Abstract:The pressure-actuated metal seal with soft metal coating has been widely used in complex working conditions such as high temperature, low temperature and high pressure. The investigation of the characteristics and binding strength of the transition layer between the soft metal coating and the superalloy substrate is important to improve the sealing performance and to model and simplify the working through-process of metal sealing. The distribution characteristics of elements at soft metal-substrate interface and the binding strength between coating and substrate under different thicknesses and material combinations of coating layer were studied by experimental methods. The results indicate that the thickness of soft metal coating has little influence on the interface morphology of GH4169-Cu, GH4169-Ag and Cu-Ag, but has an influence on the thickness of transition layer between different metals, while this influence is weakened with increasing the coating thickness, and the thickness of transition layer is about 2 μm when the coating thickness is more than 30 μm. The cross-cut test shows that the Cu, Ag and Cu-Ag coatings are all well combined with nickel-based superalloy GH4169 substrate. The materials of soft metal, i.e. the coating materials, have significant influence on the characteristic of transition layer and the surface characteristics of coating after cross-cut test.

Abstract:(TiZrHf)₅₀Ni₃₀Cu_20-xCo_x (x=2, 4, 6, at%) high-entropy high-temperature shape memory alloys were fabricated by water-cooled copper crucible in a magnetic levitation vacuum melting furnace, and the effects of Co content on microstructure and mechanical properties were investigated. The results indicate that the grain size of the alloy decreases with increasing the Co content. In the as-cast state, the alloy consists primarily of the B19′ phase, with a trace of B2 phase. The fracture morphology is predominantly composed of the B19′ phase, whereas the B2 phase is nearly absent. Increasing the Co content or reducing the sample dimensions (d) markedly enhance the compressive strength and ductility of the alloy. When d=2 mm, the (TiZrHf)₅₀Ni₃₀Cu₁₄Co₆ alloy demonstrates the optimal mechanical properties, achieving a compressive strength of 2142.39±1.8 MPa and a plasticity of 17.31±0.3%. The compressive cyclic test shows that with increasing the compressive strain, the residual strain of the (TiZrHf)₅₀Ni₃₀Cu₁₄Co₆ alloy increases while the recovery ability declines. The superelastic recovery capability of the alloy is continuously enhanced. The superelastic recovery rate increases from 1.36% to 2.12%, the residual strain rate rises from 1.79% to 5.52%, the elastic recovery rate ascends from 3.86% to 7.36%, while the total recovery rate declines from 74.48% to 63.20%.

Abstract:The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size, distribution and morphology of graphene. However, the effect of the graphene size/distribution on the mechanical properties and related strengthening mechanisms has not been fully elucidated. Herein, under the same volume fraction and distribution conditions of graphene, molecular dynamics simulations were used to investigate the effect of graphene sheet size on the hardness and deformation behavior of Cu/graphene composites under complex stress field. Two models of pure single crystalline Cu and graphene fully covered Cu matrix composite were constructed for comparison. The results show that the strengthening effect changes with varying the graphene sheet size. Besides the graphene dislocation blocking effect and the load-bearing effect, the deformation mechanisms change from stacking fault tetrahedron, dislocation bypassing and dislocation cutting to dislocation nucleation in turn with decreasing the graphene sheet size. The hardness of Cu/graphene composite, with the graphene sheet not completely covering the metal matrix, can even be higher than that of the fully covered composite. The extra strengthening mechanisms of dislocation bypassing mechanism and the stacking fault tetrahedra pinning dislocation mechanism contribute to the increase in hardness.

