Although micro-arc oxidation (MAO) coatings improve the mechanical properties of titanium alloys, their porous structural defects tend to act as pathways for corrosive agents and as adhesion sites for contaminants. In this study, a superhydrophobic coating was developed on TC-4 titanium alloy by combining in-situ hydrothermal synthesis of ZIF-8 with POTS surface modification, thereby forming a rough surface with low surface energy. The POTS/ZIF-8@MAO composite coating exhibits strong adhesion to the substrate through both physical and chemical bonding. Consequently, it demonstrates excellent chemical and thermal stability, maintaining a water contact angle (WCA) of 156.53 degrees +2.47 degrees and a sliding angle (SA) of 6.32 degrees +1.16 degrees even under extreme conditions. Due to its low water adhesion, the coating demonstrates significant self-cleaning ability against both solid and liquid contaminants. Electrochemical analysis reveals that it improves corrosion inhibition by up to 99% compared to pristine MAO-treated titanium alloy, providing an effective protective barrier for the substrate. This work proposes a promising strategy that may potentially expand the application scope of titanium alloys.

In this study, CrFeNiTixAl1-x (x=0.3, 0.7 in mole ratio) high-entropy alloy coatings (referred to as Ti0.3Al0.7, Ti0.7Al0.3 alloy coating, respectively) were prepared on AlSI1045 steel using the laser cladding (LC) method by adjusting the Al and Ti element contents. The phase constitutions, microstructures, mechanical properties, and corrosion resistance of the prepared coatings were comprehensively investigated and compared. Both Ti0.3Al0.7 and Ti0.7Al0.3 coatings exhibited rich Fe-Cr disordered BCC phase (A2) and NiAl ordered BCC phase (B2). The L21 phase in the Ti0.7Al0.3 coating accounted for as much as 47.7% when the Ti content was 0.7. The elevated Ti content significantly refined the internal structure of the coating, reducing the average grain size from 7.495 mu m to 2.281 mu m. With the combined effect of grain refinement and obstruction of dislocation motion by large angle grain boundaries, the microhardness of the Ti0.7Al0.3 alloy coatings increased from 685.12 HV0.2 to 867.20 HV0.2 compared to Ti0.3Al0.7. The precipitation strengthening effect of the noncoherent hard L21 phase, along with the protective role of the TiO2 oxide film, resulted in the lowest friction coefficient of 0.171 for Ti0.7Al0.3. Ti0.7Al0.3 exhibits the dominant wear mechanisms of abrasive and oxidative wear. Meanwhile, these coatings also exhibited excellent resistance to Cl- corrosion, with corrosion potentials shifted to -0.52 V and -0.46 V for Ti0.3Al0.7 and Ti0.7Al0.3, and corrosion current densities decreased to 1.26 x 10-6 A/cm2 and 4.35 x 10- 7A/cm2, respectively. These findings suggest that the replacement of equimolar Al with equimolar Ti in the CrFeNiTiAl high-entropy alloy compositions is a meaningful phenomenon that offers new perspectives for the design of novel high-performance HEAs.

Ni-P/Ni-Mo bilayer coatings were fabricated via pulsed electrodeposition, and the impact of heat treatment (200–600 °C) on their microstructure, mechanical, tribological, and corrosion-resistant properties was systematically investigated. Comprehensive characterization techniques revealed temperature-dependent phase evolution and performance enhancement mechanisms. At 400 °C, the outer Ni-Mo layer formed MoNi intermetallic compounds, while the inner Ni-P layer precipitated Ni2P phases, synergistically achieving peak hardness (1179 HV) and minimal wear rate (2.1 × 10−4 mm3/N·m). In contrast, heat treatment at 500 °C optimized corrosion resistance, with polarization resistance increasing to 865 kΩ·cm2 and corrosion current density decreasing to 2.85 × 10−7 A/cm2. The improved corrosion resistance was attributed to interlayer defect mismatch redirecting corrosion paths from longitudinal to transverse, coupled with intermetallic precipitation blocking corrosive substance penetration. This study establishes a temperature-dependent structure–property relationship for Ni-P/Ni-Mo coatings, demonstrating their potential as durable protective materials in harsh environments.

