Abstract:CuS-C50, the cathode materials for magnesium ion batteries, was synthesized by adding the surfactant cetyltrimethyl ammonium bromide (CTAB) and adjusting the percentage of ethylene glycol to 50vol% in hydrothermal synthesis process. Results show that CuS-C50 has the complete nanoflower structure. In aluminum chloride-pentamethylcydopentodiene/tetrahydrofuran (APC/THF) electrolyte, the CuS-C50 exhibits a high specific capacity of 331.19 mAh/g when the current density is 50 mA/g and still keeps a specific capacity of 136.92 mAh/g over 50 cycles when the current density is 200 mA/g. Results of morphology characterizations indicate that the complete nanoflower structure can provide more active sites and reduce the barriers for Mg²⁺ movement, eventually improving the charge and discharge performance of the CuS cathode materials for magnesium ion batteries.

Abstract:Fe-Mo functionally graded materials (FGMs) with different composition-change rates from 100% 304 stainless steel to 100% Mo along the composition gradient direction were prepared by electron beam-directed energy deposition (EB-DED) technique, including three samples with composition mutation of 100%, composition change rate of 10% and 30%. Results show that the composition-change rate significantly affects the microstructure and mechanical properties of the samples. In the sample with abrupt change of composition, the sharp shift in composition between 304 stainless steel and Mo leads to a great difference in the microstructure and hardness near the interface between the two materials. With the increase in the number of gradient layers, the composition changes continuously along the direction of deposition height, and the microstructure morphology shows a smooth transition from 304 stainless steel to Mo, which is gradually transformed from columnar crystal to dendritic crystal. Elements Fe, Mo, and other major elements transform linearly along the gradient direction, with sufficient interlayer diffusion between the deposited layers, leading to good metallurgical bonding. The smaller the change in composition gradient, the greater the microhardness value along the deposition direction. When the composition gradient is 10%, the gradient layer exhibits higher hardness (940 HV) and excellent resistance to surface abrasion, and the overall compressive properties of the samples are better, with the compressive fracture stress in the top region reaching 750.05±14 MPa.

Abstract:The scratching mechanism of polycrystalline γ-TiAl alloy was investigated at the atomic scale using the molecular dynamics method, with a focus on the influence of different grain sizes. The analysis encompassed tribological characteristics, scratch morphology, subsurface defect distribution, temperature variations, and stress states during the scratching process. The findings indicate that the scratch force, number of recovered atoms, and pile-up height exhibit abrupt changes when the critical size is 9.41 nm due to the influence of the inverse Hall-Petch effect. Variations in the number of grain boundaries and randomness of grain orientation result in different accumulation patterns on the scratch surface. Notably, single crystal materials and those with 3.73 nm in grain size display more regular surface morphology. Furthermore, smaller grain size leads to an increase in average coefficient of friction, removed atoms number, and wear rate. While it also causes a larger range of temperature values and distributions. Due to the barrier effect of grain boundaries, smaller grains exhibit reduced microscopic defects. Additionally, average von Mises stress and hydrostatic compressive stress at the indenter tip decrease as grain size decreases owing to grain boundary obstruction. This work is helpful to better understand the deformation mechanism of polycrystalline γ-TiAl alloy during the nano-scratching process.

Abstract:Based on simplified calculations of one-dimensional wave systems, loading pressure platform curves of Al-Cu gradient materials (GMs) impactor were designed. The Al-Cu GMs were prepared using tape-pressing sintering, and their acoustic properties were characterized to match the design path. The parallelism of the Al-Cu GM was confirmed using a three-dimensional surface profilometry machine. A one-stage light-gas gun was used to launch the Al-Cu GM, impacting an Al-LiF target at a velocity of 400 m/s. The results of the experimental strain rate demonstrate that the Al-Cu GMs can realize the precise control of the strain rate within the range of 10⁴?10⁵/s in the high-speed impact experiments.

Abstract:To enhance the mechanical properties of Mo alloys prepared through laser powder bed fusion (LPBF), a hot isostatic pressing (HIP) treatment was used. Results show that following HIP treatment, the porosity decreases from 0.27% to 0.22%, enabling the elements Mo and Ti to diffuse fully and to distribute more uniformly, and to forming a substantial number of low-angle grain boundaries. The tensile strength soars from 286±32 MPa to 598±22 MPa, while the elongation increases from 0.08%±0.02% to 0.18%±0.02%, without notable alterations in grain morphology during the tensile deformation. HIP treatment eliminates the molten pool boundaries, which are the primary source for premature failure in LPBFed Mo alloys. Consequently, HIP treatment emerges as a novel and effective approach for strengthening the mechanical properties of LPBFed Mo alloys, offering a fresh perspective on producing high-performance Mo-based alloys.