Abstract:Because of the challenge of compounding lightweight, high-strength Ti/Al alloys due to their considerable disparity in properties, Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer composite plate by explosive welding. The microscopic properties of each bonding interface were elucidated through field emission scanning electron microscope and electron backscattered diffraction (EBSD). A methodology combining finite element method-smoothed particle hydrodynamics (FEM-SPH) and molecular dynamics (MD) was proposed for the analysis of the forming and evolution characteristics of explosive welding interfaces at multi-scale. The results demonstrate that the bonding interface morphologies of TC4/Al 6063 and Al 6063/Al 7075 exhibit a flat and wavy configuration, without discernible defects or cracks. The phenomenon of grain refinement is observed in the vicinity of the two bonding interfaces. Furthermore, the degree of plastic deformation of TC4 and Al 7075 is more pronounced than that of Al 6063 in the intermediate layer. The interface morphology characteristics obtained by FEM-SPH simulation exhibit a high degree of similarity to the experimental results. MD simulations reveal that the diffusion of interfacial elements predominantly occurs during the unloading phase, and the simulated thickness of interfacial diffusion aligns well with experimental outcomes. The introduction of intermediate layer in the explosive welding process can effectively produce high-quality titanium/aluminum alloy composite plates. Furthermore, this approach offers a multi-scale simulation strategy for the study of explosive welding bonding interfaces.

Abstract:The effects of different aging processes on the precipitated phase, mechanical properties, molten salt corrosion resistance and post-weld microstructure of 347H stainless steel were studied. The results show that a large number of precipitated phases appear in the crystal after aging at 700 °C for 400 h. After aging for 3000 h, the number of precipitated phases increases and most of them are gathered at the grain boundaries. There are two forms of precipitates, one is the coarse precipitate rich in Cr, and the other is the smaller precipitates mainly consisting of NbC. After aging at 700 °C for 30 min, the yield strength and tensile strength of the samples at room temperature and 593 °C increase, but the elongation decreases. The corrosion results in nitrate at 565 °C show that the corrosion products of the aged samples are the same as that of the original samples, which are Fe₂O₃, Fe₃O₄, MgCr₂O₄, MgFe₂O₄, FeCr₂O₄ and NaFeO₂. The proportion of Fe₃O₄ that is dense and well bonded to the subtrate in the original sample is higher than that in the aged sample, so the corrosion resistance is better. At 700 °C, the aging time has no obvious effect on the microstructure after welding.

Abstract:Modification of 6061 aluminum alloy was conducted through composite addition of cerium-rich rare earths and Al-Ti-B. Results show that the composite addition of Al-Ti-B and Ce/La element at a specific ratio notably promotes the refinement of the alloy's grains. Ce and La elements are combined with Si and other elements to form rare earth phases, improving the morphology and distribution of precipitates and mitigating the adverse effects of β-Fe phases on the microstructure and mechanical properties of alloy. However, excessive rare earth content poses challenges; it not only leads to a decrease in Mg-Si strengthening phase by binding with Si but also promotes the formation of larger or numerous rare earth phases that may act as initiation points for cracks, thereby impeding the improvement of the structure and performance of alloy. The composite addition of cerium-rich rare earths and Al-Ti-B not only preserves the strength of the alloy but also significantly enhances the plasticity of the 6061 as-cast alloy. At a composite addition ratio of Al-Ti-B:RE=2:1, the newly developed 6061-RE aluminum alloy exhibits increased average elongation by 50% and 45% in its as-cast and homogenized states, respectively, compared to the baseline 6061 alloy, facilitating subsequent deformation processing. After solution treatment at 540 °C for 1 h and aging at 180 °C for 5 h, the average ultimate tensile strength and yield strength of 6061-RE alloys reach 313.2 and 283.1 MPa, increased by 12.3% and 14.5% compared with those of the original alloy, respectively, and the average elongation is improved by 41%.

Abstract:The crack initiation and early propagation are of great significance to the overall fatigue life of material. In order to investigate the anisotropic fracture behavior of laser metal deposited Ti-6Al-4V alloy (LMD Ti64) during the early stage, the four-point bending fatigue test was carried out on specimens of three different directions, as well as the forged specimens. The results indicate the anisotropic crack initiation and early propagation of LMD Ti64. The direction perpendicular to the deposition direction exhibits a better fatigue resistance than the other two. The crack initiation position and propagation path are dominated by the microstructure in the vicinity of U-notch. LMD Ti64 has a typical small crack effect, and the early crack propagation velocities in three directions are similar. Affected by the slip system of LMD Ti64, secondary cracks frequently occur, which are often found to have an angle of 60° to the main crack. The electron backscatter diffraction analysis indicates that LMD Ti64 has preferred orientations, i.e., strong //Z texture and //Z texture. Their crystallographic orientation will change as the direction of columnar β grains turns over, resulting in the fatigue anisotropy of LMD Ti64 in crack initiation and early crack propagation process.

