and EDS mapping analysis. Furthermore, the developed bilayer (Chitosan/Mg−Zn−HAP/ZrO2) coated Ti alloy samples improved mechanical properties such as adhesion strength (20.1±0.4 MPa) and hardness (446±4 Hv), compared to other coatings. An investigation of polarization curves showed a positive shift in the polarization values (Ecorr, and Icorr) of the Chitosan/M−HAP/ZrO2 bilayer coatings on Ti alloy. Bilayer‐modified Ti alloy samples show good antimicrobial response toward Gram‐negative and Gram‐positive bacteria. Meanwhile, the cell viability and proliferation of the bilayer‐coated samples were evaluated and the exhibited result improved cell proliferation, and bioactivity compared to other coated materials. From the results, it can be evident that the developed Chitosan/Mg−Zn−HAP/ZrO2 bilayer‐coated Ti alloy could be a good potential candidate for biomedical applications. [ABSTRACT FROM AUTHOR]

To investigate the wear and corrosion of titanium alloy spinal implants in vivo, we evaluated removed implants and their surrounding scar tissues from 27 patients between May 2019 and April 2021. We performed scanning electron microscopy, energy-dispersive X-ray spectroscopy, and histological analysis. The results revealed metal-like particles in the soft tissues of seven patients, without any considerable increase in inflammatory cell infiltration. Patients with fractures showed lower percentages of wear and corrosion compared with other patients (42% and 17% vs. 59% and 26%). Polyaxial screws exhibited higher wear and corrosion percentages (53% and 23%) compared with uniaxial screws (39% and 3%), although in patients with fracture, the reverse was observed (20% and 0% vs. 39% and 3%). We found that titanium alloy spinal implants experience some degree of wear and corrosion in vivo. The titanium alloy particles formed by wear exhibited good histocompatibility, not causing inflammation, foreign body reactions, or osteolysis. Therefore, spinal implants should be removed cautiously when treating titanium alloy spinal metallosis. The wear and corrosion of the implants increase with the increase in implantation time, although the screw structure does not significantly affect these changes. [ABSTRACT FROM AUTHOR]

In this paper, plasma arc welding (PAW) and plasma arc welding combined with gas tungsten arc welding (PAW + GTAW) were used to weld TC4 titanium alloy plate (thickness of 8 mm). The relationship between mechanical properties, corrosion resistance, phase composition, and microstructure of PAW welded joint (P) and PAW + GTAW welded joint (P + G) was compared. Tensile test and microhardness results show that P + G welded joints exhibit superior mechanical properties compared to P welded joints. The polarization curves and EIS results of both P and P + G samples were compared. The surface morphology of the samples was evaluated, and the potential corrosion mechanism of P and P + G samples was provided. The research results reveal that the PAW + GTAW welding has positively affected the corrosion performance of TC4 alloy welded joints. The improved corrosion resistance of welded joints is associated with a low β/α phase volume ratio, small grain size, and HAGB content. [ABSTRACT FROM AUTHOR]

Developing a high precision cross-scale model for diffusion bonded (DB) titanium alloy to predict macroscopic deformation and microstructure evolution is critical for industrial production requirements. To characterize the plastic behaviors of DB TC4 alloy, the mechanical properties experiments were carried out under elevated temperatures. The gas bulging process of the alloy sheet was predicted, which was combined with the macroscopic finite element method (FEM) and crystal plasticity FEM, and the predicted mechanical behavior and texture evolution are in good agreement with the experimental results, and the relative errors between the two scales are generally minor. The effects of different strains and stress states on the microstructure heterogeneous deformation, crystal orientation, and slip mode of titanium alloy are discussed on this basis. The results indicate that more grains undergo significant plastic deformation from the stress states of plane strain to equal biaxial tension. The active rate of Prismatic slip decreases, and the Pyramidal slip systems also start obviously. The grains with easy-to-deform orientation can gradually rotate to a stable orientation during plastic deformation and have a lower Schmid factor. [ABSTRACT FROM AUTHOR]

