- Ei，ESCI收录期刊
- 中国科学引文数据库(CSCD)核心期刊
- 中文核心期刊
- 文摘与引文数据库(Scopus)
- 剑桥科学文摘(CSA)
As a common additive manufacturing （AM） technology， selective laser melting （SLM） is a great potential manufacturing technology for special-shaped parts，such as porous and thin-walled parts. However， the traditional single beam SLM technology develops slowly due to the problems of lesser forming size and inferior efficiency. On the basis of single-beam SLM， multi-beam selective laser melting （MB-SLM） uses multiple beams and multiple galvanometers to partition scan and perform overlap forming. It greatly improves the forming size and efficiency， perfectly solves the inherent problems of single-beam SLM，and is expected to become an emerging technology to expand the application of metal additive manufacturing. The research progress of multi-beam selective laser melting in forming principle， forming equipment， and formation and control of defects is reviewed. The microstructures and mechanical properties of different alloys manufactured by multi-beam selective laser melting are summarized. Importantly， the main strategies to control defects and mechanical properties are highlighted. Finally， the development trends are forecasted， such as the impact of temporal and spatial difference characteristics between multi-beam on mechanical properties， and the consistency change of process parameters between different regions to reduce defects of formed parts.
The pulsed magnetic field treatment technology has the advantages of indirect contact， low energy consumption， green environmental protection， etc.， and has important application prospects in the metal material strengthening. This study summarizes the research status of pulsed magnetic field treatment technology in the strengthening mechanism， numerical simulation， and practical application of metal materials， and puts forward the bottleneck of pulsed magnetic field treatment technology that needs to be broken through. As a kind of high-field strength and periodic magnetic field， the pulsed magnetic field has an obvious strengthening effect on the solid phase transformation and liquid phase transformation of metal materials. The pulsed magnetic field can change the texture and magnetic domain of metal for the solid phase transformation. It can impel dislocations to spread and multiply， speed up the formation of the second phase， and control the order of exudates. During the liquid phase transition， the pulsed magnetic field can provide nucleation energy， break up coarse dendrites， restraint the growth of twisted dendrites， uniform the solute distribution， and eventually enhance the properties of metal. Numerical simulation can reproduce the changes in magnetic field， force， and internal structure in the process of pulsed magnetic field treatment， which provides an important basis for exploring the mechanism of pulsed magnetic field treatment. The strengthening effect of the pulsed magnetic field treatment mainly depends on the magnetic field intensity， pulse duty cycle， and action time of the magnetic field， and one of the key parts of pulsed magnetic field treatment is parameters optimization by numerical simulation. At present， the pulsed magnetic field treatment technology has been applied to cutting tools， coating fabrication， and metal casting. To widen the application of pulsed magnetic field treatment technology， special attention should be paid to strengthening mechanisms， parameter optimization， and device miniaturization in further research of pulsed magnetic field treatment.
3D printing， as a new manufacturing technology， has been widely applied in the forming and manufacturing of various materials with enormous development prospects. Graphite has excellent high-temperature resistance， conductivity， thermal conductivity， thermal stability， and chemical stability， widely used in fields such as metallurgy， energy industry， aerospace， and nuclear industry. Using graphite and its composite materials as the matrix and 3D printing technology to produce graphite products can reduce the graphite production cycle， improve material utilization， reduce graphite dust pollution， and provide an efficient and economical comprehensive solution for personalized customization and industrial application of high-performance and complex shaped graphite. This article focuses on the 3D printing technology of graphite and its composite materials， analyzes and discusses the advantages and disadvantages of each technology， introduces the performance and application of graphite products formed by 3D printing， discusses the opportunities and challenges of graphite and its composite materials in the development process of 3D printing， and puts forward expectations and prospects for this. The development of graphite 3D printing technology needs to develop the types of expansion of graphite composite materials and new printing equipment and its supporting equipment， and conduct 3D printed graphite post -processing technology based on traditional graphite process.