Abstract:TC4 micro-arc oxidation (MAO) coatings were prepared by adding SiO₂ nanoparticles or sodium silicate to the sodium meta-aluminate-based electrolyte. The effect of additives was investigated by XRD, SEM, EDS, electrochemical and wear tests. The results show that additives can considerably accelerate the formation of MAO coatings. The coatings are mostly composed of rutile and anatase TiO₂, α-Al₂O₃, γ-Al₂O₃, Al₂TiO₅ and SiO₂. Sodium silicate and SiO₂ nanoparticles added to the coating can effectively reduce the size of micropores and increase its thickness, whereas SiO₂ nanoparticles with superior physical properties can be directly deposited at the discharge channel, significantly increasing the coating's resistance to wear and corrosion. The coating with SiO₂ nanoparticles exhibits the best overall performance, with the lowest corrosion rate and average friction coefficient of 4.095×10^-5 mm/a and 0.30, respectively.

Abstract:Tungsten/molybdenum alloys are widely utilized in the nuclear industry, aerospace and various other fields due to their high melting points and strength characteristics. However, poor sinterability and processability make it difficult to manufacture large-size or complex-shaped parts. Hence, an in-depth study on the welding technology of tungsten/molybdenum alloys is urgent. An introduction of tungsten/molybdenum alloy welding defects and joining process was provided, along with recent advancements in brazing, spark plasma sintering diffusion bonding, electron beam welding and laser beam welding. The latest progress in alloy doping treatment applied to tungsten/molybdenum alloy dissimilar welding was also discussed, and existing welding problems were pointed out. The development prospects of weldability of tungsten/molybdenum alloy by various joining technologies were forecasted, thereby furnishing a theoretical and practical found.

Abstract:Irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steel in reactor core is one of the most important factors affecting the safety and lifetime of nuclear reactor. Numerous studies have shown that IASCC of austenitic stainless steel is related to irradiation-induced Si enrichment at grain boundary. To explore the influence of Si enrichment at grain boundary on the stress corrosion cracking rate of austenitic stainless steel, the crack growth rate (CGR) of model alloys with different Si contents in water at 320 ℃ was measured, and the crack propagation paths and fracture morphologies were analyzed. Results show that CGR of Si-containing alloy is higher in the oxygenated water environment, showing no obvious dependence on Si content; while in the hydrogenated water environment, CGR is increased with the increase in Si content and reaches the level in the oxygenated water environment. Stress corrosion cracks mainly propagate along large-angle grain boundaries, and the higher the Si content, the sharper the crack tips. The oxide film generated by oxidation of enriched Si at grain boundary in high-temperature water is easily soluble in water, resulting in a decreased strength of the grain boundary oxide film, which is more likely to crack under stress, and leading to an increased sensitivity to stress corrosion cracking.

Abstract:The wear resistance and tensile property of two low-cost, easy-to-deform Ti-44Al-3Mn-0.8Mo (TMM) and Ti-44Al-3Mn-0.4Mo-0.4W(TMMW) alloys (atomic fraction, %, the same below) were comparatively tested. The effects of replacing 0.8 Mo with 0.4Mo-0.4W on their wear resistance, microhardness, tensile property and microstructure were analyzed. The results show that replacing part of Mo with W can obviously improve the wear resistance and microhardness of Ti-Al-Mn-Mo alloy, and also increase the tensile strength of the alloy at room temperature and high temperature. The room temperature elongation is increased from 0.75% to 1.50%, while the high temperature elongation is slightly reduced. It is found that the β-stabilizing effect of W in the alloys is slightly weaker than that of Mo, and the replacement of W reduces the content of β_o phase and γ phase remaining in the structure, increases the content of α₂ phase obviously, increases the content of lamellar structure, and decreases the lamellar spacing. The higher microhardness and better wear resistance of TMMW alloy are closely related to the changes of microstructure and phase composition. The decrease in β_o phase content, the increase in lamellar content and the decrease in lamellar thickness are the main reasons for the higher tensile strength and better room temperature elongation of the alloy after W replaces part of Mo.

