Machine learning is employed to comprehensively analyze and predict the hardenability of 20CrMo steel.The hardenability dataset includes J9 and J15 hardenability values,chemical composition,and heat treatment paramete...Machine learning is employed to comprehensively analyze and predict the hardenability of 20CrMo steel.The hardenability dataset includes J9 and J15 hardenability values,chemical composition,and heat treatment parameters.Various machine learning models,including linear regression(LR),k-nearest neighbors(KNN),random forest(RF),and extreme Gradient Boosting(XGBoost),are employed to develop predictive models for the hardenability of 20CrMo steel.Among these models,the XGBoost model achieves the best performance,with coefficients of determination(R2)of 0.941 and 0.946 for predicting J9 and J15 values,respectively.The predictions fall with a±2 HRC bandwidth for 98%of J9 cases and 99%of J15 cases.Additionally,SHapley Additive exPlanations(SHAP)analysis is used to identify the key elements that significantly influence the hardenability of the 20CrMo steel.The analysis revealed that alloying elements such as Si,Cr,C,N and Mo play significant roles in hardenability.The strengths and weaknesses of various machine learning models in predicting hardenability are also discussed.展开更多
Microalloyed steels are extensively utilized in the automotive industry for their superior strength–toughness synergy.Structural components,such as cranks,wheels,and front axles,are subjected to fluctuating or repeti...Microalloyed steels are extensively utilized in the automotive industry for their superior strength–toughness synergy.Structural components,such as cranks,wheels,and front axles,are subjected to fluctuating or repetitive stresses during service,which cause fatigue damage or failure.Therefore,improving the fatigue properties of microalloyed steels is crucial to broaden their applications.An overview of the factors affecting the fatigue properties of microalloyed steels is provided,beginning with a concise description of microalloyed steels,followed by a discussion of key factors,such as microstructure,precipitation,and non-metallic inclusions,that influence fatigue performance.Strategies for enhancing fatigue properties are also explored,including non-metallic inclusion modification,surface treatment,and microstructure tailoring.Modification treatment of non-metallic inclusions can alter their morphology,size,quantity,distribution,etc.,thereby reducing the adverse effect on fatigue performance.The surface treatment enhances resistance to crack initiation by introducing compressive residual stress or refining the surface microstructure.Microstructure tailoring involves various heat treatment processes that can slow fatigue crack growth.Ultimately,the latest developments and future prospects of fatigue properties in microalloyed steels,based on academic research and industrial practices,are also summarized.展开更多
The modified precipitation theory was employed to directly predict the multi-variantε-carbide precipitation from thermodynamics and growing and ripening kinetics.Three distinct variants were identified:Variants 1 and...The modified precipitation theory was employed to directly predict the multi-variantε-carbide precipitation from thermodynamics and growing and ripening kinetics.Three distinct variants were identified:Variants 1 and 2 were the perpendicular plate-likeε-carbides,while the granularε-carbides were Variant 3.The particle sizes of Variants 1 and 2 were usually larger than those of Variant 3.The mean aspect ratios of Variants 1 and 2 were 4.96,4.62 and 4.35 larger than those(1.72,1.63 and 1.56)for the granularε-carbides when coiled at 140,200 and 250℃,respectively.Thermodynamic analysis indicated that Variants 1 and 2 are easier to nucleate than Variant 3.The growing kinetic analysis implied that the relative nucleation time and precipitation time for Variants 1 and 2 were about 8 and 5 orders of magnitude less than those for Variant 3,respectively.The ripening kinetics further displayed that the ripening rate was similar for Variants 1,2 and 3.In addition,the dislocation density has weak influence onε-carbide nucleation.These findings suggest that the precipitation thermodynamic and kinetic models could be extended to second phase precipitation in other materials systems.Besides,nano-scaleε-carbides,fine block size and nano-twins,as well as medium-density dislocations,jointly caused the optimal match between strength and total elongation when coiled at 140℃.展开更多
