High entropy alloys have special microstructure and remarkable properties. To explore their potential engineering application in high temperature structures, the microstructure evolution of bonding interface, the elemental diffusion behavior and mechanical property of the diffusion bonded joint between AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) and TiAl alloy were investigated. Four reaction layers (rodlike B2 phase, Al(Co, Ni)2Ti, τ3-Al3NiTi2 + TiAl, τ3-Al3NiTi2 + TiAl + Ti3Al) formed in the diffusion zone near FCC phase of EHEA, but three layers (Al(Co, Ni)2Ti, τ3-Al3NiTi2 + TiAl, τ3-Al3NiTi2 + TiAl + Ti3Al) formed near B2 phase. Al and Ni controlled the reaction diffusion of EHEA and TiAl alloy, coarsened the acicular precipitated B2 phase and turned TiAl phase into Al(Co, Ni)2Ti and τ3-Al3NiTi2 phases. All these reaction layers grew in a parabolic manner as a function of bonding temperature. Rodlike B2 phase has the lowest growth activation energy of 125.2 kJ/mol, and the growth activation energy of τ3-Al3NiTi2 + TiAl layer near B2 phase is much lower than that near FCC phase. The penetration phenomenon and convex structure formed in the diffusion zone, which resulted in interlocking effect and enhanced the strength of resultant joints. The highest shear strength of 449 MPa was achieved at 950 °C. And the brittle fracture generally initiated at the interface between Al(Co, Ni)2Ti and τ3-Al3NiTi2 + TiAl layers.

Scanning electrochemical microscopy (SECM) and scanning vibrating electrode technique (SVET) were used to investigate the electrochemical behaviour of the top surface of the 2098-T351 alloy welded by friction stir welding (FSW). The SVET technique was efficient in identifying the cathodic and anodic weld regions. The welding joint (WJ), which comprises the thermomechanically affected zone (TMAZ) and the stir zone (SZ), was cathodic relative to the heated affected zone (HAZ) and the base metal (BM). The reactivities of the welding joint at the advancing side (AS) and the retreating side (RS) were analyzed and compared using SECM technique in the competition mode by monitoring the dissolved oxygen as a redox mediator in 0.005 mol L-1 NaCl solution. The RS was more electrochemically active than the AS, and these results were correlated with the microstructural features of the welded alloy.

This paper details an investigation of the effects of oxide stringers on the β-phase depletion behaviour in thermally sprayed CoNiCrAlY coatings. Vacuum Plasma Sprayed (VPS) CoNiCrAlY coatings, which are free of oxide stringers, are used as the reference materials in comparison with High-Velocity Oxy-Fuel (HVOF) sprayed CoNiCrAlY coatings during isothermal oxidation at 1100 °C. An outer layer of spinel oxides and an inner layer of alumina are formed in the as-sprayed coatings, while only a single alumina scale is found in the heat-treated coatings. Less β-phase depletion occurred in the HVOF coatings than in the VPS coatings. It was found that the β phases tend to coalesce at the oxide stringers in the HVOF coatings, which is likely due to the internal oxide particles and stringers acting as short diffusion barriers to tie up the β phase and inhibit the β-phase depletion.

Comparative studies on Zr35Cu65 and Zr65Cu35 amorphous systems were performed using molecular dynamic simulations to explore whether their hydrogenated mechanical behavior depends on the content of hydride-forming elements. Although both of them present an increased strength and ductility after hydrogen microalloying, we observe the improved mechanical behavior for Zr35Cu65 is more pronounced than that for Zr65Cu35. In these two samples, the distribution of configurational potential energy and flexibility volume respectively follows a similar H-induced variation tendency; all of the hydrogenated alloys not just have more stable atoms with smaller flexibility volume, but possess a larger fraction of readily activated atoms. However, the atomic-scale details, based on the local “gradient atomic packing structure” model, indicate minor additions of hydrogen can promote more “soft spots” along with more strengthened “backbones” in the low-Zr alloy than that in the high-Zr sample, which endows the former with much higher strength and deformability after hydrogen microalloying. We regard this finding as a further step forward to distilling the tell-tale metrics of the H-dependent mechanical behavior observed in Zr-based metallic glasses.

Mg-Y-Ni alloys with different second phases were designed by changing Y/Ni atomic ratio from 1.5 to 0.5. The microstructure and mechanical properties of as-cast and as-extruded alloys were investigated. The as-cast Mg-Y-Ni alloy with Y/Ni ratio of 1.5 is composed of α-Mg and long period stacking ordered (LPSO) phase. When Y/Ni ratio is equal to 1, nanoscale lamellar γ' phase and eutectic Mg2Ni phase are formed in addition to LPSO phase. As Y/Ni ratio decreases further, the amount of eutectic Mg2Ni phase increases, while the amount of LPSO phase decreases. After extrusion, the LPSO and γ' phases are distributed along the extrusion direction, while eutectic Mg2Ni phase is broken and dispersed in the as-extruded alloys. LPSO phase and Mg2Ni phase in the alloys promote dynamic recrystallization (DRX) during extrusion, while γ' phase inhibits DRX. Consequently, the Mg96Y2Ni2 (at.%) alloy with LPSO phase and γ' phase as the main second phases shows the strongest basal texture after extrusion. The tensile yield strength of the as-extruded Mg-Y-Ni alloys increases first and then decreases with decreasing Y/Ni ratio. The as-extruded Mg96Y2Ni2 (at.%) alloy with Y/Ni = 1 exhibits excellent mechanical properties with tensile yield strength of 465 MPa, ultimate tensile strength of 510 MPa and elongation to failure of 7.2%, which is attributed to the synergistic effect of bulk LPSO phase and nanoscale γ' phase.

As an advanced solid state bonding process, plastic deformation bonding (PDB) is a highly reliable metallurgical joining method that produces significant plastic deformation at the bonding interface of welded joints through thermo-mechanical coupling. In this study, PDB behavior of IN718 superalloy was systematically investigated by performing a series of isothermal compression tests at various processing conditions. It was revealed that new grains evolved in the bonding area through discontinuous dynamic recrystallization (DDRX) at 1000 - 1150 °C. Electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) results revealed that the bonding of joints is related with interfacial grain boundary (IGB) bulging process, which is considered as a nucleation process of DRXed grain under different deformation environments. During recrystallization process, the bonded interface moved due to strain-induced boundary migration (SIBM) process. Stored energy difference (caused by accumulation of dislocations at the bonding interface) was the dominant factor for SIBM during DRX. The mechanical properties of the bonded joints were dependent upon the recrystallized microstructure and SIBM ensued during PDB.

