To develop a fundamental understanding of the flow behavior and optimal hot workability parameters of this material, the hot workability and deformation mechanisms of the as-cast 21Cr EDSS were studied using processin...To develop a fundamental understanding of the flow behavior and optimal hot workability parameters of this material, the hot workability and deformation mechanisms of the as-cast 21Cr EDSS were studied using processing map technology combined with microstructure analysis and isothermal hot compression over the temperature range of 1000-1150 ℃ and strain rate range of 0.01-10 s-1. The processing maps and constitutive equation of peak stress were developed based on Prasad＇s and Murty＇s criteria. The results show that the processing maps exhibit a stable domain at 1000-1150 ℃ and 0.01-1 s-1. The instability domain is exhibited at high strain rates （≥1 s-l）. This implies that Murty＇s criterion can predict the unstable domain with high reliability. The detailed deformation mechanisms are also studied by microstructure observation, showing that the flow localization and microcracking are responsible for the flow instability.展开更多
The creep behavior of Fe–17 Cr–1.2 Cu–0.5 Nb–0.01 C ferritic heat-resistant stainless steel was investigated at temperatures ranging from 973 to 1123 K and stresses from 15 to 90 MPa.The evolution of precipitates ...The creep behavior of Fe–17 Cr–1.2 Cu–0.5 Nb–0.01 C ferritic heat-resistant stainless steel was investigated at temperatures ranging from 973 to 1123 K and stresses from 15 to 90 MPa.The evolution of precipitates after creep deformation was analyzed by scanning electron microscopy,energy dispersion spectrum,and transmission electron microscopy.The minimum creep rate decreased with the decrease in the applied load and temperature,thereby extending the rupture life.Cu-rich phase and Nb-rich Laves particles were generated in dominant quantities during the creep process,and the co-growth relationship between them could be detected.Creep rupture was featured by ductile fracture with considerable necking.As increasing the temperature and decreasing the stress,the softening of the metal matrix was accelerated,showing more obvious plastic fl ow.The true stress exponent and activation energy were 4.9 and 375.5 kJ/mol,respectively,indicating that the creep deformation was dominated by the diffusion-controlled dislocation creep mechanism involving precipitate-dislocation interactions.Based on the creep rupture data obtained,the Monkman–Grant relation and Larson-Miller parameter were established,which described the creep rupture life for the studied steel well.展开更多
Self-designed Al8Si0.4Mg0.4Fe aluminium alloy was modified with Sr,followed by solid solution and aging treatments to regulate its microstructure and mechanical/electrical properties.The results show that after the mo...Self-designed Al8Si0.4Mg0.4Fe aluminium alloy was modified with Sr,followed by solid solution and aging treatments to regulate its microstructure and mechanical/electrical properties.The results show that after the modification treatment,the room-temperature tensile strength of the alloy remains nearly unchanged,the elongation at break slightly increases from 1.82%to 3.34%,and the electrical conductivity significantly increases from 40.1%international annealed copper standard(IACS)to 42.0%IACS.After the modification,the alloy was subjected to solid solution treatment at 515℃for 8 h,followed by aging treatment at 180,200,220 and 240℃for 6 h.With increasing aging temperature,the electrical conductivity increases monotonously from 41.4%IACS to 45.5%IACS,while the room-temperature tensile strength initially increases and then decreases.At 200℃,the alloy achieves an optimal balance between electrical conductivity and room-temperature tensile strength:the electrical conductivity is 42.5%IACS,and the room-temperature tensile strength is 282.9 MPa.When the aging temperature continues to rise,the alloy undergoes overaging.Although the conductivity continues to increase,the room-temperature tensile strength drops sharply,and it is only 177.1 MPa at 240℃.展开更多
Currently,there are a limited number of dynamic models available for braided composite plates with large overall motions,despite the incorporation of three-dimensional(3D)braided composites into rotating blade compone...Currently,there are a limited number of dynamic models available for braided composite plates with large overall motions,despite the incorporation of three-dimensional(3D)braided composites into rotating blade components.In this paper,a dynamic model of 3D 4-directional braided composite thin plates considering braiding directions is established.Based on Kirchhoff's plate assumptions,the displacement variables of the plate are expressed.By incorporating the braiding directions into the constitutive equation of the braided composites,the dynamic model of the plate considering braiding directions is obtained.The effects of the speeds,braiding directions,and braided angles on the responses of the plate with fixed-axis rotation and translational motion,respectively,are investigated.This paper presents a dynamic theory for calculating the deformation of 3D braided composite structures undergoing both translational and rotational motions.It also provides a simulation method for investigating the dynamic behavior of non-isotropic material plates in various applications.展开更多
Particulate matter(PM)from high-temperature emissions like chemical plants,coal stoves and vehicle exhausts poses a gravel challenge to human health.To address this issue,researchers have explored vari-ous fiber filte...Particulate matter(PM)from high-temperature emissions like chemical plants,coal stoves and vehicle exhausts poses a gravel challenge to human health.To address this issue,researchers have explored vari-ous fiber filters,yet the bulk struggle to withstand high temperatures.In this study,mullite fiber sponges were developed utilizing low-cost materials and Kármán vortex solution blow spinning,using surfac-tants to improve the spinnability of the sol.Optimized sponges demonstrate ultralight(19 mg cm^(-3)),temperature-resistant reversible compressibility(50% strain)and a water contact angle of 135°.These sponges exhibited exceptional thermal insulation(thermal conductivity:0.0256 W m^(-1) K^(-1))and per-formed well in high-temperature air filtration.At 800℃,the mullite sponge with a base weight of 35 mg cm^(-2),achieved an average filtration efficiency of 98.18%and 99.57% for PM_(2.5) and PM_(2.5-10),respectively,with a quality value of 0.98 Pa^(-1) at a wind speed of 4 cm s^(-1).This low-cost mullite fiber sponge offers a promising avenue for designing high-performance filtration materials.展开更多
Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerfu...Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerful numerical simulation tool,can efficiently resolve the microstructural evolution,multi-field coupling effects,and fracture behavior of SMAs and SMCs.This review begins by presenting the fundamental theoretical framework of the fracture phase field method as applied to SMAs and SMCs,covering key aspects such as the phase field modeling of martensitic transformation and brittle fracture.Subsequently,it systematically examines the phase field simulations of fracture behaviors in SMAs and SMCs,with particular emphasis on how crystallographic orientation,grain size,and grain boundary properties influence the crack propagation.Additionally,the interplay between martensite transformation and fracture mechanisms is analyzed to provide deeper insights into the material responses under mechanical loading.Finally,the review explores future prospects and emerging trends in phase field simulations of SMA and SMC fracture behavior,along with potential advancements in the fracture phase field method itself,including multi-physics coupling and enhanced computational efficiency for large-scale simulations.展开更多
Over the past few years,the Cu element has attracted much attention in duplex stainless steels.It undoubtedly holds advantageous in regulating the two-phase proportion and austenite stability and is also one of the cr...Over the past few years,the Cu element has attracted much attention in duplex stainless steels.It undoubtedly holds advantageous in regulating the two-phase proportion and austenite stability and is also one of the crucial factors affecting the corrosion resistance.However,the systematic research on the impact of Cu addition to lean duplex stainless steels remains insufficient.In this study,a novel Cu-alloyed Mn-N-type 20Cr lean duplex stainless steel was developed and the effect of Cu on the strain hardening capacity and corrosion resistance was analyzed.The results show that the Cu addition increases the volume fraction and stability of the austenite,retards the martensitic transformation,and extends the transformation-induced plasticity effect to a wider strain range.Compared to the Cu-free steel,the plasticity of Cu-containing steel can be increased by~26%.Additionally,the addition of Cu redistributes the Cr and N elements in the ferrite and austenite phases,thereby improving the corrosion resistance of the lean duplex stainless steel.展开更多
Fe–Ga sheets with large magnetostriction are required for improving the conversion efficiency under the ultra-high frequencymagnetic field. Trace Tb element doping can simultaneously improve the magnetostriction and ...Fe–Ga sheets with large magnetostriction are required for improving the conversion efficiency under the ultra-high frequencymagnetic field. Trace Tb element doping can simultaneously improve the magnetostriction and ductility of Fe–Ga alloy. However, the im-pact of trace Tb doping on the microstructure and magnetostriction of Fe–Ga thin sheets is an open question. In this paper, the effects oftrace Tb addition on the secondary recrystallization and magnetostriction of Fe–Ga thin sheets are systematically studied by comparing thecharacteristics evolution of precipitation, texture, and nanoinclusions. The results indicate that trace Tb addition accelerates the secondaryrecrystallization of Goss texture due to the combined action of the bimodal size distributed precipitates, smaller grains, and more HEGBsin primary recrystallization. After quenching at 900℃, the magnetostriction value in 0.07 at %Tb-doped Fe_(81)Ga_(19) thin sheets increases by 30% to that of Fe_(81)Ga_(19) thin sheets. The increase in magnetostriction is attributed to the decrease in the number of Tb-rich precipitates andthe higher density of the nanometer-sized modified-D0_(3) inclusions induced by the dissolving of trace Tb elements after quenching. Theseresults demonstrate a simple and efficient approach for preparing Fe–Ga thin sheets with a large magnetostrictive coefficient by a combin-ation of trace RE element addition and conventional rolling method.展开更多
Implants are inevitably subjected to stress corrosion,bringing serious challenges to the controlled degradation of biomedical Mg alloys.It is worth studying the stress corrosion cracking(SCC)behavior of Mg alloy and e...Implants are inevitably subjected to stress corrosion,bringing serious challenges to the controlled degradation of biomedical Mg alloys.It is worth studying the stress corrosion cracking(SCC)behavior of Mg alloy and exploring Mg alloy with good SCC resistance for wide biomedical applications.In this work,the as-cast and as-extruded Mg-3Gd-1Zn-0.4Zr(GZ31K)alloys with uniform corrosion were used to investigate SCC behavior.The as-extruded GZ31K alloy exhibited better corrosion resistance and mechanical properties than the as-cast one mainly owing to grain refinement and uniformly distributed fine precipitates,and possessed superior SCC resistance.To clarify the SCC mechanism,the slow strain rate tests were assisted with applied constant potentials via an electrochemical workstation.Accelerated anodic dissolution at anodic polarization deteriorated SCC resistance due to the initiation of corrosion pits and micro-cracks.However,cathodic polarization had no obvious effects on SCC resistance,along with both retarded corrosion and accelerated hydrogen evolution.Stacking faults in GZ31K alloy were hydrogen capture containers to reduce the effect of hydrogen on SCC resistance during cathodic polarization.These findings provide new insights into the evaluation of SCC mechanism,and offer more opportunities to explore Mg alloys with good SCC resistance by regulating anodic dissolution.展开更多
Four-electron oxygen evolving reaction is limited by proton adsorption and desorption,making its reaction kinetics sluggish,which poses a major challenge for catalyst design.Here,we present an unsaturated coordination...Four-electron oxygen evolving reaction is limited by proton adsorption and desorption,making its reaction kinetics sluggish,which poses a major challenge for catalyst design.Here,we present an unsaturated coordination interface by constructing a fast electron transfer channel between Cu_(2)V_(2)O_(7)(CVO)and BiVO4(BVO).X-ray absorption spectroscopy(XAS)and theoretical calculations results confirm that CVO and BVO between interfaces are bonded by the way of unsaturated coordination oxygen(Ouc).The Ouc optimizes the O-O coupled energy barrier at the V active site and promotes the disconnection of O-H bond,which increases the photocurrent intensity of CVO by 6 times.In addition,due to the high electronegativity of the Ouc,the bonding energies of Bi-O and Cu-O at the interface are enhanced,resulting in the long-term stability of the photoanode during the water splitting.Finally,by integrating the working electrode with a polysilicon solar cell,we assembled a device that demonstrated exceptional catalytic performance,achieving a hydrogen production rate of 100.6μmol·cm^(-2),and maintaining a hydrogen-to-oxygen volume ratio of 2:1 after continuous operation for 4 h.This discovery aids in a deeper understanding of photoanode design and offers further insights for industrial applications.展开更多
Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxid...Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxide coatings formed on magnesium alloys are mainly composed of MgO and MgAl2O4 phases;in addition,the content of MgO increases with increasing the current density.The morphology and surface roughness of the coatings were characterized by confocal laser scanning microscopy (CLSM).The results show that the surface roughness(Ra)decreases with increasing the current density.Moreover,the electrochemical corrosion results prove that the MgO coating produced in the electrolyte Na2SiO3 at current density of 5 A/cm 2 shows the best corrosion resistance.展开更多
Magnesium(Mg)alloys have been widely used in automobile,aviation,computer,and other fields due to their lightweight,high specific strength and stiffness,low pollution,and good electromagnetic shielding performance.How...Magnesium(Mg)alloys have been widely used in automobile,aviation,computer,and other fields due to their lightweight,high specific strength and stiffness,low pollution,and good electromagnetic shielding performance.However,the chemical stability of Mg alloys is poor,especially in the corrosive medium environment with high stress corrosion sensitivity,which causes sudden damage to structural components and restricts their application field.In recent years,owing to the increasing failure rate of engineering structures caused by stress corrosion of Mg alloys,it has become necessary to understand and pay more attention to the stress corrosion cracking(SCC)behavior of Mg alloys.In this paper,the SCC mechanisms and test methods of Mg alloys have been summarized.The recent research progress on SCC of Mg alloys has been reviewed from the aspects of alloying,preparation process,surface modification,corrosive medium,and strain rate.More importantly,future research trends in the field of SCC of Mg alloys have also been proposed.展开更多
To improve the surface corrosion resistance of the alumina films fabricated by micro-arc oxidation （MAO）,Al2O3 coatings at different current densities （5,7 and 10 A/dm 2） were produced on aluminum alloys by adding...To improve the surface corrosion resistance of the alumina films fabricated by micro-arc oxidation （MAO）,Al2O3 coatings at different current densities （5,7 and 10 A/dm 2） were produced on aluminum alloys by adding SiC nano-particles into electrolyte during MAO process.The morphology and phase composition of the coatings were investigated by scanning electron microscopy （SEM） and X-ray diffraction （XRD）,respectively.Furthermore,the corrosion performance of the coatings was evaluated via a three-electrode system in a 3.5 wt pct NaCl solution.From the obtained morphology of alumina coatings,it was believed that the Al2O3 coatings embedded with SiC nano-particles were formed.The electrochemical impedance spectroscopy （EIS） plots and potentiodynamic polarization plots of the Al2O3 coatings with and without SiC nano-particles at different current densities reveal that the Al2O3 coatings with SiC nano-particles formed at 10 A/dm 2 showed the better corrosion resistance than the other coatings produced at 5 and 7 A/dm 2.展开更多
An attempt has been made to improve the corrosion resistance of friction stir welded joints of 7075 aluminum alloys by micro-arc oxidation（MAO）, and the effects of Na2Si O3 concentration in electrolyte on the corros...An attempt has been made to improve the corrosion resistance of friction stir welded joints of 7075 aluminum alloys by micro-arc oxidation（MAO）, and the effects of Na2Si O3 concentration in electrolyte on the corrosion resistance of the coatings were discussed. Morphology and phase constituents of the MAO coatings produced in electrolyte with different Na2SiO3 concentrations were analyzed by scanning electron microscopy, confocal laser scanning microscopy and X-ray diffraction. Electrochemical tests were conducted to evaluate the corrosion resistance of the coatings. The results show that the corrosion resistance of the coated joints is much better than that without the ceramic coating, and the ceramic coating produced in the electrolyte with Na2SiO3 concentration 20 g/L showed better corrosion resistance than the others.展开更多
The oxidation behavior of a nickel-based superalloy GH738 was studied by isothermal oxidation tests in still air at different temperatures,with exposure time up to 100 h.Oxidation-kinetic curves were plotted using the...The oxidation behavior of a nickel-based superalloy GH738 was studied by isothermal oxidation tests in still air at different temperatures,with exposure time up to 100 h.Oxidation-kinetic curves were plotted using the mass gain method.The surface and cross-sectional morphologies were observed by scanning electron microscopy(SEM).A composition analysis and an oxidation-product identification were conducted using energydispersive X-ray spectroscopy(EDS) and an X-ray diffraction(XRD),respectively.The results showed that GH738 exhibited parabolic oxidation-kinetic curves,with stable parabolic-rate constants at each temperatures.The activation energy of oxide growth was calculated to be329.6 kJ·mol^(-1).Cr_(2) O_(3)(chromia) was the external oxidation product at 800℃.A TiO_(2)-Cr_(2) O_(3) double-layer structure was formed at 900℃.The position of TiO_(2) changed from the oxide-metal interface to the air-oxide interface by the diffusion of Ti atoms in chromia during the oxidation time at this temperature.Spallation was observed in the Cr_(0.12)Ti_(0.78)O_(1.74)-Cr_(2) O_(3) multi-layer oxide of at 1000℃,which increased the oxidation rate.For all the tests,the main internal oxide was always Al_(2) O_(3).The entire GH738 oxidation process was interpreted by the competitive diffusion of elements(Cr,Ti,Ni,etc.) in metal matrix and chromia,while a schematic diagram of oxidation process was proposed.展开更多
