We report on the modification of the wettability of stainless steel by picosecond laser surface microstructuring in this paper. Compared with traditional methods, picosecond laser-induced surface modification provides...We report on the modification of the wettability of stainless steel by picosecond laser surface microstructuring in this paper. Compared with traditional methods, picosecond laser-induced surface modification provides a fast and facile method for surface modification without chemical damage and environmental pollution. As a result of treatment by 100 ps laser pulses, microstructures are fabricated on the stainless steel sample surface, contributing to the increase of the contact angle from 88° to 105°, which realizes a transformation from hydrophilicity to hydrophobicity. The morphological features of fabricated microstructures are characterized by scanning electron microscopy and optical microscopy.展开更多
The influence of homogenization parameters on element segregation,dendritic structure,and the precipitate evolution in the GH3535-0.08wt%Y alloy was investigated.Additionally,some specific homogenization parameters we...The influence of homogenization parameters on element segregation,dendritic structure,and the precipitate evolution in the GH3535-0.08wt%Y alloy was investigated.Additionally,some specific homogenization parameters were maintained constant throughout the experiments.Results indicate that the heat treatment at 1150℃for 10 h is the optimal homogenization condition.Following this optimal treatment,dendrite structures and element segregation are eliminated.Furthermore,both SiC and Y_(5)Si_(3)precipitates in the as-cast alloy decrease significantly.Conversely,the homogenization at 1188℃induces overheating defects within the alloy.Although SiC and Y_(5)Si_(3)phases also decrease,some large M6C phases can still be observed,adversely affecting subsequent forging processes.展开更多
Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into...Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into the new β phase during the pulsed current-assisted aging process,and then the newly formed β phase is mainly transformed into the β_(t) phase,with occasional transition to new α_(p) phase,leading to a remarkable grain refinement,especially for the lamellarαs phases.In comparison to conventional aging treatment,the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility,yielding an excellent mechanical property combination:a yield strength of 932 MPa,a tensile strength of 1042 MPa,and an elongation of 12.2%.It is primarily ascribed to the increased fraction of β_(t) phases,the obvious grain refinement effect,and the slip block effect induced by the multiple-variantαs colonies distributed within β_(t) phases.展开更多
The combustion behavior of Ti-Al-Mo-Zr-Sn-W alloy(TC25G)was studied in a high-temperature and high-speed air flow environment using the laser ignition method combined with ultra-high temperature infrared thermometer,s...The combustion behavior of Ti-Al-Mo-Zr-Sn-W alloy(TC25G)was studied in a high-temperature and high-speed air flow environment using the laser ignition method combined with ultra-high temperature infrared thermometer,scanning electron microscope,X-ray diffractometer,and transmission electron microscope.The burn-resistant performance of TC25G and TC11 alloys was compared.Meanwhile,the microstructural characteristics,crystal structure,and formation mechanism of the combustion products of TC25G alloy were analyzed in detail.The results show that the high-temperature and high-speed air flow promotes combustion within the air flow temperature range of 200–400℃and the air flow velocity range of 0–100 m/s.The combustion path advances along the direction of the air flow.The combustion of TC25G alloy mainly relies on the diffusion of the oxygen and the expansion of the combustion area caused by the movement of the melt.Based on the microstructure and composition of combustion product,it can be divided into the combustion zone,the melting zone,and the heat affected zone.During combustion,the formation of microstructures is closely correlated with the behavior of alloying elements and their selective combination with O.The major oxidation products of Ti are TiO and TiO_(2).The oxides formed by Mo and W hinder the movement of the melt during the combustion.Al and Zr tend to undergo internal oxidation.Al_(2)O_(3)precipitates on the surface of ZrO_(2),forming a protective oxide layer that inhibits the inward diffusion of O.Moreover,the element enrichment at the interface between the melting zone and the heat affected zone increases the melting point on the solid side,hindering the migration of the solid-liquid interface.展开更多
To investigate the influence of Al-Zn-Mg-Cu alloy with as-homogenized and as-rolled initial microstructures on the tensile flow behavior,isothermal tensile tests were conducted on a GLEEBLE-3500 isothermal simulator a...To investigate the influence of Al-Zn-Mg-Cu alloy with as-homogenized and as-rolled initial microstructures on the tensile flow behavior,isothermal tensile tests were conducted on a GLEEBLE-3500 isothermal simulator at temperatures of 380-440℃and strain rates of 0.05-1 s^(−1).The Johnson-Cook model,Hensel-Spittel model,strain-compensated Arrhenius model,and critical fracture strain model were established.Results show that through the evaluation of the models using the correlation coefficient(R)and the average absolute relative error,the strain-compensated Arrhenius model can represent the flow behavior of the alloy more accurately.Shear bands are more pronounced in the as-homogenized specimens,whereas dynamic recrystallization is predominantly observed in as-rolled specimens.Fracture morphology analysis reveals that a mixed fracture mechanism is prevalent in the as-homogenized specimen,whereas a ductile fracture mechanism is predominant in the as-rolled specimen.The processing maps indicate that the unstable region is reduced in the as-rolled specimens compared with that in the as-homogenized specimens.The optimal hot working windows for the as-homogenized and as-rolled specimens are determined as 410-440℃/0.14-1 s^(−1)and 380-400℃/0.05-0.29 s^(−1),respectively.展开更多
Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate indiv...Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate individual investigation due to variations in their composition and fabrication processes.This study presents a comprehensive investigation into evolution of the mechanical properties,surface microstructure,and composition of Shicolon-Ⅱ fibers subjected to argon heat treatment at temperatures ranging from 1300℃to 1700℃.The Shicolon-Ⅱ fibers are composed of small-sized β-SiC grains,SiC_(x)O_(y) amorphous phase,and a minor amount of graphite microcrystals.Following treatment in an argon atmosphere at 1300℃,the fibers maintain a monofilament tensile strength of 3.620 GPa,corresponding to a retention of 98.32%.This strength diminishes to 2.875 GPa,equating to a retention of 78.08%,after treatment at 1500℃.The reduction in mechanical properties of the fibers can be ascribed to the decomposition of the amorphous phase and the growth of β-SiC grains.Furthermore,creep resistance is an essential factor influencing the long-term performance of composite materials.After treatment at temperatures above 1400℃,the high-temperature creep resistance of the fibers is significantly enhanced due to growth of β-SiC grains.This study offers valuable theoretical insights into high-temperature applications of second-generation fibers,contributing to an enhanced understanding of their performance under extreme conditions.展开更多