MCrAlY (M=Ni and/or Co) overlay coating is widely used as a protective coating against high temperature oxidation and corrosion. However, due to its big difference in chemical composition with the underlying superalloy, elements interdiffusion occurs inevitably. One of the direct results is the formation of interdiffusion zone (IDZ) and secondary reaction zone (SRZ) with a high density of fine topological closed-packed phases (TCPs), weakening dramatically the mechanical properties of the alloy substrate. It is by now the main problem of modern high-temperature metallic coatings, but there are still hardly any reports studying the formation, growth and transformation of IDZ and SRZ in deep, as well as the precipitation of TCPs. In this work, a typical NiCrAlY coating is deposited by arc ion plating on a single-crystal superalloy N5. Elements interdiffusion between them and its relationship on microstructure were clarified. Cr rather than Al from the coating diffuses into the alloy at high temperatures and segregates immediately beneath their interface, contributing largely to the formation of IDZ. Simultaneously, diffusion of Ni from the deep alloy to IDZ leads to the formation and continuous expansion of SRZ.

The design freedom of powder bed fusion process selective laser melting (SLM) enables flexibility to manufacture customized, geometrically complex medical implants directly from the CAD models. Co-based alloys have adequate wear and corrosion resistance, fatigue strength, and biocompatibility, which enables the alloys to be widely used in medical devices. This work aims to investigate the evolution of microstructures and their influence on tribological property of CoCrMo alloy processed by SLM and aging heat treatment. The results showed that very weak <110> texture along the building direction and microsegregation along cellular boundaries were produced. The presence of high residual stress and fine cellular dendrite structure has a pronounced hardening effect on the as-SLM and aging-treated alloys at moderate temperatures. Furthermore, the hexagonal ε phase transformed from the γ matrix during SLM became significant after subsequent aging at moderate temperatures, which further increased the nanohardness and scratch resistance. High temperature (1150 °C) heating caused homogenized recrystallization microstructure free of residual stress and ε phase, which sharply decreased the hardness and scratch resistance. The material parallel to the building direction exhibited improved tribological property in both SLMed and aging-treated alloy than that of the material perpendicular to the building direction. The anisotropy in frictional performance may be considered when designing CoCrMo dental implants using laser additive manufacturing.

The effect of the surface wettability of plasma-modified vertical Si nanowire array on the bio-fouling performance has been investigated. The Si nanowires prepared by a metal-assisted chemical etching technique exhibit a super-hydrophilic surface. The treatment in CH4/H2 gas plasma environment leads to the decoration of graphite and diamond nanoparticles around Si nanowires. The detailed interface between graphite/diamond and Si nanowire was characterized by HRTEM technique. These surface-modified nanowire samples show an increased water contact angle with ultrananocrystalline diamond decorated ones being superhydrophobic. The immersion test in chlorella solution reveals that the diamond-coated Si nanowires possess the least attachment of chlorella in comparison with other Si nanowires. This result confirms that the coating of Si nanowires with diamond nanoparticles shows the best behavior in anti-biofouling. Importantly, this work provides a method fabricated super-hydrophobic surface for the application of biofouling prevention.

First-principles methods based on density functional theory (DFT) are nowadays routinely applied to calculate the elastic constants of materials at temperature of 0 K. Nevertheless, the first-principles calculations of elastic constants at finite temperature are not straightforward. In the present work, the feasibility of the ab initio molecular dynamic (AIMD) method in calculations of the temperature dependent elastic constants of relatively “soft” metals, taking face centered cubic (FCC) aluminum (Al) as example, is explored. The AIMD calculations are performed with carefully selected strain tensors and strain magnitude. In parallel with the AIMD calculations, first-principles calculations with the quasiharmonic approximation (QHA) are performed as well. We show that all three independent elastic constant components (C11, C12 and C44) of Al from both the AIMD and QHA calculations decrease with increasing temperature T, in good agreement with those from experimental measurements. Our work allows us to quantify the individual contributions of the volume expansion, lattice vibration (excluding those contributed to the volume expansion), and electronic temperature effects to the temperature induced variation of the elastic constants. For Al with stable FCC crystal structure, the volume expansion effect contributes the major part (about 75%∼80%) in the temperature induced variation of the elastic constants. The contribution of the lattice vibration is minor (about 20%∼25%) while the electronic temperature effect is negligible. Although the elastic constants soften with increasing temperature, FCC Al satisfies the Born elastic stability criteria with temperature up to the experimental melting point.

A Mg-Gd-Y-Zn-Zr magnesium alloy with different initial states was extruded under different extrusion parameters. The effect of solution treatment and extrusion parameters on the microstructure, texture and mechanical properties were analyzed in detail, and the abnormal texture formation and strengthening mechanism was revealed. When extruded at low temperature and small extrusion ratio, the bimodal microstructure consisting of fine dynamically recrystallized grains and coarse deformed grains occurred both in the as-cast alloy and solution-treated alloy. When the extrusion temperature and extrusion ratio were increased, the amount and size of dynamically recrystallized grains increased and the grain size of the solution-treated alloy showed higher growth rate. Furthermore, an abnormal texture with <0001> parallel with extrusion direction developed due to the occurrence of non-basal slip and continuous dynamic recrystallization. This could be enhanced by solution treatment, high temperature, and large extrusion ratio. Both the as-cast alloy and solution-treated alloy exhibited the highest tensile strength after extrusion at 300 °C with an extrusion ratio of 9. Grain refinement was the main strengthening mechanism utilized in both the as-cast alloy and the solution-treated alloy. Work hardening played an important role in the sample extruded at low temperature and small extrusion ratio, with the highest contribution of about 33 MPa after extrusion at 300 °C with an extrusion ratio of 9. Texture strengthening contributed more in the sample extruded at high temperature and large extrusion ratio, but no more than 24.1 MPa. Solution strengthening was another strengthening mechanism in the extruded as-cast alloy, especially at high temperature and large extrusion ratio (no more than 9 MPa).

A TiN interlayer with high electrical conductivity was prepared between the GH3535 alloy and the Ni coating as a diffusion barrier to elements interdiffusion with the goal of increasing the corrosion resistance of GH3535 alloy in molten FLiNaK salt at 700 ℃. Results indicated that Ni coating could be directly electroplated on the TiN coated GH3535 alloy without extra conductive transition layer. TiN layer showed excellent thermal and chemical stabilities at elevated temperature in this molten salt system, without phase decomposition. The Ni/TiN composite coating was stable enough to resist corrosion in LiF-NaF-KF molten salt at 700 ℃. Elements interdiffusion between the substrate and Ni coating could be effectively inhibited and the corrosion resistance of the alloy was greatly enhanced. Besides, the TiN interlayer remained continuous and well adhered to the Ni coating as well as the substrate after corrosion test.

