The corrosion behavior and microstructure characteristics of metal inert gas(MIG)welded dissimilar joints of the 6005A alloy modified with Sc(designated as 6005A+Sc)and the 5083 alloy were investigated using corrosion...The corrosion behavior and microstructure characteristics of metal inert gas(MIG)welded dissimilar joints of the 6005A alloy modified with Sc(designated as 6005A+Sc)and the 5083 alloy were investigated using corrosion tests and microscopy techniques.Results show that the dissimilar joints exhibit strong stress corrosion cracking(SCC)resistance,maintaining substantial strength during slow strain rate tensile tests.Notably,the heat-affected zone(HAZ)and base metal(BM)on the 6005A+Sc side show superior performance in terms of inter-granular corrosion(IGC)and exfoliation corrosion(EXCO)compared to the corresponding zones on the 5083 side.The lower corrosion resistance of the 5083-BM and the 5083-HAZ can be attributed to the presence of numerous Al_(2)Mg_(3)phases and micro-scaled Al_(6)(Mn,Fe)intermetallics,mainly distributed along the rolling direction.Conversely,the enhanced corrosion resistance of the 6005A+Sc-BM and the 6005A+Sc-HAZ can be attributed to the discontinuously distributed grain boundary precipitates(β-Mg_(2)Si),the smaller grain size,and the reduced corrosive current density.展开更多
The microstructure evolution and strengthening ability of natural aging(NA),delayed aging(DA),and DA after pre-aging(PDA)of Al-Mg-Si alloy were studied.Results show that small and unstable atomic clusters are generate...The microstructure evolution and strengthening ability of natural aging(NA),delayed aging(DA),and DA after pre-aging(PDA)of Al-Mg-Si alloy were studied.Results show that small and unstable atomic clusters are generated during NA,leading to the formation of low-density coarseβʺandβ′phases,thus reducing the strength of DA alloy.However,atomic clusters and GP zones with larger sizes and high Mg/Si molar ratio form during pre-aging treatment.They prevent the generation of clusters during NA and can serve as effective nucleation sites in subsequent artificial aging,which elevates the number density of fineβʺprecipitates and improves the alloy strength.After pre-aging at 175°C,the strengthening capacity of PDA alloy is restored,with hardness and yield strength reaching 95.1%and 101.9%of peak-aged alloy.展开更多
The hot deformation behavior of Al?6.2Zn?0.70Mg?0.30Mn?0.17Zr alloy was investigated by isothermal compressiontest on a Gleeble?3500machine in the deformation temperature range between623and773K and the strain rate ra...The hot deformation behavior of Al?6.2Zn?0.70Mg?0.30Mn?0.17Zr alloy was investigated by isothermal compressiontest on a Gleeble?3500machine in the deformation temperature range between623and773K and the strain rate range between0.01and20s?1.The results show that the flow stress decreases with decreasing strain rate and increasing deformation temperature.Basedon the experimental results,Arrhenius constitutive equations and artificial neural network(ANN)model were established toinvestigate the flow behavior of the alloy.The calculated results show that the influence of strain on material constants can berepresented by a6th-order polynomial function.The ANN model with16neurons in hidden layer possesses perfect performanceprediction of the flow stress.The predictabilities of the two established models are different.The errors of results calculated by ANNmodel were more centralized and the mean absolute error corresponding to Arrhenius constitutive equations and ANN model are3.49%and1.03%,respectively.In predicting the flow stress of experimental aluminum alloy,the ANN model has a betterpredictability and greater efficiency than Arrhenius constitutive equations.展开更多
Hot compression tests in the temperature range of 340-450 ℃ and strain rate range of 0.001-1 s^-1 of spray-formed 7055 aluminum alloy were carried out to study its hot deformation behavior. Three phenomenological mod...Hot compression tests in the temperature range of 340-450 ℃ and strain rate range of 0.001-1 s^-1 of spray-formed 7055 aluminum alloy were carried out to study its hot deformation behavior. Three phenomenological models including Johnson-Cook, modified Fields-Backofen and Arrhenius-type were introduced to predict the flow stresses during the compression process. And then, a comparative predictability of the phenomenological models was estimated in terms of the relative errors, correlation coefficient（R）, and average absolute relative error（AARE）. The results indicate that Johnson-Cook model and modified Fields-Backofen model cannot well predict the hot deformation behavior due to the large deviation in the process of line regression fitting. Arrhenius-type model obtains the best fit through combining the effect of strain rate and temperature.展开更多