Ceramic coatings containing two-dimensional materials (2D materials) provide effective protection for light alloys during wear, significantly improving their anti-friction performance. MoS2 has proven highly effective in enhancing the anti-friction performance of ceramic coatings, particularly when synthesized via plasma electrolytic oxidation (PEO). However, dislocation pinning due to the incoherent interfaces in MoS2/TiO2 coatings tends to cause localized stress concentrations and brittle fracture, requiring effectively improve nanomechanical properties by optimizing interface design. To address these issues, this study used ultrasonic-assisted PEO to disperse graphene oxide (GO), which provided more possibility for in-situ synthesis MoS2, ultimately resulting in MoS2 with modified interlayer spacing. The change in interlayer spacing induced dislocation evolution at incoherent interface, leading to dual interface formation. At MoS2 (0.534 nm)/TiO2 interface: dislocation dipoles evolve to create considerable distortion, facilitating releasing shear stresses and inhibiting crack propagations. This process is followed by dislocation annihilation, keeping to stable interfacial bonding. Additionally, the others form strong dislocation pinning to obstruct dislocation slip and enhancing deformation resistance at MoS2 (0.227 nm)/TiO2 interface. The combined effects of dual interfacial enhancements resulted in a 90.0 % reduction in friction coefficients of the MoS2/GO/TiO2 coating compared to the traditional ceramic coating. This facile technique provides a new strategy to fabricate self-lubricating ceramic coatings on light alloys, while the introduction of ultrasound during PEO offers valuable guidance for applying ultrasound in the synthesis of 2D materials.

In order to meet the demand of sustainable energy development in today's world, it is imperative to implement low energy processing technologies, such as low energy surface treatment. In this study, a low energy consumption plasma electrolytic oxidation (PEO) surface treatment technology with low breakdown voltage and high coating efficiency is designed by adding graphene oxide (GO). It is found that the addition of GO provided more possibilities for the formation of interionic reactions of passivation films, which results in the passivation current density and breakdown voltage reducing by 60 % and 22.31 %, respectively. Furthermore, GO induces a shift in the discharge form from metal/oxide interface discharge to oxide/electrolyte interface discharge, which enhances the growth efficiency of the ceramic coating by 24.70 %, and decreases the energy consumption of each reaction stage by 9.00 %, 10.45 % and 10.84 %. The obtained low energy consumption coating, with low overall porosity (3.38 vol%), exhibits a smooth surface and eliminates channels for corrosive ions, which improves the anti-friction property and corrosion resistance.

Due to excellent performances and easy adjustability, more and more researchers pay attention to high-entropy ceramics, which can be applied in many fields. In this work, a high-entropy transition metal carbide ceramic, (Hf0.2Ta0.2Zr0.2Nb0.2W0.2)C, was fabricated by pressureless sintering method. To obtain highly dense ceramic, dual sintering aids (Cr3C2 and C), are employed in the sintering process. Owing to suitable microstructure (grain size and defect density), the ceramics exhibit excellent electric conductivity(0.7040MS/m) and flexural strength (378±11.4 MPa). Meanwhile, the relationship between electromagnetic shielding effectiveness and different aid content in the X-band is also investigated. The P3 ceramic with a thickness of 1 mm can achieve an EMI shielding efficiency of 92dB in the X-band as a result of the stronger interface polarization and relaxation effects. High-entropy ceramic obtained in this work would give a different way to fabricate shielding material and can promote the use of high-entropy ceramics as effective EMI shielding materials.