Measuring the temperature dependence of material properties is a standard method for better understanding the microscopic origins for that property. Surprisingly, only a few experimental studies of thermal boundary conductance at high temperatures exist. This lack of high temperature data makes it difficult to evaluate competing theories for how inelastic processes contribute to thermal conductance. To address this, we report time domain thermoreflectance measurements of the thermal boundary conductance for TiN on diamond, silicon-carbide, silicon, and germanium between 120 and 1000 K. In all systems, the interface conductance increases monotonically without stagnating at higher temperatures. For TiN/SiC interfaces, G ranges from 330 to 1000 MW/m2-K, with a room temperature conductance of 750 MW/m2-K. The interface conductance for TiN/diamond ranges from 140 to 950 MW/m2-K. Notably, for all four interfacial systems, the conductance continues to increase with temperature even after all phonon modes in the vibrationally soft material are thermally excited. This observation suggests that inelastic processes are significant contributors to the thermal conductance in all four interfacial systems, regardless of whether the materials forming the interface are vibrationally similar or dissimilar. Our study fills a notable gap in the literature for how interfacial conductance evolves at high temperatures and tests burgeoning theories for the role of inelastic processes in interfacial thermal transport. [ABSTRACT FROM AUTHOR]

Background: The bacterial persistence, responsible for therapeutic failures, can arise from the biofilm formation, which possesses a high tolerance to antibiotics. This threat often occurs when a bone and joint infection is diagnosed after a prosthesis implantation. Understanding the biofilm mechanism is pivotal to enhance prosthesis joint infection (PJI) treatment and prevention. However, little is known on the characteristics of Cutibacterium acnes biofilm formation, whereas this species is frequently involved in prosthesis infections. Methods: In this study, we compared the biofilm formation of C. acnes PJI-related strains and non-PJI-related strains on plastic support and textured titanium alloy by (i) counting adherent and viable bacteria, (ii) confocal scanning electronic microscopy observations after biofilm matrix labeling and (iii) RT-qPCR experiments. Results: We highlighted material- and strain-dependent modifications of C. acnes biofilm. Non-PJI-related strains formed aggregates on both types of support but with different matrix compositions. While the proportion of polysaccharides signal was higher on plastic, the proportions of polysaccharides and proteins signals were more similar on titanium. The changes in biofilm composition for PJI-related strains was less noticeable. For all tested strains, biofilm formation-related genes were more expressed in biofilm formed on plastic that one formed on titanium. Moreover, the impact of C. acnes internalization in osteoblasts prior to biofilm development was also investigated. After internalization, one of the non-PJI-related strains biofilm characteristics were affected: (i) a lower quantity of adhered bacteria (80.3-fold decrease), (ii) an increase of polysaccharides signal in biofilm and (iii) an activation of biofilm gene expressions on textured titanium disk. Conclusion: Taken together, these results evidenced the versatility of C. acnes biofilm, depending on the support used, the bone environment and the strain. [ABSTRACT FROM AUTHOR]

Elliptical ultrasonic vibration-assisted milling (EUVAM) introduces ultrasonic frequency vibration into conventional milling (CM) to achieve high-frequency intermittent milling. It has broad application prospects in processing difficult-to-cut materials such as titanium alloys, superalloys, carbon fiber-reinforced plastic (CFRP), and hard and brittle materials. This study focuses on the development of a dynamic model for EUVAM that considers regenerative effects and analyzes the interaction between the cutting edge and the workpiece in both radial and tangential directions, and the dynamic chip thickness is derived based on this model. To solve the model, a Runge-Kutta-based fully discrete method (RKFDM) is employed. This numerical method accurately predicts the stability of the EUVAM process under specified cutting conditions. In addition, a bisection algorithm is utilized to construct the stability lobe diagram of EUVAM, enhancing the computational efficiency of the process. Stability tests are conducted to validate the proposed stability model and solution method for EUVAM. The results of these tests confirm the accuracy and reliability of the approach presented in this paper. This study provides valuable insights and a practical framework for implementing EUVAM in the processing of difficult-to-cut materials, offering improved machining performance in various industrial applications. [ABSTRACT FROM AUTHOR]