Effects of N and Zr on the as-cast microstructure and properties after annealing of high-speed steel （HSS） were investigated by using electronic probe micro-analysis, Rockwell hardness test, X-ray diffractometry and...Effects of N and Zr on the as-cast microstructure and properties after annealing of high-speed steel （HSS） were investigated by using electronic probe micro-analysis, Rockwell hardness test, X-ray diffractometry and differential scanning calorimetry with combination of microstructure analysis. The results indicate that the addition of N and Zr will refine the eutectic structures and enhance the stability of carbides which are mainly MC, M2C and M7C3. The coarse dendritic structures decrease significantly and most of the carbides are distributed in the microstructure uniformly. Moreover, a kind of Zr-Si compound which only exists in VC is discovered, and this new phase is speculated to be related with the spheroidization of VC. The annealing process is set up to 6 different time periods which are 1, 3, 6, 10, 15 and 20 h, respectively. In different annealing processes at 750 ℃ which is lower than austenitizing temperature, the addition of N and Zr makes the decrease of hardness more obvious and restrains the precipitation of secondary carbides with the extension of time. Moreover, when the annealing time reaches 20 h, some clusters appear in the matrix of the two samples, and the density of clusters in HSS1 is lower, but the matrix of HSS1 contains more C and alloying elements which indicate more carbides precipitate.展开更多
To get a full understanding of hot extrusion,solid solution treatment and aging process on the Al−0.56Mg−0.63Si alloy,the microstructure and mechanical properties of a U-shaped profile were studied through optical mic...To get a full understanding of hot extrusion,solid solution treatment and aging process on the Al−0.56Mg−0.63Si alloy,the microstructure and mechanical properties of a U-shaped profile were studied through optical microscopy,scanning electrical microscopy,transmission electrical microscopy,hardness,and tensile tests.The coarse equiaxed grains existed near the profile edge as a result of the dynamic recrystallization nucleation and exceeding growth during hot extrusion.The fibrous deformed and sub-structured grains located between the two coarse grain layers,due to the occurrence of work-hardening and dynamic recovery.Perpendicular needle β′′precipitates were distributed inside the grain,and obvious precipitates-free zone appeared after aging treatment.The tensile strength,yield strength and elongation of the aged Al−Mg−Si alloy U-shaped profile were no less than 279.4 MPa,258.6 MPa,and 21.6%,respectively.The fracture morphology showed dimple rupture characteristics.The precipitates and grain boundaries played key role in the strengthening contribution.展开更多
Ion exchange is a promising synthetic method for alleviating severe cation mixing in traditional layered oxide materials for lithium-ion batteries,leading to enhanced structural stability.However,the underlying mechan...Ion exchange is a promising synthetic method for alleviating severe cation mixing in traditional layered oxide materials for lithium-ion batteries,leading to enhanced structural stability.However,the underlying mechanisms of ion exchange are still not fully understood.Such a fundamental study of the ion-exchange mechanism is needed for achieving the controllable synthesis of layered oxides with a stable structure.Herein,we thoroughly unearth the underlying mechanism that triggers the ion exchange of Ni-rich materials in aqueous solutions by examining time-resolved structural evolution combined with theoretical calculations.Our results reveal that the reaction pathway of ion exchange can be divided into two steps:protonation and lithiation.The proton is the key to achieving charge balance in the ion exchange process,as revealed by X-ray adsorption spectroscopy and inductive coupled plasma analysis.In addition,the intermediate product shows high lattice distortion during ion exchange,but it ends up with a most stable product with high lattice energy.Such apparent discrepancies in lattice energy between materials before and after ion exchange emphasize the importance of synthetic design in structural stability.This work provides new insights into the ion-exchange synthesis of Ni-rich oxide materials,which advances the development of cathode materials for high-performance lithium-ion batteries.展开更多
基金financially supported by the Science and Technology Innovation Program of Hunan Province,China(No.2023RC3055)the Natural Science Foundation of Hunan Province,China(Nos.2023JJ30671,2020JJ4114)+5 种基金the Natural Science Foundation of Changsha City,China(No.Kq2208264)National Key Project of Research and Development Plan of China(Nos.2021YFC1910505,2021YFC1910504)the Young Core Teacher Foundation of Hunan Province,China(No.150220001)Key Research and Development Program of Guangdong Province,China(No.2020B010186002)the National Natural Science Foundation of China(No.51601229)the Key-Area Research and Development Program of Foshan City,China(No.2230032004640).