Metallic Ni bridged [email protected] carbon nitride hybrids were for the first time fabricated through a one-pot electroless-assisted hydrothermal method. The intimate Ni bridge between the interface of mesoporous carbon nitride and NiS was confirmed by HRTEM and in-depth XPS analysis using an Ar+-cluster sputtering gun and a possible mechanism was put forward to elucidate the formation process of the unique structure. Without adding any noble metals as cocatalysts, the optimized catalyst 10% NiS/m-CN-160-12 showed a H2 evolution rate of 1419 μmol·g-1·h-1, which is about 34 and 14 fold higher than that of bare mesoporous carbon nitride and NiS, respectively. The dramatically enhanced photocatalytic performance was mainly ascribed to the synergistic effect of NiS cocatalyst loading and the formation of metallic Ni between the interface of mesoporous carbon nitride and NiS, which served as a charge-transfer bridge to facilitate the transfer and separation of photo-induced electron-hole pairs.

The high performance of Ni single crystal superalloys during high temperature low stress creep service, is intrinsically determined by the combined effects of microstructural evolution and the dislocation behaviour. In the field of the evolution of dislocation network, two main recovery mechanism based on dislocation migration dominate the process. One is superdislocations shearing into γ’ rafts through a two-superpartials-assisted approach. Another is the compact dislocations migrating along γ/γ′ interface. These two mechanisms are similarly climb-rate-controlled process. In this work, a model for the minimum creep rate based on thermodynamic and kinetic calculations and using an existing detailed dislocation dynamics model has been built by taking the dislocation migration behaviours as well as the rafted microstructure into consideration, which can well reproduce the ([100] tensile) creep properties of existing Ni superalloy grades, without the need to make the dislocation parameter values composition dependent.

Understanding the relationship between microstructure features and mechanical properties is of great significance for the improvement and specific adjustment of steel properties. The relationship between mean grain size and yield strength is established by the well-known Hall-Petch equation. But due to the complexity of the grain configuration within materials, considering only the mean value is unlikely to give a complete representation of the mechanical behavior. The classical Taylor equation is often used to account for the effect of dislocation density, but not thoroughly tested in combination with grain size influence. In the present study, systematic heat treatment routes and cold rolling followed by annealing are designed for interstitial free (IF) steel to achieve ferritic microstructures that not only vary in mean grain size, but also in grain size distribution and in dislocation density, a combination that is rarely studied in the literature. Optical microscopy is applied to determine the grain size distribution. The dislocation density is determined through XRD measurements. The hardness is analyzed on its relation with the mean grain size, as well as with the grain size distribution and the dislocation density. With the help of the variable selection tool LASSO, it is shown that dislocation density, mean grain size and kurtosis of grain size distribution are the three features which most strongly affect hardness of IF steel.

For the purpose of overcoming the lack of durability problems associated with superhydrophobic surfaces which hitherto has limited their use; we prepared multi-stimuli wettability response coatings using a mixture of fluorocarbon resin and urea-formaldehyde microcapsules filled with fluorosilane via interfacial polymerization process. The microcapsules are of good thermal stability and can be triggered to release their core content on exposure to atmospheric conditions resulting in the increase in the water contact angle from 97 ° to 151 °. The prepared coatings gave good adhesion strength, and also showed an increase in the hydrophobic property after undergoing scratch, solvent and UV accelerated aging test. In addition, they offered good self-healing of the hydrophobic property after an initial loss due to alkaline immersion and oxygen plasma etching. The electrochemical measurements revealed a remarkable impedance recovery and suppression of corrosion activities, suggesting them to be a potential candidate material for corrosion protection.

Inorganic nanocomposites have attracted continuous attention as low cost and eco-friendly adsorbents. However, low adsorption rate and poor cycle performance limit their further application. Herein, lanthanum oxide (LO) ceramic nanowires decorated with nickel nanoparticles (NiNPs) have been synthesized by a facile electrospinning method. The decomposition of polymer precursor left high pore volume in the resultant ceramic nanowires, giving the nanowires a high surface area. The NiNPs-LO nanowires can remove various dye contaminants with adsorption rate constant higher than most adsorbents. More importantly, the NiNPs-LO nanowires can be separated and reused conveniently with stable cyclic performance, avoiding not only energy consumption but also secondary pollution. The adsorption performance fits well with pseudo-second-order and Langmuir isothermal model, indicating a monolayer adsorption process. Combined with structural and FT-IR analysis, the excellent adsorption ability is mainly ascribed to the electron interaction between the composite interfaces and contaminates under the assistance of high surface area and porosity. This work provides an ideal recyclable adsorbent for the ultra-fast water purification.

An intrinsic two-way shape memory effect with a fully recoverable strain of 1.0% was achieved in an as-prepared Ni50Mn37.5Sn12.5 metamagnetic shape memory microwire fabricated by Taylor-Ulitovsky method. This two-way shape memory effect is mainly owing to the internal stress caused by the retained martensite in austenite matrix, as revealed by transmission electron microscopy observations and high-energy X-ray diffraction experiments. After superelastic training for 30 loading/unloading cycles at room temperature, the amount of retained martensite increased and the recoverable strain of two-way shape memory effect increased significantly to 2.2%. Furthermore, a giant recoverable strain of 11.2% was attained under a bias stress of 300 MPa in the trained microwire. These properties confer this microwire great potential for micro-actuation applications.

This work focuses on fundamental understanding of microstructure evolution of nanostructured ferritic alloy (NFA) and 25 vol.% Cr3C2 coated SiC(Cr3C2@SiC)-NFA composite during spark plasma sintering at 950 °C and the following thermal treatment at 1000 °C. A unique bi-phase microstructure with distinct Cr-rich and Si-rich phases has been observed for the 25 vol.% Cr3C2@SiC-NFA composite, while for the NFA sample, the traditional large grain microstructure remains. Grain sizes are significantly smaller for the 25 vol.% Cr3C2@SiC-NFA composite compared to those for the pure NFA, which can be attributed to the presence of grain boundary phases in the composite sample. During the thermal treatment, microstructure features can be directly correlated with the dissolution kinetics and phase diagrams calculated using Thermo-Calc/DICTRA/PRISMA®.

To improve the oxidation and graphitization resistances of the polycrystalline diamond (PCD), Ti coating was deposited on the diamond powders via magnetic sputtering method, which achieved a uniform TiC protection barrier in PCD during the sintering process. The phase compositions, microstructures and thermal stability of Ti-PCD were characterized by X-ray diffraction (XRD), Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and thermal gravimetric-differential scanning calorimetry (TG-DSC). The results demonstrate that the oxidation and graphitization resistances of PCD are strengthened due to the existence of TiC phase, which acts as an effective inhibitor. The as-received inhibitor delays the oxidation and graphitization of PCD, elevating their initial temperature by ∼50 °C and ∼100 °C, respectively. During the annealing treatment of Ti-PCD, the priory oxidation of TiC, which produces TiO2 as an oxygen barrier, postpones the diamond oxide. Moreover, the TiC barrier also protects diamond grains from direct contact with cobalt, thus a lower cobalt-catalytic graphitization, and yields to an improved graphitization resistance of PCD. The enhanced oxidation and graphitization resistances of PCD are of significant importance for practical applications to elevated temperatures.