The hardenability of steel is crucial for its durability and performance in engineering applications,significantly influencing mechanical properties such as hardness,strength,and wear resistance.As the engineering fie...The hardenability of steel is crucial for its durability and performance in engineering applications,significantly influencing mechanical properties such as hardness,strength,and wear resistance.As the engineering field continuously demands higher-performance steel materials,a deep understanding of the key influencing factors on hardenability is crucial for developing quality steel that meets stringent application requirements.The effects of some specific elements,including carbon(C),vanadium(V),molybdenum(Mo),and boron(B),as well as heat treatment process parameters such as austenitizing temperature,austenitizing holding time,and cooling rate,were examined.It aims to elucidate the interactions among these factors and their influence on steel hardenability.For each influencing factor,the heat treatment procedure,characteristic microstructure resulting from it,and corresponding Jominy end quench curves were discussed.Furthermore,based on the continuous development of big data technology in the field of materials,the use of machine learning to predict the hardenability of steel and guide the design of steel material was also introduced.展开更多
The microstructure and mechanical properties of the compact strip production(CSP)processed quenching and partitioning(Q&P)steels were investigated through experimental methods to address the challenge of designing...The microstructure and mechanical properties of the compact strip production(CSP)processed quenching and partitioning(Q&P)steels were investigated through experimental methods to address the challenge of designing high-performance Q&P steels.Compared with the conventional process(CP)produced samples,with slightly reduced strength,the total elongation of the CSP produced samples was increased by nearly 7%.Microstructural analysis revealed that variations in austenite stability were not the primary cause for the differences in mechanical properties between the CSP and the CP.The CSP processed Q&P steel exhibited milder center segregation behavior in contrast to the CP processed Q&P steel.Consequently,in the CSP processed Q&P steel,a higher proportion of austenite and a lower proportion of martensite were observed at the center position,delaying the crack initiation in the central region and contributing to the enhanced ductility.The investigation into the CSP process reveals its effect on alleviation of segregation and enhancement of mechanical properties of the Q&P steel.展开更多
Nanograined(NG)materials often suffer from low thermal stability owing to the high volume fraction of grain boundaries(GBs).Herein,we investigate the possibility of utilizing local chemical ordering(LCO)for improving ...Nanograined(NG)materials often suffer from low thermal stability owing to the high volume fraction of grain boundaries(GBs).Herein,we investigate the possibility of utilizing local chemical ordering(LCO)for improving the thermal stability of NG FeCoNiCrMn highentropy alloys(HE As).NG HE As with two different grain sizes were considered.Tensile tests and creep test simulations were then performed to reveal the influence of LCO on the mechanical properties and thermal stability of NG HE As.After performing hybrid molecular dynamics and Monte Carlo simulations,Cr atoms were found to accumulate at GBs.By analyzing the atomic structure evolution during the deformation process,we found that the formation of LCO effectively stabilized the GBs and inhibited GB movement.In addition,dislocation nucleation from GBs and dislocation movement was also hindered.The inhibiting effect of LCO on GB movement and dislocation activity is more prominent than in the NG model with smaller grain sizes.The current simulation results suggest a possible strategy for enhancing the thermal stability of NG HEAs for service in a high-temperature environment.展开更多
Solid-state phase transformation is usually associated with excellent mechanical properties in steel materials.A deep understanding of the formation and evolution of phase structure is essential to tailor their servic...Solid-state phase transformation is usually associated with excellent mechanical properties in steel materials.A deep understanding of the formation and evolution of phase structure is essential to tailor their service performance.As a powerful tool for capturing the evolution of complex microstructures,phase-field simulation quantitatively calculates the phase structures evolution without explicit assumptions about transient microstructures.With the development of advanced numerical technology and computing ability,phase-field methods have been successfully applied to solid-state phase transformation in steels and greatly support the research and development of advanced steel materials.The phase-field simulations of solid-phase transformation in steels were summarized,and the future development was proposed.展开更多