Abstract:As service conditions become more challenging and production complexity increases, there is an increasing demand for enhanced comprehensive performance of ceramic/metal heterostructures. At present, brazing technique has been widely utilized for ceramic-metal heterogeneous joints. However, the residual stress relief in these welding joints is complicated and necessary. Because metals and ceramics have different properties, especially their coefficients of thermal expansion. Welding joints exhibit large residual stresses during the cooling process. The relatively high residual stresses may significantly degrade the joint properties. For this issue, four alleviation routes were reviewed: optimization of process parameters, setting an intermediate layer, surface structure modulation and particle-reinforced composite solder. The states and distribution patterns of residual stress in ceramic-metal brazed joints were summarized, and the generation and detection of residual stress were introduced. Eventually, upcoming prospects and challenges of residual stress research on ceramic/metal heterostructures were pointed out.

Abstract:The traditional techniques for treating wastewater contaminated by heavy metals mostly involve chemical precipitation, solvent extraction and adsorption, ion-exchange, chemical precipitation, and membrane separation. The main shortcomings of traditional procedures are low economic efficiency, lack of environmental friendliness, and poor selectivity. Cyclodextrins are artificial compounds that resemble cages. Through host-guest interaction, pollutants can be adsorbed by its stable inner hydrophobic chamber and exterior hydrophilic surface. It is not only inexpensive and environmentally friendly, but also quite selective. The synthesis and application of materials were reviewed, as well as the primary influencing factors, and the reaction principle of cyclodextrin adsorbent materials for better separation of heavy metal ions. And the future trend of discovery was described.

Abstract:The development of high-performance structural and functional materials is vital in many industrial fields. High- and medium-entropy alloys (H/MEAs) with superior comprehensive properties owing to their specific microstructures are promising candidates for structural materials. More importantly, multitudinous efforts have been made to regulate the microstructures and the properties of H/MEAs to further expand their industrial applications. The various heterostructures have enormous potential for the development of H/MEAs with outstanding performance. Herein, multiple heterogeneous structures with single and hierarchical heterogeneities were discussed in detail. Moreover, preparation methods for compositional inhomogeneity, bimodal structures, dual-phase structures, lamella/layered structures, harmonic structures (core-shell), multiscale precipitates and heterostructures coupled with specific microstructures in H/MEAs were also systematically reviewed. The deformation mechanisms induced by the different heterostructures were thoroughly discussed to explore the relationship between the heterostructures and the optimized properties of H/MEAs. The contributions of the heterostructures and advanced microstructures to the H/MEAs were comprehensively elucidated to further improve the properties of the alloys. Finally, this review discussed the future challenges of high-performance H/MEAs for industrial applications and provides feasible methods for optimizing heterostructures to enhance the comprehensive properties of H/MEAs.

Abstract:The effects of different cooling rates on the microstructure evolution and tensile properties of TB17 titanium alloy were studied. The results show that the cooling rate has a significant effect on the microstructure. When the cooling rate is low, the alloying elements are diffused fully, resulting in higher content and larger size of coarse lamellar layers, and a small amount of secondary α phase is precipitated in the matrix. When the cooling rate is high, a large amount of microstructure at high temperature is preserved, so that the coarse lamellar content is low and the size is small, and the secondary α phase is hardly observed. Due to the absence of external forces, the lamellar α phase maintains a strict Burgers orientation correspondence with the β phase. The tensile property is greatly affected by the solution cooling rate. A large amount of secondary α phase is precipitated during air-cooling (AC), which results in the highest strength. Due to the faster cooling speed, only the coarse layer is retained during water-quenching (WQ), resulting in the lowest strength. The cooling rate of furnace-cooled (FC) is too slow, so the coarse lamellar growth is obvious. This inhibits the precipitation of secondary α phase, and leads to the middle intensity. After aging treatment, the tensile properties change differently. WQ has the highest strength, while FC has the lowest strength.

