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
A Fe-12Cr-2W-0.2Zr-0.1Ti-0.35Y_(2)O_(3)ODS ferritic alloy was prepared by ball milling,hot isostatic pressing(HIP)and thermomechanical processing herein.The evolution of oxide nanoparticles(ONPs)with differ-ent interm...A Fe-12Cr-2W-0.2Zr-0.1Ti-0.35Y_(2)O_(3)ODS ferritic alloy was prepared by ball milling,hot isostatic pressing(HIP)and thermomechanical processing herein.The evolution of oxide nanoparticles(ONPs)with differ-ent intermediate annealing temperatures of thermomechanical processing and its effect on microstructure and mechanical properties of the ODS alloy were investigated.The result shows that the intermediate annealing temperatures played a decisive role in the size,morphology and structure of nanoparticles in the final alloy since this was attributed to the fact that fine particles were dissolved through dislocation shearing during cold deformation and then re-precipitated during subsequent heat treatment.The high intermediate annealing temperature promotes the growth of the near-spherical ONPs,while the ellip-soidal nanoparticles are developed at relatively low temperature.Meanwhile,the structural change of the ONPs was also facilitated by the dissolution-reprecipitation behavior.The predominant Y_(2)(Zr_(y)Ti_(1−y))_(2)O_(7)with cubic pyrochlore phase in as-HIPed alloy can be transformed into Y_(4)Zr_(3)O_(12)particles with rhom-bohedral structure during the thermomechanical treatment.However,compared with the change in size of ONPs,the change in morphology and structure of ONPs has no obvious influence on the mechanical strength.Different intermediate annealing temperatures play a different role in the coarsening of ONPs during thermomechanical treatment,which makes the alloy annealed at low temperature exhibiting more uniform distribution of ONPs and better mechanical properties.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
While developing nuclear materials,predicting their behavior under long-term irradiation regimes span-ning decades poses a significant challenge.We developed a novel Kinetic Monte Carlo(KMC)model to explore the precip...While developing nuclear materials,predicting their behavior under long-term irradiation regimes span-ning decades poses a significant challenge.We developed a novel Kinetic Monte Carlo(KMC)model to explore the precipitation behavior of Y-Ti-O oxides along grain boundaries within nanostructured ferritic alloys(NFA).This model also assessed the response of the oxides to neutron irradiation,even up sim-ulated radiation damage levels in the desired long dpa range for reactor components.Our simulations investigated how temperature and grain boundary sinks influenced the oxide characteristics of a 12YWT-like alloy during heat treatments at 1023,1123,and 1223 K.The oxide characteristics observed in our simulations were in good agreement with existing literature.Furthermore,the impact of grain bound-aries on precipitation was found to be minimal.The resulting oxide configurations and positions were used in subsequent simulations that exposed them to simulated neutron irradiation to a total accumu-lated dose of 8 dpa at three temperatures:673,773,and 873 K,and at dose rates of 10-3,10-4,and 10-5 dpa/s.This demonstrated the expected inverse relationship between oxide size and dose rate.In a long-term irradiation simulation at 873 K and 10-3 dpa/s was taken out to 66 dpa and found the oxides in the vicinity of the grain boundary were more susceptible to dissolution.Additionally,we conducted irradia-tion simulations of a 14YWT-like alloy to reproduce findings from neutron irradiation experiments.The larger oxides in the 14YWT-like alloy did not dissolve and displayed stability similar to the experimental results.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financially supported by the Research Fund of Nuclear Materials of China Atomic Energy Authority(No.ICNM-2023-YZ-03).
文摘A Fe-12Cr-2W-0.2Zr-0.1Ti-0.35Y_(2)O_(3)ODS ferritic alloy was prepared by ball milling,hot isostatic pressing(HIP)and thermomechanical processing herein.The evolution of oxide nanoparticles(ONPs)with differ-ent intermediate annealing temperatures of thermomechanical processing and its effect on microstructure and mechanical properties of the ODS alloy were investigated.The result shows that the intermediate annealing temperatures played a decisive role in the size,morphology and structure of nanoparticles in the final alloy since this was attributed to the fact that fine particles were dissolved through dislocation shearing during cold deformation and then re-precipitated during subsequent heat treatment.The high intermediate annealing temperature promotes the growth of the near-spherical ONPs,while the ellip-soidal nanoparticles are developed at relatively low temperature.Meanwhile,the structural change of the ONPs was also facilitated by the dissolution-reprecipitation behavior.The predominant Y_(2)(Zr_(y)Ti_(1−y))_(2)O_(7)with cubic pyrochlore phase in as-HIPed alloy can be transformed into Y_(4)Zr_(3)O_(12)particles with rhom-bohedral structure during the thermomechanical treatment.However,compared with the change in size of ONPs,the change in morphology and structure of ONPs has no obvious influence on the mechanical strength.Different intermediate annealing temperatures play a different role in the coarsening of ONPs during thermomechanical treatment,which makes the alloy annealed at low temperature exhibiting more uniform distribution of ONPs and better mechanical properties.
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supported by the Nuclear Regulatory Commission Fellowship Grant No.NRC-HQ-84-14-G-0035.
文摘While developing nuclear materials,predicting their behavior under long-term irradiation regimes span-ning decades poses a significant challenge.We developed a novel Kinetic Monte Carlo(KMC)model to explore the precipitation behavior of Y-Ti-O oxides along grain boundaries within nanostructured ferritic alloys(NFA).This model also assessed the response of the oxides to neutron irradiation,even up sim-ulated radiation damage levels in the desired long dpa range for reactor components.Our simulations investigated how temperature and grain boundary sinks influenced the oxide characteristics of a 12YWT-like alloy during heat treatments at 1023,1123,and 1223 K.The oxide characteristics observed in our simulations were in good agreement with existing literature.Furthermore,the impact of grain bound-aries on precipitation was found to be minimal.The resulting oxide configurations and positions were used in subsequent simulations that exposed them to simulated neutron irradiation to a total accumu-lated dose of 8 dpa at three temperatures:673,773,and 873 K,and at dose rates of 10-3,10-4,and 10-5 dpa/s.This demonstrated the expected inverse relationship between oxide size and dose rate.In a long-term irradiation simulation at 873 K and 10-3 dpa/s was taken out to 66 dpa and found the oxides in the vicinity of the grain boundary were more susceptible to dissolution.Additionally,we conducted irradia-tion simulations of a 14YWT-like alloy to reproduce findings from neutron irradiation experiments.The larger oxides in the 14YWT-like alloy did not dissolve and displayed stability similar to the experimental results.
