The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,a...The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,and high-cycle fatigue properties,were studied.The results showed that the LSP induced residual compressive stresses on the surface and near surface of the material.The maximum surface residual compressive stress was−661 MPa,and the compressive-stress-affected depth was greater than 1000μm.The roughness and Vickers micro-hardness increased with the number of shocks,and the maximum hardness-affected depth was about 700μm after three LSP treatments.LSP enhanced the fraction of low-angle grain boundaries,changed the grain preferred orientations,and notably increased the pole density ofαphase on the near surface from 2.41 to 3.46.The surface hardness values of the LSP samples increased with the increase of the number of shocks due to work hardening,while the LSP had a limited effect on the tensile properties.The high-cycle fatigue life of the LSP-treated sample was significantly enhanced by more than 20%compared with that of the untreated sample,which was caused by the suppression of the initiation and propagation of fatigue cracks.展开更多
This work reveals the significant effects of cobalt(Co)on the microstructure and impact toughness of as-quenched highstrength steels by experimental characterizations and thermo-kinetic analyses.The results show that ...This work reveals the significant effects of cobalt(Co)on the microstructure and impact toughness of as-quenched highstrength steels by experimental characterizations and thermo-kinetic analyses.The results show that the Co-bearing steel exhibits finer blocks and a lower ductile-brittle transition temperature than the steel without Co.Moreover,the Co-bearing steel reveals higher transformation rates at the intermediate stage with bainite volume fraction ranging from around 0.1 to 0.6.The improved impact toughness of the Co-bearing steel results from the higher dense block boundaries dominated by the V1/V2 variant pair.Furthermore,the addition of Co induces a larger transformation driving force and a lower bainite start temperature(BS),thereby contributing to the refinement of blocks and the increase of the V1/V2 variant pair.These findings would be instructive for the composition,microstructure design,and property optimization of high-strength steels.展开更多
Smart manufacturing and Industry 4.0 are transforming traditional manufacturing processes by utilizing innovative technologies such as the artificial intelligence(AI)and internet of things(IoT)to enhance efficiency,re...Smart manufacturing and Industry 4.0 are transforming traditional manufacturing processes by utilizing innovative technologies such as the artificial intelligence(AI)and internet of things(IoT)to enhance efficiency,reduce costs,and ensure product quality.In light of the recent advancement of Industry 4.0,identifying defects has become important for ensuring the quality of products during the manufacturing process.In this research,we present an ensemble methodology for accurately classifying hot rolled steel surface defects by combining the strengths of four pre-trained convolutional neural network(CNN)architectures:VGG16,VGG19,Xception,and Mobile-Net V2,compensating for their individual weaknesses.We evaluated our methodology on the Xsteel surface defect dataset(XSDD),which comprises seven different classes.The ensemble methodology integrated the predictions of individual models through two methods:model averaging and weighted averaging.Our evaluation showed that the model averaging ensemble achieved an accuracy of 98.89%,a recall of 98.92%,a precision of 99.05%,and an F1-score of 98.97%,while the weighted averaging ensemble reached an accuracy of 99.72%,a recall of 99.74%,a precision of 99.67%,and an F1-score of 99.70%.The proposed weighted averaging ensemble model outperformed the model averaging method and the individual models in detecting defects in terms of accuracy,recall,precision,and F1-score.Comparative analysis with recent studies also showed the superior performance of our methodology.展开更多
Densely distributed coherent nanoparticles(DCN)in steel matrix can enhance the work-hardening ability and ductility of steel simultaneously.All the routes to this end can be generally classified into the liquid-solid ...Densely distributed coherent nanoparticles(DCN)in steel matrix can enhance the work-hardening ability and ductility of steel simultaneously.All the routes to this end can be generally classified into the liquid-solid route and the solid-solid route.However,the formation of DCN structures in steel requires long processes and complex steps.So far,obtaining steel with coherent particle enhancement in a short time remains a bottleneck,and some necessary steps remain unavoidable.Here,we show a high-efficiency liquid-phase refining process reinforced by a dynamic magnetic field.Ti-Y-Mn-O particles had an average size of around(3.53±1.21)nm and can be obtained in just around 180 s.These small nanoparticles were coherent with the matrix,implying no accumulated dislocations between the particles and the steel matrix.Our findings have a potential application for improving material machining capacity,creep resistance,and radiation resistance.展开更多
Carbon can change the phase components of low-density steels and influence the mechanical properties.In this study,a new method to control the carbon content and avoid the formation ofδ-ferrite by decarburization tre...Carbon can change the phase components of low-density steels and influence the mechanical properties.In this study,a new method to control the carbon content and avoid the formation ofδ-ferrite by decarburization treatment was proposed.The microstructural changes and mechanical characteristics with carbon content induced by decarburization were systematically examined.Crussard-Jaoul(C-J)analysis was employed to examine the work hardening characteristics during the tensile test.During decarburization by heat treatments,the carbon content within the austenite phase decreased,while Mn and Al were almost unchanged;this made the steel with full austenite transform into the austenite and ferrite dual phase.Meanwhile,(Ti,V)C carbides existed in both matrix phase and the mole fraction almost the same.In addition,the formation of other carbides restrained.Carbon loss induced a decrease in strength due to the weakening of the carbon solid solution.For the steel with the single austinite,the deformation mode of austenite was the dislocation planar glide,resulting in the formation of microbands.For the dual-phase steel,the deformation occurred by the dislocation planar glide of austenite first,with the increase in strain,the cross slip of ferrite took place,forming dislocation cells in ferrite.At the late stage of deformation,the work hardening of austinite increased rapidly,while that of ferrite increased slightly.展开更多