Abstract:In order to study the effect of strut diameter difference on the compression performance of body-centered cubic (bcc) lattice structure, five bcc-x lattice structures with different strut diameters were designed under the same density. 316L stainless steel with bcc-x lattice structures were fabricated by selective laser melting technique. A finite element analysis model of quasi-static compression of the lattice structure was established using the plastic constitutive model of the material. The experimental and finite element simulation results show that with the increase in strut scale factor x, the compressive performance of bcc lattice shows a trend of first increasing and then decreasing, and when x is greater than 1, the compressive performance is more sensitive to x. When x is equal to 1, the optimal compressive properties can be obtained. The specific stiffness, specific strength and specific energy absorption of bcc-1 are 986.794 MPa·cm³·g^-1, 25.084 MPa·cm³·g^-1 and 11.731 J/g, respectively. Compared with bcc-1, both the decrease and increase of x will destroy the axial symmetry of the cell, and the larger the x deviating from 1, the more irregular the distribution of high stress regions between layers, and the more unstable the deformation of the structure. The compressive performance of bcc-1.5 is the worst, and the specific stiffness, specific strength and specific energy absorption are reduced by 20.765%, 12.265% and 12.309%, respectively, compared with those of bcc-1.

Abstract:With the rapid progress and development of technique and equipment in the field of aerospace and weapon protection, it is of great significance to accelerate the development and research of new metal composite materials with lightweight and high-strength properties. In this research, the multiscale numerical calculation method was used to explore the variation law of interface characteristic parameters as well as atomic-scale diffusion behavior and characteristics of the interface of explosive welded multilayer metal composite materials. The results show that with the passage of time, the dynamic collision angle increases slightly in the initial stage and remains stable in the middle stage. The joining interface shows obvious waveform structure characteristics. The pressure distributed at the joining interface of the multilayer composite sheet is significantly higher than that in other regions of the sheet, and the pressure of the bonding interfaces decreases gradually from top to bottom. The effective plastic strain at the bottom interface is slightly higher than that at the other three interfaces. Under microscale collisions at different speeds, obvious atomic diffusion occurs at all three solder joints. As the impact speed decreases, the thickness of the atomic diffusion layer at the interface also decreases. The thickness of the three diffusion layers ranges from 1.12 μm to 1.58 μm, 1.8 μm to 2.55 μm and 1.22 μm to 1.73 μm.

Abstract:Titanium alloy solid welding wire was developed by optimizing the synergistic mechanism of Cr-Mo-Zr. The liquid bridge transition with uniform droplet stress and stable droplet transition was selected for laser wire filling welding. Finally, the high quality welding of 20 mm thick Ti64 titanium alloy plate was realized. Results show that Ti-Al-Cr-Mo-Zr titanium alloy solid welding wire has enough stiffness and relaxation, which provides a guarantee for the accurate alignment between the beam and the welding wire, and stable wire feed during the subsequent laser wire filling welding. In the welded seam, the proportion of large-angle grain boundaries greater than 10° is 97.8%, the geometrically necessary dislocation density is low, and the proportion of small size grains is relatively large. The overall orientation of the welded seam is not strong, the texture is not obvious and the distribution is random, and the maximum multiples of uniform distribution is only 12.66. The average tensile strength of welded joints is 901 MPa, the average elongation is 21%, and the impact toughness at room temperature ranges from 29 J to 33 J. The self-developed and designed Ti-Al-Cr-Mo-Zr titanium alloy solid welding wire plays an important role in obtaining welded joints with synergistic optimization of strength and plasticity-toughness, and provides basic technical support for the long-term safe service of titanium alloy welding structures.