To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level ...To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level orthogonal experiment design of factor levels.Results show that through range analysis,the significance order of process parameters is determined as follows:solution cooling method>solution temperature>aging time>aging temperature>solution time.Considering the strength-ductility matching and engineering application requirements,the benchmark parameters are selected as solution time of 1 h,solution cooling method of air cooling(AC),aging temperature of 525℃,and aging time of 4 h.Furthermore,the effects of solution temperature in the range of 790–870℃ on the impact toughness and micro-fracture characteristics of the alloy were studied.The results reveal that the larger the area of shear lip and fibrous zone,and the smaller the area of radiation zone,the better the toughness of the alloy.With the increase in solution temperature,the length of secondary cracks on the fracture surface increases,the number of dimples increases,and the toughness is enhanced.Based on the collaborative optimization of strength and toughness,the optimal heat treatment process for TB18 alloy is determined as 870℃/1 h,AC+525℃/4 h,AC.展开更多
The core-shell structure in bulk TiNb binary alloy was designed and studied by phase-field simulations,where various core-shell structures were obtained by precise control of the initial and boundary conditions of the...The core-shell structure in bulk TiNb binary alloy was designed and studied by phase-field simulations,where various core-shell structures were obtained by precise control of the initial and boundary conditions of the TiNb binary alloy system during spinodal decomposition,and then the formation mechanism of core-shell structure was revealed.In addition,the influences of initial temperature gradient,average temperature,and initial concentration distribution of the system on the core-shell structure were investigated.Results show that the initial concentration gradient is the key factor for forming the core-shell structure.Besides,larger initial temperature gradient and higher average temperature can promote the formation of core-shell structure,which can be stabilized by adjusting the initial concentration distribution of the Nb-rich region in TiNb binary alloy.As a theoretical basis,this research provides a novel and simple strategy for the preparation of TiNb-based alloys and other materials with peculiar core-shell structures and desirable mechanical and physical properties.展开更多
Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively invest...Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively investigated.Macroscopic morphology,microstructure,and interfacial structure of the joints were analyzed using scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer(XRD).The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer,which acts as a bridge for deformation and diffusion.Specifically,the AZ31B/AA1060 interface exhibits a typical wavy morphology,and a transition zone exists at the joint interface,which may result in an extremely complex microstructure.The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys,and it is identified as brittle intermetallic compounds(IMCs)Al_(3)Mg_(2) and Al_(12)Mg_(17).The transition zone is mainly distributed on the Al side,with the maximum thickness of Al-side transition layer reaching approximately 13.53μm.Incomplete melting layers with varying thicknesses are observed at the primary weld interface,while micron-sized hole defects appear in the transition zone of the secondary weld interface.The AA1060/DC56D interface is mainly straight,with only a small number of discontinuous transition zones distributed intermittently along the interface.These transition zones are characterized by the presence of the brittle IMC FeAl_(3),with a maximum thickness of about 4μm.展开更多
Refractory metals,including tungsten(W),tantalum(Ta),molybdenum(Mo),and niobium(Nb),play a vital role in industries,such as nuclear energy and aerospace,owing to their exceptional melting temperatures,thermal durabili...Refractory metals,including tungsten(W),tantalum(Ta),molybdenum(Mo),and niobium(Nb),play a vital role in industries,such as nuclear energy and aerospace,owing to their exceptional melting temperatures,thermal durability,and corrosion resistance.These metals have body-centered cubic crystal structure,characterized by limited slip systems and impeded dislocation motion,resulting in significant low-temperature brittleness,which poses challenges for the conventional processing.Additive manufacturing technique provides an innovative approach,enabling the production of intricate parts without molds,which significantly improves the efficiency of material usage.This review provides a comprehensive overview of the advancements in additive manufacturing techniques for the production of refractory metals,such as W,Ta,Mo,and Nb,particularly the laser powder bed fusion.In this review,the influence mechanisms of key process parameters(laser power,scan strategy,and powder characteristics)on the evolution of material microstructure,the formation of metallurgical defects,and mechanical properties were discussed.Generally,optimizing powder characteristics,such as sphericity,implementing substrate preheating,and formulating alloying strategies can significantly improve the densification and crack resistance of manufactured parts.Meanwhile,strictly controlling the oxygen impurity content and optimizing the energy density input are also the key factors to achieve the simultaneous improvement in strength and ductility of refractory metals.Although additive manufacturing technique provides an innovative solution for processing refractory metals,critical issues,such as residual stress control,microstructure and performance anisotropy,and process stability,still need to be addressed.This review not only provides a theoretical basis for the additive manufacturing of high-performance refractory metals,but also proposes forward-looking directions for their industrial application.展开更多
Due to the high efficiency,no pollution,fuel flexibility and high temperature,solid oxide fuel cell(SOFC)is expected to be applied in aeronautical hybrid power system.In this paper,a 3D mesoscopic mod⁃el was establish...Due to the high efficiency,no pollution,fuel flexibility and high temperature,solid oxide fuel cell(SOFC)is expected to be applied in aeronautical hybrid power system.In this paper,a 3D mesoscopic mod⁃el was established for SOFC heterogeneous anode.The microstructure of Ni and gadolinium-doped ceria(GDC)anode was generated via Quartet Structure Generation Set(QSGS)method.The mesoscopic model of mass trans⁃fer,charge transfer and reacting flow was built based on lattice Boltzmann method(LBM).The simulation results agreed with the experimental data from reference under 650℃and 0.1 MPa.Meanwhile,the influence of leakage current on open circuit voltage cannot be ignored,which indicates the necessity of adding electron barrier layer.Higher inlet pressure was simulated in order to predict the performance under aeronautical conditions,which shows significant benefit for the performance.The reaction current density increases by 59%,107%and 147%for inlet pressure of 0.2 MPa,0.3 MPa and 0.4 MPa under polarization of 0.161 V.The reaction current shows a significant nonlinear distribution along the thickness direction,and the current density increases faster near the electrolyte.Under the same total polarization,the activation polarization decreases with the increase of inlet pres⁃sure,while the ohmic polarization is opposite.展开更多
Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely us...Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely used in fields such as injection molding,die casting,and stamping dies.Adding reinforcing particles into steel is an effective means to improve its performance.Nb/18Ni300 composites were fabricated by LPBF using two kinds of Nb powders with different particle sizes,and their microstructures and properties were studied.The results show that the unmelted Nb particles are uniformly distributed in the 18Ni300 matrix and the grains are refined,which is particularly pronounced with fine Nb particles.In addition,element diffusion occurs between the particles and the matrix.The main phases of the base alloy are α-Fe and a small amount of γ-Fe.With the addition of Nb,part of the α-Fe is transformed into γ-Fe,and unmelted Nb phases appear.The addition of Nb also enhances the hardness and wear resistance of the composites but slightly reduces their tensile properties.After aging treatment,the molten pools and grain boundaries become blurred,grains are further refined,and the interfaces around the particles are thinned.The aging treatment also promotes the formation of reverted austenite.The hardness,ultimate tensile strength,and volumetric wear rate of the base alloy reach 51.9 HRC,1704 MPa,and 17.8×10^(-6) mm^(3)/(N·m),respectively.In contrast,the sample added with fine Nb particles has the highest hardness(56.1 HRC),ultimate tensile strength(1892 MPa)and yield strength(1842 MPa),and the volume wear rate of the sample added with coarse Nb particles is reduced by 90%to 1.7×10^(-6) mm^(3)/(N·m).展开更多