文摘The corrosion behavior and microstructure characteristics of metal inert gas(MIG)welded dissimilar joints of the 6005A alloy modified with Sc(designated as 6005A+Sc)and the 5083 alloy were investigated using corrosion tests and microscopy techniques.Results show that the dissimilar joints exhibit strong stress corrosion cracking(SCC)resistance,maintaining substantial strength during slow strain rate tensile tests.Notably,the heat-affected zone(HAZ)and base metal(BM)on the 6005A+Sc side show superior performance in terms of inter-granular corrosion(IGC)and exfoliation corrosion(EXCO)compared to the corresponding zones on the 5083 side.The lower corrosion resistance of the 5083-BM and the 5083-HAZ can be attributed to the presence of numerous Al_(2)Mg_(3)phases and micro-scaled Al_(6)(Mn,Fe)intermetallics,mainly distributed along the rolling direction.Conversely,the enhanced corrosion resistance of the 6005A+Sc-BM and the 6005A+Sc-HAZ can be attributed to the discontinuously distributed grain boundary precipitates(β-Mg_(2)Si),the smaller grain size,and the reduced corrosive current density.
基金supported by the National Natural Science Foundation of China(No.52261007)the Science and Technology Project of Guangxi,China(No.GKAD22035039)the Opening Fund for Key Laboratory of New Processing Technology for Nonferrous Metal&Materials,Ministry of Education,Guilin University of Technology,China(Nos.22KF-11,22KF-14).
文摘The microstructure evolution and strengthening ability of natural aging(NA),delayed aging(DA),and DA after pre-aging(PDA)of Al-Mg-Si alloy were studied.Results show that small and unstable atomic clusters are generated during NA,leading to the formation of low-density coarseβʺandβ′phases,thus reducing the strength of DA alloy.However,atomic clusters and GP zones with larger sizes and high Mg/Si molar ratio form during pre-aging treatment.They prevent the generation of clusters during NA and can serve as effective nucleation sites in subsequent artificial aging,which elevates the number density of fineβʺprecipitates and improves the alloy strength.After pre-aging at 175°C,the strengthening capacity of PDA alloy is restored,with hardness and yield strength reaching 95.1%and 101.9%of peak-aged alloy.
基金Project(2016GK1004) supported by the Science and Technology Major Project of Hunan Province,China
文摘The hot deformation behavior of Al?6.2Zn?0.70Mg?0.30Mn?0.17Zr alloy was investigated by isothermal compressiontest on a Gleeble?3500machine in the deformation temperature range between623and773K and the strain rate range between0.01and20s?1.The results show that the flow stress decreases with decreasing strain rate and increasing deformation temperature.Basedon the experimental results,Arrhenius constitutive equations and artificial neural network(ANN)model were established toinvestigate the flow behavior of the alloy.The calculated results show that the influence of strain on material constants can berepresented by a6th-order polynomial function.The ANN model with16neurons in hidden layer possesses perfect performanceprediction of the flow stress.The predictabilities of the two established models are different.The errors of results calculated by ANNmodel were more centralized and the mean absolute error corresponding to Arrhenius constitutive equations and ANN model are3.49%and1.03%,respectively.In predicting the flow stress of experimental aluminum alloy,the ANN model has a betterpredictability and greater efficiency than Arrhenius constitutive equations.