Abstract:The shift fork shaft is an important component in manual transmission, automatic manual transmission and dual-clutch transmission to connect the fork and adjust gear engagement. To study the relationship among welding deformation, residual stress and welding process parameters during plasma welding of shift fork shaft, based on ABAQUS simulation software, the temperature-displacement coupled finite element calculation method was adopted and double ellipsoidal heat source model was selected to numerically simulate the stress field, deformation and temperature field of the welded plate and shift fork shaft. The optimization of the welding process of shift fork shaft was completed, and the reliability of the optimized model was verified through simulation and experiments. The results show that welding deformation is decreased with the increase in welding speed. The welding deformation is relatively small at welding speed of 2.5–3.0 mm/s and is increased with the increase in welding current. The welding residual stress does not show a significant variation law with welding current and welding speed, but the peak values are distributed around 560 MPa, which is smaller than the tensile strength of the fork shaft (650 MPa), and there is a local stress concentration phenomenon. Overall, residual stress is mainly distributed at both ends of the weld seam, and deformation mainly occurs at the weld plate. The optimized model has a more balanced peak temperature of the two weld heat sources, and local welding residual stress and deformation slightly decrease. Therefore, simulation and experimental results can provide theoretical guidance for the control of welding quality in actual production process.

Abstract:The effects of low-cost Sn (1wt%) and Mn (0.5wt%) composite addition on the microstructure and properties of micro-arc oxidation coatings on extruded Mg-2Al-Zn (AZ21) alloy were studied. After the addition of Sn and Mn elements to the substrate, the phase composition of the coatings remains unchanged, mainly consisting of MgO, MgAl₂O₄ and AlPO₄ phases. The thickness and porosity of the coatings increase slightly, the thickness increases from 8.49 μm to 9.60 μm, and the porosity increases from 5.05% to 5.75%. The wear resistance and corrosion resistance of the substrates and coatings were evaluated by dry friction and wear test, immersion test and potentiodynamic polarization test. The results show that the micro-arc oxidation coating significantly improves the wear resistance and corrosion resistance of the substrate. The composite addition of Sn and Mn improves the wear resistance of the coatings, but their corrosion resistance decreases. The wear rate of the coating decreases from 3.53×10^-5 mm³·(N·m)^-1 to 2.993×10^-5 mm³·(N·m)^-1. The corrosion current density of the coating increases from 3.14×10^-6 A·cm^-2 to 4.18×10^-6 A·cm^-2.

Abstract:The nano-quasicrystal reinforced Mg-Zn-Y alloy has ultra-high elongation at room temperature and has broad application prospects. It is necessary to further study its hot deformation behavior to provide a theoretical and application basis for subsequent processing. In this research, Mg-1.92Zn-0.34Y (wt%) alloy containing nano-quasicrystalline particles was prepared by semi-solid and hot extrusion composite process. The high temperature deformation mechanism of the alloy at temperatures of 250, 300 and 350 ℃ and strain rates of 10^-3, 10^-2 and 10^-1 s^-1 was investigated. The effect of nano-quasicrystal particles on hot deformation behavior of Mg-1.92Zn-0.34Y alloy was studied. The results show that the high-ductility Mg-1.92Zn-0.34Y alloy with nano-quasicrystals can be prepared by the combination process of semi-solid and hot extrusion. The processed alloy exhibits a high tensile elongation to failure (EL) of 44%±2.6%, ultimate tensile strength (UTS) of 258±2.0 MPa and yield strength (YS) of 176±1.6 MPa at room temperature. The average deformation activation energy and stress index of Mg-1.92Zn-0.34Y alloy according to the constitutive equation are 271.7812 kJ/mol and 6.7838, respectively. The alloy has good thermoplasticity and no instability phenomenon occurs under experimental conditions, which indicates that the presence of nano-quasicrystals improves the deformation ability of the alloy. The optimal hot working region is 330–350 ℃ and 10^-3–10^-2 s^-1, that is, the high-temperature and low strain rate region.

