The evolution of the S'precipitate in Al−Cu−Mg alloy was investigated using transmission electron microscopy(TEM),high-angle annular dark-field scanning transmission electron microscopy(HAADF−STEM),molecular dynam...The evolution of the S'precipitate in Al−Cu−Mg alloy was investigated using transmission electron microscopy(TEM),high-angle annular dark-field scanning transmission electron microscopy(HAADF−STEM),molecular dynamics(MD)simulations,and other analytical techniques.The precipitation behavior during different aging stages of the supersaturated solid solution formed after rapid cold punching was focused,which induces rapid dissolution of precipitates.The findings reveal that the precipitation sequence is significantly influenced by aging temperature.At higher aging temperatures,which mitigate lattice distortion in the matrix,the precipitation sequence follows the conventional path.Conversely,at lower aging temperatures,where lattice distortion persists,the sequence deviates,suppressing the formation of Guinier−Preston−Bagaryatsky(GPB)zones.MD simulations confirm that the variations in solute atom diffusion rates at different aging temperatures lead to the differences in the S'phase precipitation sequence.展开更多
The microstructural evolution of Cu−19Ni−6Cr−7Mn alloy during aging treatment was investigated.After aging for 120 min at 500℃,the alloy exhibited excellent mechanical properties,including a tensile strength of 978 M...The microstructural evolution of Cu−19Ni−6Cr−7Mn alloy during aging treatment was investigated.After aging for 120 min at 500℃,the alloy exhibited excellent mechanical properties,including a tensile strength of 978 MPa and an elastic modulus of 145.8 GPa.After aging for 240 min at 500℃,the elastic modulus of the alloy reached 149.5 GPa,which was among the highest values reported for Cu alloys.It was worth mentioning that the tensile strength increased rapidly from 740 to 934 MPa after aging for 5 min at 500℃,which was close to the maximum tensile strength(978 MPa).Analysis of the underlying strengthening mechanisms and phase transformation behavior revealed that the Cu−19Ni−6Cr−7Mn alloy underwent spinodal decomposition and DO_(22) ordering during the first 5 min of aging at 500℃,and L1_(2) ordered phases and bcc-Cr precipitates appeared.Therefore,the enhanced mechanical properties of the Cu−19Ni−6Cr−7Mn alloy can be attributed to the stress field generated by spinodal decomposition and the presence of nanoscale ordered phase and Cr precipitates.展开更多
Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening pa...Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening particles also deteriorates the processability and it is of great importance to establish accurate processing maps to guide the thermomechanical processes to enhance the formability.In this study,we performed particle swarm optimization-based back propagation artificial neural network model to predict the high temperature flow behavior of 0.25wt%Al2O3 particle-reinforced Cu alloys,and compared the accuracy with that of derived by Arrhenius-type constitutive model and back propagation artificial neural network model.To train these models,we obtained the raw data by fabricating ODS Cu alloys using the internal oxidation and reduction method,and conducting systematic hot compression tests between 400 and800℃with strain rates of 10^(-2)-10 S^(-1).At last,processing maps for ODS Cu alloys were proposed by combining processing parameters,mechanical behavior,microstructure characterization,and the modeling results achieved a coefficient of determination higher than>99%.展开更多
The outstanding performance of O3-type NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)(NFM111)at both high and low temperatures coupled with its impressive specific capacity makes it an excellent cathode material for sodium-ion batte...The outstanding performance of O3-type NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)(NFM111)at both high and low temperatures coupled with its impressive specific capacity makes it an excellent cathode material for sodium-ion batteries.However,its poor cycling,owing to highpressure phase transitions,is one of its disadvantages.In this study,Cu/Ti was introduced into NFM111 cathode material using a solidphase method.Through both theoretically and experimentally,this study found that Cu doping provides a higher redox potential in NFM111,improving its reversible capacity and charge compensation process.The introduction of Ti would enhance the cycling stability of the material,smooth its charge and discharge curves,and suppress its high-voltage phase transitions.Accordingly,the NaNi_(0.27)Fe_(0.28)Mn_(0.33)Cu_(0.05)Ti_(0.06)O_(2)sample used in the study exhibited a remarkable rate performance of 142.97 mAh·g^(-1)at 0.1 C(2.0-4.2 V)and an excellent capacity retention of 72.81%after 300 cycles at 1C(1C=150 mA·g^(-1)).展开更多