The microstructural evolution and mechanical property of 00Crl3NiSMo2 supermartensitic stainless steel （SMSS） subjected to different heat treatments were investigated. Room tensile tests, hardness tests, scanning el...The microstructural evolution and mechanical property of 00Crl3NiSMo2 supermartensitic stainless steel （SMSS） subjected to different heat treatments were investigated. Room tensile tests, hardness tests, scanning elec- tron microscopy, transmission electron microscopy and X ray diffraction were conducted on the heat-treated steels. It is found that the microstructure of the heat-treated steel is composed of tempered lath martensite, retained austenite and ^-ferrite. The austenitizing temperature and tempering temperature have a significant effect on the microstrtlctur al changes, which leads to the complex variations of mechanical properties. The fine tempered lath martensite and more dispersed reversed austenite in the microstructure facilitate improving the comprehensive mechanical properties of the studied steel. The optimal heat treatment process of 00Crl3Ni5Mo2 SMSS is obtained by austenitizing at 1000 ℃ for 0.5 h＋air cooling followed by tempering at 630 ℃ for 2 h＋air cooling, where the excellent combination of ten- sile strength, elongation and hardness can be achieved.展开更多
The effect of pre-straining on the structure and formation mechanism of precipitates in an Al−Mg−Si−Cu alloy was systematically investigated by atomic resolution high-angle annular dark-field scanning transmission ele...The effect of pre-straining on the structure and formation mechanism of precipitates in an Al−Mg−Si−Cu alloy was systematically investigated by atomic resolution high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).Elongated and string-like precipitates are formed along the dislocations in the pre-strained Al−Mg−Si−Cu alloy.The precipitates formed along the dislocations exhibit three features:non-periodic atomic arrangement within the precipitate;Cu segregation occurring at the precipitate/α(Al)interface;different orientations presented in one individual precipitate.Four different formation mechanisms of these heterogeneous precipitates were proposed as follows:elongated precipitates are formed independently in the dislocation;string-like precipitates are formed directly along the dislocations;different precipitates encounter to form string-like precipitates;precipitates are connected by other phases or solute enrichment regions.These different formation mechanisms are responsible for forming different atomic structures and morphologies of precipitates.展开更多
Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body.In this work,the biocorrosion behaviors of AZ31B magnesium alloy under differe...Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body.In this work,the biocorrosion behaviors of AZ31B magnesium alloy under different stress forms with different magnitudes(20~150MPa)were studied.It was found that the corrosion behaviors at stressed conditions were severer than those at unstressed conditions and corrosion rates were obviously accelerated.The biocorrosion behaviors are more sensitive to the effects of tensile loads than to compressive loads.A biocorrosion numerical model on the degradation process of Mg alloy under static loads was established.The corrosion current density(i_(corr))of Mg alloy and the applied static stress(σ)matches a linear relationship of ln i_(corr)~σwell during the early stage(within 24 hrs)while deviated gradually in the latter period of corrosion.This work could provide a guidance and theoretical reference for further researches on the biocorrosion behaviors and practical clinical applications of the biomedical materials subjected to physiological loads.展开更多
It is a long-term challenge to further improve the corrosion resistance while ensuring the strength of magnesium(Mg)alloys.Revealing the effect of potential fluctuation on the micro-galvanic corrosion and the subseque...It is a long-term challenge to further improve the corrosion resistance while ensuring the strength of magnesium(Mg)alloys.Revealing the effect of potential fluctuation on the micro-galvanic corrosion and the subsequent film formation is important for understanding the corrosion mechanism of Mg alloys with multiple strengthening phases/structures.Here,we prepared the high-strength Mg-14.4Er-1.44Zn-0.3Zr(wt.%)alloys containing hybrid structures,i.e.,elongated long-period stacking ordered(LPSO)blocks+intragranular stacking faults(SFs)/LPSO lamellae.The Mg alloy with elongated LPSO blocks and intragranular LPSO lamellae(EZ-500 alloy)obtains good corrosion resistance(2.2 mm y^(–1)),while the Mg alloy containing elongated LPSO blocks and intragranular SFs(EZ-400 alloy)shows a significantly higher corrosion rate(6.9 mm y^(–1)).The results of scanning Kelvin probe force microscopy(SKPFM)show the elongated LPSO blocks act as cathode phase(87 mV in EZ-400 alloy),and the SFs serve as the weak anode(30 mV in EZ-400 alloy),resulting in high potential fluctuation in EZ-400 alloy.On the contrary,both elongated blocks and intragranular lamellae are cathodic LPSO phase(67–69 mV)in EZ-500 alloy,leading to a lower potential fluctuation.Quasi in-situ atomic force microscope(AFM)observation indicates that high potential fluctuation would cause strong micro-galvanic corrosion,and subsequently leads to the failure in rapid formation of corrosion film,finally forming a loose and porous film,while relatively low potential fluctuation could result in more uniform corrosion mode and facilitate the rapid formation of protective film.Therefore,we propose that it is an effective way to develop high-strength corrosionresistant Mg alloys by controlling the potential fluctuation to form a“uniform potential”strengthening microstructure。展开更多
基金the financial support received from the National Natural Science Foundation of China(Grant No.51505479)the Jiangsu Natural Science Foundation of China(Grant No.BK20150184)the Fundamental Research Funds for the Central Universities(Grant No.2014QNA36)
文摘To develop a fundamental understanding of the flow behavior and optimal hot workability parameters of this material, the hot workability and deformation mechanisms of the as-cast 21Cr EDSS were studied using processing map technology combined with microstructure analysis and isothermal hot compression over the temperature range of 1000-1150 ℃ and strain rate range of 0.01-10 s-1. The processing maps and constitutive equation of peak stress were developed based on Prasad＇s and Murty＇s criteria. The results show that the processing maps exhibit a stable domain at 1000-1150 ℃ and 0.01-1 s-1. The instability domain is exhibited at high strain rates （≥1 s-l）. This implies that Murty＇s criterion can predict the unstable domain with high reliability. The detailed deformation mechanisms are also studied by microstructure observation, showing that the flow localization and microcracking are responsible for the flow instability.