Direct strip casting(DSC)is one of the cutting-edge technologies for the steel industry in the twenty-first century.Under the background of carbon peak and carbon neutrality,DSC technology has a bright future of appli...Direct strip casting(DSC)is one of the cutting-edge technologies for the steel industry in the twenty-first century.Under the background of carbon peak and carbon neutrality,DSC technology has a bright future of applications as it requires less production time and space with reduced energy consumption.Owing to its sub-rapid cooling rate during solidification and low reduction during hot rolling,DSC process exhibits a series of unique physical metallurgy characteristics.The process characteristics of DSC process and the microstructural evolution during the thermomechanical processing of low-carbon microalloyed steel are reviewed.The effects of hot rolling,cooling,coiling temperatures and microalloying elements on the microstructure and mechanical properties are then discussed.Finally,the future development orientations of DSC technology are suggested to fully utilize its unique features for the enhancement of its competitiveness and for the promotion of carbon neutrality of the steel industry.展开更多
The cooling process following hot rolling has a significant effect on the shape quality of a hot-rolled strip.The temperature and stress fields in the cooling process for a 14 mm thick strip with yield strength of 500...The cooling process following hot rolling has a significant effect on the shape quality of a hot-rolled strip.The temperature and stress fields in the cooling process for a 14 mm thick strip with yield strength of 500 MPa grade were analyzed by the finite element method and actual test data,and the relationship between residual stress and shape defects was described.Subsequently,the small-crown rolling process and the coil slow cooling process were investigated.The results indicate that these processes improved the shape quality of the final product significantly.展开更多
The realization of an ideal combination of mechanical and fatigue properties is prerequisites for practical application of titanium(Ti)microalloyed steel in automotive field.The fatigue behavior of four Ti microalloye...The realization of an ideal combination of mechanical and fatigue properties is prerequisites for practical application of titanium(Ti)microalloyed steel in automotive field.The fatigue behavior of four Ti microalloyed high-strength beam steels with different Ti contents was systematically studied.The results show that the content of microalloying element Ti has a significant effect on the fatigue properties,especially in the steel with a high Ti content.For the experimental Ti microalloyed steel,inclusion-induced crack initiation is the main fatigue failure mode.Different from general fatigue fracture mechanism in Ti-contained steel,no TiN,which is the most detrimental to fatigue behavior,was found in fatigue crack initiation area.However,the large-sized TiN and oxide complex inclusion with a core-shell structure is the dominant cause of fatigue fracture.Because of the intense-localized deformation at the interface between complex inclusion and matrix,the angular TiN in the outer shell has a serious deteriorating effect on the fatigue properties,which is consistent with the result of the Kernel average misorientation map.Besides,the modification effect of a small amount of MnS on large-sized inclusion is not obvious and has little effect on the fatigue behavior.For more practical guidance,the critical inclusion sizes of the experimental steels were also investigated by experimental extrapolation method.With the increasing tensile strength,the inclusion sensitivity of the experimental steels increases,leading to the small critical inclusion size.展开更多
A systematic investigation was conducted on the influence of residual nitrogen(0.003–0.008 wt.%)on the microstructure,mechanical properties,and strain aging behavior of scrap-electric arc furnace produced SAPH440 low...A systematic investigation was conducted on the influence of residual nitrogen(0.003–0.008 wt.%)on the microstructure,mechanical properties,and strain aging behavior of scrap-electric arc furnace produced SAPH440 low-alloy steel.Through internal friction spectroscopy,transmission electron microscopy,and atom probe tomography,the occurrence state of nitrogen and its interaction with dislocations under simulated industrial pre-strain(2%,10%)and aging conditions(250°C/h)were elucidated.Increasing nitrogen content was found to refine ferrite grain size and enhance strength,but it also drastically reduced ductility and impact toughness due to heightened strain aging sensitivity.Nitrogen levels≥0.008 wt.%promoted extensive Cottrell atmosphere formation,which pinned dislocations and caused severe embrittlement after aging,leading to additional yield strength increments of up to 147 MPa(2%strain)and 164 MPa(10%strain),while elongation fell below 16%and 8.3%,respectively.Critically,even 2%pre-strain immobilized virtually all nitrogen atoms≤0.008 wt.%,precipitating significant property degradation.Nitrogen segregation at grain boundaries and dislocation networks after strain aging was directly observed.展开更多
基金supported by the Key scientific and technological project plan of Hebei Iron and Steel Group(No.HG2023235).
