Activating both metal and lattice oxygen sites for efficient oxygen evolution reactions(OER)is a critical challenge.This study pioneers a novel approach,employing cobalt-nickel glycerate solid spheres(CoNi-G SSs)as se...Activating both metal and lattice oxygen sites for efficient oxygen evolution reactions(OER)is a critical challenge.This study pioneers a novel approach,employing cobalt-nickel glycerate solid spheres(CoNi-G SSs)as self-sacrificial templates to synthesize yolk-shell structured CoNi-G SSs@ZIF-67 nanospheres.The derived NiCo2S4@CoS2/MoS2 double-shelled hollow nanospheres integrate the adsorbate evolution mechanism(AEM)and lattice oxygen mechanism(LOM),enabling synergistic dual catalytic pathways.Nickel modulation facilitates active species reconstruction in NiCo_(2)S_(4),enhancing lattice oxygen activity and optimizing the LOM pathway.Characterization results indicate that anode activation triggered the redox processes of metal and lattice oxygen sites,involving the formation and re-filling of oxygen vacancies.Additionally,the CoS_(2)/MoS_(2) heterostructure enhances the AEM pathway,as supported by density functional theory calculations,which demonstrate optimized adsorption of intermediates for both hydrogen evolution reaction and OER.The assembled anion exchange membrane water splitting device can deliver a catalytic current of 500 mA cm^(-2) at 1.74 V under commercial catalytic operating conditions(1 mol L^(-1) KOH)for 150 h,with negligible degradation.This work provides important insights into the understanding of OER mechanisms and the design of high-performance water-splitting electrocatalysts,while also opening new avenues for developing multifunctional materials with multi-shell structures.展开更多
The characterization techniques were employed like transmission electron microscope,X-ray diffraction and microstructural characterization to investigate microstructural evolution and impact of precipitate-phase preci...The characterization techniques were employed like transmission electron microscope,X-ray diffraction and microstructural characterization to investigate microstructural evolution and impact of precipitate-phase precipitation on strength and toughness of a self-developed 32Si_(2)CrNi_(2)MoVNb steel during the quenching and tempering process.Research outputs indicated that the steel microstructure under the quenching state could be composed of martensite with a high dislocation density,a small amount of residual austenite,and many dispersed spherical MC carbides.In details,after tempering at 200℃,fine needle-shapedε-carbides would precipitate,which may improve yield strength and toughness of the steel.However,as compared to that after tempering at 200℃,the average length of needle-shapedε-carbides was found to increase to 144.1±4 from 134.1±3 nm after tempering at 340℃.As a result,the yield strength may increase to 1505±40 MPa,and the impact absorption energy(V-notch)may also decrease.Moreover,after tempering at 450℃,thoseε-carbides in the steel may transform into coarse rod-shaped cementite,and dislocation recoveries at such high tempering temperature may lead to decrease of strength and toughness of the steel.Finally,the following properties could be obtained:a yield strength of 1440±35 MPa,an ultimate tensile strength of 1864±50 MPa and an impact absorption energy of 45.9±4 J,by means of rational composition design and microstructural control.展开更多
The study of the oxygen evolution reaction(OER)mechanism is vital for advancing our understanding of this pivotal energy conversion process.This review synthesizes recent advancements in OER mechanism,emphasizing the ...The study of the oxygen evolution reaction(OER)mechanism is vital for advancing our understanding of this pivotal energy conversion process.This review synthesizes recent advancements in OER mechanism,emphasizing the intricate relationship between catalytic mechanisms and catalyst design.This review discusses the connotation and cutting-edge progress of traditional mechanisms such as adsorbate evolution mechanism(AEM)and lattice oxygen mechanism(LOM)as well as emerging pathways including oxide path mechanism(OPM),oxo-oxo coupling mechanism(OCM),and intramolecular oxygen coupling mechanism(IMOC)etc.Innovative research progress on the coexistence and transformation of multiple mechanisms is highlighted,and the intrinsic factors that influence these dynamic processes are summarized.Advanced characterization techniques and theoretical modeling are underscored as indispensable tools for revealing these complex interactions.This review provides guiding principles for mechanism-based catalyst design.Finally,in view of the multidimensional challenges currently faced by OER mechanisms,prospects for future research are given to bridge the gap between mechanism innovation and experimental verification and application.This comprehensive review provides valuable perspectives for advancing clean energy technologies and achieving sustainable development.展开更多
The excavation of deep tunnels crossing faults is highly prone to triggering rockburst disasters,which has become a significant engineering issue.In this study,taking the fault-slip rockbursts from a deep tunnel in so...The excavation of deep tunnels crossing faults is highly prone to triggering rockburst disasters,which has become a significant engineering issue.In this study,taking the fault-slip rockbursts from a deep tunnel in southwestern China as the engineering prototype,large-scale three-dimensional(3D)physical model tests were conducted on a 3D-printed complex geological model containing two faults.Based on the selfdeveloped 3D loading system and excavation device,the macroscopic failure of fault-slip rockbursts was simulated indoors.The stress,strain,and fracturing characteristics of the surrounding rock near the two faults were systematically evaluated during excavation and multistage loading.The test results effectively revealed the evolution and triggering mechanism of fault-slip rockbursts.After the excavation of a highstress tunnel,stress readjustment occurred.Owing to the presence of these two faults,stress continued to accumulate in the rock mass between them,leading to the accumulation of fractures.When the shear stress on a fault surface exceeded its shear strength,sudden fault slip and dislocation occurred,thus triggering rockbursts.Rockbursts occurred twice in the vault between the two faults,showing obvious intermittent characteristics.The rockburst pit was controlled by two faults.When the faults remained stable,tensile failure predominated in the surrounding rock.However,when the fault slip was triggered,shear failure in the surrounding rock increased.These findings provide valuable insights for enhancing the comprehension of fault-slip rockbursts.展开更多
Accurate assessment of coal brittleness is crucial in the design of coal seam drilling and underground coal mining operations.This study proposes a method for evaluating the brittleness of gas-bearing coal based on a ...Accurate assessment of coal brittleness is crucial in the design of coal seam drilling and underground coal mining operations.This study proposes a method for evaluating the brittleness of gas-bearing coal based on a statistical damage constitutive model and energy evolution mechanisms.Initially,integrating the principle of effective stress and the Hoek-Brown criterion,a statistical damage constitutive model for gas-bearing coal is established and validated through triaxial compression tests under different gas pressures to verify its accuracy and applicability.Subsequently,employing energy evolution mechanism,two energy characteristic parameters(elastic energy proportion and dissipated energy proportion)are analyzed.Based on the damage stress thresholds,the damage evolution characteristics of gas bearing coal were explored.Finally,by integrating energy characteristic parameters with damage parameters,a novel brittleness index is proposed.The results demonstrate that the theoretical curves derived from the statistical damage constitutive model closely align with the test curves,accurately reflecting the stress−strain characteristics of gas-bearing coal and revealing the stress drop and softening characteristics of coal in the post-peak stage.The shape parameter and scale parameter represent the brittleness and macroscopic strength of the coal,respectively.As gas pressure increases from 1 to 5 MPa,the shape parameter and the scale parameter decrease by 22.18%and 60.45%,respectively,indicating a reduction in both brittleness and strength of the coal.Parameters such as maximum damage rate and peak elastic energy storage limit positively correlate with coal brittleness.The brittleness index effectively captures the brittleness characteristics and reveals a decrease in brittleness and an increase in sensitivity to plastic deformation under higher gas pressure conditions.展开更多