Given that graphene features high electrical conductivity, it is a kind of material with corrosion-promotion activity. This study aimed to inhibit the corrosion-promotion activity of graphene in coatings. Here, we report an exciting application of epoxy matrix (EP)/F-doped reduced graphene oxide (rGO) coatings for the long-term corrosion protection of steel. The synthesized F-doped rGO (FG) did not reduce the utilization of rGO by a wide margin and possessed distinctive electrically insulating nature. The electrical conductivity of rGO was approximately 1500 S/m, whereas those of FG-1, FG-2 and FG-3 were 1.17, 5.217 × 10-2 and 3.643 × 10-11 S/m, respectively. FG and rGO were then dispersed into epoxy coatings. The chemical structures of rGO and FG were investigated by transmission electron microscopy (TEM), scanning probe microscopy (SPM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). EP/FG coatings exhibited outstanding corrosion protection in comparison with blank EP and EP/rGO coatings mainly because the corrosion-promotion effect of rGO was eliminated. The anticorrosion ability of EP/FG coatings was improved with increased F-doped degree of FG. In addition, electrochemical impendance spectroscopy (EIS) results indicated that the Rc values of EP/FG-2 and EP/FG-3 were four orders of magnitude higher than those of EP/rGO in diluent NaCl solution (3.5 wt.%) after immersion for 90 days.

Surface-enhanced Raman spectroscopy (SERS) has been successfully applied to detect various biomolecules, but it is still in challenge to assay living cells or bacteria sensitively, selectively and quantitatively in complex environments. In this paper, 4-ATP and DTNB are assembled on Ag nanoparticle (NP) -decorated poly (styrene-co-acrylic acid) (PSA) nanospheres and then sealed by silica shells to form sensitive SERS labels based on the localized surface plasmon resonance of Ag NPs and large light scattering cross-sections of PSA nanospheres. They are further developed as encoding tags for dual detection of S. aureus and E. coli after assembling corresponding aptamers, which demonstrate ultralow detection limits of 8 cell L-1 for S. aureus and 2 cell L-1 for E. coli. Such a bioassay indicates a point-of-care strategy of ultrasensitively biomedical detections by encoding specific SERS tags.

The corrosion behavior of 304 stainless steel (SS) in the presence of aerobic halophilic archaea Natronorubrum tibetense was investigated. After 14 days of immersion, no obvious pitting pit was observed on the SS surface in the sterile medium. By contrast, the SS exhibited serious pitting corrosion with the largest pit depth of 5.0 μm in the inoculated medium after 14 days. The results of electrochemical tests showed that the barrier property of the passive film decreased faster in the inoculated medium. The X-ray photoelectron spectroscopy results indicated that the detrimental Fe2+ and Cr6+ increased in the passive film under the influence of archaea N. tibetense, which resulted in the accelerated deterioration of passive film and promoted the pitting corrosion. Combined with the energy starvation tests, the microbiologically influenced corrosion mechanism of 304 SS caused by halophilic archaea N. tibetense was discussed finally.

Due to the outstanding creep performance, nickel-based single crystal superalloys (Ni-SXs) are extensively applied in modern aero-engine and industrial gas turbine. Apart from the special single crystal structure which is disadvantageous to extension of creep cracks, Ni-SXs derive the creep strength from intrinsic two-phase microstructure (γphase and γ’ phase). Main microstructural parameters including volume fraction of γ’ phase and the lattice misfit, and the formation and distribution of precipitated phase are determined by the compositions of alloys. Besides, the creep properties are greatly influenced by these microstructural parameters and precipitated phase. This review has summarized the relationships between different alloying elements and microstructures and indicated their influence on creep properties of Ni-SXs. In addition, with the improvements of experimental methods and characterization technique, some recent discoveries have provided additional evidence to support or challenge the pervious creep theories of superalloys. In view of these new discoveries, this review has provided some perspectives which can be referenced in future compositional design of Ni-SXs.

We report first-principles results of the point defect properties in a V-Ta-Cr-W high-entropy alloy (HEA) with the body-centered cubic (bcc) structure. Different from the widely-investigated face-centered cubic (fcc) HEAs, the local lattice distortion is more pronounced in bcc ones, which has a strong influence on the defect properties and defect evolution under irradiation. Due to the large size of Ta, the exchange between vacancies and Ta exhibits lower energy barriers. On the other hand, interstitial dumbbells containing V and Cr possess lower formation energies. These defect energetics predicts an enrichment of V and Cr and a depletion of Ta and W in the vicinity of defect sinks. Besides, we find that interstitial dumbbells favor the [110] orientation in the HEA, instead of [111] direction in most nonmagnetic bcc metals, which helps to slow down interstitial diffusion significantly. Consequently, the distribution of migration energies for vacancies and interstitials exhibit much larger overlap regions in the bcc HEA compared to fcc HEAs, leading to the good irradiation resistance by enhancing defect recombination. Our results suggest that HEAs with the bcc structure may bear excellent irradiation tolerance due to the particular defect properties.

This study describes the development of a one-pot strategy to produce spherical alloy microparticles for advanced near-net-shape manufacturing processes, including additive manufacturing and powder injection molding. The AlSi12 eutectic alloy (ca. 12 wt% Si) system was chosen as the model with which the main experiments were carried out. The proposed process synergistically integrates a few common, low-cost processing techniques including the mixing of Al micrometer size particles with silicon and sodium chloride, heat-treating the mixture at temperatures of 650-810 °C, and the dissolution of salt in water to produce spherical AlSi12 alloy particles without the need to rely on costly melting and atomizing techniques. This new process can use laow-cost source Al and Si powders as the raw materials to produce 10-200 μm-sized spherical particles of AlSi12. The Ansys-CFX computational fluid dynamics software was used to analyze the flow behavior of AlSi12 liquid droplets and particle size refinement in the narrow voids of the sample.

The effect of Mo content on the microstructure revolution and corrosion behavior of cast FeCoCrNiMoxhigh-entropy alloys in chloride environments were investigated. Results indicate that FeCoCrNi and FeCoCrNiMo0.1alloys are in single FCC solid solution. The precipitates form in FeCoCrNiMo0.3 and increase in FeCoCrNiMo0.6 alloys. Pitting occurs on FeCoCrNi and FeCoCrNiMo0.1alloys while FeCoCrNiMo0.3 and FeCoCrNiMo0.6alloys suffer from preferential localized corrosion at the regions depleted in Cr and Mo. The higher Cr2O3/Cr(OH)3 ratio and the incorporation of Mo oxides make the passive film more protective and the corrosion resistance of the FeCoCrNiMo0.1alloy is thus enhanced. The correlation between microstructure and corrosion behavior and the corresponding corrosion mechanism were clarified.