文摘Machine learning is employed to comprehensively analyze and predict the hardenability of 20CrMo steel.The hardenability dataset includes J9 and J15 hardenability values,chemical composition,and heat treatment parameters.Various machine learning models,including linear regression(LR),k-nearest neighbors(KNN),random forest(RF),and extreme Gradient Boosting(XGBoost),are employed to develop predictive models for the hardenability of 20CrMo steel.Among these models,the XGBoost model achieves the best performance,with coefficients of determination(R2)of 0.941 and 0.946 for predicting J9 and J15 values,respectively.The predictions fall with a±2 HRC bandwidth for 98%of J9 cases and 99%of J15 cases.Additionally,SHapley Additive exPlanations(SHAP)analysis is used to identify the key elements that significantly influence the hardenability of the 20CrMo steel.The analysis revealed that alloying elements such as Si,Cr,C,N and Mo play significant roles in hardenability.The strengths and weaknesses of various machine learning models in predicting hardenability are also discussed.
基金financially supported by the National Key R&D Program of China(No.2021YFB3702403)financial support from the National Natural Science Foundation of China(Nos.52122408 and 52071023)。
文摘Microalloyed steels are extensively utilized in the automotive industry for their superior strength–toughness synergy.Structural components,such as cranks,wheels,and front axles,are subjected to fluctuating or repetitive stresses during service,which cause fatigue damage or failure.Therefore,improving the fatigue properties of microalloyed steels is crucial to broaden their applications.An overview of the factors affecting the fatigue properties of microalloyed steels is provided,beginning with a concise description of microalloyed steels,followed by a discussion of key factors,such as microstructure,precipitation,and non-metallic inclusions,that influence fatigue performance.Strategies for enhancing fatigue properties are also explored,including non-metallic inclusion modification,surface treatment,and microstructure tailoring.Modification treatment of non-metallic inclusions can alter their morphology,size,quantity,distribution,etc.,thereby reducing the adverse effect on fatigue performance.The surface treatment enhances resistance to crack initiation by introducing compressive residual stress or refining the surface microstructure.Microstructure tailoring involves various heat treatment processes that can slow fatigue crack growth.Ultimately,the latest developments and future prospects of fatigue properties in microalloyed steels,based on academic research and industrial practices,are also summarized.
基金supported by the National Natural Science Foundation of China(No.52293395)National Key R&D Program of China(No.2021YFB3702403).
文摘The modified precipitation theory was employed to directly predict the multi-variantε-carbide precipitation from thermodynamics and growing and ripening kinetics.Three distinct variants were identified:Variants 1 and 2 were the perpendicular plate-likeε-carbides,while the granularε-carbides were Variant 3.The particle sizes of Variants 1 and 2 were usually larger than those of Variant 3.The mean aspect ratios of Variants 1 and 2 were 4.96,4.62 and 4.35 larger than those(1.72,1.63 and 1.56)for the granularε-carbides when coiled at 140,200 and 250℃,respectively.Thermodynamic analysis indicated that Variants 1 and 2 are easier to nucleate than Variant 3.The growing kinetic analysis implied that the relative nucleation time and precipitation time for Variants 1 and 2 were about 8 and 5 orders of magnitude less than those for Variant 3,respectively.The ripening kinetics further displayed that the ripening rate was similar for Variants 1,2 and 3.In addition,the dislocation density has weak influence onε-carbide nucleation.These findings suggest that the precipitation thermodynamic and kinetic models could be extended to second phase precipitation in other materials systems.Besides,nano-scaleε-carbides,fine block size and nano-twins,as well as medium-density dislocations,jointly caused the optimal match between strength and total elongation when coiled at 140℃.
基金supported by the National Natural Science Foundation of China(Nos.52122408 and 52071023)Hong-hui Wu also thanks the financial support from the Fundamental Research Funds for the Central Universities(University of Science and Technology Beijing,Nos.FRF-TP-2021-04C1 and 06500135)supported by USTB MatCom of Beijing Advanced Innovation Center for Materials Genome Engineering.