A multi-physics approach was used to quantify the effect of process parameters (laser power, scanning speed, hatch spacing, and scanning strategy) on the thermal history and corresponding microstructure evolution of T...A multi-physics approach was used to quantify the effect of process parameters (laser power, scanning speed, hatch spacing, and scanning strategy) on the thermal history and corresponding microstructure evolution of Ti-25Nb (at%) alloy during the dual-track selective laser melting (SLM) process. Simulation results reveal that during the dual-track SLM process, increasing laser power results in greater thermal accumulation, leading to a molten pool of larger volume and coarser grains. Reducing scanning speed enhances remelting and promotes cellular growth at the top of molten pool, whereas faster scanning speed leads to rougher melt tracks and finer grains. Notably, hatch spacing significantly influences the molten pool dimensions and microstructures, and smaller hatch spacing promotes remelting. Furthermore, the orientations of grains in the second track during zigzag scanning differ markedly from those in the first track. More importantly, compared with those after the first track, both the temperature gradient and cooling rate at the boundaries of remelting molten pool are reduced after the second track scanning, resulting in slower interface velocity and significant change in solidification microstructure. This research provides a theoretical foundation for controlling non-equilibrium microstructure and offering novel insights into the optimization of SLM process parameters of titanium alloys.展开更多
In current research,Li_(2)O-Al_(2)O_(3)-SiO_(2)glass-ceramics were prepared by conventional meltquenching and subsequent heat treatment method.The effect of Al_(2)O_(3)content on microstructures,thermal properties,cry...In current research,Li_(2)O-Al_(2)O_(3)-SiO_(2)glass-ceramics were prepared by conventional meltquenching and subsequent heat treatment method.The effect of Al_(2)O_(3)content on microstructures,thermal properties,crystallization behaviours and mechanical properties were investigated.FTIR,Raman spectroscopy and nuclear magnetic resonance spectroscopy microstructure analysis showed that the silico-oxygen network was damaged,while the increase of[AlO_(4)]content repaired the glass network,and finally made the glass network have better connectivity,with the decrease of SiO_(2).The thermal analysis confirmed the increasing glass transition and crystallization temperatures from growing Al_(2)O_(3)content.In addition,different crystal phases can be precipitated in the glass matrix,such as LiAlSi_(4)O_(10),Li_(2)Si_(2)O_(5) in glass with low Al_(2)O_(3)content,the combination of Li_xAl_xSi_(1-x)O_(2),LiAlSi_(3)O_(8),Li_(2)SiO_(3)in glass with intermediate Al_(2)O_(3)content,and the combination of LiAlSi_(2)O_(6),SiO_(2)in glass with high Al_(2)O_(3)content.The hardness of as-prepared glass gradually increases with the increase of the Al_(2)O_(3)content.The Vickers hardness of the glass-ceramics is highly dependent on the Al_(2)O_(3)content in the glass and the heat treatment temperatures,reaching a maximum of 10.11 GPa.Scanning electron microscope images show that the crystals change from spherical to massive and finally to sheet.The change of glass structure,crystal phase and morphology is the main reason for the different mechanical properties.展开更多
Fiber-optic sensing technology has the advantages of passivity, anti-electromagnetic interference, longdistancemeasurement, high sensitivity and high accuracy, small size, and adaptability to harsh environments such a...Fiber-optic sensing technology has the advantages of passivity, anti-electromagnetic interference, longdistancemeasurement, high sensitivity and high accuracy, small size, and adaptability to harsh environments such ashigh-vacuum, high-pressure, and strong magnetic fields compared with the traditional electrical sensing technology.However, with the increasing application requirements, how to further improve the sensitivity of fiber-optic sensors,extend the detection limit and improve the maintenance-free capability has become one of the core issues of thecurrent research. This paper reviews the principle, preparation, and application of fiber-optic microstructured sensingbased on abrupt field type. It specifically outlines the development and applications of micro-nano optical fibers,photonic crystal optical fibers, optical fiber gratings and structured optical fibers, and lists the main preparationmethods of two types of micro-nano optical fibers from the basic theory of optical fiber microstructured sensordevices.展开更多
Mg-18Zn-3Y alloy containing an icosahedral quasicrystal phase(I-phase)was prepared using the ordinary solidification method.After solid solution treatment at 320 and 420℃,indentation creep tests were conducted for th...Mg-18Zn-3Y alloy containing an icosahedral quasicrystal phase(I-phase)was prepared using the ordinary solidification method.After solid solution treatment at 320 and 420℃,indentation creep tests were conducted for the Mg matrix and the I-phase in different solid solution states in Mg-18Zn-3Y alloy using the indentation technique with a Berkovich indenter.The quasicrystalline phases with stripy and skeletal structures were identified through the microscopic observation and energy spectrum analysis.The results indicate that the elastic modulus,microhardness,and creep stress index of the I-phase in the alloy initially increase and then decrease with increasing solution temperature.The elastic modulus and microhardness of theα-Mg alloy are the highest in the as-cast state,and the creep stress index increases with increasing solution temperature.This study provides a practical basis for microstructure measurement of quasicrystalline creep.展开更多
Introducing Ti_(2)AlC particles into TiAl alloys can effectively improve their strength,but this can also lead to stress concentration at the interface,resulting in the reduction of ductility.Therefore,Mn is adopted t...Introducing Ti_(2)AlC particles into TiAl alloys can effectively improve their strength,but this can also lead to stress concentration at the interface,resulting in the reduction of ductility.Therefore,Mn is adopted to synergistically improve the strength and ductility of the Ti_(2)AlC/TiAl composite through solid solution and interface manipulation.The first-principles calculation shows the Ti-Mn bonds are formed at the Ti_(2)AlC/TiAl interface after Mn doping,characterized primarily by metallic bonds with some covalent bonding.This combination preserves strength while enhancing ductility.Then,Ti_(2)AlC/TiAl-Mn composite is prepared.The Ti_(2)AlC,with an average size of 1.6μm,is uniformly distributed within the TiAl matrix.Mn doping reduces the lamellar colony size and lamellar thickness by 25.1%and 27.4%,respectively.A small quantity of Mn accumulates at the boundaries of the lamellar colonies.The Mn content must be controlled to avoid segregation,which may negatively impact performance.The yield stress,ultimate compressive stress,fracture strain,and product of strength and plasticity of the Ti_(2)AlC/TiAl-Mn composite have been increased by 5.5%,11.5%,10.4%,and 23.0%,respectively,compared to those of the Ti_(2)AlC/TiAl composite.The enhancement in strength is due to the combined effects of grain refinement,solid solution of Mn,and twining strengthening.Grain refinement and twin strengthening also can reduce stress concentration and improve ductility.In addition,at the electronic level,the Ti-Mn bond formed at the interface is contributed to the improvement of ductility.展开更多