The thermoplastic composites have advantages in excellent fatigue resistance， short forming cycle， secondary processing， weldable and no storage condition restrictions， it is significant to study the preparation and forming method of thermoplastic prepreg to realize the engineering preparation of thermoplastic composites and meet the application requirements of aerospace， rail transit， and other fields. In this paper， the preparation process of continuous fiber reinforced thermoplastic prepreg is introduced in detail， including solution impregnation， melt impregnation， film lamination， powder impregnation， suspension hot melt， and fiber mixing. At the same time， the thermoplastic composite molding process is emphatically discussed， including hot pressing molding， winding molding， automatic laying molding， in-situ consolidation molding and 3D printing molding. Meanwhile， the feasibility of the engineering application is sorted out according to the characteristics of each prepreg preparation and molding process. Finally， the future trends of thermoplastic composite are prospected， and development suggestions are given.
The selective laser melted （SLM） GH4169 superalloy has a significant directional columnar dendritic solidification microstructure， which can cause severe mechanical property anisotropy and increase service risk. The GH4169 superalloy prepared by laser selective melting （SLM） technology is taken as the research object， and two different heat treatment processes are designed： hot isostatic pressing+standard solid solution+double aging and hot isostatic pressing+homogenization heat treatment+standard solid solution+double aging for post-heat treatment of the prepared alloy. The effect of two heat treatment processes on the anisotropy of microstructure and high-temperature tensile properties of GH4169 superalloy prepared by laser selective melting is investigated. The results show that the homogenization heat treatment eliminates the Laves phase， and the columnar crystal structure of the as-built GH4169 alloy transforms into an equiaxed crystal structure. The high-temperature tensile results show that the high-temperature tensile strength ratio and plasticity ratio of GH4169 alloy in the transverse and longitudinal directions without homogenization treatment are 1.10（1145/1040） and 0.83（10.2/12.2）， respectively. The high-temperature tensile strength ratio and plasticity ratio of GH4169 alloy in the transverse and longitudinal directions after homogenization heat treatment are 1.00（1041/1038） and 1.00（8.6/8.6）， respectively. The anisotropy of microstructure and mechanical properties of GH4169 alloy prepared by laser selective melting is eliminated.
An inclined seeding method for Ni-based single crystal superalloy with a specific orientation is presented. The evolution of solidification microstructure and its mechanism are studied during the preparation of single crystals by this method through experiment and numerical simulation. The principle of controlling the crystal orientation of single crystal castings by inclined seeding crystals is discussed. The results show that single crystal castings with specific orientations can be produced by changing the orientation relationship between the 〈001〉 orientation seed and the casting. During the preparation process of single crystal， the seed is partially un-melted， and the un-melted interface is perpendicular to the seed axial. The melting alloy grows epitaxially along the un-melted seed to form a single crystal casting during the directional solidification process.
During the horizontal continuous casting process， a network of hard and brittle Sn-rich phase is formed at the edges of tin phosphorus bronze casting billet due to inverse segregation， which becomes crack sources during rolling and continuously propagates to induce significant edge cracks in the strip. To solve this problem， the graphite mold structure is improved， and the cooling intensity distribution law of the billet is adjusted to slow down the serious inverse segregation phenomenon caused by excessive cooling of the billet edge. Numerical simulation and experimental verification show that after the optimization of the mold structure， the thickness gradient of the air gap between the side of the billet and the mold is reduced， the solidification shrinkage of the mushy zone is more gentle； the liquid phase surface is more straight， the angle between the liquid phase and the mushy zone is reduced by 18.3°， and the solidification position difference between the middle and the side of the billet is reduced by 18.62 mm. In addition， the billet grain tends to be equiaxial， the Sn-rich phase is transformed from the inter-crystalline stripe to the point distribution， the degree of inverse segregation is reduced. The degree of inverse segregation is reduced， the content of Sn-rich phases in the inverse segregation layer is reduced by 2.3%， and the width of the inverse segregation layer is reduced by 214 μm. The number of cracks at the edge of the rough rolled strip is reduced from 21 before the structural optimization to 4.