Abstract:The pressure applied during the sintering process plays an important role in improving the final density of UN pellets. In this work, a phase field model of UN pressure-assisted sintering was established by introducing elastic strain energy and particle rigid motion process. The effects of stress on the growth of sintering neck and rigid-body motion on the pore shrinkage were analyzed, and the multi-particle sintering process under the three mechanisms was simulated. The simulation results show that the length of the sintering neck and its growth rate increase with the increase in the applied strain. There is obvious stress concentration at both ends of the sintering neck, and the stress distribution gradually becomes uniform with the increase in time. With the increase in translational mobility, the pore shrinkage rate increases, and the densification completion time is advanced, while the value of rotational mobility has little effect on the pore shrinkage process. The model can capture the formation and growth of the sintering neck, the spheroidization and closure of the pores. The coordination grain number of large volume pores is higher and the existence time is longer.

Abstract:Complex shaped TiAl alloy components can be manufactured by laser additive manufacturing technology, further expanding the engineering applications of this lightweight high-temperature alloy in the aerospace field. However, there is currently limited research on the intrinsic relationship among the laser melting deposition process, microstructure, and properties of TiAl alloys. TiAl alloy specimens with good macroscopic quality were prepared by laser melting deposition using Ti-48Al-2Cr-2Nb alloy powder as raw materials. The microstructure, phase composition, hardness distribution of the deposited layer, and room temperature mechanical properties of the deposited specimens were studied under optimized process parameters. The results show that the microstructure of the deposited layer mainly consists of a large number of γ-TiAl phases and a small amount of α₂-Ti₃Al phases; the microstructure of the deposited sample exhibits a layer characteristics formed by columnar crystals, equiaxial crystals, cytosolic crystals, and laths structure, and the grain refinement in the microstructure of the deposited layer is obvious. The hardness distribution of the deposited layer ranges from 537 HV_0.3 to 598 HV_0.3, and the Vickers hardness at the bottom is higher than that at the middle and the top. The ultimate compressive strength of the TiAl alloy specimens is (1545±64) MPa at room temperature, with a compressive strain of (17.68±0.07)%, and the ultimate tensile strength along the scanning direction of the laser is (514±92) MPa at room temperature, with an elongation of (0.2±0.04)% after break; the ultimate tensile strength along the building direction is (424±114) MPa, with an elongation of (0.15±0.07)% after break. The tensile fracture morphology of TiAl alloy specimens exhibits quasi cleavage fracture characteristics. By optimizing the scanning strategy and assisting with subsequent heat treatment, it is expected to improve the uniformity of alloy structure and the anisotropy of mechanical properties.

Abstract:In response to the issues of shallow TIG arc penetration and low welding efficiency in medium-thickness titanium alloy arc welding, TIG welding experiments were conducted on 6 mm-thick TC4 titanium alloy. The effects of different arc modes (direct current, low-frequency pulse, and low-frequency plus high-frequency dual-pulse) on the weld pool and weld bead formation were studied. Finite element simulation was employed to investigate the temperature field and flow field dynamics of the weld pool in dual-pulse welding, and the deep penetration mechanism of dual-pulse TIG welding was analyzed. The results show that compared to constant current and low-frequency pulse modes, the dual-pulse current mode increases the flow velocity of the weld pool, effectively excites the deep penetration keyhole at the center of the pool, promotes the downward movement of the heat source, and thus increases the penetration depth. The tensile strength of the dual-pulse TIG weld joint reaches 964 MPa, the joint strength coefficient is 98%, and the post-fracture elongation is 3.7%, achieving a near-equal strength match for the joint.

Abstract:WC-Co cemented carbide balls with different cobalt (Co) contents were modified by pulsed magnetic field. The effects of pulsed magnetic field treatment on tribological properties of YG6/YG8/YG12-titanium alloy (TC4) were investigated by reciprocating friction machine and SEM. The results show that pulsed magnetic field treatment can effectively reduce the coefficient of friction (COF) of YG cemented carbides-TC4 titanium alloy friction pair. Main wear forms are adhesive wear and oxidation wear. Different intensities of pulsed magnetic field change the energy amount generated. Taking YG8 as an example, the average COF are reduced by 20.5%, 29.7%, and 25.9%, after the magnetic 0.5, 1, and 1.5 T treatments, respectively, compared with that without treatment. At magnetic field intensity of 1 T, the average COF of YG6, YG8, YG12 cemented carbide decreases by 19.5%, 29.7%, 20.1%, respectively. With the increase in Co content, the effect of the magnetic field treatment increases first and then decreases, and the magnetic field response is the most significant when the Co content is 8wt%. As an external energy, the pulsed magnetic field used on cemented carbide causes the Co phase from α-Co to ε-Co and thus results in dislocation proliferation; as a result, the ability of cemented carbide to resist plastic deformation is improved, and the corresponding macro-phenomenon is an increase in strength and wear resistance, so that the friction performance is finally improved.