The transition to renewable energy sources has elevated the importance of SIBs(SIBs)as cost-effective alternatives to lithium-ion batteries(LIBs)for large-scale energy storage.This review examines the mechanisms of ga...The transition to renewable energy sources has elevated the importance of SIBs(SIBs)as cost-effective alternatives to lithium-ion batteries(LIBs)for large-scale energy storage.This review examines the mechanisms of gas generation in SIBs,identifying sources from cathode materials,anode materials,and electrolytes,which pose safety risks like swelling,leakage,and explosions.Gases such as CO_(2),H_(2),and O_(2) primarily arise from the instability of cathode materials,side reactions between electrode and electrolyte,and electrolyte decomposition under high temperatures or voltages.Enhanced mitigation strategies,encompassing electrolyte design,buffer layer construction,and electrode material optimization,are deliberated upon.Accordingly,subsequent research endeavors should prioritize long-term high-precision gas detection to bolster the safety and performance of SIBs,thereby fortifying their commercial viability and furnishing dependable solutions for large-scale energy storage and electric vehicles.展开更多
Hydrogen production from water electrolysis,in particular from proton exchange membrane water electrolyzers(PEMWE),is a key approach to realizing a carbon-free energy cycle.However,the high anodic potential and strong...Hydrogen production from water electrolysis,in particular from proton exchange membrane water electrolyzers(PEMWE),is a key approach to realizing a carbon-free energy cycle.However,the high anodic potential and strong acid in PEMWE systems pose a major challenge to the stability of electrocatalysts,and the development of efficient and corrosion-resistant catalysts is urgently needed.Currently,iridium(Ir)-based catalysts have gained great attention due to their promising activity and stability,while the extremely low reserves of Ir in the earth seriously hinder the commercialization of PEMWE.Therefore,a systematic understanding of the latest advances in Ir-based catalysts is necessary to guide their rational design to meet the industrial requirements.In this review,the general reaction mechanisms and advanced characterization techniques for mechanism recognition are first introduced.Afterwards,the systematic design strategies and performances of Ir-based catalysts,including metallic Ir,Ir oxides,and Ir-based perovskites,are summarized in detail.Finally,the conclusions,challenges,and prospects for Ir-based electrocatalysts are presented.展开更多
（TiB2＋Al2O3）/NiAl composites were synthesized by self-propagation high-temperature synthesis, and their phase compositions, microstructures and evolution modes were studied. The microstructures and shapes vary with...（TiB2＋Al2O3）/NiAl composites were synthesized by self-propagation high-temperature synthesis, and their phase compositions, microstructures and evolution modes were studied. The microstructures and shapes vary with the TiB2＋Al2O3 content in the NiAl matrix. TiB2 particles take a great variety of elementary shapes such as white bars, plates, herringbones, regular cubes and cuboids. These results outline a strategy of self-assembly processes in real time to build diversified microstructures. Some TiB2 grains in sizes of 2-5μm are embeded in Al2O3 clusters, while a small number of TiB2 particles disperse in the NiAl matrix. It is believed that the higher the TiB2＋Al2O3 content is, the more the regular shapes and homogeneous distributions of TiB2 and Al2O3 will be present in the NiAl matrix.展开更多
According to the distribution of abutment stress in a stope,this research established the mechanical model of mining abutment pressure transmission in floor base on the theory of semi-infnite plate body in elasticity....According to the distribution of abutment stress in a stope,this research established the mechanical model of mining abutment pressure transmission in floor base on the theory of semi-infnite plate body in elasticity.This study takes the 762 working face of Haizi Coal Mine as a case in point,and analyzed the dynamic evolution law of seam floor stress during the mining process.With an organic combination of the mining floor stress and surrounding rock stress,the study obtained the change laws of the maximum principle stress and the minimum one for the floor roadway surrounding rock when mining the upper working face.Considering the non-constant pressure force state and the cracks revolution mechanisms of floor roadway surrounding rock,the research built the mechanical model of roadway stress.Simulation results verify the reliability of the above conclusions.Moreover,this model could provide the theoretical basis and technical support for controlling floor roadway surrounding rock.展开更多
Explosion welding was carried out on the basis of vacuum hot melt W/CuCrZr composite plate.Metallurgical microscope,scanning electron microscope and energy dispersive X-ray spectroscope were used to observe the micros...Explosion welding was carried out on the basis of vacuum hot melt W/CuCrZr composite plate.Metallurgical microscope,scanning electron microscope and energy dispersive X-ray spectroscope were used to observe the microscopic morphology of the bonding interface.At the same time,combined with finite element calculations,the evolution mechanism of the interface of the hot melt explosion welded W/CuCrZr composite plate was explored.The results show that the interface bonding of the hot melt explosion welded W/CuCrZr composite plate is good and there is a cross-melting zone with 3–8μm in thickness,but cracks are developed on the W side.The numerical simulation reproduces the changes of pressure,stress,strain and internal energy at the bonding interface in the process of hot melt explosion welding.The location of the crack generated in the experiment coincides with the high stress position calculated by numerical simulation.The high pressure and high temperature near the hot melt explosion welding interface further promote the bonding of the interface.展开更多
The object of this article is to investigate the energy evolution mechanism and failure criteria of cross-jointed samples containing an opening during deformation and failure based on the uniaxial compression test and...The object of this article is to investigate the energy evolution mechanism and failure criteria of cross-jointed samples containing an opening during deformation and failure based on the uniaxial compression test and rock energy principle.The results show that the energy evolution characteristics of the samples correspond to a typical progressive damage mode.The peak total energy,peak elastic energy,and total input energy of the samples all first decrease and then increase with an increase of half of the included angle,reaching their minimum values when this angle is 45°,while the dissipated energy generally increases with this angle.The existence of the opening and cross joints can obviously weaken the energy storage capacity of the rock,and the change in the included angle of the cross joint has a great influence on the elastic energy ratio of the sample before the peak stress,which leads to some differences in the distribution laws of the input energy.The continuous change and the subsequent sharp change in the rate of change in the energy consumption ratio can be used as the criteria of the crack initiation and propagation and the unstable failure of the sample,respectively.展开更多