Abstract:Aiming to explore the oxidation mechanism of thermal barrier coatings with air-film cooling holes, in this research, femtosecond laser was used to prepare the thermal barrier coatings with air-film cooling holes. The microscopic morphology of the air-film cooling holes was observed, and the static oxidation of the perforated thermal barrier coatings was studied at 1000 and 1150 ℃. The growth rate constant of thermally grown oxide (TGO) of the perforated coating is 0.372 μm²·h^-1 after the static oxidation at 1000 ℃. The thickness of TGO is increased rapidly and then slowly with the prolongation of the oxidation time. After the static oxidation at 1150 ℃, the growth rate constant of TGO of the perforated coating is 1.26 μm²·h^-1, which is slightly larger than that of the unprocessed coating. After oxidation for 100 h, the thickness of TGO at the interface of the ceramic layer and the bonding layer is 11.610 μm, which is close to that of the unprocessed coating. The results show that the growth rate of TGO at the interface of the ceramic layer and the bonding layer is significantly increased and the oxidation process is accelerated with the increase in oxidation temperature. At the same oxidation temperature, the air-film cooling holes accelerate the growth rate of TGO during the short-time oxidation process, which has little effect on the thickness of TGO after oxidation for 100 h.

Abstract:This research applied Cr₂O₃ coating on the surface of silicon-based ceramic core through multi-arc ion plating method. The effect of Cr₂O₃ coating on wetting behavior and interface reaction behavior of silicon-based ceramic core and nickel-based single crystal superalloy after contact at 1550 ℃ were studied using high-temperature in-situ droplet method. The interface morphology, element distribution, and reaction products after the interface reaction were analyzed using SEM, EDS, and XRD. The results show that the wetting angle between nickel-based single crystal superalloy and silicon-based ceramic core coated with Cr₂O₃ is 98.29°. Hf and Al in superalloy melt react with Cr₂O₃ coating, generating HfO₂, Al₂O₃, and free Cr at the bottom of superalloy. The generated Al₂O₃ forms a protective layer to prevent the diffusion of active elements in superalloy to the interface. However, a small amount of superalloy melt still reacts with the silicon-based ceramic substrate without coating protection, generating Al₂O₃ and free Si at the interface. The generated Cr and Si are enriched at the interface and form CrSi₂ on the superalloy surface. Part of Si diffuses from the surface of the superalloy to the interior, forming (Mo,W,Re)₅Si₃ with refractory elements such as W near the surface of superalloy. The results indicate that the wetting angle of nickel-based single crystal superalloy on silicon-based ceramic core coated with Cr₂O₃ is smaller than that on unmodified silicon-based ceramic cores, and its wettability is better. Based on the above analyses, the Cr₂O₃ coating on the surface of silicon-based cores is beneficial to improve the filling of alloy at local positions of castings, but its control effect on interface reactions is limited.

Abstract:A metastable β titanium alloy Ti-5.5Cr-5Al-4Mo-3Nb-2Zr was designed. Three types of microstructure with different α phases were obtained by different heat treatment methods. The effects of α phase on stress corrosion behavior of the alloy were investigated by SEM, TEM, electrochemical test, and slow strain rate tensile test. The results show that after aging treatment at 650 ℃ for 6 h, the secondary α_s phase is coarsened (microstructure No.: M1). After solution treatment at 790 ℃ for 0.5 h at the two-phase zone, a coarse primary α_p phase (microstructure No.: M2) is formed. After solution treatment at 790 ℃ for 0.5 h and aging treatment at 650 ℃ for 6 h, coarse primary α_p phase and delicate secondary α_s phase (microstructure No.: M3) exist simultaneously. The electrochemical test results show that the self-corrosion current density of M3 is relatively low of 1.10×10^-8 A/cm². The polarization resistance of M3 is the highest at 2.30×10¹⁰ Ω·cm², which indicates the best corrosion resistance of M3, followed by M2, and M1 has the worst corrosion resistance. The results of slow strain rate tensile tests indicate that M3 has the lowest stress corrosion susceptibility index of 5.0%, and its stress corrosion cracking susceptibility is relatively low. The interaction of the hydrogen absorption-induced dislocation emission and the hydrogen-enhanced localized plasticity can explain the stress corrosion cracking mechanism.