To comprehensively explore the impact of binder content on the mechanical properties of the Polymer bonded explosive(PBX)substitute material(Polymer-bonded Analogue Explosive(PAE)—it is renowned for its outstanding h...To comprehensively explore the impact of binder content on the mechanical properties of the Polymer bonded explosive(PBX)substitute material(Polymer-bonded Analogue Explosive(PAE)—it is renowned for its outstanding high-temperature resistance,exceptional mechanical properties,excellent chemical stability,and superior electrical insulation),a series of experiments are meticulously carried out.The dynamic and static mechanical properties,along with the microstructure of PAE,are precisely measured through the Split Hopkinson Pressure Bar(SHPB)test,static compression tests,and Scanning Electron Microscopy(SEM).The dynamic performance test outcomes clearly indicate that both the binder content(2%,4%,6%)and temperature(25℃,45℃,70℃)exert a substantial influence on the dynamic mechanical properties of PAE.Specifically,as the binder content increases,the elasticmodulus increases,demonstrating higher stiffness,and the longer failure duration represents a prolonged fracture process rather than an improved deformation strain to failure.This means the strength-related stiffness rises with binder content,but the overall ductility does not increase.Notably,PAE with 2%the Ethylene-Vinyl Acetate Copolymer(EVA)—it bonds well with a variety ofmaterials,such asmetal,wood,and plastic—exhibits distinct plastic deformation behavior,while PAE samples with 4%and 6%EVA display evident brittle fracture characteristics.Additionally,the mechanical properties of PAE are highly sensitive to temperature variations.Among the tested temperatures,PAE showcases the most favorable performance at 45℃.The static performance test results reveal that an increment in binder content effectively helps to reduce the temperature sensitivity of temperature(-40℃,25℃,50℃,70℃)on PAE and enhance its static mechanical properties.The maximum compressive strength gradually diminishes as the temperature rises.However,it should be noted that an excessively high binder content will undermine the mechanical properties of PAE.With the increase in binder content,the compressive modulus demonstrates relatively stable changes under both lowtemperature and high-temperature conditions.The SEM analysis results demonstrate that,aside fromthe initial defects inherent in the material preparation process,the components of PAE are firmly combined.Throughout the tests,no new pores or microcracks emerge,which strongly indicates that the mechanical properties of PAE remain stable.展开更多
Heterogeneous nucleation,characterized by its low nucleation barrier and controllable nucleation sites,has been widely employed to manipulate the microstructures and properties of metallic materials.In recent years,th...Heterogeneous nucleation,characterized by its low nucleation barrier and controllable nucleation sites,has been widely employed to manipulate the microstructures and properties of metallic materials.In recent years,the dispersion of inclusions,carbides,and microstructure refinement in steel have emerged as one of the key research directions in the development of high-quality steel.The current research status regarding the regulation of inclusions,carbides,and microstructures in steel through heterogeneous nucleation are reviewed.The key points and challenges in refining the second phase and microstructure in steel using inclusion particles are highlighted,aiming to provide inspiration and references for future scholars.Deoxidized inclusions,when refined and dispersed,exhibit favorable lattice matching with second phases(e.g.,nitrides,sulfides,carbides)in steel.This characteristic serves as the fundamental mechanism for achieving refinement of the second phase.Concurrently,the solid-solution alloying effect from deoxidizing metals contributes to second-phase refinement,an aspect that requires prioritized investigation.In addition to the single heterogeneous nucleation refinement effect,the two-stage heterogeneous nucleation refinement of the second phase and microstructure offers a new approach for follow-up research.Notably,second-phase particles added as heterogeneous nucleation sites via external addition often require surface modification to ensure their stable retention in steel at high temperatures,which remains a major challenge restricting the widespread application of this method.Currently,the explanation of heterogeneous nucleation phenomena primarily relies on empirical calculations of lattice mismatch between the substrate and the nucleating phase,which cannot fully elucidate the quantitative relationship on the interface between the substrate and the nucleation phase.On this basis,quantifying the electronic structure and nucleation barrier at the interface between the substrate and the nucleation phase is a critical direction worthy of increased attention in the future.展开更多
A critical scientific gap exists in quantifying the intrinsic mechanisms of shale mechanical property degradation induced by the combined effects of perforation(impact)and acidization—two core techniques for shale re...A critical scientific gap exists in quantifying the intrinsic mechanisms of shale mechanical property degradation induced by the combined effects of perforation(impact)and acidization—two core techniques for shale reservoir permeability enhancement.To address this gap,this study proposed an innovative coupled experimental framework integrating dynamic-static cyclic loading(to simulate perforation impact)and acid erosion.Static uniaxial compression tests were performed on treated damaged shale samples,with microstructural characterization via X-ray diffraction(XRD)and scanning electron microscopy(SEM).Key findings include:(1)The damage factor(characterized by longitudinal wave velocity)showed a significant positive correlation with acid concentration;(2)Combined damage(impact+acidization)caused far more severe mechanical deterioration than single damage modes—for instance,samples under combined damage with 20%hydrochloric acid exhibited a strength reduction to 158.97 MPa,with sharp decreases in peak strength and elastic modulus;(3)Damage reduced total energy and elastic strain energy of samples while increasing dissipated energy proportion,leading to more developed internal fractures and severe failure in combined damage samples;(4)Acidization promoted sample fragmentation into smaller debris,resulting in significantly higher fractal dimensions of acidized shale than other damage types under the same acid concentration;(5)XRD and SEM analyses confirmed that high-concentration acid erosion reduced shale carbonate content,and the synergy of mechanical pre-damage and chemical dissolution in combined damage accelerated acid-rock reactions,significantly increasing micro-interfacial pores and degrading shale structural integrity.This study’s innovation lies in establishing a coupled experimental framework that reproduces the actual“perforation-acidization”sequence,quantitatively revealing the synergistic degradation mechanism of shale mechanical properties under combined damage—providing a novel theoretical basis for optimizing shale reservoir stimulation parameters.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 61178024 and 11374316)partially supported by the National Basic Research Program of China (Grant No.2011CB808103)
文摘We report on the modification of the wettability of stainless steel by picosecond laser surface microstructuring in this paper. Compared with traditional methods, picosecond laser-induced surface modification provides a fast and facile method for surface modification without chemical damage and environmental pollution. As a result of treatment by 100 ps laser pulses, microstructures are fabricated on the stainless steel sample surface, contributing to the increase of the contact angle from 88° to 105°, which realizes a transformation from hydrophilicity to hydrophobicity. The morphological features of fabricated microstructures are characterized by scanning electron microscopy and optical microscopy.