Al0.6CoCrFeNiSix high-entropy alloy coatings were obtained by laser cladding on the surface of 45# steel, and their microstructure evolution and wear mechanism were investigated. The surface morphology, element composition, and phase structure were analyzed, and the results showed that an increase in Si content led to a refinement of the Al0.6CoCrFeNiSix alloy coatings with a gradual transition from face-centered cubic (FCC) phase to body-centered cubic (BCC/B2) phase in alignment with the equilibrium phase diagram calculated using Pandat thermodynamic calculation software. The dissolution of Si into the solid solution caused lattice distortion which provided the driving force for this phase transition, while segregation of Si, Fe, and Cr facilitated the formation of Al-Ni-rich B2 phase promoting transformation from FCC to BCC phase. Microhardness improved with increasing Si content, reaching 770 Hv0.2 for the Al0.6Si0.4 alloy coating, demonstrating superior performance, while the wear mechanisms differed among the alloys where abrasive wear dominated in the Al0.6Si0.0, Al0.6Si0.1, and Al0.6Si0.2 alloys, whereas oxidation wear was prominent in the Al0.6Si0.3 and Al0.6Si0.4 alloys. The coating's wear resistance was enhanced due to the formation of a dense oxide film as lubricant resulting from the reaction between Si and oxygen acting leading to significant improvement in the tribological properties.

In the current study, a HA/TiO2 composite coating is effectively fabricated on a Ti-13Nb-13Zr alloy using the plasma electrolytic oxidation (PEO) technique. Electrolytes with different Ca/P contents are selected to study the evolution of phase composition and microstructure of PEO coating. The relationship between Ca/P contents and the wear resistance and corrosion resistance of the coatings are evaluated. The Ca/P-30 g coating exhibits the best performance with Ca/P≈1.66. The average thickness and roughness of the coating manufactured by this system are about 159 µm and 1.591 µm. The HA/TiO2 coatings akin to honeycomb have analogous pore size and uniform distribution, and the phase composition is mainly anatase. Compared with the substrate, the corrosion current density decreases by 19.65

In this study, Ni-Mo coatings with various sodium molybdate concentrations were designed and successfully electrodeposited. The effects of treatment with different temperatures (200 degrees C,400 degrees C, 600 degrees C) on the microstructure and properties of the best-performing coating (4 g/L) were investigated. The surface morphologies, elemental content, and phase structure of the prepared coatings were obtained and analyzed by SEM, EDS, XRD, WFI and TEM. The Ni-Mo coating after heat treatment at 400 degrees C formed the compact and uniform amorphous/ nanocrystalline coating. As shown by the electrochemical and wear test. Heat treatment at 400 degrees C improved the coating properties, and the corrosion current density was decreased by 66 % to 6.2532 x 10- 7A/cm2. The wear rate reduced from 8.3 x 10-4 mm3/N center dot m to 3.6 x 10-4 mm3/N center dot m, and the average friction coefficient minimized to 0.079. Additionally, compared with the as-deposited coating, the microhardness reaches the maximum (1048 HV). The formation of the oxide layer and the intermetallic compound MoNi on the surface of the coating plays a carrying and hindering role, thus the surface of the coating shows excellent wear and corrosion resistance. In addition, the corrosion inhibition mechanism during the heat treatment of Ni-Mo coatings was further explored.

In this study, a dual amorphous/crystalline nanocomposite coating of Ni-P/Ni-Mo-ZrO2 was designed and successfully deposited on pure copper substrates by pulse electrodeposition. The design of the Ni-P/Ni-Mo-ZrO2 dual coating takes advantage of the properties of the different structures and incorporates second phase reinforcing particles resulting in more comprehensive protective coatings. The surface morphology and microstructure were evaluated by SEM, EDS, WLI, XRD and TEM. The mechanical properties and electrochemical behaviors of the coating in a 3.5 wt% NaCl solution were investigated by wear tests, Tafel and EIS. The results show that the Ni-P/Ni-Mo and Ni-P/Ni-Mo-ZrO2 dual coatings are uniform, dense and crack-free, and the duplex interface is homogeneous. Compared with the Ni-Mo coating, the average friction coefficient and wear rate of the Ni-P/Ni-Mo duplex coating decreased to 0.18 and 5.433 x 10-4 mm3/N & sdot;m, respectively. The corrosion potential is positively shifted to -0.43 with a maximum impedance of 308 k omega cm2. The mismatch of the interlayer defects causes a deviation in the corrosion path, resulting in a transformation from longitudinal pinhole corrosion into extended transverse corrosion, which effectively strengthens the capacity of the coating for corrosion resistance while maintaining the high hardness of its outer coating. Furthermore, the hardness of the dual Ni-P/Ni-Mo coating can be obviously reinforced by nanoparticles from 730 HV to 810 HV, the corrosion potential is shifted to -0.41 V, and the corrosion current density decrease to 7.7803 x 10-7 A/cm2. The improvement in the mechanical properties can be attributed to the ZrO2 nanoparticles, which could carry stress and transfer loads during the wear process. Meanwhile, the ZrO2 nanoparticles can reduce the nodule size by filling the binding boundary which is the main corrosion path, and reduce the number of surface defects, such as pinholes, which leads to a lower corrosion rate. In addition, the corrosion inhibition and nanoparticle codeposition mechanisms of the duplex coatings were further discussed.