基金supported by the National Natural Science Foundation of China (Nos. 51604034 and 51974032)the Science and Technology Project of Jilin Education Department in 13th Five–Year (No. JJKH20181008KJ)the Science and Technology Development Program of Jilin Province (No. 20190302003GX)。
文摘The creep behavior of Fe–17 Cr–1.2 Cu–0.5 Nb–0.01 C ferritic heat-resistant stainless steel was investigated at temperatures ranging from 973 to 1123 K and stresses from 15 to 90 MPa.The evolution of precipitates after creep deformation was analyzed by scanning electron microscopy,energy dispersion spectrum,and transmission electron microscopy.The minimum creep rate decreased with the decrease in the applied load and temperature,thereby extending the rupture life.Cu-rich phase and Nb-rich Laves particles were generated in dominant quantities during the creep process,and the co-growth relationship between them could be detected.Creep rupture was featured by ductile fracture with considerable necking.As increasing the temperature and decreasing the stress,the softening of the metal matrix was accelerated,showing more obvious plastic fl ow.The true stress exponent and activation energy were 4.9 and 375.5 kJ/mol,respectively,indicating that the creep deformation was dominated by the diffusion-controlled dislocation creep mechanism involving precipitate-dislocation interactions.Based on the creep rupture data obtained,the Monkman–Grant relation and Larson-Miller parameter were established,which described the creep rupture life for the studied steel well.
基金Applied Basic Research Program of Liaoning Province(CN)(2022JH2/101300078)。
文摘Self-designed Al8Si0.4Mg0.4Fe aluminium alloy was modified with Sr,followed by solid solution and aging treatments to regulate its microstructure and mechanical/electrical properties.The results show that after the modification treatment,the room-temperature tensile strength of the alloy remains nearly unchanged,the elongation at break slightly increases from 1.82%to 3.34%,and the electrical conductivity significantly increases from 40.1%international annealed copper standard(IACS)to 42.0%IACS.After the modification,the alloy was subjected to solid solution treatment at 515℃for 8 h,followed by aging treatment at 180,200,220 and 240℃for 6 h.With increasing aging temperature,the electrical conductivity increases monotonously from 41.4%IACS to 45.5%IACS,while the room-temperature tensile strength initially increases and then decreases.At 200℃,the alloy achieves an optimal balance between electrical conductivity and room-temperature tensile strength:the electrical conductivity is 42.5%IACS,and the room-temperature tensile strength is 282.9 MPa.When the aging temperature continues to rise,the alloy undergoes overaging.Although the conductivity continues to increase,the room-temperature tensile strength drops sharply,and it is only 177.1 MPa at 240℃.
基金Project supported by the National Natural Science Foundation of China(Nos.12372071 and 12372070)the Aeronautical Science Fund of China(No.2022Z055052001)the Foundation of China Scholarship Council(No.202306830079)。
文摘Currently,there are a limited number of dynamic models available for braided composite plates with large overall motions,despite the incorporation of three-dimensional(3D)braided composites into rotating blade components.In this paper,a dynamic model of 3D 4-directional braided composite thin plates considering braiding directions is established.Based on Kirchhoff's plate assumptions,the displacement variables of the plate are expressed.By incorporating the braiding directions into the constitutive equation of the braided composites,the dynamic model of the plate considering braiding directions is obtained.The effects of the speeds,braiding directions,and braided angles on the responses of the plate with fixed-axis rotation and translational motion,respectively,are investigated.This paper presents a dynamic theory for calculating the deformation of 3D braided composite structures undergoing both translational and rotational motions.It also provides a simulation method for investigating the dynamic behavior of non-isotropic material plates in various applications.
基金sponsored by the National Key R&D Program of China(No.2020YFC1910000)the National Natural Science Foundation of China(Grants No 51978153).
文摘Particulate matter(PM)from high-temperature emissions like chemical plants,coal stoves and vehicle exhausts poses a gravel challenge to human health.To address this issue,researchers have explored vari-ous fiber filters,yet the bulk struggle to withstand high temperatures.In this study,mullite fiber sponges were developed utilizing low-cost materials and Kármán vortex solution blow spinning,using surfac-tants to improve the spinnability of the sol.Optimized sponges demonstrate ultralight(19 mg cm^(-3)),temperature-resistant reversible compressibility(50% strain)and a water contact angle of 135°.These sponges exhibited exceptional thermal insulation(thermal conductivity:0.0256 W m^(-1) K^(-1))and per-formed well in high-temperature air filtration.At 800℃,the mullite sponge with a base weight of 35 mg cm^(-2),achieved an average filtration efficiency of 98.18%and 99.57% for PM_(2.5) and PM_(2.5-10),respectively,with a quality value of 0.98 Pa^(-1) at a wind speed of 4 cm s^(-1).This low-cost mullite fiber sponge offers a promising avenue for designing high-performance filtration materials.
基金supported by the National Natural Science Foundation of China(12202294)the Sichuan Science and Technology Program(2024NSFSC1346).