Martensite is an important microstructure in ultrahigh-strength steels,and enhancing the strength of martensitic steels often involves the introduction of precipitated phases within the martensitic matrix.Despite cons...Martensite is an important microstructure in ultrahigh-strength steels,and enhancing the strength of martensitic steels often involves the introduction of precipitated phases within the martensitic matrix.Despite considerable research efforts devoted to this area,a systematic summary of these advancements is lacking.This review focuses on the precipitates prevalent in ultrahigh-strength martensitic steel,primarily carbides(e.g.,MC,M_(2)C,and M_(3)C)and intermetallic compounds(e.g.,Ni Al,Ni_(3)X,and Fe_(2)Mo).The precipitation-strengthening effect of these precipitates on ultrahigh-strength martensitic steel is discussed from the aspects of heat treatment processes,microstructure of precipitate-strengthened martensite matrix,and mechanical performance.Finally,a perspective on the development of precipitation-strengthened martensitic steel is presented to contribute to the advancement of ultrahigh-strength martensitic steel.This review highlights significant findings,ongoing challenges,and opportunities in the development of ultrahigh-strength martensitic steel.展开更多
The influence of Nb-V microalloying on the hot deformation behavior and microstructures of medium Mn steel(MMS)was investigated by uniaxial hot compression tests.By establishing the constitutive equations for simulati...The influence of Nb-V microalloying on the hot deformation behavior and microstructures of medium Mn steel(MMS)was investigated by uniaxial hot compression tests.By establishing the constitutive equations for simulating the measured flow curves,we successfully constructed deformation activation energy(Q)maps and processing maps for identifying the region of flow instability.We concluded the following consequences of Nb-V alloying for MMS.(i)The critical strain increases and the increment diminishes with the increasing deformation temperature,suggesting that NbC precipitates more efficiently retard dynamic recrystallization(DRX)in MMS compared with solute Nb.(ii)The deformation activation energy of MMS is significantly increased and even higher than that of some reported high Mn steels,suggesting that its ability to retard DRX is greater than that of the high Mn content.(iii)The hot workability of MMS is improved by narrowing the hot processing window for the unstable flow stress,in which fine recrystallized and coarse unrecrystallized grains are present.展开更多
In-situ formed high Mn steel coating reinforced by carbides was formed by laser surface alloying(LSA).Laser alloyed layers on 1Cr18Ni9Ti steel with Mn+W_(2)C(specimen A),Mn+NiWC(specimen B)and Mn+SiC(specimen C)powder...In-situ formed high Mn steel coating reinforced by carbides was formed by laser surface alloying(LSA).Laser alloyed layers on 1Cr18Ni9Ti steel with Mn+W_(2)C(specimen A),Mn+NiWC(specimen B)and Mn+SiC(specimen C)powders were fabricated to improve the wear and corrosion behavior of 1Cr18Ni9Ti steel blades in high speed mixers.Microstructure evolution,phases,element distribution,microhardness,wear and corrosion behavior of the laser alloyed layers were investigated.Results indicated that high Mn steel matrix composites with undissolved W_(2)C,WC and other in-situ formed carbides were formed by LSA with Mn+W_(2)C and Mn+NiWC while SiC totally dissolved into the high Mn matrix when adding Mn+SiC.Ni as the binding phase in Ni-WC powder decreased the crack sensitivity of the alloyed layer as compared with the addition of W_(2)C powder.An improvement in average microhardness was achieved in the matrix in specimen A,B and C,with the value of 615,602 and 277 HV_(0.5),while that of the substrate was 212 HV_(0.5).The increase of microhardness,wear and corrosion resistance is highly corelated to microstructure,formed phases,type and content of carbides,micro-hardness and toughness of the alloyed layers.展开更多
Grain-oriented silicon steels were prepared at different heating rates during high temperature annealing,in which the evolution of magnetic properties,grain orientations and precipitates were studied.To illustrate the...Grain-oriented silicon steels were prepared at different heating rates during high temperature annealing,in which the evolution of magnetic properties,grain orientations and precipitates were studied.To illustrate the Zener factor,the diameter and number density of precipitates of interrupted testing samples were statistically calculated.The effect of precipitate ripening on the Goss texture and magnetic property was investigated.Data indicated that the trend of Zener factor was similar under different heating rates,first increasing and then decreasing,and that the precipitate maturing was greatly inhibited as the heating rate increased.Secondary recrystallization was developed at the temperature of 1010℃when a heating rate of 5℃/h was used,resulting in Goss,Brass and{110}<227>oriented grains growing abnormally and a magnetic induction intensity of 1.90T.Furthermore,increasing the heating rate to 20℃/h would inhibit the development of undesirable oriented grains and obtain a sharp Goss texture.However,when the heating rate was extremely fast,such as 40℃/h,poor secondary recrystallization was developed with many island grains,corresponding to a decrease in magnetic induction intensity to 1.87 T.At a suitable heating rate of 20℃/h,the sharpest Goss texture and the highest magnetic induction of 1.94 T with an onset secondary recrystallization temperature of 1020℃were found among the experimental variables in this study.The heating rate affected the initial temperature of secondary recrystallization by controlling the maturation of precipitates,leading to the deviation and dispersion of Goss texture,thereby reducing the magnetic properties.展开更多
The microstructural evolution of a cold-rolled and intercritical annealed medium-Mn steel(Fe-0.10C-5Mn)was investigated during uniaxial tensile testing.In-situ observations under scanning electron microscopy,transmiss...The microstructural evolution of a cold-rolled and intercritical annealed medium-Mn steel(Fe-0.10C-5Mn)was investigated during uniaxial tensile testing.In-situ observations under scanning electron microscopy,transmission electron microscopy,and X-ray diffraction analysis were conducted to characterize the progressive transformation-induced plasticity process and associated fracture initiation mechanisms.These findings were discussed with the local strain measurements via digital image correlation.The results indicated that Lüders band formation in the steel was limited to 1.5%strain,which was mainly due to the early-stage martensitic phase transformation of a very small amount of the less stable large-sized retained austenite(RA),which led to localized stress concentrations and strain hardening and further retardation of yielding.The small-sized RA exhibited high stability and progressively transformed into martensite and contributed to a stably extended Portevin-Le Chatelier effect.The volume fraction of RA gradually decreased from 26.8%to 8.2%prior to fracture.In the late deformation stage,fracture initiation primarily occurred at the austenite/martensite and ferrite/martensite interfaces and the ferrite phase.展开更多