In this study, Al0.9CoCrNi2.1 EHEA was prepared by directional solidification at various withdrawal rates from 6 to 120 mu m/s. The lamellar eutectic structure is formed containing FCC (L12) and BCC (B2) at different withdrawal rates during directional solidification. The solid-liquid interface of the alloy transfers from nearly-planer to cellular eutectic interface and the lamellar spacing decreases from 7.17 mu m to 1.65 mu m as the withdrawal rate increases. The lamellar spacing is negatively correlated with withdrawal rates which was identified by the Jackson-Hunt model and its growth rate index (0.484) is closely related to the theoretical value (0.5). The tensile experiment demonstrates that the structure of Al0.9CoCrNi2.1 EHEA is finer and the ultimate tensile strength and elongation increase as the withdrawal rate increases. The elongation of Al0.9CoCrNi2.1 EHEA is two times higher than that of the as-cast alloy at the withdrawal rate of 120 mu m/s. It is concluded that the formation of the L12 phase and Cr-rich precipitated phases in the directional solidified eutectic structure are associated with the enhancement of mechanical properties due to grain refinement at high withdrawal rates.

选取通过轧制工艺制备的四种不同厚度的CT20钛合金板材,采用多种技术对其微观组织进行表征,测试板材的硬度以及沿轧件的轧制方向(RD)和横向方向(TD)拉伸的力学性能,分析微观组织与力学性能之间的内在联系.结果表明:在冷轧过程中,高密度的位错触发了合金的非晶化转变,变形量的增大使α相沿RD伸长,β相和βt组织破碎.位错和亚结构数量的提高不仅使合金硬度上升,而且使RD和TD的拉伸强度增大,伸长率下降.RD的断裂类型属于韧性断裂,TD的断裂类型属于韧脆混合型断裂.在冷轧过程中,基面滑移和柱面滑移共同参与织构的演变,由此形成的织构取向对板材RD和TD两方向的滑移行为和力学性能产生了重要影响;同时,由于位错在RD和TD两方向上的滑移距离不同导致不同的加工硬化阶段.

In this work, crack propagation behaviors and fracture mechanism of CT20 alloy with lamellar α at the temperatures ranging from 20 to -90°C were investigated and revealed. The results showed the fracture toughness of CT20 alloy was decreased from 430.89 KJ/m2 to 171.67 KJ/m2, and the fracture mechanism was gradually changed from typical ductile fracture to quasi-cleavage fracture with the decreasing testing temperature. The reduction of fracture toughness was mainly influenced by the internal factor (the crack tip plastic zone) and external factor (the tortuosity of the crack propagation path), in which the contribution of the internal factor increased from 87.06% to 95.68% as the temperature decreased. Therefore, the high contribution of the internal factor means the plastic zone at the crack tip could mainly affect the crack propagation behaviors. The lamellar α was found to be deformed by the plastic zone, and then inhibited the crack propagation and deflected its propagation direction at 20°C, which consumed the additional deformation energy and increased the fracture toughness. With the decline of the plastic zone from 0.526 mm to 0.107 mm, the lamellar α deformation and the crack propagation resistance were significantly reduced at -90°C, which accelerated crack propagation and decreased the fracture toughness.