Abstract:Ti/Al micro-laminated composite sheet with alternate arrangement of Ti/TiAl₃/Al laminate microstructure was fabricated through vacuum hot-pressing method. The uniaxial tensile deformation behavior at high temperature and the bulging formability were investigated by uniaxial tensile experiment and gas bulging experiment, respectively. The results show that the composite sheet hot pressed for 15 min exhibits better plastic deformation behavior because the hard and brittle TiAl₃ layer is thin. When the composite is deformed at elevated temperatures, the cracks of the composite sheet are blunted, which inhibits the propagation of cracks in TiAl₃ layer, so the elongation and limiting bulging rate at 600 ℃ reach 135% and 45%, respectively. At the top region of the bulged spherical shell, the Ti layer and Al layer both undergo severe deformation and are necked, the Ti/Al interface is wavy, the TiAl₃ layer breaks into islands, with Al layer filling their gaps, and no cracks are formed.

Abstract:Lithium-sulfur batteries (LSBs) have extremely high theoretical energy density and low-cost cathode materials. However, the recycling of LSBs will produce polysulfides (LiPSs), which has a serious “shuttle effect”, resulting in highly polarized batteries, impaired battery performance, and even safety issues, and making the application of LSBs still extremely challenging. In this work, the binding energy of was used to discuss the absorption capacity of Cs₂F₅Li₃ to Li₂S, i.e., the ability to inhibit its “shuttle effect”. Based on the first-principles method of density functional theory, Cs₂F₅Li₃ and Li₂S were simulated by CASTEP software, and the binding energy of Cs₂F₅Li₃ to Li₂S is –2.53 eV. In order to explore the mechanism of adsorption, the basic properties, electronic structures, and charge transfer of Cs₂F₅Li₃ and Li₂S bulk phases, Li₂S(100), Cs₂F₅Li₃(001), and Cs₂F₅Li₃(001)-Li₂S(100) were used for analysis. The results show that the binding energy is provided by the ionic bond between F 2p and Li 1s2s as well as S 3p and Li 1s2s, the covalent bond between S 3p and F 2p, and the relaxation exchange energy of the bonds in the system. After the section, Cs₂F₅Li₃(001) has stronger chemical activity than Cs₂F₅Li₃, and Li₂S crystal changes from semiconductor property to metallic property. The metallic property of Cs₂F₅Li₃(001)-Li₂S(100) system improves, electrical conductivity is stronger, and photoelectric effect is stronger than that of Cs₂F₅Li₃(001). The adsorption energy calculation results show that Cs₂F₅Li₃ can inhibit the “shuttle effect” caused by the diffusion of Li₂S, which is conducive to alleviate the problems such as slow reaction kinetics, low activity, and reduced battery capacity caused by Li₂S, and it has a strong theoretical reference value for improving the performance of LSBs.

Abstract:Infections associated with titanium (Ti)-based implants present significant challenges in clinical treatments, especially when biofilms already form on the implant surface. Many antimicrobial agents, including antibiotics, metallic nanoparticles and antimicrobial peptides, have been extensively used to deal with Ti implant infections. However, these chemical approaches suffer from potential toxicity, antibiotic resistance and poor long-term antibacterial performance. Hence, physical antibacterial surfaces on Ti-based implants have attracted increasing attention. The antibacterial behavior of different surfaces on Ti-based biomaterials against various bacteria only by physical properties of the implants themselves (e.g., nanotopography) or exogenous physical stimulus (e.g., photocatalysis) was reviewed, as well as parameters influencing the physical antibacterial processes, such as size, shape and density of the surface nanotextures, and bacterial growth phases. Besides, mechanisms of different fabrication techniques for the physical antibacterial surfaces on Ti-based biomaterials were also summarized.

Abstract:Titanium alloys, characterized by their high specific strength, low density, corrosion resistance, oxidation resistance, high-temperature stability, and low neutron cross-section, are increasingly utilized as critical components in marine and space nuclear power systems. To enhance the radiation resistance of titanium alloys and advance their widespread use in nuclear engineering, considerable efforts have been made to address key issues related to the irradiation effects of titanium alloys. This paper reviews the development and irradiation effect studies of titanium and its alloys in the nuclear domain and provides a comprehensive overview of defect evolution and interaction mechanism of different advanced titanium alloys under various particle irradiations (such as neutrons and ions). Additionally, it summarizes the impact of service conditions (temperature, stress, and irradiation) on the mechanical properties of titanium alloys, including hardness, tensile strength, fatigue, and creep. Finally, based on the research status on titanium alloys for nuclear applications, the paper explores future research directions of irradiation effect and trends to improve irradiation resistance.