Abstract:A WE43 (Mg-4Y-3Nd-0.5Zr, wt%) magnesium-rare earth alloy thin-wall component was fabricated by wire arc additive manufacturing, and its microstructure and mechanical properties were investigated by multiscale characterization, microhardness, and tensile tests. The influences of direct aging (T5) and solid solution+aging (T6) on the microstructure evolution and mechanical properties were studied. Results indicate that the as-deposited WE43 alloy has a uniform equiaxed crystal matrix, with an average grain size of 25.3 μm. Reticulated eutectic structure (α-Mg+Mg₄₁Nd₅/Mg₂₄Y₅) is formed due to Nd and Y element liquid segregation at grain boundaries. Tensile strength of as-deposited alloys is 190 MPa. Peak hardness increases from 74 HV_0.2 to 91 HV_0.2 after T5 aging with persistence of significant eutectic structures. Peak aging hardness is 108 HV_0.2 after T6 treatment, and the eutectic structure is dissolved completely, while a small amount of Mg₂₄Y₅ remains in matrix. Tensile strength of alloys is enhanced to 283 MPa after T6 treatment, but it also induces significant grain growth and reduces the elongation in vertical direction more obviously than in horizontal direction.

Abstract:The mechanical behavior and fracture failure characteristics of Mg-9Gd-4Y-2Zn-0.5Zr alloy at various strain rates were investigated, including parameter calibration and verification based on the Johnson-Cook (J-C) constitutive model and failure model. Quasi-static tensile tests at different temperatures were conducted by a universal testing machine, while dynamic tensile tests at high strain rates (1000–3000 s^-1) were performed by a Hopkinson bar apparatus. Based on the experimental data, modifications were made to the strain rate hardening and thermal softening terms of the J-C constitutive model were modificated, and relevant model parameters were calibrated. Further numerical simulations were carried out; the fracture locations and true stress-strain curves between experimental and simulated results were compared to validate the reliability of the failure model parameters. The fracture morphology of the magnesium alloy was observed and the microstructural characteristics influencing failure under different temperatures and strain rates were explored. Both dimples and cleavage steps were observed in the fracture morphologies during quasi-static and dynamic tensile processes, indicating a mixed fracture mechanism. Slightly more cleavage steps are found at higher strain rates, which is related to the strain rate sensitivity of the magnesium alloy. In contrast, ductile fracture is predominant during high-temperature tensile tests.

Abstract:Steel material is the main structural material of marine equipment, but its corrosion usually occurs in the marine atmosphere environment, thus affecting its service performance. Compared with general atmospheric corrosion, marine atmospheric corrosion is affected by sea salt aerosols, chloride ions and other specific factors of marine atmosphere. In addition, the marine atmospheric corrosion properties of steel materials are closely related to the alloying elements of the materials. This paper reviewed the relevant studies of worldwide scholars on the effect of rare metal doping on the marine atmospheric corrosion resistance of steel materials in recent years, and summarized the corrosion mechanism of carbon steel, stainless steel, weathering steel and other common structural steels under marine atmospheric environment. The effects of Nb, Mo, Sb, Sn, Ce, La, Y and other rare metal elements on the marine atmospheric corrosion resistance of steel materials were analyzed. For weathering steel and carbon steel, the effect of rare metal elements on the structure of rust layer was mainly discussed. For stainless steel, the effect mechanism of rare metal elements on inclusion modification and pitting behavior of stainless steel was discussed. The future research directions were prospected, in order to provide references for the application of rare metal doped steel in marine atmospheric environment and for the improvement of marine atmospheric corrosion resistance.

Abstract:The TiAl alloy is considered a promising material for aerospace and other high temperature applications due to its low density, high strength and excellent creep resistance. However, its application is currently limited by its poor oxidation resistance above 750 ℃. In this paper, the classification, development, and high temperature oxidation behavior of TiAl alloys were reviewed. The formation mechanism and structural evolution of oxide films were discussed. The research progress of the preparation processing, bulk alloying, reinforcing phase and surface modification technologies aimed at improving the high temperature oxidation resistance of TiAl alloys since the 21st century were summarized. Furthermore, the application of theoretical calculation in oxidation process was discussed and the development trend of this field was prospected.