Prognostics and health management （PHM） significantly improves system availability and reliability, and reduces the cost of system operations. Design for testability （DFT） developed concurrently with system design...Prognostics and health management （PHM） significantly improves system availability and reliability, and reduces the cost of system operations. Design for testability （DFT） developed concurrently with system design is an important way to improve PHM capability. Testability modeling and analysis are the foundation of DFT. This paper proposes a novel approach of testability modeling and analysis based on failure evolution mechanisms. At the component level, the fault progression-related information of each unit under test （UUT） in a system is obtained by means of failure modes, evolution mechanisms, effects and criticality analysis （FMEMECA）, and then the failure-symptom dependency can be generated. At the system level, the dynamic attributes of UUTs are assigned by using the bond graph methodology, and then the symptom-test dependency can be obtained by means of the functional flow method. Based on the failure-symptom and symptom-test dependencies, testability analysis for PHM systems can be realized. A shunt motor is used to verify the application of the approach proposed in this paper. Experimental results show that this approach is able to be applied to testability modeling and analysis for PHM systems very well, and the analysis results can provide a guide for engineers to design for testability in order to improve PHM performance.展开更多
Semisolid rheoforming （SSR） is a promising technology for the production of Mg wrought alloy in foundry settings. In order to realize SSR, it is necessary to characterize the grain structure evolution during slurry ...Semisolid rheoforming （SSR） is a promising technology for the production of Mg wrought alloy in foundry settings. In order to realize SSR, it is necessary to characterize the grain structure evolution during slurry preparation. In this paper, slurry of AZ31 alloy was produced by a novel rheocast process known as self-inoculation method （SIM）. Interrupted quenching technology was applied to investigate the primary a-Mg evolution during continuous cooling and isothermal holding. Results indicate that the initial microstructure of slurry produced by SIM is a mixture of irregular grains, which becomes ideally globular when the slurry slowly cools to 620 ~C and isothermally held for at least 30 s. The local solute diffusion leads to dendritic fragmentation and forms separated particles. During prolonged holding, the particle surface gradually becomes smooth because of protuberance melting and groove advancement. Coarsening of a-Mg grains in isothermal holding was analyzed using Lifshitz-Slyozov-Wagner theory. Results suggest that coalescence is most likely the dominant coarsening mechanism in the early stage while Ostwald ripening tends to be the principal one later. The EDS results indicate that a longer holding time leads to AI solute element segregation at the grain boundaries, but Zn distribution within liquid matrix has no obvious change.展开更多
The laboratory experiments,thermodynamic analysis,dynamic analysis,and industrial trials were carried out to investigate the influence of refining slag on the evolution and removal of oxide inclusions in 55SiCrA sprin...The laboratory experiments,thermodynamic analysis,dynamic analysis,and industrial trials were carried out to investigate the influence of refining slag on the evolution and removal of oxide inclusions in 55SiCrA spring steel.The reduction in basicity and Al_(2)O_(3) content in refining slag can reduce the[Al]s content in the molten steel,which is conducive to the control of the low melting point of inclusions.However,the refining slag with excessively low basicity transfers the oxygen element to molten steel and increases the Al_(2)O_(3) content in inclusions,which is harmful to the control of inclusions.According to the chemical compositions of inclusions and refining slag in laboratory experiments,their physical parameters were calculated.The maximum separation ratio and the moving time of inclusions to reach the maximum separation ratio(t_(max))of inclusions under different laboratory experimental conditions were studied.The maximum separation ratio of inclusions is positively correlated with the overall wettability(coshIMS)among the slag,steel,and inclusions.The maximum separation ratio of inclusions obtained by laboratory experiments is between 85%and 91%.The t_(max) decreases with the decline in basicity and Al_(2)O_(3) content of refining slag,but excessively low basicity will increase the t_(max).The basicity of refining slag in the range of 0.88–0.97 and the content of Al_(2)O_(3) less than 6%is not only conducive to reducing the content of Al_(2)O_(3) and the melting point of inclusions but also beneficial to removing the inclusions to the slag.The slag system shows good metallurgical results in industrial trials.展开更多
The test selection and optimization （TSO） can improve the abilities of fault diagnosis, prognosis and health-state evalua- tion for prognostics and health management （PHM） systems. Traditionally, TSO mainly focuse...The test selection and optimization （TSO） can improve the abilities of fault diagnosis, prognosis and health-state evalua- tion for prognostics and health management （PHM） systems. Traditionally, TSO mainly focuses on fault detection and isolation, but they cannot provide an effective guide for the design for testability （DFT） to improve the PHM performance level. To solve the problem, a model of TSO for PHM systems is proposed. Firstly, through integrating the characteristics of fault severity and propa- gation time, and analyzing the test timing and sensitivity, a testability model based on failure evolution mechanism model （FEMM） for PHM systems is built up. This model describes the fault evolution- test dependency using the fault-symptom parameter matrix and symptom parameter-test matrix. Secondly, a novel method of in- herent testability analysis for PHM systems is developed based on the above information. Having completed the analysis, a TSO model, whose objective is to maximize fault trackability and mini- mize the test cost, is proposed through inherent testability analysis results, and an adaptive simulated annealing genetic algorithm （ASAGA） is introduced to solve the TSO problem. Finally, a case of a centrifugal pump system is used to verify the feasibility and effectiveness of the proposed models and methods. The results show that the proposed technology is important for PHM systems to select and optimize the test set in order to improve their performance level.展开更多
Iron carbon agglomerates(ICA)are the composite burden for low-carbon blast furnace(BF)ironmaking.In order to optimize the reactivity of ICA according to the evolution characteristics of ICA in the BF smelting process,...Iron carbon agglomerates(ICA)are the composite burden for low-carbon blast furnace(BF)ironmaking.In order to optimize the reactivity of ICA according to the evolution characteristics of ICA in the BF smelting process,the evolution behavior and mechanism of different reactive ICA under simulated BF smelting conditions were studied.The results show that the existence of more sillimanite and aluminosilicate and less active sites of metallic iron will weaken gasification reaction and carburization ability of ICA-1(containing 10%iron ore).It weakens the promoting effect of ICA-1 on the reduction,softening,and melting of ferrous burdens and the dripping of slag-iron.The aluminosilicate with a high melting point decreases,the low melting point slag phase and Fe–Si alloy increase,and many active sites of metallic iron exist,which strengthen the gasification reaction and carburization ability of ICA-2(containing 30%iron ore).The promoting effect of ICA-2 on the reduction,softening,and melting of ferrous burdens and the dripping of slag-iron is significantly improved.The gasification reaction capacity of ICA-3(containing 35%iron ore)is reduced,and the improvement in ICA-3 on the softening–melting performance of mixed burdens is reduced.The appropriate proportion of iron ore in ICA is about 30%.展开更多