Abstract:Metallic glasses with excellent physical and chemical properties are hindered by their size constraints, limiting their practical applications. However, welding technique holds the potential to overcome these limitations. Welding methods of metallic glasses can be classified into liquid phase welding and solid phase welding, each involving distinct mechanisms to form amorphous joints. Effective preventing crystallization is crucial for obtaining high quality joints. This paper provides a systematic and comprehensive review of the research in the field of metallic glass welding, and summarizes the research status of metallic glass and metallic glass welding as well as metallic glass and crystalline metal welding. It focuses on the characteristics and limitations of different welding techniques to achieve fully amorphous welded parts. Additionally, it reviews the research status of metallic glasses as solder materials in brazing process and analyzes the potential applications of metallic glass-based brazing materials, and summarizes approaches for enhancing the mechanical properties of brazed joints. Finally, this paper outlines prospects for the future research and development of metallic glass welding.

Abstract:In recent years, the rapid development of aviation industry, low temperature superconductivity, hydrogen energy power and other fields has increased the demand for the reliability of equipment operation in low temperature environment. Low temperature will cause the failure of lubricants and the deterioration of mechanical properties of metals, resulting in increasingly terrible lubrication problems. Metal materials are confronted with the severe service environment of dry friction at low temperature. Therefore, the excellent friction and wear performance of the material is a key factor to ensure the long-term stable operation of the mechanical equipment at low temperature. This paper describes the challenges of low temperature lubrication, including low temperature lubrication failure and metal ductile-to-brittle transition. Then we introduce the common low temperature friction environment of metal materials. Finally, the steel, titanium alloy, aluminum alloy and multi-principal element alloy with excellent properties at low temperature are introduced, and the future development trend in this field is prospected.

Abstract:Titanium and its alloys exhibit inherent limitations in complex environments due to their low hardness, poor wear resistance, and weak high-temperature oxidation resistance. Solid powder-pack infiltration technique can effectively enhance the surface hardness, wear resistance, and high-temperature performance of titanium and its alloys. The morphology of the infiltration layer is significantly influenced by temperature, holding time, and infiltration agent. The incorporation of carbon and boron elements can substantially improve surface hardness and wear resistance, while aluminum infiltration enhances high-temperature oxidation resistance and strengthens the interfacial bonding between the infiltration layer and substrate. By optimizing process parameters, multi-component layers can be fabricated to achieve superior comprehensive properties. However, there are still some problems to be solved, including surface porosity in borided layers, weak adhesion between the infiltration layer and substrate, incomplete development of multi-element solid powder-pack infiltration techniques, long processing time, and high temperature.

Abstract:High-strength titanium alloys, represented by near/metastable β titanium alloys, have high specific strength, good plastic processing properties, and excellent hardenability, and they can be strengthened through heat treatment to get a better match of strength-plasticity-toughness. They have been widely used in load-bearing components of major equipment in aerospace and other fields. Selective laser melting (SLM), as an important technique in the field of titanium alloy additive manufacturing, has significant advantages such as near-net shaping and integrated forming of complex structures. So it has become a key development technique and cutting-edge direction in the aerospace manufacturing field. This review focuses on the principle and characteristics of SLM, starting from the extremely high heating/cooling rate and unique thermal cycle history of SLMed high-strength titanium alloy, and primarily discusses the microstructural features, phase composition, and mechanical properties of high-strength titanium alloys. The types of heat treatment processes of SLMed high-strength titanium alloy and their main influencing rules are summarized, aiming to provide a reference for obtaining excellent mechanical property match. Finally, drawing upon an analysis of existing research outcomes, the challenges of SLMed high-strength titanium alloys are summarized. It also offers a forward-looking perspective on potential research directions in this field.