基金National Natural Science Foundation of China(51801227,52071331)。
文摘The influence of homogenization parameters on element segregation,dendritic structure,and the precipitate evolution in the GH3535-0.08wt%Y alloy was investigated.Additionally,some specific homogenization parameters were maintained constant throughout the experiments.Results indicate that the heat treatment at 1150℃for 10 h is the optimal homogenization condition.Following this optimal treatment,dendrite structures and element segregation are eliminated.Furthermore,both SiC and Y_(5)Si_(3)precipitates in the as-cast alloy decrease significantly.Conversely,the homogenization at 1188℃induces overheating defects within the alloy.Although SiC and Y_(5)Si_(3)phases also decrease,some large M6C phases can still be observed,adversely affecting subsequent forging processes.
基金National Key Research and Development Program of China(2021YFB3700801)。
文摘Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into the new β phase during the pulsed current-assisted aging process,and then the newly formed β phase is mainly transformed into the β_(t) phase,with occasional transition to new α_(p) phase,leading to a remarkable grain refinement,especially for the lamellarαs phases.In comparison to conventional aging treatment,the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility,yielding an excellent mechanical property combination:a yield strength of 932 MPa,a tensile strength of 1042 MPa,and an elongation of 12.2%.It is primarily ascribed to the increased fraction of β_(t) phases,the obvious grain refinement effect,and the slip block effect induced by the multiple-variantαs colonies distributed within β_(t) phases.
基金China“Ye Qisun”Science Foundation Project of National Natural Science Foundation(U2141222)Innovation Fund(8F231527Z)。
文摘The combustion behavior of Ti-Al-Mo-Zr-Sn-W alloy(TC25G)was studied in a high-temperature and high-speed air flow environment using the laser ignition method combined with ultra-high temperature infrared thermometer,scanning electron microscope,X-ray diffractometer,and transmission electron microscope.The burn-resistant performance of TC25G and TC11 alloys was compared.Meanwhile,the microstructural characteristics,crystal structure,and formation mechanism of the combustion products of TC25G alloy were analyzed in detail.The results show that the high-temperature and high-speed air flow promotes combustion within the air flow temperature range of 200–400℃and the air flow velocity range of 0–100 m/s.The combustion path advances along the direction of the air flow.The combustion of TC25G alloy mainly relies on the diffusion of the oxygen and the expansion of the combustion area caused by the movement of the melt.Based on the microstructure and composition of combustion product,it can be divided into the combustion zone,the melting zone,and the heat affected zone.During combustion,the formation of microstructures is closely correlated with the behavior of alloying elements and their selective combination with O.The major oxidation products of Ti are TiO and TiO_(2).The oxides formed by Mo and W hinder the movement of the melt during the combustion.Al and Zr tend to undergo internal oxidation.Al_(2)O_(3)precipitates on the surface of ZrO_(2),forming a protective oxide layer that inhibits the inward diffusion of O.Moreover,the element enrichment at the interface between the melting zone and the heat affected zone increases the melting point on the solid side,hindering the migration of the solid-liquid interface.
文摘To investigate the influence of Al-Zn-Mg-Cu alloy with as-homogenized and as-rolled initial microstructures on the tensile flow behavior,isothermal tensile tests were conducted on a GLEEBLE-3500 isothermal simulator at temperatures of 380-440℃and strain rates of 0.05-1 s^(−1).The Johnson-Cook model,Hensel-Spittel model,strain-compensated Arrhenius model,and critical fracture strain model were established.Results show that through the evaluation of the models using the correlation coefficient(R)and the average absolute relative error,the strain-compensated Arrhenius model can represent the flow behavior of the alloy more accurately.Shear bands are more pronounced in the as-homogenized specimens,whereas dynamic recrystallization is predominantly observed in as-rolled specimens.Fracture morphology analysis reveals that a mixed fracture mechanism is prevalent in the as-homogenized specimen,whereas a ductile fracture mechanism is predominant in the as-rolled specimen.The processing maps indicate that the unstable region is reduced in the as-rolled specimens compared with that in the as-homogenized specimens.The optimal hot working windows for the as-homogenized and as-rolled specimens are determined as 410-440℃/0.14-1 s^(−1)and 380-400℃/0.05-0.29 s^(−1),respectively.
基金National Natural Science Foundation of China(52172108)National Key R&D Program of China(2022YFB3707700)Strategic Priority Research Program of the Chinese Academy of Sciences(XDC0144005)。
文摘Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate individual investigation due to variations in their composition and fabrication processes.This study presents a comprehensive investigation into evolution of the mechanical properties,surface microstructure,and composition of Shicolon-Ⅱ fibers subjected to argon heat treatment at temperatures ranging from 1300℃to 1700℃.The Shicolon-Ⅱ fibers are composed of small-sized β-SiC grains,SiC_(x)O_(y) amorphous phase,and a minor amount of graphite microcrystals.Following treatment in an argon atmosphere at 1300℃,the fibers maintain a monofilament tensile strength of 3.620 GPa,corresponding to a retention of 98.32%.This strength diminishes to 2.875 GPa,equating to a retention of 78.08%,after treatment at 1500℃.The reduction in mechanical properties of the fibers can be ascribed to the decomposition of the amorphous phase and the growth of β-SiC grains.Furthermore,creep resistance is an essential factor influencing the long-term performance of composite materials.After treatment at temperatures above 1400℃,the high-temperature creep resistance of the fibers is significantly enhanced due to growth of β-SiC grains.This study offers valuable theoretical insights into high-temperature applications of second-generation fibers,contributing to an enhanced understanding of their performance under extreme conditions.