The strategy of a reliable transition temperature control of vanadium dioxide (VO2) is reported. Rectangular VO2 nanobeams were synthesized by a thermal chemical vapor deposition (TCVD) system. The metal-insulator transition (MIT) temperature increases to above 380 K when the TiO2 ratio of the source is 5 at.%, although the Ti source is not physically doped into VO2 nanobeams. The XPS spectra of the V 2p orbital reveal the excessive oxidation of V after the TCVD processes with a higher TiO2 ratio, indicating that the TiO2 precursor is important in the O-doping of the surface V-O bonds when forming volatile Ti-O gas species. Thus, TiO2 reactants can be used as a VO2 surface chemical modifier to manipulate the MIT transition temperature and maintain a homogenous VO2 phase, which is useful for a Mott device application with a record on/off switching ratio > 104 and Mott transition temperature > 380 K.

In this study, three kinds of A380/Al2O3 composite coatings were prepared by cold spray (CS) using spherical, irregular and spherical + irregular shaped Al2O3 particulates separately mixed in the original A380 alloy powders. The influence of Al2O3 particulates’ morphology on the microstructural characteristics (i.e. retention of Al2O3 content in coatings, coating/matrix interfacial bonding, pore size distribution and morphology etc.) and wear performance of the coatings was investigated by scanning electron microscopy (SEM), X-ray computed tomography (XCT) and 3-D optical profilometry. Results indicated that the spherical Al2O3 shows obvious tamping effect during deposition process. As a result, the interface showed a wavy shape while the matrix and particulates were mechanical interlocked with much improved adhesion. In addition, the porosity of the coating was minimized and the pores exhibited curved spherical structure with reduced dimensions. The irregular Al2O3 particles predominantly displayed the embedding effect together with fragmentation of Al2O3 particulates. Consequently, poor coating/ matrix interfacial bonding, high porosity and the formation of angular-shaped pores were resulted in the coating. Dry sliding wear tests results revealed that the wear resistance of the coating is directly related with the retained content of Al2O3 in the coating. The coating containing irregular Al2O3 particulates displayed superior wear performance with its wear rate one seventh of that of the pure A380 alloy coating. The coating containing both kinds of Al2O3 particulates showed mixed characteristics of above two kinds of Al2O3 composite coatings.

The structures of tungsten and tungsten carbide scaffolds play a key role in determining the properties of their infiltrated composites for multifunctional applications. However, it is challenging to construct and control the architectures by means of self-assembly in W/WC systems because of their large densities. Here we present the development of unidirectionally porous architectures, with high porosities exceeding 65%, for W and WC scaffolds which in many respects reproduce the design motif of natural wood using a direct ice-templating technique. This was achieved by adjusting the viscosities of suspensions to retard sedimentation during freezing. The processing, structural characteristics and mechanical properties of the resulting scaffolds were investigated with the correlations between them explored. Quantitative relationships were established to describe their strengths based on the mechanics of cellular solids by taking into account both inter- and intra-lamellar pores. The fracture mechanisms were also identified, especially in light of the porosity. This study extends the effectiveness of the ice-templating technique for systems with large densities or particle sizes. It further provides preforms for developing new nature-inspired multifunctional materials, as represented by W/WC-Cu composites.

This work gives a comparison on the microstructural characteristics, textural discrepancies, and twinning behaviors of lamellar and equiaxed near β-Ti alloys during multi-pass cross rolling with a rolling reduction of 20%, 50% and 80%. The results showed that the restoration mechanism of the alloy in β phase is strongly dependent on the α morphologies, and in comparison, strain path has weaker influences on the grain refinement of the β matrix. Therefore, the texture intensities of both α and β phases were weakened owing to the dynamic recrystallization (DRX) of the two phases in the equiaxed microstructure. While, with regard to the lamellar microstructure, dynamic recovery (DRV) of the β phase predominated, forming elongated β subgrains. Besides, the α and β matrix in lamellar microstructures obeyed the Burgers orientation relationship, which was gradually broken down until the final reduction. Lastly, the 11¯01 twinning exhibits a strong size effect. With the continuous DRX of α phases, the α-twinning is suppressed owing to progressive grain refinement. The activation of β-twinning, namely 332〈113〉 and 112〈111〉, in near β-Ti alloys is heavily dependent on the deficient β-stabilizing elements and the local stress concentration. These findings provide an effective way to obtain ultra-fine grain microstructures of this alloy.

The immiscible Cu-Fe alloy was characterized by a metastable miscibility gap. With the addition element Zr, the miscibility gap can be extended into the Cu-Fe-Zr ternary system. The effect of the atomic ratio of Cu to Fe and Zr content on the behavior of liquid-liquid phase separation was studied. The results show that liquid-liquid phase separation into Cu-rich and Fe-rich liquids took place in the as-quenched Cu-Fe-Zr alloy. A glassy structure with nanoscale phase separation was obtained in the as-quenched (Cu0.5Fe0.5)40Zr60 alloy sample, exhibiting a homogeneous distribution of glassy Cu-rich nanoparticles in glassy Fe-rich matrix. The microstructural evolution and the competitive mechanism of phase formation in the rapidly solidified Cu-Fe-Zr system were discussed in detail. Moreover, the electrical property of the as-quenched Cu-Fe-Zr alloy samples was examined. It displays an abnormal change of electrical resistivity upon temperature in the nanoscale-phase-separation metallic glass. The crystallization behavior of such metallic glass has been discussed.

An eco-friendly and effective corrosion inhibitor (N-CDs) was acquired by hydrothermal method in methacrylic acid and ethyl(methyl)amine precursors. Afterwards, the weight loss and electrochemistry measurement were chosen to appraise the corrosion inhibition behavior of as-prepared N-CDs for Q235 steel in Cl- contained solutions. The change rules of EIS and Tafel data displayed that the as-prepared N-CDs revealed a high-efficiency protection for steel in all test environments. Meanwhile, the inhibition efficiency of steel reached up to 93.93% (1 M HCl) and 88.96% (3.5 wt% NaCl) at 200 mg/L of N-CDs. Furthermore, the N-CDs could form the adsorption film on steel surface to avoid the strong attack of Cl-. By analysis, the adsorption mechanism of as-prepared N-CDs on steel surface was physicochemical interaction, which strictly complied with the Langmuir adsorption model in both solutions.

To resolve the strength-ductility trade-off problem for high-strength Mg alloys, we prepared a high performance Mg-8Gd-3Y-0.5 Zr (wt%) alloy with yield strength of 371 MPa, ultimate tensile strength of 419 MPa and elongation of 15.8%. The processing route involves extrusion, pre-deformation and aging, which leads to a bimodal structure and nano-precipitates. Back-stress originated from the deformation-incompatibility in the bimodal-structure alloy can improve ductility. In addition, dislocation density in coarse grains increased during the pre-deformation strain of 2%, and the dislocations in coarse grains can promote the formation of chain-like nano-precipitates during aging treatment. The chain-like nano-precipitates can act as barriers for dislocations slip and the existing mobile dislocations enable good ductility.