The elastic limit is a critical parameter in spring design， which has a significant impact on the spring characteristic. The influence of cold drawing on the strength， elastic limit， elastic after-effect， and microstructure of 07Cr17Ni7Al ultrafine wire with a diameter of 0.3 mm for valve springs is investigated using room temperature tensile tests， single arm bending method， optical microscope（OM）， X-ray diffraction（XRD） and scanning electron microscope（SEM）. Different mathematical models are used to fit and analyze the deformation and martensite content， deformation-elastic limit， and stress-elastic after-effect. The results show that the solid solution 07Cr17Ni7Al wire is composed of austenite and a small amount of ferrite. Cold drawing transforms austenite into martensite， the content of deformation-induced martensite （DIM） increases with increasing deformation. The relationship between DIM content and cold-drawn equivalent strain （η） conforms to the Olson-Cohen model. When η reaches 1.64， the DIM content is about 92%， and the DIM reaches saturation. The tensile strength of wire exhibits a linear relationship with η， and the larger the deformation， the higher the tensile strength. The relationship between the elastic limit and the η follows an “S” shaped curve and conforms to the DoseResp model. The elastic limit increases with increasing deformation. When the η reaches 1.64 or more， the elastic limit tends to be gentle. The elastic after-effect increases with increasing stress， which conforms to the PWL2 model. There exists a “critical stress for elastic after-effect”. When the stress exceeds this critical value， the rate of elastic after-effect increases by 2-11 times with increasing stress. When the η is 1.64-2.41， the 07Cr17Ni7Al wire has good mechanical and elastic properties.
The development of advanced aero-engines with high thrust-to-weight ratios in the future has an urgent need for new high-performance lightweight high-temperature compressor blisks. Laser additive manufacturing TC25G-TiAl4822 gradient structure material is an important material system for the blisk of the lightweight high-temperature compressor. The composition selection and solidification structure research of gradient transition layer alloy have a key influence on guiding the structural performance design of related components. To understand the solidification structure evolution behavior of （1-x）TC25G-xTiAl4822 transition layer alloy with the change of TiAl4822 pre-alloyed powder content in powder raw materials， two kinds of single raw material （TC25G or TiAl4822） alloy ingots and alloy ingots with nine kinds of mixed raw materials are prepared by laser melting technology. Material characterization equipment and hardness measurement devices such as optical microscope， scanning electron microscope， XRD， and TEM are used for the study. The research results show that with the increase of the content of TiAl4822 alloy powder in the raw material， the characteristics of solidified grains change to dendrite → equiaxed → dendrite. The microstructure of the alloy at room temperature changes as follows： αp+αs+β+α2→αp+ αs+α2+β/B2 → α+α2+β/B2 → α2+B2 → α2+γ+B2 → α2+γ. Due to the change of the phase content of different alloy compositions， the Vickers hardness of the matrix first increases and then decreases， the overall hardness value changes in the range of about 450-620HV when the powder proportion is 50%-70%. If the intermediate composition alloy is directly used as the transition layer， the hardness will suddenly change. Therefore， the selection of the transition layer alloy composition should consider the range close to pure TC25G or TiAl4822.The above results provide the basis for the composition selection of bimetallic transition layer alloys to avoid the intermediate proportion of powder content range.
As-deposited parts of 2024 aluminum alloy are fabricated by cold metal transfer and pulse （CMT+P） hybrid wire arc additive manufacturing. The distributions of pore defects， grain morphology， and secondary phase precipitation of CMT+P wire arc additive manufacturing 2024 aluminum alloy， and the influence of different process parameters on pore defects， grain morphology and secondary phase precipitation， and corrosion resistance are investigated. The results show that the pores of the as-deposited parts of 2024 aluminum alloy are mainly distributed near the fusion line. In the same heat input， the larger wire feed speed and travel speed result in higher porosity. In a deposition layer， the upper part is the equiaxed grain without preferred orientation， and the lower part is the columnar grain with preferred orientation. In the same heat input， the texture is weakened and the percentage of equiaxed grains is increased due to the fine grain region in the higher wire feed speed and travel speed. The precipitated secondary phases are mainly Al2CuMg， Al2Cu， and rich-Fe， Mn phases. The secondary phases distribute continuously along the grain boundaries. In the early stage of corrosion， the main factor affecting the corrosion resistance of as-deposited parts is the precipitation amount of Al2CuMg. The better local corrosion resistance is mainly caused by lower Al2CuMg phase fraction in lower wire feed speed and travel speed.