The far-field microdynamic disturbance caused by the excavation of deep mineral resources and underground engineering can induce surrounding rock damage in high-stress conditions and even lead to disasters.However,the...The far-field microdynamic disturbance caused by the excavation of deep mineral resources and underground engineering can induce surrounding rock damage in high-stress conditions and even lead to disasters.However,the mechanical properties and damage/fracture evolution mechanisms of deep rock induced by microdynamic disturbance under three-dimensional stress states are unclear.Therefore,a true triaxial multilevel disturbance test method is proposed,which can completely simulate natural geostress,excavation stress redistribution(such as stress unloading,concentration and rotation),and subsequently the microdynamic disturbance triggering damaged rock failure.Based on a dynamic true triaxial test platform,true triaxial microdynamic disturbance tests under different frequency and amplitudes were carried out on monzogabbro.The results show that increasing amplitude or decreasing frequency diminishes the failure strength of monzogabbro.Deformation modulus gradually decreases during disturbance failure.As frequency and amplitude increase,the degradation rate of deformation modulus decreases slightly,disturbance dissipated energy increases significantly,and disturbance deformation anisotropy strengthens obviously.A damage model has been proposed to quantitatively characterize the disturbance-induced damage evolution at different frequency and amplitude under true triaxial stress.Before disturbance failure,the micro-tensile crack mechanism is dominant,and the micro-shear crack mechanism increases significantly at failure.With the increase of amplitude and frequency,the micro-shear crack mechanism increases.When approaching disturbance failure,the acoustic emission fractal dimension changes from a stable value to local large oscillation,and finally increases sharply to a high value at failure.Finally,the disturbance-induced failure mechanism of surrounding rock in deep engineering is clearly elucidated.展开更多
The influence of cerium（Ce）treatment on the morphologies,size and distributions of Al_2O_3 inclusions in low carbon high manganese steel was investigated by OM,SEM-EDS and theoretical calculation.The results showed ...The influence of cerium（Ce）treatment on the morphologies,size and distributions of Al_2O_3 inclusions in low carbon high manganese steel was investigated by OM,SEM-EDS and theoretical calculation.The results showed that Ce can modify the morphologies and types of Al_2O_3 inclusions.After Ce treatment,the irregular Al_2O_3 inclusions were replaced by smaller and dispersive spherical cerium oxysulfides.The effects of treatment time and Ce content on the evolution of Al_2O_3 inclusions were examined.It indicated that Al_2O_3 inclusions were wrapped by rare earth inclusions to form a ring like shape Ce-enriched band around the inclusions.Model was established to elucidate the evolution mechanism of Al_2O_3 inclusions.Evolution kinetics of inclusions was discussed qualitatively to analyze the velocity controlled step.It was found that diffusion of Ce^（3＋）and Al^（3＋）in solid inclusion core and the formed intermediate layer would be the limited step during the evolution process.展开更多
Water electrolysis,a process for producing green hydrogen from renewable energy,plays a crucial role in the transition toward a sustainable energy landscape and the realization of the hydrogen economy.Oxygen evolution...Water electrolysis,a process for producing green hydrogen from renewable energy,plays a crucial role in the transition toward a sustainable energy landscape and the realization of the hydrogen economy.Oxygen evolution reaction(OER)is a critical step in water electrolysis and is often limited by its slow kinetics.Two main mechanisms,namely the adsorbate evolution mechanism(AEM)and lattice oxygen oxidation mechanism(LOM),are commonly considered in the context of OER.However,designing efficient catalysts based on either the AEM or the LOM remains a topic of debate,and there is no consensus on whether activity and stability are directly related to a certain mechanism.Considering the above,we discuss the characteristics,advantages,and disadvantages of AEM and LOM.Additionally,we provide insights on leveraging the LOM to develop highly active and stable OER catalysts in future.For instance,it is essential to accurately differentiate between reversible and irreversible lattice oxygen redox reactions to elucidate the LOM.Furthermore,we discuss strategies for effectively activating lattice oxygen to achieve controllable steady-state exchange between lattice oxygen and an electrolyte(OH^(-)or H_(2)O).Additionally,we discuss the use of in situ characterization techniques and theoretical calculations as promising avenues for further elucidating the LOM.展开更多
Microstructure evolution and the changes in mechanical properties of HR3 Csteel during long-term aging at650,700 and 750℃ were investigated.The precipitated phases of the aging steel included M23C6 carbides,Z-phase a...Microstructure evolution and the changes in mechanical properties of HR3 Csteel during long-term aging at650,700 and 750℃ were investigated.The precipitated phases of the aging steel included M23C6 carbides,Z-phase and a trace amount of Nb（C,N）.The M23C6 carbides were distributed mainly at the grain boundary,while Z-phase was mainly inside the grains.Amounts of both M23C6 carbides and Z-phase during the aging process increased with increasing aging period and temperature.Coarsening of M23C6 carbides was influenced significantly by aging time and temperature,while the size of the Z-phase was relatively less affected by the aging time and temperature,which had a steady strengthening effect.Coarsening of the M23C6 carbides was the main reason for the decline in high temperature yield strength during long-term aging at 750℃.The M23C6 carbides were linked into a continuous chain along the grain boundary which accounted for the decrease of toughness during aging.展开更多
文摘Activating both metal and lattice oxygen sites for efficient oxygen evolution reactions(OER)is a critical challenge.This study pioneers a novel approach,employing cobalt-nickel glycerate solid spheres(CoNi-G SSs)as self-sacrificial templates to synthesize yolk-shell structured CoNi-G SSs@ZIF-67 nanospheres.The derived NiCo2S4@CoS2/MoS2 double-shelled hollow nanospheres integrate the adsorbate evolution mechanism(AEM)and lattice oxygen mechanism(LOM),enabling synergistic dual catalytic pathways.Nickel modulation facilitates active species reconstruction in NiCo_(2)S_(4),enhancing lattice oxygen activity and optimizing the LOM pathway.Characterization results indicate that anode activation triggered the redox processes of metal and lattice oxygen sites,involving the formation and re-filling of oxygen vacancies.Additionally,the CoS_(2)/MoS_(2) heterostructure enhances the AEM pathway,as supported by density functional theory calculations,which demonstrate optimized adsorption of intermediates for both hydrogen evolution reaction and OER.The assembled anion exchange membrane water splitting device can deliver a catalytic current of 500 mA cm^(-2) at 1.74 V under commercial catalytic operating conditions(1 mol L^(-1) KOH)for 150 h,with negligible degradation.This work provides important insights into the understanding of OER mechanisms and the design of high-performance water-splitting electrocatalysts,while also opening new avenues for developing multifunctional materials with multi-shell structures.