Multistage heat treatment involving quenching(Q),lamellarizing(L),and tempering(T)is applied to marine 10Ni5CrMoV steel.The microstructure and mechanical properties were studied by multiscale characterizations,and the...Multistage heat treatment involving quenching(Q),lamellarizing(L),and tempering(T)is applied to marine 10Ni5CrMoV steel.The microstructure and mechanical properties were studied by multiscale characterizations,and the kinetics of reverse austenite transformation,strain hardening behavior,and toughening mechanism were further investigated.The lamellarized specimens possess low yield strength but high toughness,especially cryogenic toughness.Lamellarization leads to the development of film-like reversed austenite at the martensite block and lath boundaries,refining the martensite structure and lowering the equivalent grain size.Kinetic analysis of austenite reversion based on the JMAK model shows that the isothermal transformation is dominated by the growth of reversed austenite,and the maximum transformation of reversed austenite is reached at the peak temperature(750℃).The strain hardening behavior based on the modified Crussard-Jaoul analysis indicates that the reversed austenite obtained from lamellarization reduces the proportion of martensite,significantly hindering crack propagation via martensitic transformation during the deformation.As a consequence,the QLT specimens exhibit high machinability and low yield strength.Compared with the QT specimen,the ductile-brittle transition temperature of the QLT specimens decreases from-116 to-130℃due to the low equivalent grain size and reversed austenite,which increases the cleavage force required for crack propagation and absorbs the energy of external load,respectively.This work provides an idea to improve the cryogenic toughness of marine 10Ni5CrMoV steel and lays a theoretical foundation for its industrial application and comprehensive performance improvement.展开更多
Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crac...Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crack,strengthened by steel wire wrapping.The effects of the thread tensile force of the steel winding in the form of single rings at the crack edges and the wires with different winding diameters and pitches were also studied.The results showed that the strengthening was preferably executed at a minimum value of the thread tensile force,which was 6.4%more effective than that at its maximum value.The analysis of the influence of the winding dia-meters showed that the equivalent stresses increased by 32%from the beginning of the crack growth until the wire broke.The increment in winding diameter decelerated the disclosure of the edge crack and reduced its length by 8.2%.The analysis of the influence of the winding pitch showed that decreasing the distance between the winding turns also led to a 33.6%reduction in the length of the straight crack and a 7.9%reduction in the maximum stres-ses on the strengthened pipeline cross-section.The analysis of the temperature effect on the pipeline material,within a range from-40℃ to+50℃,resulted in a crack length change of up to 5.8%.As the temperature dropped,the crack length decreased.Within such a temperature range,the maximum stresses were observed along the cen-tral area of the crack,which were equal to 413 MPa at+50℃ and 440 MPa at-40℃.The results also showed that the presence of the steel winding in the pipeline significantly reduced the length of crack propagation up to 8.4 times,depending on the temperature effect and design parameters of prestressing.This work integrated the existing methods for crack localization along steel gas pipelines.展开更多
Two international standards, ISO 6331:2024, Chromium ores and concentrates—Determination of chromium content—Titrimetric method, and ISO 6934-2:2024, Steel for the prestressing of concrete—Part 2:Cold-drawn wire, w...Two international standards, ISO 6331:2024, Chromium ores and concentrates—Determination of chromium content—Titrimetric method, and ISO 6934-2:2024, Steel for the prestressing of concrete—Part 2:Cold-drawn wire, were officially published, to which Chinese experts have contributed efforts.展开更多
New stared compounds including norfloxacin fragments were prepared via a multi-step route,which were employed as the target corrosion inhibitors(TCIs)for mild steel in 1 mol/L HCl solution.For comparisons,the linear c...New stared compounds including norfloxacin fragments were prepared via a multi-step route,which were employed as the target corrosion inhibitors(TCIs)for mild steel in 1 mol/L HCl solution.For comparisons,the linear compounds including a single norfloxacin part employed as the reference corrosion inhibitors(RCIs)were synthesized.The molecular structures of the stared compounds were confirmed.The material simulation calculations suggest the presence of large binding energies of the stared compounds on mild steel surface.The enhanced chemisorption of the stared compounds on mild steel surface was demonstrated,which could be resulted by the chemical complexion of the target stared molecules with iron atoms.The reinforced adsorption of the target compounds on mild steel surface was investigated by atomic force microscopy(AFM)and scanning electron microscopy(SEM).The electrochemical analyses reveal the super protection of the TCIs for mild steel in HCl solution,and the anticorrosion efficiency reaches 96.45%(TCI1,0.050 mM)and 96.61%(TCI2,0.010 mM)at 298 K.展开更多
Geosynthetic-encased stone column(GESC)technology for strengthening soft clay offers significant advantages in terms of cost-effectiveness,environmental sustainability,and engineering applicability.It is widely applie...Geosynthetic-encased stone column(GESC)technology for strengthening soft clay offers significant advantages in terms of cost-effectiveness,environmental sustainability,and engineering applicability.It is widely applied in treating soft foundations for railways,bridges,and embankments.This study evaluates the cyclic response of the geosynthetic-encased steel slag column(GESSC)composite foundation employing three-dimensional nonlinear finite element analysis.A numerical study is conducted to assess the cyclic response of floating GESSC considering the influence of key design variables,including cyclic load amplitude,loading frequency,geosynthetic encasement stiffness,and length-to-diameter ratio.Results show that both cyclic load amplitude and frequency affect the cumulative settlement and excess pore pressure within the GESSC foundation.Within specified limits,increasing the encasement stiffness and column length can significantly improve the GESSC load-bearing characteristics.The parametric study suggests an optimal geosynthetic encasement stiffness for the field prototype columns within the range of 4480–5760 kN/m and a critical steel slag column length of 10 times the column diameter.展开更多