Topological crystalline insulator (TCI) as a new type of topological materials has attracted extensive research interests for its tunable topological properties. Due its symmetry topological protection essence, the structure investigation provides a solid basement for tuning its topological transport properties. On SrTiO3 (111) substrate, the SnTe film was found to be epitaxial growth only along [001] while not [111] direction. The detailed structural study was performed and a structural model was proposed to elucidate epitaxial growth of the SnTe (001) film. The transport properties of SnTe (001) film were further investigated and a typical weak anti-localization effect was observed. By Pb-doping into SnTe, the bulk carriers were inhibited and its topological surface states were strengthened to induce the enhanced surface transport contribution. With tunable multiple transport channels from the even Dirac cones, the TCI SnTe film systems will have the potential application in future spintronics devices.

In this work, TiO2 nanotube arrays (NTAs) sensitized with MoS2 microspheres (MoS2/TiO2 nanocomposites) were prepared on a flat Ti substrate via two-step anodization and hydrothermal method sequentially. TiO2 NTAs were composed of many orderly nanotubes, whose large specific surface area was favorable for light absorption and MoS2 microsphere adhesion. The MoS2 microsphere as a narrow band gap semiconductor extended the TiO2 NTAs’ absorption band edge to the visible region. The 2D structure of MoS2 microspheres and the construction of heterojunction electronic field at the interface of MoS2 microspheres and TiO2 NTAs promoted the separation of photoinduced carriers. The MoS2/TiO2 nanocomposites could provide higher photoelectrochemical cathodic protection for 304 stainless steel (304 SS) under visible light than pristine TiO2 NTAs.

Intensive power ultrasound is introduced to Zr46.75Cu46.75Al6.5 bulk metallic glass (BMG) as an easy-procurable, non-destructive physical method to modulate its atomic rearrangement and shear deformation behavior. The microstructure after ultrasonic excitation with amplitude about 15 μm in 20 kHz for 2 h is characterized by large amount of Cu10Zr7 nanocrystals with size of 20-50 nm embedded in the glass matrix. This leads to a sharp increase in the critical stress for the first pop-in event of shear banding, and thus simultaneously improves both compressive plasticity and yield strength. Our findings provide a novel approach for overcoming the strength-ductility trade-off dilemma.

In this work, the phase transformation sequence during the continuous heating process (3 °C/min) was investigated in a near β titanium alloy. The results show that the staring formation of ω phase is about 267 °C, and the ending precipitation temperature about 386 °C during the heating process. When the heating temperature is greater than 485 °C, there are no ω phase detected within the β matrix. Combined with the microstructural characterization, it is found that ω phase facilitates the nucleation of α phase nearby the ω/β interface and has a great effect on the refinement for α phase. As compared with the specimens directly aged, the specimens with ω-assisted refinement of α phase possess high tensile strength, but there is no yield stage detected on their stress-strain curve. Combined with the analyses of the fracture morphology, the specimens with ω-assisted refinement of α phase present a brittle fracture. This is mainly ascribed to its relatively lager width of grain boundaries and the absence of widmanstätten α precipitates.

The urgent need of high-performance of energy storage devices triggers us to design newly class of materials. Generally, the materials feature with high conductivity, abundant pores and excellent stability. Here, a sandwiched hybrid composite containing reduced graphene oxide, polypyrrole and Ni-Co layered double hydroxides (RGO/PPy/NiCo-LDH) was prepared in a facile way. The polypyrrole was incorporated in the two dimensional (2D) nanosheets, which not only serve as the spacer to increase the surface area, but also enhance the conductivity of the nanocomposite. The obtained architecture was employed as an advanced electrode in a supercapacitor. The electrode shows an ultrahigh specific capacitance (2534 F g−1 at 1 A g −1) and good cycling efficiency (78% after 5000 cycles). Moreover, an asymmetric cell based RGO/PPy/NiCo-LDH composite demonstrates excellent electrochemical properties and good prospect of practical use.

In this work, the computational complexity of a spin-glass three-dimensional (3D) Ising model (for the lattice size N = lmn, where l, m, n are the numbers of lattice points along three crystallographic directions) is studied. We prove that an absolute minimum core (AMC) model consisting of a spin-glass 2D Ising model interacting with its nearest neighboring plane, has its computational complexity O(2mn). Any algorithms to make the model smaller (or simpler) than the AMC model will cut the basic element of the spin-glass 3D Ising model and lost many important information of the original model. Therefore, the computational complexity of the spin-glass 3D Ising model cannot be reduced to be less than O(2mn) by any algorithms, which is in subexponential time, superpolynomial.

The martensitic transformation, kinetics, elastic and magnetic properties of the Ni2-xMn1.5In0.5Cox (x = 0-0.33) ferromagnetic shape memory alloys were investigated experimentally and theoretically by first-principles calculations. First-principles calculations show that Co directly occupies the site of Ni sublattice, and Co atoms prefer to distribute evenly in the structure. The optimized lattice constants are consistent with the experimental results. The martensitic transformation paths are as follows: PA ↔ FA ↔ 6 MFIM ↔ NMFIM when 0 ≤ x < 0.25; PA ↔ FA ↔ 6 MFM ↔ NMFIM with 0.25 ≤ x < 0.3 and PA ↔ FA ↔ NMFM with 0.3 ≤ x ≤ 0.33 for Ni2-xMn1.5In0.5Cox (x = 0-0.33) alloys. The fundamental reasons for the decrease of TM with increasing Co content are explained from the aspects of first-principles calculations and martensitic transformation kinetics. The component interval of the magnetostructural coupling is determined as 0 ≤ x ≤ 0.25 by the first-principles calculations. Furthermore, the origin of the demagnetization effect during martensitic transformation is attributed to the shortening of the nearest neighboring distance for Ni-Ni (Co) and Mn-Mn. Combining the theoretical calculations with experimental results, it is verified that the TM of the Co6 alloy is near room temperature and its magnetization difference ΔM is 94.6 emu/g. Therefore, magnetic materials with high performance can be obtained, which may be useful for new magnetic applications.

Ti2AlNb-based intermetallic compounds are considered as a new category of promising lightweight aerospace materials due to their balanced mechanical properties. The aim of this study was to evaluate monotonic and cyclic deformation behavior of an as-cast Ti-22A1-20Nb-2V-1Mo-0.25Si (at.%) intermetallic compound in relation to its microstructure. The alloy containing an abundant fine lamellar O-Ti2AlNb phase exhibited a good combination of strength and plasticity, and superb fatigue resistance in comparison with other intermetallic compounds. Cyclic stabilization largely remained except slight cyclic hardening occurring at higher strain amplitudes. While fatigue life could be described using the common Coffin-Mason-Basquin equation, it could be better predicted via a weighted energy-based approach. Fatigue crack growth was characterized mainly by crystallographic cracking, along with fatigue striation-like features being unique to appear in the intermetallics. The results obtained in this study lay the foundation for the safe and durable applications of Ti2AlNb-based lightweight intermetallic compounds.