The microwave absorption performances of different contents and superimposed layers of large sheet reduced graphene oxide （rGO） absorbers have been studied， and the rGO is obtained from the thermal reduction of graphene oxide by the improved Hummers method. The calculated results indicate that the absorption performance is first enhanced and then weakened with the increased rGO content. When the mass fraction of rGO is 1.0% and the thickness is 2.2 mm， the effective absorption bandwidth （EAB，≤-10 dB） reaches 5.4 GHz （12.0-17.4 GHz）. When the mass fraction of rGO is 1.5% and the thickness is 1.8 mm， the EAB reaches 5.0 GHz （13.0-18.0 GHz）. Because the EAB of the single-layer rGO absorbing material is narrow， an improved genetic algorithm has been used to optimize the EAB of multi-layer superimposed rGO absorbing material， with the different content rGO absorbing material as the material library. The EAB of multi-layer rGO absorbing material is significantly improved after optimization. The 3-layer rGO absorbing material with a thickness of 3.94 mm exhibits the widest EAB of 11.5 GHz （6.5-18.0 GHz）. This study greatly improves the ultra-wide band absorption performance of graphene， which has important scientific significance and engineering value.
To improve the comprehensive mechanical properties of selective laser melting （SLM） TA15 alloy， the microstructure and mechanical properties of SLM TA15 alloy are studied under annealing conditions of 800 ℃+air cooling， 950 ℃+air cooling， and 1050 ℃+air cooling. The microstructure characteristics of TA15 alloy under annealing conditions are characterized by electron backscatter diffraction. The results show that the orientation and texture of the α phase are not changed after the heat treatment at 800 ℃ or 950 ℃， showing the characteristics of a net basket structure. After the heat treatment at 1050 ℃， the texture with the maximum strength of 9.18 appears along the direction ［0001］， showing the characteristic of the weistenite structure. With the increase of annealing temperature： the width of both α' and α phase increases gradually； the aspect ratio of both α' and α phase increases first and then decreases； the geometrically necessary dislocation density of both α' and α phase decreases gradually； the Vickers hardness of the sample decreases first and then increases， with the highest Vickers hardness of （397.2±10）HV for the unheat treated sample； the strength of TA15 sample decreases gradually； and the elongation increases first and then decreases. After tensile tests， the unheat treated samples show mixed fracture characteristics， the samples treated at 800 ℃ and 900 ℃ show plastic fracture characteristics， and the sample treated at 1050 ℃ show brittle fracture characteristics.
To promote the large-scale commercial application of fuel cells， efficient， stable， and low-cost oxygen reduction reaction （ORR） catalysts should be developed. In this study， a Fe-doped ZIF-8 is used as the precursor， and the Fe-N-C non-precious metal catalyst is obtained by ball milling， calcination under a high-temperature argon atmosphere， pickling， and secondary calcination under an ammonia atmosphere. The results of various characterization methods show that Fe atoms are uniformly dispersed on the nitrogen-doped carbon framework， thus forming abundant Fe-N x active sites. The electrochemical performance test results show that the Fe-N-C-5% catalyst with optimized preparation process and metal contents exhibits excellent ORR activity in 0.1 mol/L HClO4 acidic solution， with a half-wave potential of 0.845 V. Meantime， it has good stability， and the half-wave potential does not drop significantly after 20000 cycles. These results provide an effective strategy for the rational design of precious metal-free ORR catalysts in the future.
The long-term oxidation resistance of TiC ceramics is a key parameter for their application in aerospace industries and must be carefully evaluated at high temperatures and various airflow environments. TiC single-phase ceramics are prepared by hot-pressed sintering. The non-isothermal oxidation properties of TiC ceramics from room temperature to 1500 ℃ are analyzed by thermogravimetry-differential scanning calorimeter （TG-DSC） thermal analyzer. The isothermal oxidation properties of TiC ceramics in different environments （temperature： 1000，1200，1500 ℃， atmosphere： static air， one-way air flow， low oxygen partial pressure air flow） are analyzed by a tubular oxidation furnace， and its oxidation rate is characterized by monitoring the change in mass per unit area. The results show that the diffusion activation energy of TiC ceramics at 1200-1500 ℃ is about 378.78 kJ/mol， and the reaction activation energy is about 17.82 kJ/mol. TiC ceramics have a three-layer structure of TiO2 oxide layer， TiC x O y interlayer and TiC substrate after oxidation. The results of oxidation kinetics indicate that the oxidation rate is controlled by reaction rate at 1200 ℃， and is controlled by oxygen diffusion at 1500 ℃. At 1000 ℃， the oxidation rate in the initial stage （the first 100 min） is controlled by diffusion， then by reaction. In the low oxygen partial pressure air flow environment， the reaction rate and diffusion rate of high-temperature molecular oxygen oxidation of TiC ceramics are both inhibited， and a relatively dense TiO2 oxide layer can be formed.