To tackle the issue of notch frequency and center frequency drift of the L(0,1)mode guided wave in ultra⁃sonic guided wave⁃based stress monitoring of prestressed steel strands,a method using higher⁃order mode plateau ...To tackle the issue of notch frequency and center frequency drift of the L(0,1)mode guided wave in ultra⁃sonic guided wave⁃based stress monitoring of prestressed steel strands,a method using higher⁃order mode plateau fre⁃quencies is adopted.First,the correlation between group velocity peaks and phase velocities at these plateau frequen⁃cies is analyzed.This analysis establishes a quantitative rela⁃tionship between phase velocity and stress in the steel strand,providing a theoretical foundation for stress monitor⁃ing.Then the two⁃dimensional Fourier transform is em⁃ployed to separate wave modes.Dynamic programming techniques are applied in the frequency⁃velocity domain to extract higher⁃order modes.By identifying the group veloc⁃ity peaks of these separated higher⁃order modes,the plateau frequencies of guided waves are determined,enabling indi⁃rect measurement of stress in the steel strand.To validate this method,finite element simulations are conducted under three scenarios.Results show that the higher⁃order modes of transient signals from three different positions can be ac⁃curately extracted,leading to successful cable stress moni⁃toring.This approach effectively circumvents the issue of guided wave frequency drift and improves stress monitoring accuracy.Consequently,it significantly improves the appli⁃cation of ultrasonic guided wave technology in structural health monitoring.展开更多
The aluminum(Al)/steel transition joints used in ships are processed from composite plates,and their mechanical properties have a significant impact on the safety of ships.In this paper,the Al/steel composite plate wa...The aluminum(Al)/steel transition joints used in ships are processed from composite plates,and their mechanical properties have a significant impact on the safety of ships.In this paper,the Al/steel composite plate was prepared using rolling,with 5083 aluminum plate as the cladding plate,Q235 steel plate as the substrate,and TA1 titanium(Ti)plate and DT4 pure iron(Fe)plate as the intermediate layers.The heterothermic billet was prepared through induction heating by the magnetic effects of the steel plate and the pure Fe plate,and then the Al/steel composite plate was obtained by rolling.The impacts of post-rolling cooling process on the microstructure and properties of the Al/Ti/pure Fe/steel composite plate were studied.The results manifested that the pure Fe/steel interface had a good composite effect.With the increase in the cooling rate,the bonding strength of the Al/Ti interface was raised,and that of the Ti/Fe interface was increased first and then decreased.When the oil cooling process was adopted,the Al/Ti/pure Fe/steel composite plate exhibited the highest comprehensive performance.The shear strength of the Al/Ti interface and the Ti/Fe interface was 102 MPa and 186 MPa,respectively.The plastic fracture was determined as the mode of interface fracture.展开更多
In view of the volume instability of steel slag aggregate leading to the quality problem of expansion damage in asphalt road construction,the 4.75-9.5 mm steel slag particles were treated by autoclaved carbonation tec...In view of the volume instability of steel slag aggregate leading to the quality problem of expansion damage in asphalt road construction,the 4.75-9.5 mm steel slag particles were treated by autoclaved carbonation technology,and the effects of the carbonation system(temperature and time)on the autoclaved pulverization rate,f-CaO content,and the relationship between them for the carbonated steel slag were investigated.In addition,the microstructure of the carbonated steel slag was analyzed by X-ray diffractometer(XRD),scanning electron microscope and energy dispersive spectrometer(SEM-EDS),metallographic microscope and X-ray fluorescence imaging spectrometer(XRF).The experimental results indicate that,under the initial CO_(2)pressure of 1.0 MPa,increasing the carbonation temperature leads to the increase in the crystal plane spacing of Ca(OH)_(2)that was generated by the hydration of minerals in steel slag,and promotes the transformation of carbonated CaCO_(3)from the orthorhombic system to the hexagonal system,resulting in the increase of the crystal planes spacing of them,meantime,accelerates the decomposition of RO phases and also the outward migration of Ca^(2+),Fe^(2+),and Mn^(2+)ions to cover and coat on the Si^(4+),Al^(3+)ions,and impels the formation of hydroxides such as Fe(OH)_(3)and the formation of carbonates such as Ca(Mg)CO_(3),FeCO_(3)and MnCO_(3).Carbonation at the temperature of 90℃for 3 h can reach the center of 4.75-9.5 mm steel slag particles.Meanwhile,the increase of temperature can promote the mineral reaction in steel slag,resulting in the fuzzy interface between mineral phases,increase of burrs,dispersion,crossover,reduction of grain size,and rearrangement of mineral particles.展开更多
High-voltage electrical post equipment is generally installed on steel supports,which amplifies the seismic inputs and degrades the seismic performance of equipment.This study proposed a variable cross-section damped ...High-voltage electrical post equipment is generally installed on steel supports,which amplifies the seismic inputs and degrades the seismic performance of equipment.This study proposed a variable cross-section damped steel support frame(VCDFS)with viscous dampers to reduce seismic responses of both tall and low-rise electrical equipment.The VCDFS contains a trapezoidal damper layer to generate rocking motions,enabling the diagonal viscous dampers to dissipate seismic inputs.A theoretical model of post equipment with VCDFS is established,and an optimal design procedure is proposed.The analysis shows that the remaining static stiffness ratio λ_(k) is the key parameter that determines the effectiveness of the VCDFS.The VCDFS reduces the average displacement and stress response of a post insulator by 39.4%and 44.6%,respectively,together with a significant decrease in the dynamic amplification factor.Therefore,it is recommended to use the VCDFS instead of the conventional latticed-steel frame in earthquake zones.展开更多
This paper presents a new type of steel pipe pile wharf connection node.The steel pipe and concrete are connected by ultra-high performance concrete(UHPC)grouting to improve the bonding performance between the concret...This paper presents a new type of steel pipe pile wharf connection node.The steel pipe and concrete are connected by ultra-high performance concrete(UHPC)grouting to improve the bonding performance between the concrete and steel pipe and enhance the mechanical performance of the specimen under earthquake action.A bond test between the steel tube and the concrete was carried out.Considering the interaction between materials,the proposed concrete constitutive model was proposed.The finite element analysis method was used to simulate the structural response of the UHPC grouting connection concrete-filled steel tube(UCFST)beam-pile joint and the normal strength concretefilled steel tube(NCFST)beam-pile joint under earthquake action.The results indicate that the bond performance between the UHPC and the steel tube is stronger.The UCFST specimen has a relatively high bearing capacity and stiffness.When the ratio of the UHPC grouting layer to the component diameter is 0.5,the bearing capacity is the highest.When the ratio is 0.37,the ductility is the highest.When the ratio is 0.25,it combines the advantages of the two situations mentioned above.UCFST specimens have better energy dissipation capacity and damage,which can effectively improve the seismic performance of components.展开更多
基金the National Natural Science Foundation of China(No.52205240).