Upon non-equilibrium solidifications, dendrite growth, generally as precursor of as-solidified structures, has severe effects on subsequent phase transformations. Considering synergy of thermodynamics and kinetics controlling interface migration and following conservation of heat flux in solid temperature field, a more flexible modeling for the dendrite growth is herein developed for multi-component alloys, where, two inherent problems, i.e. correlation between thermodynamics and kinetics (i.e. the thermo-kinetic correlation), and theoretical connection between dendrite growth model and practical processing, have been successfully solved. Accordingly, both the thermodynamic driving force ΔG and the effective kinetic energy barrier Qeff have been found to control quantitatively the dendrite growth (i.e. especially the growth velocity, V), as reflected by the thermo-kinetic trade-off. Compared with previous models, it is the thermo-kinetic correlation that guarantees quantitative connection between the practical processing parameters and the current theoretical framework, as well as more reasonable description for kinetic behaviors involved. Applied to the vertical twin-roll casting (VTC), the present model, realizes a good prediction for kissing points, which influences significantly alloy design and processing optimization. This work deduces quantitatively the thermo-kinetic correlation controlling the dendrite growth, and by proposing the parameter-triplets (i.e. ΔG - Qeff - V), further opens a new beginning for connecting solidification theories with industrial applications, such as the VTC.

The metallic phase of molybdenum disulfide (M-MoS2) and semiconductor phase of molybdenum disulfide (S-MoS2) was synthesized by hydrothermal method, using cetyltrimethylammonium bromide (CTAB) as a surfactant. The structural and elemental composition confirmed the formation of M-MoS2 and S-MoS2. From the morphological analysis layered nanosheets with an inter-layered distance of 0.62 nm for M-MoS2 and 0.95 nm for S-MoS2 was observed. Fourier-transform infrared (FT-IR) spectral analysis was used to investigate the existence of CTAB functional group. The peak at 885 cm-1 attributed to the CH3 bond which confirmed the presence of CTAB in the S-MoS2. The anodic and cathodic peak separation (Epp) values of the counter electrode (CE) has showed at 468.28 mV (M-MoS2) and 540.87 mV (S-MoS2). The M-MoS2 thin film shows higher catalytic activity when compared to S-MoS2 due to more active sites and electronic conductivity. The power conversion efficiency of M-MoS2 CE based device exhibits higher efficiency compared to S-MoS2 CE based device.

Laser-assisted gas nitriding of selective Ti-6Al-4 V surfaces has been achieved during laser powder bed fusion fabrication by exchanging the argon build gas environment with nitrogen. Systematic variation of processing parameters allowed microdendritic TiN surface coatings to be formed having thicknesses ranging from a few tens of microns to several hundred microns, with TiN dendrite microstructure volume fractions ranging from 0.6 to 0.75; and corresponding Vickers microindentation hardness values ranging from ∼ 7.5 GPa to 9.5 GPa. Embedded TiN hard layers ranging from 50 μm to 150 μm thick were also fabricated in the laser-beam additively manufactured Ti-6Al-4 V alloy producing prototype, hybrid, planar composites having alternating, ductile Ti-6Al-4 V layers with a hardness of ∼ 4.5 GPa and a stiff, TiN layer with a hardness of ∼8.5 GPa. The results demonstrate prospects for fabricating novel, additively manufactured components having selective, hard, wear and corrosion resistant coatings along with periodic, planar or complex metal matrix composite regimes exhibiting superior toughness and related mechanical properties.

This study investigated the deterioration of a lubricant-infused anodic aluminium oxide surface in a 1 M NaCl solution for ∼200 days. Direct observation by cryo-SEM and quantitative analyses by UV spectroscopy and EIS revealed that the long-term deterioration of the lubricant-infused surface was divided into two stages: the surface-adhered lubricant layer gradually dissolved at a constant rate until the substrate was exposed; afterwards the lubricant infused in the nanochannels began to diffuse and was depleted after ∼200 days. The EIS results also revealed that the defects reduced the corrosion resistance of the lubricant-infused surface considerably.

Atmospheric corrosion monitoring (ACM) sensors were employed to study the initial atmospheric corrosion of carbon steels over a one-month period in six outdoor dynamic atmospheric environments in China. Based on the ∼250000 corrosion data sets collected, the environmental impacts of relative humidity, temperature and rainfall on the initial corrosion behavior of carbon steels were investigated. The results showed that rainfall was the strongest environmental factor influencing the initial atmospheric corrosion rate. Relative humidity significantly influenced the corrosion of carbon steels in low-precipitation environments and non-rainfall period.

The CsPbBr3@Cs4PbBr6 nanocrystals (NCs) could be synthesized by multiple Cs-oleate injections as adding the 1,9-dibromnonane in the reaction solution. The 1,9-dibromnonane could provide Br- ions and the rich Br- ions effectively restrain the generation of CsBr. The Cs4PbBr6 wrapped around the CsPbBr3 NCs and the size of crystalline grain was increased with increasing the Cs-oleate as excess oleylamine. The quantum yield for 14S4DN reached to 99.3% due to the decrease of defects and the surface passivation of Cs4PbBr6. There are more oleylammonium bromide on the surface of CsPbBr3 NCs as synthesized with 1,9-dibromnonane. The ligand shell and the surface passivation of Cs4PbBr6 restrained the decomposition of surface, consequently improved the stability of moisture and light for CsPbBr3 NCs. When the CsPbBr3@Cs4PbBr6 NCs were immersed in water under UV light (365 nm) for 2 h, the PL intensity could retain 90.4%, while the 11S1 (traditional CsPbBr3 NCs) was only 10.9%. It indicated the stability of moisture and light for CsPbBr3 NCs were greatly improved, because Cs4PbBr6 NCs effectively passivated the surface of CsPbBr3 NCs and restrained the generation of traps states.

The deformation behavior in Zr36Cu64 metallic glasses with pre-introduced indent-notches has been studied by molecular dynamics simulation at the atomic scale. The indent-notches can trigger the formation of densely-packed clusters composed of solid-like atoms in the indent-notch affected zone. These densely-packed clusters are highly resistant to the nucleation of shear bands. Hence, there is more tendency for the shear bands to nucleate outside the indent-notch affected zone, which enlarges the deformation region and enhances both the strengthening effect and the plastic deformation ability. For indent-notched MGs, when determining the initial yielding level, there is a competition process occurring between the densely-packed clusters leading to the shear band formation outside the indent-notch affected zone and the stress-concentration localizing deformation around the notch roots. When the indent-notch depth is small, the stress-concentration around the notch root plays a dominant role, leading to the shear bands initiating from the notch root, reminiscence of the cut-notches. As the indent-notch depth increases, there are many densely-packed clusters with high resistance to deformation in the indent-notch affected zone, leading to the shear band formation from the interface between the indent-notch affected zone and the matrix. Current research findings provide a feasible means for improving the strength and the plasticity of metallic glasses at room temperature.