基金the National Natural Science Foundation of China(Key Program)(52031004).
文摘The characterization techniques were employed like transmission electron microscope,X-ray diffraction and microstructural characterization to investigate microstructural evolution and impact of precipitate-phase precipitation on strength and toughness of a self-developed 32Si_(2)CrNi_(2)MoVNb steel during the quenching and tempering process.Research outputs indicated that the steel microstructure under the quenching state could be composed of martensite with a high dislocation density,a small amount of residual austenite,and many dispersed spherical MC carbides.In details,after tempering at 200℃,fine needle-shapedε-carbides would precipitate,which may improve yield strength and toughness of the steel.However,as compared to that after tempering at 200℃,the average length of needle-shapedε-carbides was found to increase to 144.1±4 from 134.1±3 nm after tempering at 340℃.As a result,the yield strength may increase to 1505±40 MPa,and the impact absorption energy(V-notch)may also decrease.Moreover,after tempering at 450℃,thoseε-carbides in the steel may transform into coarse rod-shaped cementite,and dislocation recoveries at such high tempering temperature may lead to decrease of strength and toughness of the steel.Finally,the following properties could be obtained:a yield strength of 1440±35 MPa,an ultimate tensile strength of 1864±50 MPa and an impact absorption energy of 45.9±4 J,by means of rational composition design and microstructural control.
文摘The study of the oxygen evolution reaction(OER)mechanism is vital for advancing our understanding of this pivotal energy conversion process.This review synthesizes recent advancements in OER mechanism,emphasizing the intricate relationship between catalytic mechanisms and catalyst design.This review discusses the connotation and cutting-edge progress of traditional mechanisms such as adsorbate evolution mechanism(AEM)and lattice oxygen mechanism(LOM)as well as emerging pathways including oxide path mechanism(OPM),oxo-oxo coupling mechanism(OCM),and intramolecular oxygen coupling mechanism(IMOC)etc.Innovative research progress on the coexistence and transformation of multiple mechanisms is highlighted,and the intrinsic factors that influence these dynamic processes are summarized.Advanced characterization techniques and theoretical modeling are underscored as indispensable tools for revealing these complex interactions.This review provides guiding principles for mechanism-based catalyst design.Finally,in view of the multidimensional challenges currently faced by OER mechanisms,prospects for future research are given to bridge the gap between mechanism innovation and experimental verification and application.This comprehensive review provides valuable perspectives for advancing clean energy technologies and achieving sustainable development.
基金funding support from the National Natural Science Foundation of China(Grant Nos.42177136 and 52309126).
文摘The excavation of deep tunnels crossing faults is highly prone to triggering rockburst disasters,which has become a significant engineering issue.In this study,taking the fault-slip rockbursts from a deep tunnel in southwestern China as the engineering prototype,large-scale three-dimensional(3D)physical model tests were conducted on a 3D-printed complex geological model containing two faults.Based on the selfdeveloped 3D loading system and excavation device,the macroscopic failure of fault-slip rockbursts was simulated indoors.The stress,strain,and fracturing characteristics of the surrounding rock near the two faults were systematically evaluated during excavation and multistage loading.The test results effectively revealed the evolution and triggering mechanism of fault-slip rockbursts.After the excavation of a highstress tunnel,stress readjustment occurred.Owing to the presence of these two faults,stress continued to accumulate in the rock mass between them,leading to the accumulation of fractures.When the shear stress on a fault surface exceeded its shear strength,sudden fault slip and dislocation occurred,thus triggering rockbursts.Rockbursts occurred twice in the vault between the two faults,showing obvious intermittent characteristics.The rockburst pit was controlled by two faults.When the faults remained stable,tensile failure predominated in the surrounding rock.However,when the fault slip was triggered,shear failure in the surrounding rock increased.These findings provide valuable insights for enhancing the comprehension of fault-slip rockbursts.
基金Project(52274096)supported by the National Natural Science Foundation of ChinaProject(WS2023A03)supported by the State Key Laboratory Cultivation Base for Gas Geology and Gas Control,China。
文摘Accurate assessment of coal brittleness is crucial in the design of coal seam drilling and underground coal mining operations.This study proposes a method for evaluating the brittleness of gas-bearing coal based on a statistical damage constitutive model and energy evolution mechanisms.Initially,integrating the principle of effective stress and the Hoek-Brown criterion,a statistical damage constitutive model for gas-bearing coal is established and validated through triaxial compression tests under different gas pressures to verify its accuracy and applicability.Subsequently,employing energy evolution mechanism,two energy characteristic parameters(elastic energy proportion and dissipated energy proportion)are analyzed.Based on the damage stress thresholds,the damage evolution characteristics of gas bearing coal were explored.Finally,by integrating energy characteristic parameters with damage parameters,a novel brittleness index is proposed.The results demonstrate that the theoretical curves derived from the statistical damage constitutive model closely align with the test curves,accurately reflecting the stress−strain characteristics of gas-bearing coal and revealing the stress drop and softening characteristics of coal in the post-peak stage.The shape parameter and scale parameter represent the brittleness and macroscopic strength of the coal,respectively.As gas pressure increases from 1 to 5 MPa,the shape parameter and the scale parameter decrease by 22.18%and 60.45%,respectively,indicating a reduction in both brittleness and strength of the coal.Parameters such as maximum damage rate and peak elastic energy storage limit positively correlate with coal brittleness.The brittleness index effectively captures the brittleness characteristics and reveals a decrease in brittleness and an increase in sensitivity to plastic deformation under higher gas pressure conditions.