基金Key Program of National Natural Science Foundation of China(52431001)。
文摘To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level orthogonal experiment design of factor levels.Results show that through range analysis,the significance order of process parameters is determined as follows:solution cooling method>solution temperature>aging time>aging temperature>solution time.Considering the strength-ductility matching and engineering application requirements,the benchmark parameters are selected as solution time of 1 h,solution cooling method of air cooling(AC),aging temperature of 525℃,and aging time of 4 h.Furthermore,the effects of solution temperature in the range of 790–870℃ on the impact toughness and micro-fracture characteristics of the alloy were studied.The results reveal that the larger the area of shear lip and fibrous zone,and the smaller the area of radiation zone,the better the toughness of the alloy.With the increase in solution temperature,the length of secondary cracks on the fracture surface increases,the number of dimples increases,and the toughness is enhanced.Based on the collaborative optimization of strength and toughness,the optimal heat treatment process for TB18 alloy is determined as 870℃/1 h,AC+525℃/4 h,AC.
基金National Natural Science Foundation of China(12372152)Guangdong Basic and Applied Basic Research Foundation(2023A1515011819,2024A1515012469)Shandong Provincial Natural Science Foundation(ZR2023MA058)。
文摘The core-shell structure in bulk TiNb binary alloy was designed and studied by phase-field simulations,where various core-shell structures were obtained by precise control of the initial and boundary conditions of the TiNb binary alloy system during spinodal decomposition,and then the formation mechanism of core-shell structure was revealed.In addition,the influences of initial temperature gradient,average temperature,and initial concentration distribution of the system on the core-shell structure were investigated.Results show that the initial concentration gradient is the key factor for forming the core-shell structure.Besides,larger initial temperature gradient and higher average temperature can promote the formation of core-shell structure,which can be stabilized by adjusting the initial concentration distribution of the Nb-rich region in TiNb binary alloy.As a theoretical basis,this research provides a novel and simple strategy for the preparation of TiNb-based alloys and other materials with peculiar core-shell structures and desirable mechanical and physical properties.
文摘Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively investigated.Macroscopic morphology,microstructure,and interfacial structure of the joints were analyzed using scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer(XRD).The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer,which acts as a bridge for deformation and diffusion.Specifically,the AZ31B/AA1060 interface exhibits a typical wavy morphology,and a transition zone exists at the joint interface,which may result in an extremely complex microstructure.The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys,and it is identified as brittle intermetallic compounds(IMCs)Al_(3)Mg_(2) and Al_(12)Mg_(17).The transition zone is mainly distributed on the Al side,with the maximum thickness of Al-side transition layer reaching approximately 13.53μm.Incomplete melting layers with varying thicknesses are observed at the primary weld interface,while micron-sized hole defects appear in the transition zone of the secondary weld interface.The AA1060/DC56D interface is mainly straight,with only a small number of discontinuous transition zones distributed intermittently along the interface.These transition zones are characterized by the presence of the brittle IMC FeAl_(3),with a maximum thickness of about 4μm.
基金National MCF Energy R&D Program(2024YFE03260300)。
文摘Refractory metals,including tungsten(W),tantalum(Ta),molybdenum(Mo),and niobium(Nb),play a vital role in industries,such as nuclear energy and aerospace,owing to their exceptional melting temperatures,thermal durability,and corrosion resistance.These metals have body-centered cubic crystal structure,characterized by limited slip systems and impeded dislocation motion,resulting in significant low-temperature brittleness,which poses challenges for the conventional processing.Additive manufacturing technique provides an innovative approach,enabling the production of intricate parts without molds,which significantly improves the efficiency of material usage.This review provides a comprehensive overview of the advancements in additive manufacturing techniques for the production of refractory metals,such as W,Ta,Mo,and Nb,particularly the laser powder bed fusion.In this review,the influence mechanisms of key process parameters(laser power,scan strategy,and powder characteristics)on the evolution of material microstructure,the formation of metallurgical defects,and mechanical properties were discussed.Generally,optimizing powder characteristics,such as sphericity,implementing substrate preheating,and formulating alloying strategies can significantly improve the densification and crack resistance of manufactured parts.Meanwhile,strictly controlling the oxygen impurity content and optimizing the energy density input are also the key factors to achieve the simultaneous improvement in strength and ductility of refractory metals.Although additive manufacturing technique provides an innovative solution for processing refractory metals,critical issues,such as residual stress control,microstructure and performance anisotropy,and process stability,still need to be addressed.This review not only provides a theoretical basis for the additive manufacturing of high-performance refractory metals,but also proposes forward-looking directions for their industrial application.
文摘Due to the high efficiency,no pollution,fuel flexibility and high temperature,solid oxide fuel cell(SOFC)is expected to be applied in aeronautical hybrid power system.In this paper,a 3D mesoscopic mod⁃el was established for SOFC heterogeneous anode.The microstructure of Ni and gadolinium-doped ceria(GDC)anode was generated via Quartet Structure Generation Set(QSGS)method.The mesoscopic model of mass trans⁃fer,charge transfer and reacting flow was built based on lattice Boltzmann method(LBM).The simulation results agreed with the experimental data from reference under 650℃and 0.1 MPa.Meanwhile,the influence of leakage current on open circuit voltage cannot be ignored,which indicates the necessity of adding electron barrier layer.Higher inlet pressure was simulated in order to predict the performance under aeronautical conditions,which shows significant benefit for the performance.The reaction current density increases by 59%,107%and 147%for inlet pressure of 0.2 MPa,0.3 MPa and 0.4 MPa under polarization of 0.161 V.The reaction current shows a significant nonlinear distribution along the thickness direction,and the current density increases faster near the electrolyte.Under the same total polarization,the activation polarization decreases with the increase of inlet pres⁃sure,while the ohmic polarization is opposite.
基金Key-Area Research and Development Program of Guangdong Province(2023B0909020004)Project of Innovation Research Team in Zhongshan(CXTD2023006)+1 种基金Natural Science Foundation of Guangdong Province(2023A1515011573)Zhongshan Social Welfare Science and Technology Research Project(2024B2022)。
文摘Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely used in fields such as injection molding,die casting,and stamping dies.Adding reinforcing particles into steel is an effective means to improve its performance.Nb/18Ni300 composites were fabricated by LPBF using two kinds of Nb powders with different particle sizes,and their microstructures and properties were studied.The results show that the unmelted Nb particles are uniformly distributed in the 18Ni300 matrix and the grains are refined,which is particularly pronounced with fine Nb particles.In addition,element diffusion occurs between the particles and the matrix.The main phases of the base alloy are α-Fe and a small amount of γ-Fe.With the addition of Nb,part of the α-Fe is transformed into γ-Fe,and unmelted Nb phases appear.The addition of Nb also enhances the hardness and wear resistance of the composites but slightly reduces their tensile properties.After aging treatment,the molten pools and grain boundaries become blurred,grains are further refined,and the interfaces around the particles are thinned.The aging treatment also promotes the formation of reverted austenite.The hardness,ultimate tensile strength,and volumetric wear rate of the base alloy reach 51.9 HRC,1704 MPa,and 17.8×10^(-6) mm^(3)/(N·m),respectively.In contrast,the sample added with fine Nb particles has the highest hardness(56.1 HRC),ultimate tensile strength(1892 MPa)and yield strength(1842 MPa),and the volume wear rate of the sample added with coarse Nb particles is reduced by 90%to 1.7×10^(-6) mm^(3)/(N·m).