Electronic skin (e-skin) and flexible wearable devices are currently being developed with broad application prospects. Transforming electronic skin (e-skin) into true "skin" is the ultimate goal. Tactile sensing is a fundamental function of skin and the development of high-performance flexible pressure sensors is necessary to realize thus. Many reports on flexible pressure sensors have been published in recent years, including numerous studies on improving sensor performance, and in particular, sensitivity. In addition, a number of studies have investigated self-healing materials, multifunctional sensing, and so on. Here, we review recent developments in flexible pressure sensors. First, working principles of flexible pressure sensors, including piezoresistivity, capacitance, and piezoelectricity, are introduced, as well as working mechanisms such as triboelectricity. Then studies on improving the performance of piezoresistive and capacitive flexible pressure sensors are discussed, in addition to other important aspects of this intriguing research field. Finally, we summarize future challenges in developing novel flexible pressure sensors.

In the present investigation, an austenitic AISI 304 stainless steel was subjected to high strain rate surface deformation by Pipe Inner-Surface Grinding (PISG) technique. The depth-dependent deformation parameters (strain, strain rate and strain gradient) were evaluated and the microstructures were systematically characterized. Microstructural evolution from millimeter- to nano-scale was explored, with special attention paid to the localized deformation. Microstructural evolution begins with the formation of planar dislocation arrays and the twin-matrix lamellae, which is followed by the localized deformation characterized by the initiation and the development of shear bands. A twinning-dominated process that was supplemented with dislocation slip-dominated one governed the microstructural evolution inside shear bands. The twin-matrix lamellae transform into extended/lamellar structure and finally the nano-sized grains. Austenitic grains were substantially refined and martensitic transformation was effectively suppressed, of which the underlying mechanisms were analyzed.

The thickness dependence of mechanical properties of nacre in Cristaria plicata shell was studied under three-point bending tests. The results show that the mechanical behavior of nacre exhibits a strong thickness dependence. The bending strength firstly increases with the increase of specimen thickness and then becomes roughly constant as the thickness reaches a certain value of ∼2.5 mm. However, the mean value of work per unit volume increases constantly with increasing specimen thickness; meanwhile, the cracking mode changes from penetration into the platelets to deflection along the interfaces. The theoretical analyses indicate that the thickness-dependent mechanical properties of nacre are mainly caused by the variation in the number of inter-lamellar interfaces. The more the number of inter-lamellar interfaces is, the higher the strength and work of fracture of nacre under bending tests will be. However, as the number of inter-lamellar interfaces reaches a certain value (e.g., in the present specimen with 2.5 mm thickness), the strength tends to remain constant, while the work of fracture still increases. Therefore, the present research findings are expected to provide a valuable guidance for the interfacial design of nacre-like materials with high strength and toughness.

The temperature and stress profiles of porous cubic Ti-6Al-4 V titanium alloy grids by additive manufacturing via electron beam melting (EBM) based on finite element (FE) method were investigated. Three-dimensional FE models were developed to simulate the single-layer and five-layer girds under annular and lateral scanning. The results showed that the molten pool temperature in five-layer girds was higher than that in single-layer grids owing to the larger mass and higher heat capacity. More energies accumulated by the longer scanning time for annular path than lateral path led to the higher temperature and steeper temperature gradient. The thermal stress drastically fluctuated during EBM process and the residual stress decreased with the increase of powder layer where the largest stress appeared at the first layer along the build direction. The stress under lateral scanning was slightly larger but relatively more homogeneous distribution than those under annular scanning. The stress distribution showed anisotropy and the maximum Von Mises stress occurred around the central node. The stress profiles were explained by the temperature fields and grids structure.

Low material cost and high extrudability for ensuring price competitiveness with Al alloys, as well as excellent mechanical properties, are essential for expanding the application range of Mg extrudates. Bi is a promising alloying element for developing extruded Mg alloys that satisfy such requirements. Bi is inexpensive, exhibits a high solubility limit, and forms a thermally stable Mg3Bi2 phase, which improves the commercial viability and enables the high-speed extrusion of Mg–Bi alloys. In this study, the effects of Bi addition on the dynamic recrystallization (DRX) and dynamic precipitation behaviors during hot extrusion of a pure Mg and the resultant microstructure and mechanical properties of the extruded materials were investigated. The addition of 6 wt% and 9 wt% Bi to a pure Mg yielded numerous fine Mg3Bi2 precipitates during the early stage of hot extrusion. Consequently, the area fraction of dynamic recrystallized (DRXed) grains decreased because of DRX-behavior suppression by the Zener pinning effect. However, the DRXed grain size was substantially reduced through the grain-boundary pinning effect. The size and number of undissolved Mg3Bi2 particles in the homogenized billets increased when the Bi content was increased, which resulted in increased DRX fractions owing to the enhanced levels of particle stimulated nucleation. Bi addition yielded considerable strength improvement of the extruded pure Mg. However, the extruded Mg–Bi binary materials were less ductile than the extruded pure Mg material. This lower ductility resulted from the cracking at twins formed in the coarse unDRXed grains of the Mg-6Bi material and the cracking at large undissolved Mg3Bi2 particles in the Mg-9Bi material.

Flexible sensors have been widely investigated due to their broad application prospects in various flexible electronics. However, the most of the presently studied flexible sensors are only suitable for working at room temperature, and their applications at high or low temperatures are still a big challenge. In this work, we present a multimodal flexible sensor based on functional oxide La0.7Sr0.3MnO3 (LSMO) thin film deposited on mica substrate. As a strain sensor, it shows excellent sensitivity to mechanical bending and high bending durability (up to 3600 cycles). Moreover, the LSMO/Mica sensor also shows a sensitive response to the magnetic field, implying its multimodal sensing ability. Most importantly, it can work in a wide temperature range from extreme low temperature down to 20 K to high temperature up to 773 K. The flexible sensor based on the flexible LSMO/mica hetero-structure shows great potential applications for flexible electronics using at extreme temperature environment in the future.

The porous titanium with a channel-like pore structure fabricated by infiltration casting followed by selectively dissolving the precursor woven three dimensional (3D) structure technique was comprehensively investigated by means of mechanical tests, in vitro and in vivo evaluation. Such porous structure exhibited superiority in compressive, tensile strength and osseointegration. At 40% porosity, the average compressive and tensile strength reached about 145 MPa and 85 MPa, which was superior to that of other porous titanium, e.g., Selective Laser Melting or powder sintered ones, and was comparable to that of the human cortical bone. Without any bioactive surface treatment, this porous titanium exhibited good cell adhesion, rapid cell proliferation and excellent osseointegration. Based on the study, the 0.4 mm pore size resulted in the most rapid cell proliferation and the maximal BV/TV ratio and trabecular bone number of the new bone that ingrew into the porous titanium. To balance the excellent osseointegration and adequate mechanical properties, the optimal structural parameters were 0.4 mm pore size with 40% porosity. This porous titanium is very promising for orthopedic applications where compressive and tensile load-bearing is extremely important.