基金financial support of Shenzhen Science and Technology Program(No.KJZD20230923115005009)Xiangjiang Lab(22XJ01007)+3 种基金National Natural Science Foundation(NNSF)of China(No.52202269)Shenzhen Science and Technology program(No.20220810155330003)Shenzhen Science and Technology Program(NO.KJZD20230923115005009)Project of Department of Education of Guangdong Province(No.2022ZDZX3018).
文摘The transition to renewable energy sources has elevated the importance of SIBs(SIBs)as cost-effective alternatives to lithium-ion batteries(LIBs)for large-scale energy storage.This review examines the mechanisms of gas generation in SIBs,identifying sources from cathode materials,anode materials,and electrolytes,which pose safety risks like swelling,leakage,and explosions.Gases such as CO_(2),H_(2),and O_(2) primarily arise from the instability of cathode materials,side reactions between electrode and electrolyte,and electrolyte decomposition under high temperatures or voltages.Enhanced mitigation strategies,encompassing electrolyte design,buffer layer construction,and electrode material optimization,are deliberated upon.Accordingly,subsequent research endeavors should prioritize long-term high-precision gas detection to bolster the safety and performance of SIBs,thereby fortifying their commercial viability and furnishing dependable solutions for large-scale energy storage and electric vehicles.
基金supported by the National Natural Science Foundation of China(22202053,22109035,52362031,and 52274297)the start-up Research Foundation of Hainan University(KYQD(ZR)-20008,20083,20084,23068,and 23169)+4 种基金the Hainan Province Science and Technology Special Fund(ZDYF2024SHFZ074)the Collaborative Innovation Center of Marine Science and Technology,Hainan University(XTCX2022HYC04)the specific research fund of The Innovation Platform for Academicians of Hainan Province(YSPTZX202315)the Research Fund Program of Guangdong Provincial Key Laboratory of Fuel Cell Technology(FC202307)the Open Fund Project of Key Laboratory of Electrochemical Energy Storage and Energy Conversion in Hainan Province of China(KFKT2023002)。
文摘Hydrogen production from water electrolysis,in particular from proton exchange membrane water electrolyzers(PEMWE),is a key approach to realizing a carbon-free energy cycle.However,the high anodic potential and strong acid in PEMWE systems pose a major challenge to the stability of electrocatalysts,and the development of efficient and corrosion-resistant catalysts is urgently needed.Currently,iridium(Ir)-based catalysts have gained great attention due to their promising activity and stability,while the extremely low reserves of Ir in the earth seriously hinder the commercialization of PEMWE.Therefore,a systematic understanding of the latest advances in Ir-based catalysts is necessary to guide their rational design to meet the industrial requirements.In this review,the general reaction mechanisms and advanced characterization techniques for mechanism recognition are first introduced.Afterwards,the systematic design strategies and performances of Ir-based catalysts,including metallic Ir,Ir oxides,and Ir-based perovskites,are summarized in detail.Finally,the conclusions,challenges,and prospects for Ir-based electrocatalysts are presented.
基金Project(51272141)supported by the National Natural Science Foundation of ChinaProject(ts20110828)supported by the Taishan Scholars Project of Shandong Province,ChinaProject(2015AA034404)supported by the Ministry of Science and Technology of China
文摘（TiB2＋Al2O3）/NiAl composites were synthesized by self-propagation high-temperature synthesis, and their phase compositions, microstructures and evolution modes were studied. The microstructures and shapes vary with the TiB2＋Al2O3 content in the NiAl matrix. TiB2 particles take a great variety of elementary shapes such as white bars, plates, herringbones, regular cubes and cuboids. These results outline a strategy of self-assembly processes in real time to build diversified microstructures. Some TiB2 grains in sizes of 2-5μm are embeded in Al2O3 clusters, while a small number of TiB2 particles disperse in the NiAl matrix. It is believed that the higher the TiB2＋Al2O3 content is, the more the regular shapes and homogeneous distributions of TiB2 and Al2O3 will be present in the NiAl matrix.
基金supported by the National Natural Science Foundation of China(No.51074004)the Open Project of State Key Laboratory Breeding Base for Mining Disaster Prevention and Control of Shandong University of Science and Technology of China(No.MDPC2012KF06)+1 种基金the Natural Science Foundation of Anhui Province of China(No.11040606M102)Young Teachers Science Foundation of Anhui University of Science&Technology of China(No.2012QNZ14)
文摘According to the distribution of abutment stress in a stope,this research established the mechanical model of mining abutment pressure transmission in floor base on the theory of semi-infnite plate body in elasticity.This study takes the 762 working face of Haizi Coal Mine as a case in point,and analyzed the dynamic evolution law of seam floor stress during the mining process.With an organic combination of the mining floor stress and surrounding rock stress,the study obtained the change laws of the maximum principle stress and the minimum one for the floor roadway surrounding rock when mining the upper working face.Considering the non-constant pressure force state and the cracks revolution mechanisms of floor roadway surrounding rock,the research built the mechanical model of roadway stress.Simulation results verify the reliability of the above conclusions.Moreover,this model could provide the theoretical basis and technical support for controlling floor roadway surrounding rock.
基金National Natural Science Foundation of China(12072363,12272374,12372373)Special Fund for Fundamental Research of the Central Universities(WK2480000008,WK2480000007,WK2320000049)Anhui Provincial Science and Technology Major Project(202003A05020035)。
文摘Explosion welding was carried out on the basis of vacuum hot melt W/CuCrZr composite plate.Metallurgical microscope,scanning electron microscope and energy dispersive X-ray spectroscope were used to observe the microscopic morphology of the bonding interface.At the same time,combined with finite element calculations,the evolution mechanism of the interface of the hot melt explosion welded W/CuCrZr composite plate was explored.The results show that the interface bonding of the hot melt explosion welded W/CuCrZr composite plate is good and there is a cross-melting zone with 3–8μm in thickness,but cracks are developed on the W side.The numerical simulation reproduces the changes of pressure,stress,strain and internal energy at the bonding interface in the process of hot melt explosion welding.The location of the crack generated in the experiment coincides with the high stress position calculated by numerical simulation.The high pressure and high temperature near the hot melt explosion welding interface further promote the bonding of the interface.