文摘The hardenability of steel is crucial for its durability and performance in engineering applications,significantly influencing mechanical properties such as hardness,strength,and wear resistance.As the engineering field continuously demands higher-performance steel materials,a deep understanding of the key influencing factors on hardenability is crucial for developing quality steel that meets stringent application requirements.The effects of some specific elements,including carbon(C),vanadium(V),molybdenum(Mo),and boron(B),as well as heat treatment process parameters such as austenitizing temperature,austenitizing holding time,and cooling rate,were examined.It aims to elucidate the interactions among these factors and their influence on steel hardenability.For each influencing factor,the heat treatment procedure,characteristic microstructure resulting from it,and corresponding Jominy end quench curves were discussed.Furthermore,based on the continuous development of big data technology in the field of materials,the use of machine learning to predict the hardenability of steel and guide the design of steel material was also introduced.
基金support from the National Key R&D Program of China(No.2021YFB3702403).
文摘The microstructure and mechanical properties of the compact strip production(CSP)processed quenching and partitioning(Q&P)steels were investigated through experimental methods to address the challenge of designing high-performance Q&P steels.Compared with the conventional process(CP)produced samples,with slightly reduced strength,the total elongation of the CSP produced samples was increased by nearly 7%.Microstructural analysis revealed that variations in austenite stability were not the primary cause for the differences in mechanical properties between the CSP and the CP.The CSP processed Q&P steel exhibited milder center segregation behavior in contrast to the CP processed Q&P steel.Consequently,in the CSP processed Q&P steel,a higher proportion of austenite and a lower proportion of martensite were observed at the center position,delaying the crack initiation in the central region and contributing to the enhanced ductility.The investigation into the CSP process reveals its effect on alleviation of segregation and enhancement of mechanical properties of the Q&P steel.
基金financially supported by the National Natural Science Foundation of China(Nos.52101019,52071023,51901013,52122408)the financial support from the Fundamental Research Funds for theCentral Universities(University of Science and Technology Beijing,Nos.FRF-TP-2021-04C1,06500135)supported by USTB MatCom of Beijing Advanced Innovation Center for Materials Genome Engineering。
文摘Nanograined(NG)materials often suffer from low thermal stability owing to the high volume fraction of grain boundaries(GBs).Herein,we investigate the possibility of utilizing local chemical ordering(LCO)for improving the thermal stability of NG FeCoNiCrMn highentropy alloys(HE As).NG HE As with two different grain sizes were considered.Tensile tests and creep test simulations were then performed to reveal the influence of LCO on the mechanical properties and thermal stability of NG HE As.After performing hybrid molecular dynamics and Monte Carlo simulations,Cr atoms were found to accumulate at GBs.By analyzing the atomic structure evolution during the deformation process,we found that the formation of LCO effectively stabilized the GBs and inhibited GB movement.In addition,dislocation nucleation from GBs and dislocation movement was also hindered.The inhibiting effect of LCO on GB movement and dislocation activity is more prominent than in the NG model with smaller grain sizes.The current simulation results suggest a possible strategy for enhancing the thermal stability of NG HEAs for service in a high-temperature environment.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52071023,51901013,and 52122408)H.H.Wu also thanks to the financial support from the Fundamental Research Funds for the Central Universities(University of Science and Technology Beijing,Nos.FRF-TP-2021-04C1 and 06500135).
文摘Solid-state phase transformation is usually associated with excellent mechanical properties in steel materials.A deep understanding of the formation and evolution of phase structure is essential to tailor their service performance.As a powerful tool for capturing the evolution of complex microstructures,phase-field simulation quantitatively calculates the phase structures evolution without explicit assumptions about transient microstructures.With the development of advanced numerical technology and computing ability,phase-field methods have been successfully applied to solid-state phase transformation in steels and greatly support the research and development of advanced steel materials.The phase-field simulations of solid-phase transformation in steels were summarized,and the future development was proposed.