Abstract:The basic properties, structural, and functional applications of copper were described and the process characteristics and joint properties of copper brazing were and analyzed. The current research status of brazing between copper and dissimilar materials such as steel, aluminum, titanium, ceramics, and carbon-based materials were reviewed and examples of studies on brazing copper with heterogeneous structures were listed. Specific considerations in the brazing process were also examined, including brazing filler metal selection, process formulation, interlayer design, use of brazing equipment, and performance inspection. The importance of joining structure and joint interface design was emphasized. Furthermore, it is proposed that the development direction of copper brazing should focus on being green, intelligent, reliable, and low-cost, providing a technical reference for the engineering applications of copper and the brazing fabrication of heterogeneous structures containing copper.

Abstract:Low-oxygen TZM alloy (oxygen content of 0.03vol%) was subjected to solid-solution heat treatment at various temperatures followed by quenching. Results show that the tensile strength of the alloy gradually decreases with the increase in solid-solution temperature, and the elongation first increases and then decreases. The the amount of nanoscale Ti-rich phases precipitated in low-oxygen TZM alloys gradually increases with the increase in solid-solution temperature. Special strip-shaped Ti-rich areas appear in the samples solidified at 1200 and 1300 °C. The nanoscale Ti-rich phases ensure the uniform distribution of dislocations throughout TZM alloy, while significantly improving the plasticity of low-oxygen TZM alloy samples.

Abstract:The predictive model and design of heavy-duty metal rubber shock absorber for the powertrains of heavy-load mining vehicles were investigated. The microstructural characteristics of the wire mesh were elucidated using fractal graphs. A numerical model based on virtual fabrication technique was established to propose a design scheme for the wire mesh component. Four sets of wire mesh shock absorbers with various relative densities were prepared and a predictive model based on these relative densities was established through mechanical testing. To further enhance the predictive accuracy, a variable transposition fitting method was proposed to refine the model. Residual analysis was employed to quantitatively validate the results against those obtained from an experimental control group. The results show that the improved model exhibits higher predictive accuracy than the original model, with the determination coefficient (R²) of 0.9624. This study provides theoretical support for designing wire mesh shock absorbers with reduced testing requirements and enhanced design efficiency.

Abstract:Mg-4.8Zn-0.8Y, Mg-18Zn-3Y, Mg-15Zn-5Y, Mg-30Zn-5Y and Mg-42Zn-7Y (wt%) alloys containing icosahedral quasi-crystalline phases were prepared using the ordinary solidification method. The impact of Mg matrix porosity on the tensile strength and hardness of the alloys was studied. The porosity of the Mg matrix was quantitatively assessed using scanning electron microscope and Image-Pro Plus 6.0 software. Tensile tests were conducted at room temperature. Results show that the maximum tensile strength of the alloy is 175.56 MPa, with a corresponding Mg matrix porosity of 76.74%. Through fitting analysis, it is determined that the maximum tensile strength is achieved when the porosity of the Mg matrix is 64.87%. The microhardness test results indicate a gradual decrease in alloy hardness with increasing the porosity of Mg matrix. This study provides an effective quantitative analysis method for enhancing the mechanical properties of magnesium alloys.

Abstract:The relationship between the mechanical properties and precipitation behavior of Al-Zn-Mg-Cu-Zr aluminum alloys with low Sc content (0.02wt%, 0.07wt%, 0.12wt%) was investigated by OM, SEM, TEM, and universal material testing machine. With the increase in Sc content, microstructure of as-cast alloy is gradually refined, and the coarse secondary phase at the grain boundary increases, thus weakening the effect of fine grain strengthening. In the alloy at rolling+T6 state, the Al₃(Sc,Zr) phase inhibits the precipitation of the main strengthening phase η', and the inhibition effect becomes more obvious with the increase in Sc content, thus weakening the precipitation strengthening effect. The grain refinement is conducive to the formation of more and finer dimples during the tensile deformation, thus improving the ductility of the alloy. The low Sc content alloy (0.02wt%) shows the excellent mechanical properties after rolling and T6 heat treatment, whose tensile strength and elongation are 683 MPa and 21%, respectively.