基金Project(FRF-TP-20-041A1)supported by the Fundamental Research Funds for the Central Universities,ChinaProjects(2016YFC0600801,2017YFC0804103)supported by the State Key Research Development Program of ChinaProjects(51774022,52074020)supported by the National Natural Science Foundation of China.
文摘The object of this article is to investigate the energy evolution mechanism and failure criteria of cross-jointed samples containing an opening during deformation and failure based on the uniaxial compression test and rock energy principle.The results show that the energy evolution characteristics of the samples correspond to a typical progressive damage mode.The peak total energy,peak elastic energy,and total input energy of the samples all first decrease and then increase with an increase of half of the included angle,reaching their minimum values when this angle is 45°,while the dissipated energy generally increases with this angle.The existence of the opening and cross joints can obviously weaken the energy storage capacity of the rock,and the change in the included angle of the cross joint has a great influence on the elastic energy ratio of the sample before the peak stress,which leads to some differences in the distribution laws of the input energy.The continuous change and the subsequent sharp change in the rate of change in the energy consumption ratio can be used as the criteria of the crack initiation and propagation and the unstable failure of the sample,respectively.
基金the National Natural Science Foundation of China(No.51175502)
文摘Prognostics and health management （PHM） significantly improves system availability and reliability, and reduces the cost of system operations. Design for testability （DFT） developed concurrently with system design is an important way to improve PHM capability. Testability modeling and analysis are the foundation of DFT. This paper proposes a novel approach of testability modeling and analysis based on failure evolution mechanisms. At the component level, the fault progression-related information of each unit under test （UUT） in a system is obtained by means of failure modes, evolution mechanisms, effects and criticality analysis （FMEMECA）, and then the failure-symptom dependency can be generated. At the system level, the dynamic attributes of UUTs are assigned by using the bond graph methodology, and then the symptom-test dependency can be obtained by means of the functional flow method. Based on the failure-symptom and symptom-test dependencies, testability analysis for PHM systems can be realized. A shunt motor is used to verify the application of the approach proposed in this paper. Experimental results show that this approach is able to be applied to testability modeling and analysis for PHM systems very well, and the analysis results can provide a guide for engineers to design for testability in order to improve PHM performance.
基金supported by the National Natural Science Foundation of China(50964010)
文摘Semisolid rheoforming （SSR） is a promising technology for the production of Mg wrought alloy in foundry settings. In order to realize SSR, it is necessary to characterize the grain structure evolution during slurry preparation. In this paper, slurry of AZ31 alloy was produced by a novel rheocast process known as self-inoculation method （SIM）. Interrupted quenching technology was applied to investigate the primary a-Mg evolution during continuous cooling and isothermal holding. Results indicate that the initial microstructure of slurry produced by SIM is a mixture of irregular grains, which becomes ideally globular when the slurry slowly cools to 620 ~C and isothermally held for at least 30 s. The local solute diffusion leads to dendritic fragmentation and forms separated particles. During prolonged holding, the particle surface gradually becomes smooth because of protuberance melting and groove advancement. Coarsening of a-Mg grains in isothermal holding was analyzed using Lifshitz-Slyozov-Wagner theory. Results suggest that coalescence is most likely the dominant coarsening mechanism in the early stage while Ostwald ripening tends to be the principal one later. The EDS results indicate that a longer holding time leads to AI solute element segregation at the grain boundaries, but Zn distribution within liquid matrix has no obvious change.
基金This work was financially supported by the State Key Laboratory of Advanced Metallurgy Foundation(No.41621005)the Subject of Xiangtan Branch,Hunan Valin Iron&Steel Co.,Ltd.,China(No.2018386).
文摘The laboratory experiments,thermodynamic analysis,dynamic analysis,and industrial trials were carried out to investigate the influence of refining slag on the evolution and removal of oxide inclusions in 55SiCrA spring steel.The reduction in basicity and Al_(2)O_(3) content in refining slag can reduce the[Al]s content in the molten steel,which is conducive to the control of the low melting point of inclusions.However,the refining slag with excessively low basicity transfers the oxygen element to molten steel and increases the Al_(2)O_(3) content in inclusions,which is harmful to the control of inclusions.According to the chemical compositions of inclusions and refining slag in laboratory experiments,their physical parameters were calculated.The maximum separation ratio and the moving time of inclusions to reach the maximum separation ratio(t_(max))of inclusions under different laboratory experimental conditions were studied.The maximum separation ratio of inclusions is positively correlated with the overall wettability(coshIMS)among the slag,steel,and inclusions.The maximum separation ratio of inclusions obtained by laboratory experiments is between 85%and 91%.The t_(max) decreases with the decline in basicity and Al_(2)O_(3) content of refining slag,but excessively low basicity will increase the t_(max).The basicity of refining slag in the range of 0.88–0.97 and the content of Al_(2)O_(3) less than 6%is not only conducive to reducing the content of Al_(2)O_(3) and the melting point of inclusions but also beneficial to removing the inclusions to the slag.The slag system shows good metallurgical results in industrial trials.
基金supported by the National Natural Science Foundation of China(51175502)
文摘The test selection and optimization （TSO） can improve the abilities of fault diagnosis, prognosis and health-state evalua- tion for prognostics and health management （PHM） systems. Traditionally, TSO mainly focuses on fault detection and isolation, but they cannot provide an effective guide for the design for testability （DFT） to improve the PHM performance level. To solve the problem, a model of TSO for PHM systems is proposed. Firstly, through integrating the characteristics of fault severity and propa- gation time, and analyzing the test timing and sensitivity, a testability model based on failure evolution mechanism model （FEMM） for PHM systems is built up. This model describes the fault evolution- test dependency using the fault-symptom parameter matrix and symptom parameter-test matrix. Secondly, a novel method of in- herent testability analysis for PHM systems is developed based on the above information. Having completed the analysis, a TSO model, whose objective is to maximize fault trackability and mini- mize the test cost, is proposed through inherent testability analysis results, and an adaptive simulated annealing genetic algorithm （ASAGA） is introduced to solve the TSO problem. Finally, a case of a centrifugal pump system is used to verify the feasibility and effectiveness of the proposed models and methods. The results show that the proposed technology is important for PHM systems to select and optimize the test set in order to improve their performance level.
基金This work was financially supported by the National Natural Science Foundation of China-Liaoning Joint Funds(U1808212)National Natural Science Foundation of China(52074080)Xingliao Talent Plan(XLYC1902118).