Titanium alloy Ti-6Al-4 V holds a prominent status within the aerospace sector owing to its remarkable strength-to-weight ratio. However, its low thermal conductivity and high tensile strength present machining obstacles, resulting in elevated tool temperatures and mechanical stress. In aircraft manufacturing, drilling is essential, yet using solid carbide drills conventionally leads to considerable tool wear. Prior investigations aimed at enhancing tool longevity have explored diverse cutting methodologies, spanning from flood cooling to minimum quantity lubrication (MQL). Despite these efforts, persistent challenges endure. Therefore, this study introduces an innovative approach, leveraging titanium aluminum nitride (TiAlN)-coated indexable centerless inserts to bore holes in Ti-6Al-4 V under three distinct cutting conditions: dry, flood cooling, and MQL. These conditions are scrutinized across varied feed rates (60 mm/min, 100 mm/min, and 120 mm/min) with a fixed spindle speed of 1200 rpm. The study's primary focus is on key output parameters, including surface roughness (SR), tool life, and cutting temperature. From the parametric and surface topographic analysis, the findings reveal that under the flood cutting approach with a 60-mm/min feed rate, the indexable inserts excelled when drilling Ti-6Al-4 V. This combination delivered a better surface quality (Ra = 1.66 µm), extended tool life (27,814.27 mm3 material removed and 18 holes drilled), and lower cutting temperature (881°F). Additionally, scanning electron microscopy (SEM) analysis corroborates that most common types of wear observed were abrasion, delamination, cracking, and edge fracture. [ABSTRACT FROM AUTHOR]

Rib fractures are one of the most common blunt injuries, accounting for approximately 10% of all trauma patients and 60% of thoracic injuries. Multiple rib fractures, especially flail chest, can cause local chest wall softening due to the loss of rib support, leading to paradoxical breathing, severe pain, and a high likelihood of accompanying lung contusions. This study investigates the mechanical properties of a new polymer material rib internal fixator to provide theoretical data for its clinical use. We conducted in vitro mechanical tests on 20 fresh caudal fin sheep ribs, using different fracture models across four randomly assigned groups (five ribs per group). The fixators were assessed using non-destructive three-point bending, torsion, and unilateral compression tests, with results averaged. Additionally, finite element analysis compared stress and strain in the polymer fixators and titanium alloy rib plates during bending and torsion tests. In vitro tests showed that the polymer fixators handled loads effectively up to a maximum without increase beyond a certain displacement. Bending and torsion tests via finite element analysis showed the polymer material sustained lower maximum equivalent stresses (84.455 MPa and 14.426 MPa) compared to titanium alloy plates (219.88 MPa and 46.47 MPa). The polymer rib fixator demonstrated sufficient strength for rib fracture fixation and was superior in stress management compared to titanium alloy plates in both bending and torsion tests, supporting its potential clinical application. [ABSTRACT FROM AUTHOR]

Laser powder bed-fused Ti6Al4V alloy has numerous applications in biomedical and aerospace industries due to its high strength-to-weight ratio. The brittle α′-martensite laths confer both the highest yield and ultimate tensile strengths; however, they result in low elongation. Several post-process heat treatments must be considered to improve both the ductility behavior and the work-hardening of as-built Ti6Al4V alloy, especially for aerospace applications. The present paper aims to evaluate the work-hardening behavior and the ductility of laser powder bed-fused Ti6Al4V alloy heat-treated below (704 and 740 °C) and above (1050 °C) the β-transus temperature. Microstructural analysis was carried out using an optical microscope, while the work-hardening investigations were based on the fundamentals of mechanical metallurgy. The work-hardening rate of annealed Ti6Al4V samples is higher than that observed in the solution-heat-treated alloy. The recrystallized microstructure indeed shows higher work-hardening capacity and lower dynamic recovery. The Considère criterion demonstrates that all analyzed samples reached necking instability conditions, and uniform elongations (>7.8%) increased with heat-treatment temperatures. [ABSTRACT FROM AUTHOR]

Axial loading fatigue tests were conducted for α + β titanium alloy with two stress ratios to elucidate the microstructure-based interior cracking behavior at 150 °C temperature. The interior failure is attributed to the cleavage of the large primary α-grains (αp) and facet–facet cluster zone–fisheye formation, which is the primary failure mode in the very high-cycle fatigue regime. Furthermore, microcracks are generated through soft-oriented large αp-grains along the {0001} slip plane in the direction of maximum shear stress, forming the crystallographic facets. Moreover, due to the variation in the grain orientation, significant plastic deformation is produced within the facet-cluster zone. The low-angle grain boundaries offer limited resistance in the propagation of the formed crack, which can pass through neighboring grains easily, exhibiting characteristic transcrystalline failure. Based on the analysis above, the interior fracture mechanism was summarized as related to the microstructure characteristics. In addition, dislocation configurations, slip bands, and stacking faults indicate that the deformation behavior with faceting-induced fracture occurs by joint action of dislocation bypassing, stacking fault shearing, and increasing thermal activation energy at intermediate temperature. The microstructure-based interior failure mechanism is presented based on electron backscatter diffraction, focused-ion beam, and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