基金Guangdong Basic and Applied Basic Research Foundation (2024A1515011873)Shenzhen Basic Research Project (JCYJ20241202123504007)Shenzhen Science and Technology Innovation Commission (KJZD20240903101400001, KJZD20240903102006009)。
文摘A multi-physics approach was used to quantify the effect of process parameters (laser power, scanning speed, hatch spacing, and scanning strategy) on the thermal history and corresponding microstructure evolution of Ti-25Nb (at%) alloy during the dual-track selective laser melting (SLM) process. Simulation results reveal that during the dual-track SLM process, increasing laser power results in greater thermal accumulation, leading to a molten pool of larger volume and coarser grains. Reducing scanning speed enhances remelting and promotes cellular growth at the top of molten pool, whereas faster scanning speed leads to rougher melt tracks and finer grains. Notably, hatch spacing significantly influences the molten pool dimensions and microstructures, and smaller hatch spacing promotes remelting. Furthermore, the orientations of grains in the second track during zigzag scanning differ markedly from those in the first track. More importantly, compared with those after the first track, both the temperature gradient and cooling rate at the boundaries of remelting molten pool are reduced after the second track scanning, resulting in slower interface velocity and significant change in solidification microstructure. This research provides a theoretical foundation for controlling non-equilibrium microstructure and offering novel insights into the optimization of SLM process parameters of titanium alloys.
基金Funded by the National Key Research Program(No.2024-1129-954-112)National Natural Science Foundation of China(No.52372033)Guangxi Science and Technology Major Program(No.AA24263054)。
文摘In current research,Li_(2)O-Al_(2)O_(3)-SiO_(2)glass-ceramics were prepared by conventional meltquenching and subsequent heat treatment method.The effect of Al_(2)O_(3)content on microstructures,thermal properties,crystallization behaviours and mechanical properties were investigated.FTIR,Raman spectroscopy and nuclear magnetic resonance spectroscopy microstructure analysis showed that the silico-oxygen network was damaged,while the increase of[AlO_(4)]content repaired the glass network,and finally made the glass network have better connectivity,with the decrease of SiO_(2).The thermal analysis confirmed the increasing glass transition and crystallization temperatures from growing Al_(2)O_(3)content.In addition,different crystal phases can be precipitated in the glass matrix,such as LiAlSi_(4)O_(10),Li_(2)Si_(2)O_(5) in glass with low Al_(2)O_(3)content,the combination of Li_xAl_xSi_(1-x)O_(2),LiAlSi_(3)O_(8),Li_(2)SiO_(3)in glass with intermediate Al_(2)O_(3)content,and the combination of LiAlSi_(2)O_(6),SiO_(2)in glass with high Al_(2)O_(3)content.The hardness of as-prepared glass gradually increases with the increase of the Al_(2)O_(3)content.The Vickers hardness of the glass-ceramics is highly dependent on the Al_(2)O_(3)content in the glass and the heat treatment temperatures,reaching a maximum of 10.11 GPa.Scanning electron microscope images show that the crystals change from spherical to massive and finally to sheet.The change of glass structure,crystal phase and morphology is the main reason for the different mechanical properties.
基金support by National Natural Science Foundation of China (Nos. 51606158, 12104402)
文摘Fiber-optic sensing technology has the advantages of passivity, anti-electromagnetic interference, longdistancemeasurement, high sensitivity and high accuracy, small size, and adaptability to harsh environments such ashigh-vacuum, high-pressure, and strong magnetic fields compared with the traditional electrical sensing technology.However, with the increasing application requirements, how to further improve the sensitivity of fiber-optic sensors,extend the detection limit and improve the maintenance-free capability has become one of the core issues of thecurrent research. This paper reviews the principle, preparation, and application of fiber-optic microstructured sensingbased on abrupt field type. It specifically outlines the development and applications of micro-nano optical fibers,photonic crystal optical fibers, optical fiber gratings and structured optical fibers, and lists the main preparationmethods of two types of micro-nano optical fibers from the basic theory of optical fiber microstructured sensordevices.
基金Funded by the National Natural Science Foundation of China(Nos.12462007 and 12072166)the Inner Mongolia Autonomous Region Science and Technology Plan Project(No.2021GG0254)the Inner Mongolia Autonomous Region's Science and Technology'Breakthrough'Project(No.2025KJTW0019)。
文摘Mg-18Zn-3Y alloy containing an icosahedral quasicrystal phase(I-phase)was prepared using the ordinary solidification method.After solid solution treatment at 320 and 420℃,indentation creep tests were conducted for the Mg matrix and the I-phase in different solid solution states in Mg-18Zn-3Y alloy using the indentation technique with a Berkovich indenter.The quasicrystalline phases with stripy and skeletal structures were identified through the microscopic observation and energy spectrum analysis.The results indicate that the elastic modulus,microhardness,and creep stress index of the I-phase in the alloy initially increase and then decrease with increasing solution temperature.The elastic modulus and microhardness of theα-Mg alloy are the highest in the as-cast state,and the creep stress index increases with increasing solution temperature.This study provides a practical basis for microstructure measurement of quasicrystalline creep.
基金supported by the National Natural Science Foundation of China(Nos.52371031 and 52574435)the Science and Technology Development Program of Jilin Province,China(No.20250102103JC)+2 种基金the Science and Technology Development Program of Changchun City,China(No.23JQ03)Changbaishan Laboratory,China(No.CBS2025004-03)the Undergraduate Innovation Fund of Jilin University,China(No.S202410183310).
