The corrosion performance of oxide dispersion strengthened(ODS)steel is crucial for SCWR application.Machine learning(ML)models were established to predict the mass gain of ODS steels under corrosion conditions(i.e.,s...The corrosion performance of oxide dispersion strengthened(ODS)steel is crucial for SCWR application.Machine learning(ML)models were established to predict the mass gain of ODS steels under corrosion conditions(i.e.,supercritical water),thereby evaluating their corrosion resistance.The grain and particle morphologies and crystal and interface structures of nanoparticles of six ODS steels were studied by transmission electron microscopy,scanning transmission electron microscopy,and high-resolution transmission electron microscopy.Among six ML models employed,the LightGBM(LGBM)model shows the highest accuracy(root mean square error of 43.18 mg/dm^(2) and 50.21 mg/dm^(2),mean absolute error of 25.91 mg/dm^(2) and 27.82 mg/dm^(2),and coefficient of determination R^(2) of 0.97 and 0.96 for training set and testing set,respectively)in predicting the mass gain of ODS steels.The LGBM feature importance coefficients were also applied to denote the degree of the feature on corrosion resistance.For microstructural features,the parameters that greatly influence corrosion resistance are inter-particle spacing and grain diameter,with importance scores of 73 and 63,respectively.Moreover,there is a strong synergistic influence between Cr and Al on the corrosion resistance of ODS steels.Developing this efficient and accurate LGBM model not only enhances the understanding of ODS steel corrosion mechanisms but also provides valuable insights for the targeted optimization and design of high-performance ODS alloys.展开更多
Laser powder bed fusion(LPBF)is a widely used and well-developed approach in additive manufacturing.To meet the high material performance requirements of fourth-generation nuclear power reactors,the combination of LPB...Laser powder bed fusion(LPBF)is a widely used and well-developed approach in additive manufacturing.To meet the high material performance requirements of fourth-generation nuclear power reactors,the combination of LPBF processing with oxide dispersion strengthening(ODS)is currently of interest for the design and development of new materials.In this approach,nanoscale Y_(2)O_(3)particles are dispersed into the feeding powders to produce LPBF-ODS materials.Oxygen exposure and the introduction of oxygen into the solvation cell during LPBF are usually considered as detrimental processes that are impossible to eliminate completely.However,our understanding of these unavoidable processes is still limited.In this study,we developed a new LPBF-ODS design approach based on in situ oxygen content regulation during the LPBF process.The oxygen content of the environmental chamber was artificially adjusted using an online monitoring system to activate reactions between oxygen and the metallic elements for the in situ formation of dispersed oxide particles.Four batches of LPBF 304 L stainless steel samples were successfully processed under different oxygen levels to investigate the reinforcement effect of in situ chemical alloying.The results show that dispersed oxide particles were formed with an average nanoscale size of approximately 46 nm through the LPBF in situ alloying approach.The increase in the number density of oxide particles to 11.4 particles∕μm^(2)as the oxygen content increased played a role in refining and stabilizing the cellular structure.The yield strength of the in situ alloyed ODS material was enhanced(to up to~675 MPa)while its ductility was not significantly degraded(elongation of up to~39%).These tensile properties are competitive within the ranges reported for ODS alloys prepared by mechanical alloying.The main mechanisms for yield strength enhancement through interactions between nanoscale oxide particles and dislocation entanglement cells were analyzed.This study provides a new approach for the future preparation of high-performance LPBF-ODS alloys.展开更多
To develop a melting-based larger-scale fabrication process for oxide dispersion strengthened(ODS)steel,this study proposed a method of zone melting with built-in precursor powder(ZMPP),followed by hot forging and agi...To develop a melting-based larger-scale fabrication process for oxide dispersion strengthened(ODS)steel,this study proposed a method of zone melting with built-in precursor powder(ZMPP),followed by hot forging and aging treatments.A 50 kg ingot was successfully prepared,highlighting the scalability of this innovative process.Microstructural analysis revealed a predominantly lath martensite matrix with a small amount of ferrite in the hot-forged ODS steel,without oxide particle aggregation.Aging at 750℃ resulted in the formation of sub-micron-sized Cr_(23)C_(6) particles at grain boundaries and martensitic lath interfaces,accompanied by a high-density(7.64×1023 m^(-3))nano-scale(~6 nm)Y-Si-O complex oxides after 25 h.Additionally,the hot-forged sample exhibited a high yield strength(871 MPa)but limited ductility(5.0%).Aging treatments led to an increase in ductility but a decrease in yield strength.Notably,prolonged aging maintained the strength level of steels while enhancing ductility,with a 23.3% total elongation observed after 25 h.The novel ZMPP method,preparing high-quality ODS steels with uniform microstructure and good mechanical properties,provided a new avenue for large-scale production of ODS steels.展开更多
基金sponsored by the National Natural Science Foundation of China(Grants Nos.52171004,52471066,and 51871034).