The high rate of rejection and failure of orthopedic implants is primarily attributed to incomplete osseointegration and stress at the implant-to-bone interface due to significant differences in the mechanical properties of the implant and the surrounding bone. Various surface treatments have been developed to enhance the osteoconductive properties of implants. The aim of this work was the in vitro characterization of titanium alloy modified with a nanocrystalline hydroxyapatite surface layer in relative comparison to unmodified controls. This investigation focused on the behavior of the surface treatment in relation to the physiological environment. Moreover, the osteogenic response of human osteoblasts and adipose stem cells was assessed. Qualitative characterization of cellular interaction was performed via confocal laser scanning microscopy focusing on the cell nuclei and cytoskeletons. Filipodia were assessed using scanning electron microscopy. The results highlight that the HA treatment promotes protein adhesion as well as gene expression of osteoblasts and stem cells, which is relevant for the inorganic and organic components of the extracellular matrix and bone. In particular, cells grown onto HA-modified titanium alloy are able to promote ECM production, leading to a high expression of collagen I and non-collagenous proteins, which are crucial for regulating mineral matrix formation. Moreover, they present an impressive amount of filipodia having long extensions all over the test surface. These findings suggest that the HA surface treatment under investigation effectively enhances the osteoconductive properties of Ti6Al4V ELI. [ABSTRACT FROM AUTHOR]

This study focused on effective methods of laser engraving treatment (LET), plasma spraying, and resin pre-coating (RPC) to manufacture the reinforced adhesive joints of titanium alloy and carbon fiber-reinforced polymer (TA-CFRP) composites. The combined treatments contributed to the creation of a better adhesive bonding condition and offer a vertical gap between circular protrusions to form epoxy pins and carbon nanotube (CNT)-reinforced epoxy pins. The bonding strength of the TA-CFRP composite was reinforced by 130.6% via treatments with a twice-engraving unit of 0.8 mm, plasma spraying, and RPC. The original debonding failure on the TA surface was changed into the cohesive failure of the epoxy adhesive and delamination-dominated failure of the CFRP panel. Overall, laser engraving has been confirmed as an effective and controllable treatment method to reinforce the bonding strength of the TA-CFRP joint combined with plasma spraying and RPC. It may be considered as an alternative in industry for manufacturing high-performance metal–CFRP composites. [ABSTRACT FROM AUTHOR]

In the current study, micro-electric discharge drilling (µEDD) is conducted on a titanium grade 2 alloy using a tungsten carbide (WC) tool electrode of 496 µm diameter. Capacitance, voltage, and feed rate are selected as machining variables to conduct the experiments based on the full factorial experimental design method. Overcut, material removal rate (MRR), circularity, and hole taper are considered as performance measures. Furthermore, overall evaluation criteria (OEC) is utilized for multiple-objective optimization by allotting varying and equal weight percentages to each response measure. The results of OECs are compared with a revolutionary heuristic multi-objective genetic algorithm (MOGA), resulting in a similar optimal parametric combination and close response measures are obtained. Micrographic investigation demonstrates that at lower capacitance and voltage levels, there is less burr formation, recast layer, and circularity error. Moreover, FESEM and EDS analyses are employed to investigate the machined surface topology and elemental composition respectively. [ABSTRACT FROM AUTHOR]

The mechanical properties of beta titanium alloys can be improved by precipitating the α phase in the β-phase matrix and controlling the microstructure via appropriate aging treatments. In this study, heat treatment in the range of 400 to 550 °C is performed to optimize the aging of Ti-3Al-8V-6Cr-4Mo-4Zr alloys. The increase in the aging temperature and holding time increases the hardness and compressive yield strength owing to the precipitation of the secondary α phase in the β matrix. The precipitation driving force at 400 °C is low because of the slow diffusion rate, and therefore the improvements in the hardness and strength are small. At temperatures above 500 °C, phase separation occurs rapidly (β → β + β′), and the β′ phase acts as a nucleation site for the secondary α phase. The phase transformation from the β′ to the secondary α phase is promoted at 500 °C, resulting in the highest hardness (406.3 HV) and compressive yield strength (1433.8 MPa) at 24 h. At 550 °C, the secondary α phase grows and the hardness and compressive yield strength degrade. These results can be effectively applied to manufacture springs with excellent formability and mechanical properties. [ABSTRACT FROM AUTHOR]