The nickel foam （the average pore diameter is about 2.7 mm，and the porosity is 93.1%） is used for the epoxy resin to coat the pore-struts， and the porous nickel foam/epoxy resin composite is obtained with such pore-struts as a multi-layer structure. The compression performance experiments are conducted on the obtained composite samples， and the mechanical strength is emphatically analyzed. The results show that the compressive strength and the specific strength of the composite samples are both significantly higher than those of the original nickel foam， respectively. When the nickel foam （with a bulk density of about 0.6 g·cm-3） is coated to make nickel foam/resin composite samples （with a bulk density of about 0.72-0.82 g·cm-3）， the compressive strength increases from 0.75 MPa to 2.24-2.68 MPa， and the specific strength increases from 1.23 MPa·cm3·g-1 to 3.09-3.27 MPa·cm3·g-1. The relationship between compressive strength and porosity of composite samples conforms to the corresponding mathematical relationship based on the octahedral model theory. According to the relevant mechanical model， the overall failure of the composite samples is caused by the priority failure of the pore-strut core.
With the development of heavy-duty gas turbines， its gas inlet temperature keeps increasing， and the traditional YSZ coatings could not service above 1200 ℃. The LaMgAl11O19（LMA） and YSZ coatings are fabricated byair plasma spray method， and the static oxidation tests are carried out at 1100 ℃ and 1300 ℃. The porosity， microstructure， and phase transformation process are investigated comparatively by SEM and XRD. The results show that the porosity of LMA coatings increases with the sintering time increasing at 1100 ℃ and 1300 ℃， while the porosity of YSZ coatings decreases obviously. The amorphous phase of LMA coatings is transformed rapidly at high temperatures. The needle-like grain at LMA coating fracture is formed， and the grain growth becomes platelet-shaped grains with the sintering time increasing， which improves the sintering resistance of LMA coatings. The results of YSZ coatings Rietveld refinement show that the content of the T′ phase decreases from 82.67% to 27.69% with the sintering time increasing to 1000 h at 1300 ℃. Meanwhile， the content of the C phase rises from 1.50% to 46.84%， and the M phase increases from 0.19% to 15.39%. This phase transformation causes volume transformation， which generates large residual stress，leading to the coating falling off.
The effects of different heat treatment processes on the anisotropy of TB6 titanium alloy fabricated by laser deposition manufacturing were investigated.The evolution of microstructure was analyzed by using optical microscope （OM）， scanning electron microscope （SEM）， and transmission electron microscope （TEM）. The variation trend and influence mechanism of anisotropy with heat treatment were investigated. The present research shows that the original β grains and the morphology of the primary α phase （αp phase） are greatly affected by the thermal gradient. The original β grains in the microstructure of TB6 titanium alloy fabricated by laser deposition manufacturing are elongated along the deposition direction and are ellipsoidal. In addition， the relative slender αp phase parallel to the deposition direction is found. These two factors jointly lead to the anisotropy of room temperature tensile property of the as-deposited samples. The tensile strength in the vertical deposition direction （X-direction ） is 7.3% higher， the yield strength is 5% higher， and the elongation is 32.4% lower than that in the deposition direction （Z-direction）. The low-temperature annealing treatment has little effect on microstructure， only the anisotropy of plasticity is decreased. After high-temperature annealing treatment， the difference in aspect ratio of αp phase is significantly reduced， leading to the anisotropy of the room temperature tensile property decreases. The strength are still higher in the X-direction， and the elongation is higher in the Z-direction. The strengthening mechanism of the solution-aging treating sample is completely changed due to the precipitation of the secondary α phase （αs phase）. In addition， there is no obvious preferential growth of αs phase after heat treatment， so the anisotropy of the room temperature tensile property tends to be eliminated as the strength increases.