HA/TiO2 composite coatings were prepared on Ti-13Nb- 13Zr alloy by micro-arc oxidation. By changing the ratio of Ca/P in the electrolyte, the phase composition and microstructure changes, as well as the effects of different Ca/P ratios on the wear resistance, corrosion resistance and in vitro biological activity of micro-arc oxidation coating were studied. The results show that the coating roughness and porosity increase with the increase of electrolyte Ca/P ratio. The coating phase is mainly composed of anatase and rutile, and the rutile phase content increases with the increase of Ca/P ratio of electrolyte. The coating thickness of CA35 prepared with 35 g/L calcium acetate electrolyte is 80.59 mu m and the surface Ca/ P ratio is 1.98, showing the best wear and corrosion resistance. Compared with the substrate, the average friction coefficient of CA35 coating is about 0.19, which decreases by 43%. The corrosion resistance of the coating was tested by Pt reference electrode and 0.9wt% NaCl test solution. The corrosion current density of CA35 coating is 4.94 mu A/cm2, and the corrosion potential is - 221.73 mV. The CA35 coating produces the fastest mineralized products in Kokubo solution. It is proved that increasing the Ca/P ratio of electrolyte can effectively promote the formation of HA and improve the wear resistance. In addition, the influence mechanism of Ca/P ratio on coating properties was discussed.

Constructing large lattice mismatch interfaces, especially two-dimensional materials such as MoS2, is the key to reaching the structural lubricity of heterogeneous structures. Large lattice mismatch prevents the nucleation of reinforcement of composite material, such as in situ synthesized MoS2 during the PEO process, thus affecting the mechanical performance. In this work, a precursor reaction, which can form an amorphous MoS3/TiO2 mixtures, is proposed, and the MoS2/TiO2 noncoherent interface with large mismatch is obtained through solid-state in situ desulfurization of suspended S with the action of reheat. Meanwhile, the precursor reaction is strongly dependent on the sulfur source concentration, which can form the interface with a large number of interfacial dislocations by regulating the concentration of sulfur source. Such edge pining noncoherent interface enables more dislocation and distortion near interface during scratch, which reduces the twist-angle dependence thus further improving the tribological properties. Additionally, these results render the herein presented amorphous precursor reaction strategy generally applicable for exhibiting broad application of in situ synthesis of reinforcement.

In this work, mechanical properties, microstructure evolution mechanism, texture variation process and deformation mechanism of a near-α CT20 titanium alloy with different hot and cold rolling reductions are investigated and uncovered comprehensively. The tensile strength of the alloy gradually increases, and the ductility decreases as the rolling reduction grows along both rolling direction (RD) and transverse direction (TD) due to the increase in grain boundary and dislocation density, while the mechanical properties along RD are better than those along TD. The high strain carried in α phases reduces the proportion of high-angle grain boundaries and increases the content of low-angle grain boundaries, with growing dislocation density in α phase. During cold rolling process, basal slip shifts {0001} pole toward ND, and prismatic slip inclines {11 2‾0} pole and {10 1‾ 0} pole toward TD. The intragranular orientation is enhanced with increasing rolling reduction, and the texture intensity of α and β phase is weakened as rolling reduction gradually grows. It is also noteworthy that prismatic slip dominates the slip mode along RD, while basal slip and pyramidal slip are activated along TD during cold rolling. The work-hardening rates of cold-rolled alloys are higher than that of the hot-rolled alloy as a large number of dislocations and grain boundaries were introduced by severe plastic deformation. The different work-hardening rates and mechanical properties of the rolled alloy along RD and TD are verified to be associated with the preferred orientation of α phase and the slip distances of dislocation during deformation.

Ceramic coatings are in general a kind of brittle material because they are predominantly made up of ionic crystals that avoid dislocation motion caused by lattice distortion. In this regard, a remarkable toughened ZrO2/MgO nanocomposite coating is obtained by the plasma electrolytic oxidation (PEO) process and in-situ synthesized ZrO2 with quantitative control approach. It is revealed that the toughening behavior of the ZrO2/MgO coating is related to the coordination and diversion of lattice distortion at the metallic oxide interface, which induces distinct dislocation motion at the interface. The semicoherent interface between m-ZrO2 and MgO is verified to act as a buffer to realize toughening of the nanocomposite coating through dislocation slipping induced by lattice coordinated distortion. Simultaneously, significant interfacial lattice distortion transfer and dislocation pinning are discovered at the semicoherent interface between t-ZrO2 and MgO, which are beneficial to toughness enhancement of the nanocomposite coating. The results indicate that the toughening effect occurs along with dislocation slipping and pinning caused by lattice distortion of the ZrO2/MgO semicoherent interface, which enables the toughness of novel nanocomposite coating to reach 2.7 times of the traditional PEO coating.