文摘The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,and high-cycle fatigue properties,were studied.The results showed that the LSP induced residual compressive stresses on the surface and near surface of the material.The maximum surface residual compressive stress was−661 MPa,and the compressive-stress-affected depth was greater than 1000μm.The roughness and Vickers micro-hardness increased with the number of shocks,and the maximum hardness-affected depth was about 700μm after three LSP treatments.LSP enhanced the fraction of low-angle grain boundaries,changed the grain preferred orientations,and notably increased the pole density ofαphase on the near surface from 2.41 to 3.46.The surface hardness values of the LSP samples increased with the increase of the number of shocks due to work hardening,while the LSP had a limited effect on the tensile properties.The high-cycle fatigue life of the LSP-treated sample was significantly enhanced by more than 20%compared with that of the untreated sample,which was caused by the suppression of the initiation and propagation of fatigue cracks.
基金supported by the National Natural Science Foundation of China(No.52271089)the financial support from the C hina Postdoctoral Science Foundation(No.2023M732192)。
文摘This work reveals the significant effects of cobalt(Co)on the microstructure and impact toughness of as-quenched highstrength steels by experimental characterizations and thermo-kinetic analyses.The results show that the Co-bearing steel exhibits finer blocks and a lower ductile-brittle transition temperature than the steel without Co.Moreover,the Co-bearing steel reveals higher transformation rates at the intermediate stage with bainite volume fraction ranging from around 0.1 to 0.6.The improved impact toughness of the Co-bearing steel results from the higher dense block boundaries dominated by the V1/V2 variant pair.Furthermore,the addition of Co induces a larger transformation driving force and a lower bainite start temperature(BS),thereby contributing to the refinement of blocks and the increase of the V1/V2 variant pair.These findings would be instructive for the composition,microstructure design,and property optimization of high-strength steels.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2022R1I1A3063493).
文摘Smart manufacturing and Industry 4.0 are transforming traditional manufacturing processes by utilizing innovative technologies such as the artificial intelligence(AI)and internet of things(IoT)to enhance efficiency,reduce costs,and ensure product quality.In light of the recent advancement of Industry 4.0,identifying defects has become important for ensuring the quality of products during the manufacturing process.In this research,we present an ensemble methodology for accurately classifying hot rolled steel surface defects by combining the strengths of four pre-trained convolutional neural network(CNN)architectures:VGG16,VGG19,Xception,and Mobile-Net V2,compensating for their individual weaknesses.We evaluated our methodology on the Xsteel surface defect dataset(XSDD),which comprises seven different classes.The ensemble methodology integrated the predictions of individual models through two methods:model averaging and weighted averaging.Our evaluation showed that the model averaging ensemble achieved an accuracy of 98.89%,a recall of 98.92%,a precision of 99.05%,and an F1-score of 98.97%,while the weighted averaging ensemble reached an accuracy of 99.72%,a recall of 99.74%,a precision of 99.67%,and an F1-score of 99.70%.The proposed weighted averaging ensemble model outperformed the model averaging method and the individual models in detecting defects in terms of accuracy,recall,precision,and F1-score.Comparative analysis with recent studies also showed the superior performance of our methodology.
基金financially supported by the National Natural Science Foundation of China(No.51771125)the Sichuan Province Science and Technology Support Program(No.2020YFG0102)。
文摘Densely distributed coherent nanoparticles(DCN)in steel matrix can enhance the work-hardening ability and ductility of steel simultaneously.All the routes to this end can be generally classified into the liquid-solid route and the solid-solid route.However,the formation of DCN structures in steel requires long processes and complex steps.So far,obtaining steel with coherent particle enhancement in a short time remains a bottleneck,and some necessary steps remain unavoidable.Here,we show a high-efficiency liquid-phase refining process reinforced by a dynamic magnetic field.Ti-Y-Mn-O particles had an average size of around(3.53±1.21)nm and can be obtained in just around 180 s.These small nanoparticles were coherent with the matrix,implying no accumulated dislocations between the particles and the steel matrix.Our findings have a potential application for improving material machining capacity,creep resistance,and radiation resistance.
基金financially supported by the National Natural Science Foundation of China(Nos.U2141207,52171111,and 52001083)the Youth Talent Project of China National Nuclear Corporation(No.CNNC2021Y-TEPHEU01)+3 种基金the China Postdoctoral Science Foundation(No.2020M681077)the Natural Science Foundation of Heilongjiang,China(No.LH2019E030)the Heilongjiang Postdoctoral Science Foundation,China(No.LBH-Z19125)he Heilongjiang Touyan Innovation Team Program,China,and the Natural Science Foundation of Heilongjiang(No.LH2020E060)。
文摘Carbon can change the phase components of low-density steels and influence the mechanical properties.In this study,a new method to control the carbon content and avoid the formation ofδ-ferrite by decarburization treatment was proposed.The microstructural changes and mechanical characteristics with carbon content induced by decarburization were systematically examined.Crussard-Jaoul(C-J)analysis was employed to examine the work hardening characteristics during the tensile test.During decarburization by heat treatments,the carbon content within the austenite phase decreased,while Mn and Al were almost unchanged;this made the steel with full austenite transform into the austenite and ferrite dual phase.Meanwhile,(Ti,V)C carbides existed in both matrix phase and the mole fraction almost the same.In addition,the formation of other carbides restrained.Carbon loss induced a decrease in strength due to the weakening of the carbon solid solution.For the steel with the single austinite,the deformation mode of austenite was the dislocation planar glide,resulting in the formation of microbands.For the dual-phase steel,the deformation occurred by the dislocation planar glide of austenite first,with the increase in strain,the cross slip of ferrite took place,forming dislocation cells in ferrite.At the late stage of deformation,the work hardening of austinite increased rapidly,while that of ferrite increased slightly.
