Tribocorrosion readily removes the protective corrosion product,creates new reactive corrosion sites and thus accelerates material loss in metallic materials.This is evidenced by a pronounced or gradual decline in ope...Tribocorrosion readily removes the protective corrosion product,creates new reactive corrosion sites and thus accelerates material loss in metallic materials.This is evidenced by a pronounced or gradual decline in open circuit potential(OCP)during tribocorrosion assessments.Here we report that grain refinement can not only enhance wear resistance in dry conditions,but also induce an anomalously stable OCP variation and fortify tribocorrosion resistance in ultrahigh-purity magnesium during tribocorrosion.The tribocorrosion tests revealed that the fine-grained Mg(FG-Mg)sample exhibited a wear rate(4.56×10^(−4) mm^(3)/(N m))approximately half that of the coarse-grained Mg(CG-Mg)sample(7.87×10^(−4) mm^(3)/(N m)).CG-Mg showed a gradual OCP decrease,associated with a thin,unprotective tribocorrosion layer,even thinner than that resulting from dry sliding.Conversely,FG-Mg exhibited stable OCP evolution and quasi-linear tribocorrosion kinetics over time,attributed to a thick,protective tribocorrosion layer.Transmission electron microscopy data suggest that high-diffusivity pathways for oxygen along grain boundaries at the early tribocorrosion stages facilitate the formation of a continuous,protective MgO layer and an adjacent oxidized layer with a depth-dependent oxygen content gradient,enhancing tribocorrosion resistance in FG-Mg.Our findings offer valuable insights for strategically tailoring tribocorrosion resistance by modulating the OCP variation of highly active metals and alloys.展开更多
Pourbaix diagrams are calculated to describe electrochemical processes for alloys in aqueous solution.With the multi-component differentiation of alloy systems,the construction of Pourbaix diagrams is fac-ing challeng...Pourbaix diagrams are calculated to describe electrochemical processes for alloys in aqueous solution.With the multi-component differentiation of alloy systems,the construction of Pourbaix diagrams is fac-ing challenges,especially for non-single-phase alloy systems.In this study,the simultaneous construction of phase diagrams and Pourbaix diagrams were implemented for predicting the evolution of the phases in the immune and passive regions.The CALPHAD(CALculation of PHAse Diagram)approach was used to quickly access the Gibbs free energies of various phases and the chemical potential of the elements in the phases from the thermodynamic database of the Ni-Si-Al-Y system.The corrosion behavior of two typical Ni-Al-Si and Ni-Al-Y systems was investigated.Si and Y were added to Ni-based alloys to produce the solid solutions L12-Ni_(3)(Al,Si)and L12-Ni_(3)Al+Ni_(5)Y,respectively.Calculations showed that NiO and Al_(2)O_(3)make up the passive area of the Ni_(3)Al 1 alloy.The introduction of SiO_(2)and Y(OH)3 in the passive region separately helped to minimize the alloys’susceptibility to corrosion.However,Si reduced the thermody-namical possibility of NiO for mation in the passive film,and the addition of Y caused extreme galvanic corrosion.Experiments on Ni-based alloys validated the results through electrochemical corrosion.It was also discovered that the presence of Ni_(5)Y produced galvanic corrosion and that Si reduced the oxide in the passive film,causing pitting corrosion.The corrosion prediction of the quaternary alloys indicates that the solid solution of Si in Ni_(5)Y reduces the galvanic corrosion effect and the dissolution of passive film.The current work demonstrates that phase diagrams and Pourbaix diagrams may be efficiently and accurately predicted using a well-constructed thermodynamic database,which has major implications for future studies on the corrosion behavior of multi-component alloys.展开更多
Rare-earth(RE)elements,known as“industrial vitamins”,have permeated modern lives,especially in high-tech applications.Although the RE elements possess close chemical similarities and have been treated as“one elemen...Rare-earth(RE)elements,known as“industrial vitamins”,have permeated modern lives,especially in high-tech applications.Although the RE elements possess close chemical similarities and have been treated as“one element”in the periodic table,their characteristics differ from each other.The RE microalloying effect is the crux to ameliorate the physicomechanical and thermochemical properties of materials,thereby the study of RE-related phase diagrams becomes indispensable to the design and optimization of RE-containing materials.However,in reality,the knowledge base in this area is considerably scarce compared with that of other commonly-used elements.In this work,the phase equilibria,phase diagrams,phase transformations,and some recent examples of RE-containing materials design are summarized,with which one can predict the RE solubilities,the RE precipitates,as well as the corresponding service behaviors.The attainment of enhanced materials’properties suggests that the thermodynamic rules extracted from the phase diagrams could serve as fundamental criteria for the successful development of novel RE-containing materials.展开更多