Abstract:Fe₃O₄ magnetic nanoparticles were prepared by co-precipitation method, the surface of the magnetic particles was modified by SiO₂ and CM-β-CD, and Fe₃O₄-based magnetic nanomaterials (Fe₃O₄@SiO₂@CM-β-CD) with high adsorption properties were prepared. Single factor optimization experiments were carried out, and the physical and chemical properties of magnetic nanocomposites were characterized by TEM, EDS and BET. The adsorption behavior of Fe₃O₄@SiO₂@CM-β-CD on rare earth Er(Ⅲ) was investigated. The effects of adsorbent dosage, temperature and rotational speed on erbium removal rate were also investigated. The results show that when the dosage of SDBS is 1 g, the dosage of TEOS is 6 mL, the dosage of APTES is 1 mL, and the dosage of CM-β-CD is 0.5 g, the adsorption rate of Er(Ⅲ) can preferably reach more than 95%. When the contact time is 30 min, the initial concentration of Er(Ⅲ) is 10 mg/L, the initial pH is 4.5, the dosage of adsorbent is 30 mg, the temperature is 298 K, and the rotational speed is 150 r/min, the removal rate of Er(Ⅲ) is about 98%. After the adsorption of erbium, the nanomaterials were desorbed with 0.1 mol/L HNO₃ for 20 min, and the desorption efficiency of rare earth Er(Ⅲ) can be more than 87%. The adsorption mechanism of Fe₃O₄@SiO₂@CM-β-CD was investigated by XPS analysis. It is found that the adsorption of Fe₃O₄@SiO₂@CM-β-CD on Er(Ⅲ) is mainly by the inclusion of cyclodextrin cavity, supplemented by electrostatic adsorption and chemisorption. The results of this study can provide a new method for efficient recovery of rare earth elements with low concentration in aqueous solution.

Abstract:Self-passivating W-Si-Zr alloys were prepared by mechanical alloying and spark plasma sintering. Microstructures of alloys were characterized by XRD, XPS, SEM and EPMA, and their oxidation resistance was tested. The results show that the alloy contains W-enriched, W₅Si₃, SiO_x (x=1, 1.5, 2) and ZrO_x (x=1, 1.5, 2) phases. The W₅Si₃ phase distributes continuously. SiO_x and ZrO_x particles are dispersed in the matrix with the sizes of 1.0–2.5 μm and 0.7–2.7 μm, respectively, and ZrO_x particles are often associated with SiO_x particles. The W₅Si₃ plays a key role in the oxidation resistance of the alloy. The addition of Zr contributes to the formation of W₅Si₃ phase, whose area reaches 70.2%. The oxidation rate of W-Si-Zr alloy is about 1/2 of that of W-Si alloy and 1/36 of that of pure W at 1000 ℃ in the air.

Abstract:To study the effect of Mg on super ferritic stainless steel, the content of Mg in S44660 super ferritic stainless steel was adjusted, and four kinds of test steels without Mg and with Mg additions of 0.0002%, 0.0004% and 0.0010% (mass fraction) were prepared. The effects of Mg on the cast microstructure and mechanical properties of S44660 super ferritic stainless steel were studied. The results show that the average grain size of the steel decreases from 1.14 mm to about 0.83 mm after 0.0002% Mg is added, and with the further increase in Mg content to 0.0004% and 0.0010%, the average grain size decreases to about 0.62 and 0.59 mm. It is confirmed that Mg can refine the grain of S44660 steel. Typical inclusion type of the S44660 steel is Ti-O-N composite inclusion, while it changes into Ti-O-Al-Mg-N composite inclusion after adding Mg, and the inclusion content and size decrease at the same time. The yield strength and tensile strength of the steel increase after adding Mg. Therefore, Mg can improve the impact absorption energy and hardness of S44660 super ferritic stainless steel.