The pores formed by molten material ejection from the discharge channel and rapidly solidification during plasma electrolytic oxidation (PEO) act as passageways for corrosive particles. The overall porosity and pore shape, the inevitable features of ceramic coatings, are main factors that determines the corrosion resistance. In this work, we propose a novel approach that utilizes the advantages of graphene oxide (GO) to alter the pore shape and plasma discharge to effectively reduce the overall porosity. Simultaneously, the overall porosity and pore shape were deconstructed by X-ray microscopy. We found that the GO additive not only formed covalent bonds with the metal oxide, limiting the amount and distribution of molten oxide, but also changed the discharge form of the plasma reaction. The obtained coating exhibited an ultra-low surface porosity (1.10%), ultra-low overall porosity (2.11 vol%), and high aspect ratio (0.7-0.8), which are lowered for 94.8%, 90.9%, and increased for 66.9% than that of the traditional coating, respectively. The ultra-low porosity eliminates channels inside the coating and reduces the number of corrosive ions invading the substrate, resulting in superior corrosion resistance.

Ceramic coatings on the surface of titanium alloys have good synergy for antibacterial ability and tribocorrosion resistance, which are essential for dental implants in the human body. In this work, CuxO (CuO and Cu2O) was in-situ synthesized on the ceramic coating by plasma electrolytic oxidation (PEO) to study systematically the biological activity and tribocorrosion behavior. It was found that the presence of CuxO allows composite coatings to have an outstanding antibacterial performance through contact sterilization, and the ability to inhibit Staphylococcus aureus ATCC 25923 (S. aureus) is positively correlated with the Cu content of coating surfaces. During tribocorrosion process, the formation of hydroxyapatite and CuO on the worn surface prevented direct contact between the coating and the counterpart, which produces effective lubrication and contributes to the reduction of the mass loss for the prepared coating by 53.5% compared with traditional PEO coating. More importantly, the sliding process accelerated the enrichment of Cu on the worn surface, the high surface Cu content strengthened the long-term antibacterial activity of CuxO/TiO2 coatings. It is expected that the developed in-situ preparation strategy of CuxO will provide more opportunities for the antibacterial and tribocorrosion resistance coating on titanium alloy applications for dental implants.

Thermomechanical processing (TMP) is especially crucial for metastable beta titanium alloys, which has received significant attention in the community for a long time. In this contribution, the processing-responding behaviour including microstructure evolution process, texture variation mechanism, and underlying deformation process of powder metallurgy Ti-5553 alloy in a wide processing parameter range was comprehensively investigated. Thermal physical simulation was performed on the alloy at temperatures ranging from 800 degrees C to 1100 degrees C, and strain rates between 0.001 s(-1) and 10 s(-1), to varied deformation degrees of 20-80% height reduction. It was found that the processing parameters (i.e. temperature, strain rate, and deformation degree) are influential on the deformation process and resultant microstructure. Varied microstructural evolution processes for beta phase including flow localization, dynamic recovery, dynamic recrystallization, and grain coarsening are activated in different processing domains, while different evolution mechanisms for alpha phase including dynamic precipitation, phase separation, dynamic coarsening, and mechanical shearing also play their roles under different processing conditions. In particular, four exceptional evolution mechanisms of alpha precipitation which have not been previously reported in titanium alloys were discovered and clearly demonstrated, more specifically, they are multi-interior twinning, internal compositing, layered coarsening and selective diffusion-actuated separation. After the establishment of comprehensive microstructural evolution mechanism maps, the guidance for precise processing and the knowledge reserve extension for deformation process of metastable beta titanium alloys can be effectively achieved. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.