基金supported by the National Natural Science Foundation of China(Nos.52122408 and 52071023)financial support from the Fundamental Research Funds for the Central Universities(University of Science and Technology Beijing,No.FRF-TP-2021-04C1,and 06500135)。
文摘Martensite is an important microstructure in ultrahigh-strength steels,and enhancing the strength of martensitic steels often involves the introduction of precipitated phases within the martensitic matrix.Despite considerable research efforts devoted to this area,a systematic summary of these advancements is lacking.This review focuses on the precipitates prevalent in ultrahigh-strength martensitic steel,primarily carbides(e.g.,MC,M_(2)C,and M_(3)C)and intermetallic compounds(e.g.,Ni Al,Ni_(3)X,and Fe_(2)Mo).The precipitation-strengthening effect of these precipitates on ultrahigh-strength martensitic steel is discussed from the aspects of heat treatment processes,microstructure of precipitate-strengthened martensite matrix,and mechanical performance.Finally,a perspective on the development of precipitation-strengthened martensitic steel is presented to contribute to the advancement of ultrahigh-strength martensitic steel.This review highlights significant findings,ongoing challenges,and opportunities in the development of ultrahigh-strength martensitic steel.
基金financial support from the National Natural Science Foundation of China(Nos.52233018 and 51831002)the China Baowu Low Carbon Metallurgy Innovation Foudation(No.BWLCF202213)。
文摘The influence of Nb-V microalloying on the hot deformation behavior and microstructures of medium Mn steel(MMS)was investigated by uniaxial hot compression tests.By establishing the constitutive equations for simulating the measured flow curves,we successfully constructed deformation activation energy(Q)maps and processing maps for identifying the region of flow instability.We concluded the following consequences of Nb-V alloying for MMS.(i)The critical strain increases and the increment diminishes with the increasing deformation temperature,suggesting that NbC precipitates more efficiently retard dynamic recrystallization(DRX)in MMS compared with solute Nb.(ii)The deformation activation energy of MMS is significantly increased and even higher than that of some reported high Mn steels,suggesting that its ability to retard DRX is greater than that of the high Mn content.(iii)The hot workability of MMS is improved by narrowing the hot processing window for the unstable flow stress,in which fine recrystallized and coarse unrecrystallized grains are present.
文摘In-situ formed high Mn steel coating reinforced by carbides was formed by laser surface alloying(LSA).Laser alloyed layers on 1Cr18Ni9Ti steel with Mn+W_(2)C(specimen A),Mn+NiWC(specimen B)and Mn+SiC(specimen C)powders were fabricated to improve the wear and corrosion behavior of 1Cr18Ni9Ti steel blades in high speed mixers.Microstructure evolution,phases,element distribution,microhardness,wear and corrosion behavior of the laser alloyed layers were investigated.Results indicated that high Mn steel matrix composites with undissolved W_(2)C,WC and other in-situ formed carbides were formed by LSA with Mn+W_(2)C and Mn+NiWC while SiC totally dissolved into the high Mn matrix when adding Mn+SiC.Ni as the binding phase in Ni-WC powder decreased the crack sensitivity of the alloyed layer as compared with the addition of W_(2)C powder.An improvement in average microhardness was achieved in the matrix in specimen A,B and C,with the value of 615,602 and 277 HV_(0.5),while that of the substrate was 212 HV_(0.5).The increase of microhardness,wear and corrosion resistance is highly corelated to microstructure,formed phases,type and content of carbides,micro-hardness and toughness of the alloyed layers.
文摘Grain-oriented silicon steels were prepared at different heating rates during high temperature annealing,in which the evolution of magnetic properties,grain orientations and precipitates were studied.To illustrate the Zener factor,the diameter and number density of precipitates of interrupted testing samples were statistically calculated.The effect of precipitate ripening on the Goss texture and magnetic property was investigated.Data indicated that the trend of Zener factor was similar under different heating rates,first increasing and then decreasing,and that the precipitate maturing was greatly inhibited as the heating rate increased.Secondary recrystallization was developed at the temperature of 1010℃when a heating rate of 5℃/h was used,resulting in Goss,Brass and{110}<227>oriented grains growing abnormally and a magnetic induction intensity of 1.90T.Furthermore,increasing the heating rate to 20℃/h would inhibit the development of undesirable oriented grains and obtain a sharp Goss texture.However,when the heating rate was extremely fast,such as 40℃/h,poor secondary recrystallization was developed with many island grains,corresponding to a decrease in magnetic induction intensity to 1.87 T.At a suitable heating rate of 20℃/h,the sharpest Goss texture and the highest magnetic induction of 1.94 T with an onset secondary recrystallization temperature of 1020℃were found among the experimental variables in this study.The heating rate affected the initial temperature of secondary recrystallization by controlling the maturation of precipitates,leading to the deviation and dispersion of Goss texture,thereby reducing the magnetic properties.
基金supported by the National Key R&D Program of China(No.2017YFB0304402)。
文摘The microstructural evolution of a cold-rolled and intercritical annealed medium-Mn steel(Fe-0.10C-5Mn)was investigated during uniaxial tensile testing.In-situ observations under scanning electron microscopy,transmission electron microscopy,and X-ray diffraction analysis were conducted to characterize the progressive transformation-induced plasticity process and associated fracture initiation mechanisms.These findings were discussed with the local strain measurements via digital image correlation.The results indicated that Lüders band formation in the steel was limited to 1.5%strain,which was mainly due to the early-stage martensitic phase transformation of a very small amount of the less stable large-sized retained austenite(RA),which led to localized stress concentrations and strain hardening and further retardation of yielding.The small-sized RA exhibited high stability and progressively transformed into martensite and contributed to a stably extended Portevin-Le Chatelier effect.The volume fraction of RA gradually decreased from 26.8%to 8.2%prior to fracture.In the late deformation stage,fracture initiation primarily occurred at the austenite/martensite and ferrite/martensite interfaces and the ferrite phase.