Ultrathin-gauge non-oriented silicon steel sheets are produced by both one-stage and two-stage cold-rolling processes.The effects of rolling and annealing on the evolution of microstructure， texture， mechanical， and magnetic properties are investigated. It is found that the microstructure resulting from one-stage cold-rolling primarily comprised fibrous deformation structures， resulting in refined grain size after final recrystallization. Notably， the ｛001｝〈110〉 and ｛223｝〈110〉 textures persisted in the low-temperature recrystallized state，which is inherited from cold-rolled sheets. Conversely， during high-temperature annealing， a notable texture transformation occurs， with the α* and γ textures emerging as the dominant features. The two-stage cold-rolling method promotes the formation of shear bands， leading to a larger grain size in the final annealed structure. These shear bands served as crucial nucleation sites for Goss grains， thereby facilitating the development of Goss texture during the annealing process. Furthermore， the ｛001｝〈110〉 texture aligned along the λ orientation line towards the ｛001｝〈010〉 texture， accompanied by a gradual decrease in the intensity of the γ texture. As the annealing temperature increases， the iron loss initially decreases rapidly and slowly， whereas the magnetic induction intensity initially rises before stabilizing. Compared with the one-stage cold-rolling method， the ultrathin-gauge non-oriented silicon steel prepared by the two-stage cold-rolling method has lower iron loss and higher magnetic induction intensity. This superior performance can be attributed to the formation of shear bands， which enhance the formation of favorable Goss and Cube textures， the suppression of detrimental γ texture， and the attainment of a larger recrystallized grain size.With increasing the annealing temperature， the yield strength of both the one-stage and two-stage cold-rolling annealed sheets initially decreases dramatically before trending to be stabilized. The yield strength of ultra-thin non-oriented silicon steel produced by the one-stage cold-rolling method is higher than that produced by two-stage cold-rolling. The optimal comprehensive properties （both mechanical and magnetic properties） are achieved through a two-stage cold-rolling process followed by annealing at 800 ℃， which yields a mid/high frequency-iron loss P 10/400 of 12.34 W/kg， P of 36.12 W/kg， a magnetic induction intensity B 50 of 1.71 T and a yield strength of 389 MPa.
To investigate the applicability and temperature dependence of several commonly used constitutive models of rubber materials for seismic isolation bearings in our country at low temperatures， uniaxial tensile tests are conducted on four different formulations of rubber materials used in seismic isolation bearings. These tests are performed at temperatures ranging from 23 ℃ to -60 ℃. The material parameters of seven constitutive models are determined using the least squares fitting method， and their suitability at low temperatures is analyzed. Additionally， ABAQUS software is employed to conduct uniaxial tensile simulations of the four rubber materials at various temperatures， aiming to verify parameter accuracy and assess model convergence for each constitutive model. The results demonstrate that the Yeoh model exhibits superior stability and computational accuracy compared to other constitutive models at temperatures ranging from 23 ℃ to -40 ℃. However， at -60 ℃， the rubber material undergoes complete solidification， and none of the seven constitutive models considered in this study accurately capture its mechanical characteristics. Consequently， by investigating the temperature dependency of the Yeoh model， this study proposes a functional expression incorporating temperature effects. This expression enables the predicting of mechanical properties for rubber materials with similar shear modulus at different temperatures.
Due to the increasing interference and pollution of electromagnetic radiation， there is an urgent need for lightweight and low-cost electromagnetic absorbing materials. In this study， carbon fiber Co/C functional composites with Co nanoparticle coatings are prepared. Among them， ZIF-67 particles are in-situ grown on the surface of cosmetic cotton， and then the lightweight Co/C precursor is prepared by direct carbonization method. The SEM image shows that the Co particles are uniformly distributed on the surface of the carbon fiber， and the uniformly distributed cobalt nanoparticles provide a magnetic coupling network and form a rich non-homogeneous interface with the carbon fiber， enhancing the interfacial polarization， and benefiting the broadband absorption behavior of the composite. The test results show that the thickness of Co/C-650 material is only 1.5 mm， the minimum reflection loss at 17.76 GHz is -42.03 dB， the effective absorption bandwidth is up to 3.68 GHz， and the radar cross section value is up to -26.8 dB·m2. This excellent electromagnetic wave absorption performance is attributed to the dielectric loss by interfacial polarization， magnetic loss by magnetic resonance， and multiple reflections and scatterings in the micro- and nano-level fiber structure. This study provides an idea for preparing ultralight， low-cost， sustainable microwave absorbers with excellent electromagnetic wave absorption capability.
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