文摘Direct strip casting(DSC)is one of the cutting-edge technologies for the steel industry in the twenty-first century.Under the background of carbon peak and carbon neutrality,DSC technology has a bright future of applications as it requires less production time and space with reduced energy consumption.Owing to its sub-rapid cooling rate during solidification and low reduction during hot rolling,DSC process exhibits a series of unique physical metallurgy characteristics.The process characteristics of DSC process and the microstructural evolution during the thermomechanical processing of low-carbon microalloyed steel are reviewed.The effects of hot rolling,cooling,coiling temperatures and microalloying elements on the microstructure and mechanical properties are then discussed.Finally,the future development orientations of DSC technology are suggested to fully utilize its unique features for the enhancement of its competitiveness and for the promotion of carbon neutrality of the steel industry.
基金Item Sponsored by National Natural Science Foundation of China(U1460101)
文摘The cooling process following hot rolling has a significant effect on the shape quality of a hot-rolled strip.The temperature and stress fields in the cooling process for a 14 mm thick strip with yield strength of 500 MPa grade were analyzed by the finite element method and actual test data,and the relationship between residual stress and shape defects was described.Subsequently,the small-crown rolling process and the coil slow cooling process were investigated.The results indicate that these processes improved the shape quality of the final product significantly.
基金supported by the National Natural Science Foundation of China(No.52104369)the China Postdoctoral Science Foundation(No.2021M700374).
文摘The realization of an ideal combination of mechanical and fatigue properties is prerequisites for practical application of titanium(Ti)microalloyed steel in automotive field.The fatigue behavior of four Ti microalloyed high-strength beam steels with different Ti contents was systematically studied.The results show that the content of microalloying element Ti has a significant effect on the fatigue properties,especially in the steel with a high Ti content.For the experimental Ti microalloyed steel,inclusion-induced crack initiation is the main fatigue failure mode.Different from general fatigue fracture mechanism in Ti-contained steel,no TiN,which is the most detrimental to fatigue behavior,was found in fatigue crack initiation area.However,the large-sized TiN and oxide complex inclusion with a core-shell structure is the dominant cause of fatigue fracture.Because of the intense-localized deformation at the interface between complex inclusion and matrix,the angular TiN in the outer shell has a serious deteriorating effect on the fatigue properties,which is consistent with the result of the Kernel average misorientation map.Besides,the modification effect of a small amount of MnS on large-sized inclusion is not obvious and has little effect on the fatigue behavior.For more practical guidance,the critical inclusion sizes of the experimental steels were also investigated by experimental extrapolation method.With the increasing tensile strength,the inclusion sensitivity of the experimental steels increases,leading to the small critical inclusion size.
基金financial supports from the National Science and Technology Major Project of China(No.2025ZD0611202)National Key R&D Program of China(No.2021YFB3702403)+1 种基金the National Natural Science Foundation of China(Nos.52371017,52293395,and 52401137)Open Fund Project of State Key Laboratory of Materials Processing and Die and Mould Technology(P2024-005).
文摘A systematic investigation was conducted on the influence of residual nitrogen(0.003–0.008 wt.%)on the microstructure,mechanical properties,and strain aging behavior of scrap-electric arc furnace produced SAPH440 low-alloy steel.Through internal friction spectroscopy,transmission electron microscopy,and atom probe tomography,the occurrence state of nitrogen and its interaction with dislocations under simulated industrial pre-strain(2%,10%)and aging conditions(250°C/h)were elucidated.Increasing nitrogen content was found to refine ferrite grain size and enhance strength,but it also drastically reduced ductility and impact toughness due to heightened strain aging sensitivity.Nitrogen levels≥0.008 wt.%promoted extensive Cottrell atmosphere formation,which pinned dislocations and caused severe embrittlement after aging,leading to additional yield strength increments of up to 147 MPa(2%strain)and 164 MPa(10%strain),while elongation fell below 16%and 8.3%,respectively.Critically,even 2%pre-strain immobilized virtually all nitrogen atoms≤0.008 wt.%,precipitating significant property degradation.Nitrogen segregation at grain boundaries and dislocation networks after strain aging was directly observed.