基金financially supported by the National Key K&D Program of China(No.2023YFE0200300)the National Natural Science Foundation of China(Nos.52174303and 51874084)the Program of Introducing Talents of Discipline to Universities(No.B21001)。
文摘Multistage heat treatment involving quenching(Q),lamellarizing(L),and tempering(T)is applied to marine 10Ni5CrMoV steel.The microstructure and mechanical properties were studied by multiscale characterizations,and the kinetics of reverse austenite transformation,strain hardening behavior,and toughening mechanism were further investigated.The lamellarized specimens possess low yield strength but high toughness,especially cryogenic toughness.Lamellarization leads to the development of film-like reversed austenite at the martensite block and lath boundaries,refining the martensite structure and lowering the equivalent grain size.Kinetic analysis of austenite reversion based on the JMAK model shows that the isothermal transformation is dominated by the growth of reversed austenite,and the maximum transformation of reversed austenite is reached at the peak temperature(750℃).The strain hardening behavior based on the modified Crussard-Jaoul analysis indicates that the reversed austenite obtained from lamellarization reduces the proportion of martensite,significantly hindering crack propagation via martensitic transformation during the deformation.As a consequence,the QLT specimens exhibit high machinability and low yield strength.Compared with the QT specimen,the ductile-brittle transition temperature of the QLT specimens decreases from-116 to-130℃due to the low equivalent grain size and reversed austenite,which increases the cleavage force required for crack propagation and absorbs the energy of external load,respectively.This work provides an idea to improve the cryogenic toughness of marine 10Ni5CrMoV steel and lays a theoretical foundation for its industrial application and comprehensive performance improvement.
基金funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan(Grant No.AP19680589).
文摘Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crack,strengthened by steel wire wrapping.The effects of the thread tensile force of the steel winding in the form of single rings at the crack edges and the wires with different winding diameters and pitches were also studied.The results showed that the strengthening was preferably executed at a minimum value of the thread tensile force,which was 6.4%more effective than that at its maximum value.The analysis of the influence of the winding dia-meters showed that the equivalent stresses increased by 32%from the beginning of the crack growth until the wire broke.The increment in winding diameter decelerated the disclosure of the edge crack and reduced its length by 8.2%.The analysis of the influence of the winding pitch showed that decreasing the distance between the winding turns also led to a 33.6%reduction in the length of the straight crack and a 7.9%reduction in the maximum stres-ses on the strengthened pipeline cross-section.The analysis of the temperature effect on the pipeline material,within a range from-40℃ to+50℃,resulted in a crack length change of up to 5.8%.As the temperature dropped,the crack length decreased.Within such a temperature range,the maximum stresses were observed along the cen-tral area of the crack,which were equal to 413 MPa at+50℃ and 440 MPa at-40℃.The results also showed that the presence of the steel winding in the pipeline significantly reduced the length of crack propagation up to 8.4 times,depending on the temperature effect and design parameters of prestressing.This work integrated the existing methods for crack localization along steel gas pipelines.
文摘Two international standards, ISO 6331:2024, Chromium ores and concentrates—Determination of chromium content—Titrimetric method, and ISO 6934-2:2024, Steel for the prestressing of concrete—Part 2:Cold-drawn wire, were officially published, to which Chinese experts have contributed efforts.
基金Funded by the National Natural Science Foundation of China(NSFC)of China(No.21878029)the Chongqing Science and Technology Commission(Nos.2022NSCQ-MSX1298 and CSTB2023NSCQ-MSX0345)。
文摘New stared compounds including norfloxacin fragments were prepared via a multi-step route,which were employed as the target corrosion inhibitors(TCIs)for mild steel in 1 mol/L HCl solution.For comparisons,the linear compounds including a single norfloxacin part employed as the reference corrosion inhibitors(RCIs)were synthesized.The molecular structures of the stared compounds were confirmed.The material simulation calculations suggest the presence of large binding energies of the stared compounds on mild steel surface.The enhanced chemisorption of the stared compounds on mild steel surface was demonstrated,which could be resulted by the chemical complexion of the target stared molecules with iron atoms.The reinforced adsorption of the target compounds on mild steel surface was investigated by atomic force microscopy(AFM)and scanning electron microscopy(SEM).The electrochemical analyses reveal the super protection of the TCIs for mild steel in HCl solution,and the anticorrosion efficiency reaches 96.45%(TCI1,0.050 mM)and 96.61%(TCI2,0.010 mM)at 298 K.
基金support from the National Natural Science Foundation of China(Grant Nos.52078427 and 51608461)is greatly acknowledged.
文摘Geosynthetic-encased stone column(GESC)technology for strengthening soft clay offers significant advantages in terms of cost-effectiveness,environmental sustainability,and engineering applicability.It is widely applied in treating soft foundations for railways,bridges,and embankments.This study evaluates the cyclic response of the geosynthetic-encased steel slag column(GESSC)composite foundation employing three-dimensional nonlinear finite element analysis.A numerical study is conducted to assess the cyclic response of floating GESSC considering the influence of key design variables,including cyclic load amplitude,loading frequency,geosynthetic encasement stiffness,and length-to-diameter ratio.Results show that both cyclic load amplitude and frequency affect the cumulative settlement and excess pore pressure within the GESSC foundation.Within specified limits,increasing the encasement stiffness and column length can significantly improve the GESSC load-bearing characteristics.The parametric study suggests an optimal geosynthetic encasement stiffness for the field prototype columns within the range of 4480–5760 kN/m and a critical steel slag column length of 10 times the column diameter.
基金The National Natural Science Foundation of China(No.52278303).
文摘To tackle the issue of notch frequency and center frequency drift of the L(0,1)mode guided wave in ultra⁃sonic guided wave⁃based stress monitoring of prestressed steel strands,a method using higher⁃order mode plateau fre⁃quencies is adopted.First,the correlation between group velocity peaks and phase velocities at these plateau frequen⁃cies is analyzed.This analysis establishes a quantitative rela⁃tionship between phase velocity and stress in the steel strand,providing a theoretical foundation for stress monitor⁃ing.Then the two⁃dimensional Fourier transform is em⁃ployed to separate wave modes.Dynamic programming techniques are applied in the frequency⁃velocity domain to extract higher⁃order modes.By identifying the group veloc⁃ity peaks of these separated higher⁃order modes,the plateau frequencies of guided waves are determined,enabling indi⁃rect measurement of stress in the steel strand.To validate this method,finite element simulations are conducted under three scenarios.Results show that the higher⁃order modes of transient signals from three different positions can be ac⁃curately extracted,leading to successful cable stress moni⁃toring.This approach effectively circumvents the issue of guided wave frequency drift and improves stress monitoring accuracy.Consequently,it significantly improves the appli⁃cation of ultrasonic guided wave technology in structural health monitoring.