Monocrystalline Cu exhibits excellent electrical and signal-transmission properties due to its absence of grain boundaries,making it a critical material for the production of micro-machinery and micro-components;howev...Monocrystalline Cu exhibits excellent electrical and signal-transmission properties due to its absence of grain boundaries,making it a critical material for the production of micro-machinery and micro-components;however,achieving ultrahigh precision and ultralow damage machining of functional devices using traditional techniques such as grinding and polishing is extremely challenging.Consequently,nanocutting has emerged as an efficient means to fabricate monocrystalline materials with complex surface characteristics and high surface integrity.Nevertheless,the macroscopic cutting theory of metal materials cannot be applied to nanocutting.Accordingly,in this paper,both simulations and experiments were conducted to examine the chip deformation mechanisms of monocrystalline Cu.First,large-scale molecular dynamics(MD)simulations were conducted to gain a comprehensive understanding of the deformation behavior during nanocutting.This included examining the influencing factors and the variation patterns of the chip deformation coefficient,cutting force,and minimum cutting thickness.Subsequently,nanocutting experiments were performed using a specially designed nanocutting platform with high-resolution online observation by scanning electron microscopy.The experimental results served to verify the accuracy and reliability of theMDmodeling,as they exhibited excellent consistency with the simulated results.Although this work considered monocrystalline Cu,it is believed that the elucidated chip deformation mechanisms could also be applied to other face-centered-cubic metals.These results are of great value for advancing the understanding of the mechanisms of ultraprecision cutting.展开更多
基金supported by the China Scholarship Council (CSC) Local Cooperation Program (No. 202308430176)the National Natural Science Foundation of China (No. 52271177)the Hunan Provincial Natural Science Foundation Regional Joint Fund, China (No. 2023JJ50173)。
文摘The evolution of the S'precipitate in Al−Cu−Mg alloy was investigated using transmission electron microscopy(TEM),high-angle annular dark-field scanning transmission electron microscopy(HAADF−STEM),molecular dynamics(MD)simulations,and other analytical techniques.The precipitation behavior during different aging stages of the supersaturated solid solution formed after rapid cold punching was focused,which induces rapid dissolution of precipitates.The findings reveal that the precipitation sequence is significantly influenced by aging temperature.At higher aging temperatures,which mitigate lattice distortion in the matrix,the precipitation sequence follows the conventional path.Conversely,at lower aging temperatures,where lattice distortion persists,the sequence deviates,suppressing the formation of Guinier−Preston−Bagaryatsky(GPB)zones.MD simulations confirm that the variations in solute atom diffusion rates at different aging temperatures lead to the differences in the S'phase precipitation sequence.
基金supported by the National Key R&D Program of China (No. 2021YFB3700700)the Henan Province Top Talent Training Program Project, China (No. 244500510020)the High-level Talent Research Start-up Project Funding of Henan Academy of Sciences, China (No. 242017001)。
文摘The microstructural evolution of Cu−19Ni−6Cr−7Mn alloy during aging treatment was investigated.After aging for 120 min at 500℃,the alloy exhibited excellent mechanical properties,including a tensile strength of 978 MPa and an elastic modulus of 145.8 GPa.After aging for 240 min at 500℃,the elastic modulus of the alloy reached 149.5 GPa,which was among the highest values reported for Cu alloys.It was worth mentioning that the tensile strength increased rapidly from 740 to 934 MPa after aging for 5 min at 500℃,which was close to the maximum tensile strength(978 MPa).Analysis of the underlying strengthening mechanisms and phase transformation behavior revealed that the Cu−19Ni−6Cr−7Mn alloy underwent spinodal decomposition and DO_(22) ordering during the first 5 min of aging at 500℃,and L1_(2) ordered phases and bcc-Cr precipitates appeared.Therefore,the enhanced mechanical properties of the Cu−19Ni−6Cr−7Mn alloy can be attributed to the stress field generated by spinodal decomposition and the presence of nanoscale ordered phase and Cr precipitates.