文摘Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerful numerical simulation tool,can efficiently resolve the microstructural evolution,multi-field coupling effects,and fracture behavior of SMAs and SMCs.This review begins by presenting the fundamental theoretical framework of the fracture phase field method as applied to SMAs and SMCs,covering key aspects such as the phase field modeling of martensitic transformation and brittle fracture.Subsequently,it systematically examines the phase field simulations of fracture behaviors in SMAs and SMCs,with particular emphasis on how crystallographic orientation,grain size,and grain boundary properties influence the crack propagation.Additionally,the interplay between martensite transformation and fracture mechanisms is analyzed to provide deeper insights into the material responses under mechanical loading.Finally,the review explores future prospects and emerging trends in phase field simulations of SMA and SMC fracture behavior,along with potential advancements in the fracture phase field method itself,including multi-physics coupling and enhanced computational efficiency for large-scale simulations.
基金supported by the Jilin Scientific and Technological Development Program(No.YDZJ202201ZYTS669)the National Natural Science Foundation of China(Nos.51974032,52174355,51874043 and 51604034).
文摘Over the past few years,the Cu element has attracted much attention in duplex stainless steels.It undoubtedly holds advantageous in regulating the two-phase proportion and austenite stability and is also one of the crucial factors affecting the corrosion resistance.However,the systematic research on the impact of Cu addition to lean duplex stainless steels remains insufficient.In this study,a novel Cu-alloyed Mn-N-type 20Cr lean duplex stainless steel was developed and the effect of Cu on the strain hardening capacity and corrosion resistance was analyzed.The results show that the Cu addition increases the volume fraction and stability of the austenite,retards the martensitic transformation,and extends the transformation-induced plasticity effect to a wider strain range.Compared to the Cu-free steel,the plasticity of Cu-containing steel can be increased by~26%.Additionally,the addition of Cu redistributes the Cr and N elements in the ferrite and austenite phases,thereby improving the corrosion resistance of the lean duplex stainless steel.
基金financially supported by the National Natural Science Foundation of China (No. 52004164)the Funding Program of Science and Technology Department of Liaoning Province, China (No. 2023-MSLH-249)the Funding Program of Education Department of Liaoning P rovince, China (No. LMGD2023018)。
文摘Fe–Ga sheets with large magnetostriction are required for improving the conversion efficiency under the ultra-high frequencymagnetic field. Trace Tb element doping can simultaneously improve the magnetostriction and ductility of Fe–Ga alloy. However, the im-pact of trace Tb doping on the microstructure and magnetostriction of Fe–Ga thin sheets is an open question. In this paper, the effects oftrace Tb addition on the secondary recrystallization and magnetostriction of Fe–Ga thin sheets are systematically studied by comparing thecharacteristics evolution of precipitation, texture, and nanoinclusions. The results indicate that trace Tb addition accelerates the secondaryrecrystallization of Goss texture due to the combined action of the bimodal size distributed precipitates, smaller grains, and more HEGBsin primary recrystallization. After quenching at 900℃, the magnetostriction value in 0.07 at %Tb-doped Fe_(81)Ga_(19) thin sheets increases by 30% to that of Fe_(81)Ga_(19) thin sheets. The increase in magnetostriction is attributed to the decrease in the number of Tb-rich precipitates andthe higher density of the nanometer-sized modified-D0_(3) inclusions induced by the dissolving of trace Tb elements after quenching. Theseresults demonstrate a simple and efficient approach for preparing Fe–Ga thin sheets with a large magnetostrictive coefficient by a combin-ation of trace RE element addition and conventional rolling method.
基金supported by the National Natural Science Foundation of China(52071175,52301304)the Natural Science Foundation of Jiangsu Province(BK20230704)+3 种基金the China Postdoctoral Science Foundation Funded Project(2023M731742)the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province(23KJB430019)the Research Fund of Nanjing Institute of Technology(YKJ202402)the Open Research Fund of Jiangsu Key Laboratory for Light Metal Alloys(LMA202401).
文摘Implants are inevitably subjected to stress corrosion,bringing serious challenges to the controlled degradation of biomedical Mg alloys.It is worth studying the stress corrosion cracking(SCC)behavior of Mg alloy and exploring Mg alloy with good SCC resistance for wide biomedical applications.In this work,the as-cast and as-extruded Mg-3Gd-1Zn-0.4Zr(GZ31K)alloys with uniform corrosion were used to investigate SCC behavior.The as-extruded GZ31K alloy exhibited better corrosion resistance and mechanical properties than the as-cast one mainly owing to grain refinement and uniformly distributed fine precipitates,and possessed superior SCC resistance.To clarify the SCC mechanism,the slow strain rate tests were assisted with applied constant potentials via an electrochemical workstation.Accelerated anodic dissolution at anodic polarization deteriorated SCC resistance due to the initiation of corrosion pits and micro-cracks.However,cathodic polarization had no obvious effects on SCC resistance,along with both retarded corrosion and accelerated hydrogen evolution.Stacking faults in GZ31K alloy were hydrogen capture containers to reduce the effect of hydrogen on SCC resistance during cathodic polarization.These findings provide new insights into the evaluation of SCC mechanism,and offer more opportunities to explore Mg alloys with good SCC resistance by regulating anodic dissolution.
基金supported by the Natural Science Foundation of China(Nos.22278094 and 22379033)Guangdong Graduate Education Innovation Program(No.2023JGXM_102)+2 种基金the Basic and Applied Basic Research Program of Guangzhou(No.SL2024A03J00499)the University Innovation Team Scientific Research Project of Guangzhou(No.202235246)Hainan Province Graduate Innovation Research Project(No.Qhyb2023-143).