基金Supported by Science Research Project of Hebei Education Department(Grant No.BJK2024138)Hebei Provincial Natural Science Foundation(Grant No.E2023203129)National Natural Science Foundation of China(Grant Nos.52004242,52075472).
文摘The aluminum(Al)/steel transition joints used in ships are processed from composite plates,and their mechanical properties have a significant impact on the safety of ships.In this paper,the Al/steel composite plate was prepared using rolling,with 5083 aluminum plate as the cladding plate,Q235 steel plate as the substrate,and TA1 titanium(Ti)plate and DT4 pure iron(Fe)plate as the intermediate layers.The heterothermic billet was prepared through induction heating by the magnetic effects of the steel plate and the pure Fe plate,and then the Al/steel composite plate was obtained by rolling.The impacts of post-rolling cooling process on the microstructure and properties of the Al/Ti/pure Fe/steel composite plate were studied.The results manifested that the pure Fe/steel interface had a good composite effect.With the increase in the cooling rate,the bonding strength of the Al/Ti interface was raised,and that of the Ti/Fe interface was increased first and then decreased.When the oil cooling process was adopted,the Al/Ti/pure Fe/steel composite plate exhibited the highest comprehensive performance.The shear strength of the Al/Ti interface and the Ti/Fe interface was 102 MPa and 186 MPa,respectively.The plastic fracture was determined as the mode of interface fracture.
基金Funded by the Natural Science Foundation of Hebei Province(No.E2020209010)the Science and Technology Plan Project of Tangshan(No.19150225E)the Key R&D Projects of North China University of Science and Technology(No.ZD-ST-202301)。
文摘In view of the volume instability of steel slag aggregate leading to the quality problem of expansion damage in asphalt road construction,the 4.75-9.5 mm steel slag particles were treated by autoclaved carbonation technology,and the effects of the carbonation system(temperature and time)on the autoclaved pulverization rate,f-CaO content,and the relationship between them for the carbonated steel slag were investigated.In addition,the microstructure of the carbonated steel slag was analyzed by X-ray diffractometer(XRD),scanning electron microscope and energy dispersive spectrometer(SEM-EDS),metallographic microscope and X-ray fluorescence imaging spectrometer(XRF).The experimental results indicate that,under the initial CO_(2)pressure of 1.0 MPa,increasing the carbonation temperature leads to the increase in the crystal plane spacing of Ca(OH)_(2)that was generated by the hydration of minerals in steel slag,and promotes the transformation of carbonated CaCO_(3)from the orthorhombic system to the hexagonal system,resulting in the increase of the crystal planes spacing of them,meantime,accelerates the decomposition of RO phases and also the outward migration of Ca^(2+),Fe^(2+),and Mn^(2+)ions to cover and coat on the Si^(4+),Al^(3+)ions,and impels the formation of hydroxides such as Fe(OH)_(3)and the formation of carbonates such as Ca(Mg)CO_(3),FeCO_(3)and MnCO_(3).Carbonation at the temperature of 90℃for 3 h can reach the center of 4.75-9.5 mm steel slag particles.Meanwhile,the increase of temperature can promote the mineral reaction in steel slag,resulting in the fuzzy interface between mineral phases,increase of burrs,dispersion,crossover,reduction of grain size,and rearrangement of mineral particles.
基金Guangdong Basic and Applied Basic Research Foundation under Grant Nos.2022A1515110561 and 2023A1515010072Natural Science Foundation of China under Grant Nos.52308488 and 52378499。
文摘High-voltage electrical post equipment is generally installed on steel supports,which amplifies the seismic inputs and degrades the seismic performance of equipment.This study proposed a variable cross-section damped steel support frame(VCDFS)with viscous dampers to reduce seismic responses of both tall and low-rise electrical equipment.The VCDFS contains a trapezoidal damper layer to generate rocking motions,enabling the diagonal viscous dampers to dissipate seismic inputs.A theoretical model of post equipment with VCDFS is established,and an optimal design procedure is proposed.The analysis shows that the remaining static stiffness ratio λ_(k) is the key parameter that determines the effectiveness of the VCDFS.The VCDFS reduces the average displacement and stress response of a post insulator by 39.4%and 44.6%,respectively,together with a significant decrease in the dynamic amplification factor.Therefore,it is recommended to use the VCDFS instead of the conventional latticed-steel frame in earthquake zones.
基金financially supported by the National Key Research and Development Program of China(Grant No.2022YFC3102305)the Taishan Scholar Program of Shandong Province(Grant No.tsqn202211049)the Key Engineering Innovation Project of Shandong Province(Grant No.2019JZZY010301).
文摘This paper presents a new type of steel pipe pile wharf connection node.The steel pipe and concrete are connected by ultra-high performance concrete(UHPC)grouting to improve the bonding performance between the concrete and steel pipe and enhance the mechanical performance of the specimen under earthquake action.A bond test between the steel tube and the concrete was carried out.Considering the interaction between materials,the proposed concrete constitutive model was proposed.The finite element analysis method was used to simulate the structural response of the UHPC grouting connection concrete-filled steel tube(UCFST)beam-pile joint and the normal strength concretefilled steel tube(NCFST)beam-pile joint under earthquake action.The results indicate that the bond performance between the UHPC and the steel tube is stronger.The UCFST specimen has a relatively high bearing capacity and stiffness.When the ratio of the UHPC grouting layer to the component diameter is 0.5,the bearing capacity is the highest.When the ratio is 0.37,the ductility is the highest.When the ratio is 0.25,it combines the advantages of the two situations mentioned above.UCFST specimens have better energy dissipation capacity and damage,which can effectively improve the seismic performance of components.