基金financial support of the National Natural Science Foundation of China(No.52371103)the Fundamental Research Funds for the Central Universities,China(No.2242023K40028)+1 种基金the Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials,China(No.AMM2023B01).financial support of the Research Fund of Shihezi Key Laboratory of AluminumBased Advanced Materials,China(No.2023PT02)financial support of Guangdong Province Science and Technology Major Project,China(No.2021B0301030005)。
文摘Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening particles also deteriorates the processability and it is of great importance to establish accurate processing maps to guide the thermomechanical processes to enhance the formability.In this study,we performed particle swarm optimization-based back propagation artificial neural network model to predict the high temperature flow behavior of 0.25wt%Al2O3 particle-reinforced Cu alloys,and compared the accuracy with that of derived by Arrhenius-type constitutive model and back propagation artificial neural network model.To train these models,we obtained the raw data by fabricating ODS Cu alloys using the internal oxidation and reduction method,and conducting systematic hot compression tests between 400 and800℃with strain rates of 10^(-2)-10 S^(-1).At last,processing maps for ODS Cu alloys were proposed by combining processing parameters,mechanical behavior,microstructure characterization,and the modeling results achieved a coefficient of determination higher than>99%.
基金supported by the Low-Cost Long-Life Batteries program,China(No.WL-24-08-01)the National Natural Science Foundation of China(No.22279007)。
文摘The outstanding performance of O3-type NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)(NFM111)at both high and low temperatures coupled with its impressive specific capacity makes it an excellent cathode material for sodium-ion batteries.However,its poor cycling,owing to highpressure phase transitions,is one of its disadvantages.In this study,Cu/Ti was introduced into NFM111 cathode material using a solidphase method.Through both theoretically and experimentally,this study found that Cu doping provides a higher redox potential in NFM111,improving its reversible capacity and charge compensation process.The introduction of Ti would enhance the cycling stability of the material,smooth its charge and discharge curves,and suppress its high-voltage phase transitions.Accordingly,the NaNi_(0.27)Fe_(0.28)Mn_(0.33)Cu_(0.05)Ti_(0.06)O_(2)sample used in the study exhibited a remarkable rate performance of 142.97 mAh·g^(-1)at 0.1 C(2.0-4.2 V)and an excellent capacity retention of 72.81%after 300 cycles at 1C(1C=150 mA·g^(-1)).
基金support of the National Natural Science Foundation of China(Grant No.51805371)the Innovation and Entrepreneurship Training Program of Tianjin University of Commerce(Grant No.202310069067).
文摘Monocrystalline Cu exhibits excellent electrical and signal-transmission properties due to its absence of grain boundaries,making it a critical material for the production of micro-machinery and micro-components;however,achieving ultrahigh precision and ultralow damage machining of functional devices using traditional techniques such as grinding and polishing is extremely challenging.Consequently,nanocutting has emerged as an efficient means to fabricate monocrystalline materials with complex surface characteristics and high surface integrity.Nevertheless,the macroscopic cutting theory of metal materials cannot be applied to nanocutting.Accordingly,in this paper,both simulations and experiments were conducted to examine the chip deformation mechanisms of monocrystalline Cu.First,large-scale molecular dynamics(MD)simulations were conducted to gain a comprehensive understanding of the deformation behavior during nanocutting.This included examining the influencing factors and the variation patterns of the chip deformation coefficient,cutting force,and minimum cutting thickness.Subsequently,nanocutting experiments were performed using a specially designed nanocutting platform with high-resolution online observation by scanning electron microscopy.The experimental results served to verify the accuracy and reliability of theMDmodeling,as they exhibited excellent consistency with the simulated results.Although this work considered monocrystalline Cu,it is believed that the elucidated chip deformation mechanisms could also be applied to other face-centered-cubic metals.These results are of great value for advancing the understanding of the mechanisms of ultraprecision cutting.