文摘The corrosion performance of oxide dispersion strengthened(ODS)steel is crucial for SCWR application.Machine learning(ML)models were established to predict the mass gain of ODS steels under corrosion conditions(i.e.,supercritical water),thereby evaluating their corrosion resistance.The grain and particle morphologies and crystal and interface structures of nanoparticles of six ODS steels were studied by transmission electron microscopy,scanning transmission electron microscopy,and high-resolution transmission electron microscopy.Among six ML models employed,the LightGBM(LGBM)model shows the highest accuracy(root mean square error of 43.18 mg/dm^(2) and 50.21 mg/dm^(2),mean absolute error of 25.91 mg/dm^(2) and 27.82 mg/dm^(2),and coefficient of determination R^(2) of 0.97 and 0.96 for training set and testing set,respectively)in predicting the mass gain of ODS steels.The LGBM feature importance coefficients were also applied to denote the degree of the feature on corrosion resistance.For microstructural features,the parameters that greatly influence corrosion resistance are inter-particle spacing and grain diameter,with importance scores of 73 and 63,respectively.Moreover,there is a strong synergistic influence between Cr and Al on the corrosion resistance of ODS steels.Developing this efficient and accurate LGBM model not only enhances the understanding of ODS steel corrosion mechanisms but also provides valuable insights for the targeted optimization and design of high-performance ODS alloys.
基金supported by the National Natural Science Foundation of China(Nos.U22B2067 and 52073176)。
文摘Laser powder bed fusion(LPBF)is a widely used and well-developed approach in additive manufacturing.To meet the high material performance requirements of fourth-generation nuclear power reactors,the combination of LPBF processing with oxide dispersion strengthening(ODS)is currently of interest for the design and development of new materials.In this approach,nanoscale Y_(2)O_(3)particles are dispersed into the feeding powders to produce LPBF-ODS materials.Oxygen exposure and the introduction of oxygen into the solvation cell during LPBF are usually considered as detrimental processes that are impossible to eliminate completely.However,our understanding of these unavoidable processes is still limited.In this study,we developed a new LPBF-ODS design approach based on in situ oxygen content regulation during the LPBF process.The oxygen content of the environmental chamber was artificially adjusted using an online monitoring system to activate reactions between oxygen and the metallic elements for the in situ formation of dispersed oxide particles.Four batches of LPBF 304 L stainless steel samples were successfully processed under different oxygen levels to investigate the reinforcement effect of in situ chemical alloying.The results show that dispersed oxide particles were formed with an average nanoscale size of approximately 46 nm through the LPBF in situ alloying approach.The increase in the number density of oxide particles to 11.4 particles∕μm^(2)as the oxygen content increased played a role in refining and stabilizing the cellular structure.The yield strength of the in situ alloyed ODS material was enhanced(to up to~675 MPa)while its ductility was not significantly degraded(elongation of up to~39%).These tensile properties are competitive within the ranges reported for ODS alloys prepared by mechanical alloying.The main mechanisms for yield strength enhancement through interactions between nanoscale oxide particles and dislocation entanglement cells were analyzed.This study provides a new approach for the future preparation of high-performance LPBF-ODS alloys.
基金financially supported by the National Natural Science Foundation of China(Nos.52271034,52301058 and 52471042)the National MCF Energy R&D Program of China(No.2018YFE0306102)+1 种基金the China Postdoctoral Science Foundation(No.2023M732183)the Postdoctoral Fellowship Program of CPSF(No.GZB20230399).
文摘To develop a melting-based larger-scale fabrication process for oxide dispersion strengthened(ODS)steel,this study proposed a method of zone melting with built-in precursor powder(ZMPP),followed by hot forging and aging treatments.A 50 kg ingot was successfully prepared,highlighting the scalability of this innovative process.Microstructural analysis revealed a predominantly lath martensite matrix with a small amount of ferrite in the hot-forged ODS steel,without oxide particle aggregation.Aging at 750℃ resulted in the formation of sub-micron-sized Cr_(23)C_(6) particles at grain boundaries and martensitic lath interfaces,accompanied by a high-density(7.64×1023 m^(-3))nano-scale(~6 nm)Y-Si-O complex oxides after 25 h.Additionally,the hot-forged sample exhibited a high yield strength(871 MPa)but limited ductility(5.0%).Aging treatments led to an increase in ductility but a decrease in yield strength.Notably,prolonged aging maintained the strength level of steels while enhancing ductility,with a 23.3% total elongation observed after 25 h.The novel ZMPP method,preparing high-quality ODS steels with uniform microstructure and good mechanical properties,provided a new avenue for large-scale production of ODS steels.