基金Project(2013HH100055) supported by the Basic Research and Science and Technology Innovation Fund of Foshan City,China
文摘Hot compression tests in the temperature range of 340-450 ℃ and strain rate range of 0.001-1 s^-1 of spray-formed 7055 aluminum alloy were carried out to study its hot deformation behavior. Three phenomenological models including Johnson-Cook, modified Fields-Backofen and Arrhenius-type were introduced to predict the flow stresses during the compression process. And then, a comparative predictability of the phenomenological models was estimated in terms of the relative errors, correlation coefficient（R）, and average absolute relative error（AARE）. The results indicate that Johnson-Cook model and modified Fields-Backofen model cannot well predict the hot deformation behavior due to the large deviation in the process of line regression fitting. Arrhenius-type model obtains the best fit through combining the effect of strain rate and temperature.
文摘Effects of N and Zr on the as-cast microstructure and properties after annealing of high-speed steel （HSS） were investigated by using electronic probe micro-analysis, Rockwell hardness test, X-ray diffractometry and differential scanning calorimetry with combination of microstructure analysis. The results indicate that the addition of N and Zr will refine the eutectic structures and enhance the stability of carbides which are mainly MC, M2C and M7C3. The coarse dendritic structures decrease significantly and most of the carbides are distributed in the microstructure uniformly. Moreover, a kind of Zr-Si compound which only exists in VC is discovered, and this new phase is speculated to be related with the spheroidization of VC. The annealing process is set up to 6 different time periods which are 1, 3, 6, 10, 15 and 20 h, respectively. In different annealing processes at 750 ℃ which is lower than austenitizing temperature, the addition of N and Zr makes the decrease of hardness more obvious and restrains the precipitation of secondary carbides with the extension of time. Moreover, when the annealing time reaches 20 h, some clusters appear in the matrix of the two samples, and the density of clusters in HSS1 is lower, but the matrix of HSS1 contains more C and alloying elements which indicate more carbides precipitate.
基金financial support of project on reliability and life research of typical components in rail trains (K10TZ20P0500) of CRRC Zhuzhou Electric Locomotive Research Institute.
文摘To get a full understanding of hot extrusion,solid solution treatment and aging process on the Al−0.56Mg−0.63Si alloy,the microstructure and mechanical properties of a U-shaped profile were studied through optical microscopy,scanning electrical microscopy,transmission electrical microscopy,hardness,and tensile tests.The coarse equiaxed grains existed near the profile edge as a result of the dynamic recrystallization nucleation and exceeding growth during hot extrusion.The fibrous deformed and sub-structured grains located between the two coarse grain layers,due to the occurrence of work-hardening and dynamic recovery.Perpendicular needle β′′precipitates were distributed inside the grain,and obvious precipitates-free zone appeared after aging treatment.The tensile strength,yield strength and elongation of the aged Al−Mg−Si alloy U-shaped profile were no less than 279.4 MPa,258.6 MPa,and 21.6%,respectively.The fracture morphology showed dimple rupture characteristics.The precipitates and grain boundaries played key role in the strengthening contribution.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51974368)This work was supported in part by the High Performance Computing Center of Central South UniversityThis work was supported by the Beamlines 1W1B-XAFS at BSRF.
文摘Ion exchange is a promising synthetic method for alleviating severe cation mixing in traditional layered oxide materials for lithium-ion batteries,leading to enhanced structural stability.However,the underlying mechanisms of ion exchange are still not fully understood.Such a fundamental study of the ion-exchange mechanism is needed for achieving the controllable synthesis of layered oxides with a stable structure.Herein,we thoroughly unearth the underlying mechanism that triggers the ion exchange of Ni-rich materials in aqueous solutions by examining time-resolved structural evolution combined with theoretical calculations.Our results reveal that the reaction pathway of ion exchange can be divided into two steps:protonation and lithiation.The proton is the key to achieving charge balance in the ion exchange process,as revealed by X-ray adsorption spectroscopy and inductive coupled plasma analysis.In addition,the intermediate product shows high lattice distortion during ion exchange,but it ends up with a most stable product with high lattice energy.Such apparent discrepancies in lattice energy between materials before and after ion exchange emphasize the importance of synthetic design in structural stability.This work provides new insights into the ion-exchange synthesis of Ni-rich oxide materials,which advances the development of cathode materials for high-performance lithium-ion batteries.