文摘Iron carbon agglomerates(ICA)are the composite burden for low-carbon blast furnace(BF)ironmaking.In order to optimize the reactivity of ICA according to the evolution characteristics of ICA in the BF smelting process,the evolution behavior and mechanism of different reactive ICA under simulated BF smelting conditions were studied.The results show that the existence of more sillimanite and aluminosilicate and less active sites of metallic iron will weaken gasification reaction and carburization ability of ICA-1(containing 10%iron ore).It weakens the promoting effect of ICA-1 on the reduction,softening,and melting of ferrous burdens and the dripping of slag-iron.The aluminosilicate with a high melting point decreases,the low melting point slag phase and Fe–Si alloy increase,and many active sites of metallic iron exist,which strengthen the gasification reaction and carburization ability of ICA-2(containing 30%iron ore).The promoting effect of ICA-2 on the reduction,softening,and melting of ferrous burdens and the dripping of slag-iron is significantly improved.The gasification reaction capacity of ICA-3(containing 35%iron ore)is reduced,and the improvement in ICA-3 on the softening–melting performance of mixed burdens is reduced.The appropriate proportion of iron ore in ICA is about 30%.
基金the financial support from the National Natural Science Foundation of China(No.52109119)the Guangxi Natural Science Foundation(No.2021GXNSFBA075030)+2 种基金the Guangxi Science and Technology Project(No.Guike AD20325002)the Chinese Postdoctoral Science Fund Project(No.2022M723408)the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin(China Institute of Water Resources and Hydropower Research)(No.IWHR-SKL-202202)。
文摘The far-field microdynamic disturbance caused by the excavation of deep mineral resources and underground engineering can induce surrounding rock damage in high-stress conditions and even lead to disasters.However,the mechanical properties and damage/fracture evolution mechanisms of deep rock induced by microdynamic disturbance under three-dimensional stress states are unclear.Therefore,a true triaxial multilevel disturbance test method is proposed,which can completely simulate natural geostress,excavation stress redistribution(such as stress unloading,concentration and rotation),and subsequently the microdynamic disturbance triggering damaged rock failure.Based on a dynamic true triaxial test platform,true triaxial microdynamic disturbance tests under different frequency and amplitudes were carried out on monzogabbro.The results show that increasing amplitude or decreasing frequency diminishes the failure strength of monzogabbro.Deformation modulus gradually decreases during disturbance failure.As frequency and amplitude increase,the degradation rate of deformation modulus decreases slightly,disturbance dissipated energy increases significantly,and disturbance deformation anisotropy strengthens obviously.A damage model has been proposed to quantitatively characterize the disturbance-induced damage evolution at different frequency and amplitude under true triaxial stress.Before disturbance failure,the micro-tensile crack mechanism is dominant,and the micro-shear crack mechanism increases significantly at failure.With the increase of amplitude and frequency,the micro-shear crack mechanism increases.When approaching disturbance failure,the acoustic emission fractal dimension changes from a stable value to local large oscillation,and finally increases sharply to a high value at failure.Finally,the disturbance-induced failure mechanism of surrounding rock in deep engineering is clearly elucidated.
基金financially sponsored by Nature Science Foundation of Shanxi Province of China(No.2015011068)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2017138)
文摘The influence of cerium（Ce）treatment on the morphologies,size and distributions of Al_2O_3 inclusions in low carbon high manganese steel was investigated by OM,SEM-EDS and theoretical calculation.The results showed that Ce can modify the morphologies and types of Al_2O_3 inclusions.After Ce treatment,the irregular Al_2O_3 inclusions were replaced by smaller and dispersive spherical cerium oxysulfides.The effects of treatment time and Ce content on the evolution of Al_2O_3 inclusions were examined.It indicated that Al_2O_3 inclusions were wrapped by rare earth inclusions to form a ring like shape Ce-enriched band around the inclusions.Model was established to elucidate the evolution mechanism of Al_2O_3 inclusions.Evolution kinetics of inclusions was discussed qualitatively to analyze the velocity controlled step.It was found that diffusion of Ce^（3＋）and Al^（3＋）in solid inclusion core and the formed intermediate layer would be the limited step during the evolution process.
基金the support from the National Key R&D Program of China(2020YFA0710000)the National Natural Science Foundation of China(Nos.22008170,22278307,22222808,21978200)+1 种基金the Haihe Laboratory of Sustainable Chemical Transformationsthe Tianjin Research Innovation Project for Postgraduate Students(2022B KYZ035)。
文摘Water electrolysis,a process for producing green hydrogen from renewable energy,plays a crucial role in the transition toward a sustainable energy landscape and the realization of the hydrogen economy.Oxygen evolution reaction(OER)is a critical step in water electrolysis and is often limited by its slow kinetics.Two main mechanisms,namely the adsorbate evolution mechanism(AEM)and lattice oxygen oxidation mechanism(LOM),are commonly considered in the context of OER.However,designing efficient catalysts based on either the AEM or the LOM remains a topic of debate,and there is no consensus on whether activity and stability are directly related to a certain mechanism.Considering the above,we discuss the characteristics,advantages,and disadvantages of AEM and LOM.Additionally,we provide insights on leveraging the LOM to develop highly active and stable OER catalysts in future.For instance,it is essential to accurately differentiate between reversible and irreversible lattice oxygen redox reactions to elucidate the LOM.Furthermore,we discuss strategies for effectively activating lattice oxygen to achieve controllable steady-state exchange between lattice oxygen and an electrolyte(OH^(-)or H_(2)O).Additionally,we discuss the use of in situ characterization techniques and theoretical calculations as promising avenues for further elucidating the LOM.
基金Item Sponsored by National High-Tech Research and Development Program(863Program)of China(2012AA03A501)International Science and Technology Cooperation Program of China(2012DFG51670)
文摘Microstructure evolution and the changes in mechanical properties of HR3 Csteel during long-term aging at650,700 and 750℃ were investigated.The precipitated phases of the aging steel included M23C6 carbides,Z-phase and a trace amount of Nb（C,N）.The M23C6 carbides were distributed mainly at the grain boundary,while Z-phase was mainly inside the grains.Amounts of both M23C6 carbides and Z-phase during the aging process increased with increasing aging period and temperature.Coarsening of M23C6 carbides was influenced significantly by aging time and temperature,while the size of the Z-phase was relatively less affected by the aging time and temperature,which had a steady strengthening effect.Coarsening of the M23C6 carbides was the main reason for the decline in high temperature yield strength during long-term aging at 750℃.The M23C6 carbides were linked into a continuous chain along the grain boundary which accounted for the decrease of toughness during aging.