文摘Four-electron oxygen evolving reaction is limited by proton adsorption and desorption,making its reaction kinetics sluggish,which poses a major challenge for catalyst design.Here,we present an unsaturated coordination interface by constructing a fast electron transfer channel between Cu_(2)V_(2)O_(7)(CVO)and BiVO4(BVO).X-ray absorption spectroscopy(XAS)and theoretical calculations results confirm that CVO and BVO between interfaces are bonded by the way of unsaturated coordination oxygen(Ouc).The Ouc optimizes the O-O coupled energy barrier at the V active site and promotes the disconnection of O-H bond,which increases the photocurrent intensity of CVO by 6 times.In addition,due to the high electronegativity of the Ouc,the bonding energies of Bi-O and Cu-O at the interface are enhanced,resulting in the long-term stability of the photoanode during the water splitting.Finally,by integrating the working electrode with a polysilicon solar cell,we assembled a device that demonstrated exceptional catalytic performance,achieving a hydrogen production rate of 100.6μmol·cm^(-2),and maintaining a hydrogen-to-oxygen volume ratio of 2:1 after continuous operation for 4 h.This discovery aids in a deeper understanding of photoanode design and offers further insights for industrial applications.
基金Project(20080505)supported by Science and Technology Department of Jilin Province,China
文摘Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxide coatings formed on magnesium alloys are mainly composed of MgO and MgAl2O4 phases;in addition,the content of MgO increases with increasing the current density.The morphology and surface roughness of the coatings were characterized by confocal laser scanning microscopy (CLSM).The results show that the surface roughness(Ra)decreases with increasing the current density.Moreover,the electrochemical corrosion results prove that the MgO coating produced in the electrolyte Na2SiO3 at current density of 5 A/cm 2 shows the best corrosion resistance.
基金supported by the National Natural Science Foundation of China(52071175)the Key Research&Development Plan(Social Development)of Jiangsu Province(BE2020702)。
文摘Magnesium(Mg)alloys have been widely used in automobile,aviation,computer,and other fields due to their lightweight,high specific strength and stiffness,low pollution,and good electromagnetic shielding performance.However,the chemical stability of Mg alloys is poor,especially in the corrosive medium environment with high stress corrosion sensitivity,which causes sudden damage to structural components and restricts their application field.In recent years,owing to the increasing failure rate of engineering structures caused by stress corrosion of Mg alloys,it has become necessary to understand and pay more attention to the stress corrosion cracking(SCC)behavior of Mg alloys.In this paper,the SCC mechanisms and test methods of Mg alloys have been summarized.The recent research progress on SCC of Mg alloys has been reviewed from the aspects of alloying,preparation process,surface modification,corrosive medium,and strain rate.More importantly,future research trends in the field of SCC of Mg alloys have also been proposed.
基金supported by the Ministry of Education of the People's Republic of China (Contract No. 210051)
文摘To improve the surface corrosion resistance of the alumina films fabricated by micro-arc oxidation （MAO）,Al2O3 coatings at different current densities （5,7 and 10 A/dm 2） were produced on aluminum alloys by adding SiC nano-particles into electrolyte during MAO process.The morphology and phase composition of the coatings were investigated by scanning electron microscopy （SEM） and X-ray diffraction （XRD）,respectively.Furthermore,the corrosion performance of the coatings was evaluated via a three-electrode system in a 3.5 wt pct NaCl solution.From the obtained morphology of alumina coatings,it was believed that the Al2O3 coatings embedded with SiC nano-particles were formed.The electrochemical impedance spectroscopy （EIS） plots and potentiodynamic polarization plots of the Al2O3 coatings with and without SiC nano-particles at different current densities reveal that the Al2O3 coatings with SiC nano-particles formed at 10 A/dm 2 showed the better corrosion resistance than the other coatings produced at 5 and 7 A/dm 2.
基金supported by the Program for New Century Excellent Talents from the Ministry of Education (Grant No. NCET-11-0984)
文摘An attempt has been made to improve the corrosion resistance of friction stir welded joints of 7075 aluminum alloys by micro-arc oxidation（MAO）, and the effects of Na2Si O3 concentration in electrolyte on the corrosion resistance of the coatings were discussed. Morphology and phase constituents of the MAO coatings produced in electrolyte with different Na2SiO3 concentrations were analyzed by scanning electron microscopy, confocal laser scanning microscopy and X-ray diffraction. Electrochemical tests were conducted to evaluate the corrosion resistance of the coatings. The results show that the corrosion resistance of the coated joints is much better than that without the ceramic coating, and the ceramic coating produced in the electrolyte with Na2SiO3 concentration 20 g/L showed better corrosion resistance than the others.
基金financially supported by the Scientific Research Fund of Nanjing Institute of Technology(No.CKJA201802)the Opening Project of Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology(No.ASMA201802)。
文摘The oxidation behavior of a nickel-based superalloy GH738 was studied by isothermal oxidation tests in still air at different temperatures,with exposure time up to 100 h.Oxidation-kinetic curves were plotted using the mass gain method.The surface and cross-sectional morphologies were observed by scanning electron microscopy(SEM).A composition analysis and an oxidation-product identification were conducted using energydispersive X-ray spectroscopy(EDS) and an X-ray diffraction(XRD),respectively.The results showed that GH738 exhibited parabolic oxidation-kinetic curves,with stable parabolic-rate constants at each temperatures.The activation energy of oxide growth was calculated to be329.6 kJ·mol^(-1).Cr_(2) O_(3)(chromia) was the external oxidation product at 800℃.A TiO_(2)-Cr_(2) O_(3) double-layer structure was formed at 900℃.The position of TiO_(2) changed from the oxide-metal interface to the air-oxide interface by the diffusion of Ti atoms in chromia during the oxidation time at this temperature.Spallation was observed in the Cr_(0.12)Ti_(0.78)O_(1.74)-Cr_(2) O_(3) multi-layer oxide of at 1000℃,which increased the oxidation rate.For all the tests,the main internal oxide was always Al_(2) O_(3).The entire GH738 oxidation process was interpreted by the competitive diffusion of elements(Cr,Ti,Ni,etc.) in metal matrix and chromia,while a schematic diagram of oxidation process was proposed.