Abstract:AZ91-La-Yb magnesium alloy as anode of seawater batteries was prepared by combining mechanical alloying with spark plasma sintering processes. The effects of rare earth La-Yb doping on the microstructure and electrochemical behavior of AZ91 anode were studied. The results show that the AZ91-La-Yb alloy prepared by mechanical alloying-spark plasma sintering processes consists of equiaxed grains. On the one hand, La-Yb doping results in the formation of micron-scale (0.5–2 μm) RE-rich phase that are uniformly distributed at grain boundaries. This phase is mainly composed of rare earth metals (RE=La, Yb) and Mg(RE) solid solution. On the other hand, the plastic deformation caused by discharge plasma sintering and the doping effect of rare earth elements La-Yb significantly improve the morphology of β-Mg₁₇Al₁₂ phase, transforming from a coarse network structure to a slender elongated shape. The combination of uniform distribution of nearly micron-scale RE-rich phase and the smaller β phase promotes the uniform dissolution of magnesium alloys and effectively alleviates localized corrosion of magnesium alloys. Compared to the AZ91 anode magnesium alloy, the AZ91-La-Yb alloy doped with rare earth La-Yb exhibits more stable discharge voltage and excellent discharge performance. At a current density of 20 mA/cm², its specific capacity can reach 1068 mAh/g, and the anode utilization efficiency is 50.4%.

Abstract:Brittleness of traditional Ni-Mn-Ga alloy is a marjor obstacle for its practical applications, as actuators and sensors. The Ni-rich Ni-Mn-Ga alloy can significantly improve the ductility. However, the shape memory strain is significantly reduced. Higher martensitic transformation temperature, good thermal stability and moderate shape memory property are shown in Mn-rich Ni-Mn-Ga. In the present work, microstructural feature, mechanical properties and thermal property of Ni₅₄Mn_28+xGa_18-x(x=0, 4, 7, 9, 13) were investigated. As the Mn content increases, the γ phase appears, with is a face centered tetragonal (fct) structure, and a γ grain contains a hierarchical "nano-lamellae forming within micro-lamellae" microstructure. A micro-lamella consists of two variants, each variant has a pair of nano-lamellae, and they are {011} twin related. Owing to the introduction of lamellar γ, the ductility is improved. With the increase in Mn content, the compressive stress increases from 914 MPa to 2175 MPa, and the compressive strain increases from 14% to 26%. The martensitic transformation temperature of such series of alloys increases from 352 ℃ to 585 ℃. For Mn-rich Ni-Mn-Ga alloy, the ductility improvement is inferior to that of Ni-rich alloy, but the martensitic transformation temperature is higher.

Abstract:CuW/CuCr integral materials with Cu-Cr-Zr powder interlayer was prepared by integral sintering infiltration method. The effects of Cr and Zr content and solution aging heat treatment on the microstructure and properties of the interface and both sides of the material were studied. The results show that with the increase in Zr content in Cu-15%Cr-x%Zr (mass fraction, similarly hereinafter) interlayer, the eutectic phase amount on CuCr side of the integral material increases, and the conductivity at CuCr end decreases. The hardness increases first and then decreases. At the same time, the addition of Zr promotes the diffusion of Cr into W. The tensile test bars of integral materials with different interlayers were prepared, and the interfacial tensile strength was tested and the fracture morphology was analyzed. It is found that when the Zr content in the interlayer is 0.5%, the interfacial tensile strength of the whole material reaches the maximum value of 517 MPa, which is 18% higher than that of the CuW/CuCr integral material with Cu-15%Cr interlayer without Zr. The tearing edge of Cu phase in the tensile fracture becomes shallower and shorter, and the number of cleavage fractures of W particles increases, which indicates that the interfacial strength of Cu/W phase and the end strength of CuCr are improved.

Abstract:The Cu-Ti bimetallic composites were prepared by liquid-solid composite process, and the diffusion behavior of Cu and Ti elements at the composite interface was investigated by OM, SEM, EPMA and other testing methods. The results show that the grain boundaries are the main channels for diffusion in the process of Cu/Ti composite. Except for part of the Cu₄Ti phase formed on the Cu matrix, the rest of the compound phases of the diffusively-dissolved layer are generated on the Ti matrix. The compounds generated at the Cu-Ti composite interface are Cu₄Ti, Cu₃Ti₂, CuTi and CuTi₂, where the Cu₃Ti₂ phase grows in a “jagged” manner, the CuTi phase grows in a “bamboo shoot” manner, and the CuTi₂ phase grows in a “planar” manner. The hardness values of the diffusion-dissolved layer are significantly higher than those of the two pure components. As verified by the Miedema model, the sequence of interfacial phase precipitation is CuTi, Cu₃Ti₂, CuTi₂ and Cu₄Ti. The bonding of Cu and Ti is a combined action of Cu diffusion in Ti matrix and Ti dissolution in the Cu solution.