文摘Introducing Ti_(2)AlC particles into TiAl alloys can effectively improve their strength,but this can also lead to stress concentration at the interface,resulting in the reduction of ductility.Therefore,Mn is adopted to synergistically improve the strength and ductility of the Ti_(2)AlC/TiAl composite through solid solution and interface manipulation.The first-principles calculation shows the Ti-Mn bonds are formed at the Ti_(2)AlC/TiAl interface after Mn doping,characterized primarily by metallic bonds with some covalent bonding.This combination preserves strength while enhancing ductility.Then,Ti_(2)AlC/TiAl-Mn composite is prepared.The Ti_(2)AlC,with an average size of 1.6μm,is uniformly distributed within the TiAl matrix.Mn doping reduces the lamellar colony size and lamellar thickness by 25.1%and 27.4%,respectively.A small quantity of Mn accumulates at the boundaries of the lamellar colonies.The Mn content must be controlled to avoid segregation,which may negatively impact performance.The yield stress,ultimate compressive stress,fracture strain,and product of strength and plasticity of the Ti_(2)AlC/TiAl-Mn composite have been increased by 5.5%,11.5%,10.4%,and 23.0%,respectively,compared to those of the Ti_(2)AlC/TiAl composite.The enhancement in strength is due to the combined effects of grain refinement,solid solution of Mn,and twining strengthening.Grain refinement and twin strengthening also can reduce stress concentration and improve ductility.In addition,at the electronic level,the Ti-Mn bond formed at the interface is contributed to the improvement of ductility.
文摘To comprehensively explore the impact of binder content on the mechanical properties of the Polymer bonded explosive(PBX)substitute material(Polymer-bonded Analogue Explosive(PAE)—it is renowned for its outstanding high-temperature resistance,exceptional mechanical properties,excellent chemical stability,and superior electrical insulation),a series of experiments are meticulously carried out.The dynamic and static mechanical properties,along with the microstructure of PAE,are precisely measured through the Split Hopkinson Pressure Bar(SHPB)test,static compression tests,and Scanning Electron Microscopy(SEM).The dynamic performance test outcomes clearly indicate that both the binder content(2%,4%,6%)and temperature(25℃,45℃,70℃)exert a substantial influence on the dynamic mechanical properties of PAE.Specifically,as the binder content increases,the elasticmodulus increases,demonstrating higher stiffness,and the longer failure duration represents a prolonged fracture process rather than an improved deformation strain to failure.This means the strength-related stiffness rises with binder content,but the overall ductility does not increase.Notably,PAE with 2%the Ethylene-Vinyl Acetate Copolymer(EVA)—it bonds well with a variety ofmaterials,such asmetal,wood,and plastic—exhibits distinct plastic deformation behavior,while PAE samples with 4%and 6%EVA display evident brittle fracture characteristics.Additionally,the mechanical properties of PAE are highly sensitive to temperature variations.Among the tested temperatures,PAE showcases the most favorable performance at 45℃.The static performance test results reveal that an increment in binder content effectively helps to reduce the temperature sensitivity of temperature(-40℃,25℃,50℃,70℃)on PAE and enhance its static mechanical properties.The maximum compressive strength gradually diminishes as the temperature rises.However,it should be noted that an excessively high binder content will undermine the mechanical properties of PAE.With the increase in binder content,the compressive modulus demonstrates relatively stable changes under both lowtemperature and high-temperature conditions.The SEM analysis results demonstrate that,aside fromthe initial defects inherent in the material preparation process,the components of PAE are firmly combined.Throughout the tests,no new pores or microcracks emerge,which strongly indicates that the mechanical properties of PAE remain stable.
基金supported by the National Natural Science Foundation of China(No.52304358)Young Elite Scientists Sponsorship Program by CAST(No.YESS20230462).
文摘Heterogeneous nucleation,characterized by its low nucleation barrier and controllable nucleation sites,has been widely employed to manipulate the microstructures and properties of metallic materials.In recent years,the dispersion of inclusions,carbides,and microstructure refinement in steel have emerged as one of the key research directions in the development of high-quality steel.The current research status regarding the regulation of inclusions,carbides,and microstructures in steel through heterogeneous nucleation are reviewed.The key points and challenges in refining the second phase and microstructure in steel using inclusion particles are highlighted,aiming to provide inspiration and references for future scholars.Deoxidized inclusions,when refined and dispersed,exhibit favorable lattice matching with second phases(e.g.,nitrides,sulfides,carbides)in steel.This characteristic serves as the fundamental mechanism for achieving refinement of the second phase.Concurrently,the solid-solution alloying effect from deoxidizing metals contributes to second-phase refinement,an aspect that requires prioritized investigation.In addition to the single heterogeneous nucleation refinement effect,the two-stage heterogeneous nucleation refinement of the second phase and microstructure offers a new approach for follow-up research.Notably,second-phase particles added as heterogeneous nucleation sites via external addition often require surface modification to ensure their stable retention in steel at high temperatures,which remains a major challenge restricting the widespread application of this method.Currently,the explanation of heterogeneous nucleation phenomena primarily relies on empirical calculations of lattice mismatch between the substrate and the nucleating phase,which cannot fully elucidate the quantitative relationship on the interface between the substrate and the nucleation phase.On this basis,quantifying the electronic structure and nucleation barrier at the interface between the substrate and the nucleation phase is a critical direction worthy of increased attention in the future.
基金funded by the National Natural Science Foundation of China(No.52474120)the National Key Research and Development Program of China—2023 Key Special Project(No.2023YFC2907400)+1 种基金the Fundamental Research Funds for the Central Universities(No.2023CXQD045)the Hunan Provincial Natural Science Foundation for Distinguished Young Scholars(No.2023JJ10072).
文摘A critical scientific gap exists in quantifying the intrinsic mechanisms of shale mechanical property degradation induced by the combined effects of perforation(impact)and acidization—two core techniques for shale reservoir permeability enhancement.To address this gap,this study proposed an innovative coupled experimental framework integrating dynamic-static cyclic loading(to simulate perforation impact)and acid erosion.Static uniaxial compression tests were performed on treated damaged shale samples,with microstructural characterization via X-ray diffraction(XRD)and scanning electron microscopy(SEM).Key findings include:(1)The damage factor(characterized by longitudinal wave velocity)showed a significant positive correlation with acid concentration;(2)Combined damage(impact+acidization)caused far more severe mechanical deterioration than single damage modes—for instance,samples under combined damage with 20%hydrochloric acid exhibited a strength reduction to 158.97 MPa,with sharp decreases in peak strength and elastic modulus;(3)Damage reduced total energy and elastic strain energy of samples while increasing dissipated energy proportion,leading to more developed internal fractures and severe failure in combined damage samples;(4)Acidization promoted sample fragmentation into smaller debris,resulting in significantly higher fractal dimensions of acidized shale than other damage types under the same acid concentration;(5)XRD and SEM analyses confirmed that high-concentration acid erosion reduced shale carbonate content,and the synergy of mechanical pre-damage and chemical dissolution in combined damage accelerated acid-rock reactions,significantly increasing micro-interfacial pores and degrading shale structural integrity.This study’s innovation lies in establishing a coupled experimental framework that reproduces the actual“perforation-acidization”sequence,quantitatively revealing the synergistic degradation mechanism of shale mechanical properties under combined damage—providing a novel theoretical basis for optimizing shale reservoir stimulation parameters.