基金sponsored by Science and Technology Projects from Xi'an City(CX1261⑤)the State Key Laboratory of Solidification Processing in NWPU(SKLSP201322)
文摘The microstructural evolution and mechanical property of 00Crl3NiSMo2 supermartensitic stainless steel （SMSS） subjected to different heat treatments were investigated. Room tensile tests, hardness tests, scanning elec- tron microscopy, transmission electron microscopy and X ray diffraction were conducted on the heat-treated steels. It is found that the microstructure of the heat-treated steel is composed of tempered lath martensite, retained austenite and ^-ferrite. The austenitizing temperature and tempering temperature have a significant effect on the microstrtlctur al changes, which leads to the complex variations of mechanical properties. The fine tempered lath martensite and more dispersed reversed austenite in the microstructure facilitate improving the comprehensive mechanical properties of the studied steel. The optimal heat treatment process of 00Crl3Ni5Mo2 SMSS is obtained by austenitizing at 1000 ℃ for 0.5 h＋air cooling followed by tempering at 630 ℃ for 2 h＋air cooling, where the excellent combination of ten- sile strength, elongation and hardness can be achieved.
基金the Natural Science Foundation of Jiangsu Province,China(No.BK20201035)the Talent Research Fund in Nanjing Institute of Technology,China(No.YKJ201957)+1 种基金the National Natural Science Foundation of China(Nos.51871035,52001159)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Nos.20KJB430016,20KJB430012).
文摘The effect of pre-straining on the structure and formation mechanism of precipitates in an Al−Mg−Si−Cu alloy was systematically investigated by atomic resolution high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).Elongated and string-like precipitates are formed along the dislocations in the pre-strained Al−Mg−Si−Cu alloy.The precipitates formed along the dislocations exhibit three features:non-periodic atomic arrangement within the precipitate;Cu segregation occurring at the precipitate/α(Al)interface;different orientations presented in one individual precipitate.Four different formation mechanisms of these heterogeneous precipitates were proposed as follows:elongated precipitates are formed independently in the dislocation;string-like precipitates are formed directly along the dislocations;different precipitates encounter to form string-like precipitates;precipitates are connected by other phases or solute enrichment regions.These different formation mechanisms are responsible for forming different atomic structures and morphologies of precipitates.
基金supported by the National Natural Science Foundation of China(Grant No.51771054,52171236)State Key Program of National Natural Science Foundation of China(Grant No.51631003)+5 种基金National Key Research and Development Program of China(Grant No.2016YFC1102402)Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials(Grant No.AMM2021A01)the Opening Project of Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology(Grant No.ASMA201901)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX20_0091)Natural Science Foundation of Jiangsu Province(BK20181020)the Introduction of Talent Research Fund in Nanjing Institute of Technology(YKJ201705)
文摘Biomedical degradable materials would be subjected to different degrees and forms of static stress after being implanted in the human body.In this work,the biocorrosion behaviors of AZ31B magnesium alloy under different stress forms with different magnitudes(20~150MPa)were studied.It was found that the corrosion behaviors at stressed conditions were severer than those at unstressed conditions and corrosion rates were obviously accelerated.The biocorrosion behaviors are more sensitive to the effects of tensile loads than to compressive loads.A biocorrosion numerical model on the degradation process of Mg alloy under static loads was established.The corrosion current density(i_(corr))of Mg alloy and the applied static stress(σ)matches a linear relationship of ln i_(corr)~σwell during the early stage(within 24 hrs)while deviated gradually in the latter period of corrosion.This work could provide a guidance and theoretical reference for further researches on the biocorrosion behaviors and practical clinical applications of the biomedical materials subjected to physiological loads.
基金supported by the National Natural Science Foundation of China(Nos.51871069,52071093,and 52201137)the Opening Project of Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology(No.ASMA202205)+1 种基金the Student Research and Innovation Fund of the Fundamental Research Funds for the Central Universities(No.3072022GIP1004)the Beijing Municipal Natural Science Foundation(No.2202004).
文摘It is a long-term challenge to further improve the corrosion resistance while ensuring the strength of magnesium(Mg)alloys.Revealing the effect of potential fluctuation on the micro-galvanic corrosion and the subsequent film formation is important for understanding the corrosion mechanism of Mg alloys with multiple strengthening phases/structures.Here,we prepared the high-strength Mg-14.4Er-1.44Zn-0.3Zr(wt.%)alloys containing hybrid structures,i.e.,elongated long-period stacking ordered(LPSO)blocks+intragranular stacking faults(SFs)/LPSO lamellae.The Mg alloy with elongated LPSO blocks and intragranular LPSO lamellae(EZ-500 alloy)obtains good corrosion resistance(2.2 mm y^(–1)),while the Mg alloy containing elongated LPSO blocks and intragranular SFs(EZ-400 alloy)shows a significantly higher corrosion rate(6.9 mm y^(–1)).The results of scanning Kelvin probe force microscopy(SKPFM)show the elongated LPSO blocks act as cathode phase(87 mV in EZ-400 alloy),and the SFs serve as the weak anode(30 mV in EZ-400 alloy),resulting in high potential fluctuation in EZ-400 alloy.On the contrary,both elongated blocks and intragranular lamellae are cathodic LPSO phase(67–69 mV)in EZ-500 alloy,leading to a lower potential fluctuation.Quasi in-situ atomic force microscope(AFM)observation indicates that high potential fluctuation would cause strong micro-galvanic corrosion,and subsequently leads to the failure in rapid formation of corrosion film,finally forming a loose and porous film,while relatively low potential fluctuation could result in more uniform corrosion mode and facilitate the rapid formation of protective film.Therefore,we propose that it is an effective way to develop high-strength corrosionresistant Mg alloys by controlling the potential fluctuation to form a“uniform potential”strengthening microstructure。