Graphene-metal(G-M)composites have attracted tremendous interests due to their promising applications in electronics,optics,energy-storage devices and nano-electromechanical systems.Especially,phase formations of grap...Graphene-metal(G-M)composites have attracted tremendous interests due to their promising applications in electronics,optics,energy-storage devices and nano-electromechanical systems.Especially,phase formations of graphene combined with different metals are considered valuable for discovering and designing advanced G-M composites.However,the phase formations in G-M systems have rarely been systematically described since graphene wasfirst extracted from graphite in 2004.Here,we propose a data-driven approach to predict the phase formations in G-M systems leveraging G-M binary phase diagrams,which were established using the calculation of phase diagrams method.Phase relationships obtained from G-M phase diagrams of 34 systems and formation enthalpies of corresponding carbides were employed as the training dataset in a machine learning model to further predict the phase formations in additional 13 G-M systems.Phase formation predictions achieved an accuracy of 87.5%in the test dataset.Three distinct phase formations were characterised in G-M systems.Finally,we propose a general phase formation rule in the G-M systems:metals with smaller atomic numbers in the same period are more likely to form secondary solutions with graphene.展开更多
Réfractory high/medium entropy nitrides(HENs/MENs)exhibit comprehensive application prospects as protective films on mechanical parts,particularly those subjected to sliding contacts at elevated temperatures.In t...Réfractory high/medium entropy nitrides(HENs/MENs)exhibit comprehensive application prospects as protective films on mechanical parts,particularly those subjected to sliding contacts at elevated temperatures.In this study,a new MEN system TiNbWN,forming a single fc solution,is designed and its wear performance at temperatures ranging from 25 to 750℃is explored.The wear mechanisms can be rationalized by examining the subsurface microstructural evolutions using the transmission electron microscopy as well as calculating the phase diagrams and interfacial adhesion behavior employing calculation of phase diagram(CALPHAD)and density functional theory(DFT).To be specific,increased wear losses occur in a temperature range of 25-600℃,being predominantly caused by the thermally-induced hardness degradation;whereas at the ultimate temperature(750℃),the wear loss is refrained due to the formation of nanocrystalline oxides(WnO_(3n-2r)TiO_(2),and TiOx),as synergistically revealed by microscopy and CALPHAD,which not only enhance the mechanical properties of the pristine nitride film,but also act as solid lubricants,reducing the interfacial adhesion.Thus,our work delineates the role of the in situ formed nanocrystalline oxides in the wear mechanism transition of TiNbWN thin films,which could shed light on the high-temperature wear behavior of refractory HEN/MENfilms.展开更多
基金financially supported by the National Natu-ral Science Foundation of China(Nos.92366201 and 52371068)Natural Science Foundation of Jiangsu Province(No.BK20220965)the Fundamental Research Funds for the Central Universities(No.30923010911).
文摘Tribocorrosion readily removes the protective corrosion product,creates new reactive corrosion sites and thus accelerates material loss in metallic materials.This is evidenced by a pronounced or gradual decline in open circuit potential(OCP)during tribocorrosion assessments.Here we report that grain refinement can not only enhance wear resistance in dry conditions,but also induce an anomalously stable OCP variation and fortify tribocorrosion resistance in ultrahigh-purity magnesium during tribocorrosion.The tribocorrosion tests revealed that the fine-grained Mg(FG-Mg)sample exhibited a wear rate(4.56×10^(−4) mm^(3)/(N m))approximately half that of the coarse-grained Mg(CG-Mg)sample(7.87×10^(−4) mm^(3)/(N m)).CG-Mg showed a gradual OCP decrease,associated with a thin,unprotective tribocorrosion layer,even thinner than that resulting from dry sliding.Conversely,FG-Mg exhibited stable OCP evolution and quasi-linear tribocorrosion kinetics over time,attributed to a thick,protective tribocorrosion layer.Transmission electron microscopy data suggest that high-diffusivity pathways for oxygen along grain boundaries at the early tribocorrosion stages facilitate the formation of a continuous,protective MgO layer and an adjacent oxidized layer with a depth-dependent oxygen content gradient,enhancing tribocorrosion resistance in FG-Mg.Our findings offer valuable insights for strategically tailoring tribocorrosion resistance by modulating the OCP variation of highly active metals and alloys.
基金financially supported by the National Natural Science Foundation of China(No.U21A20127)Excellent Young Scientists Fund of National Natural Science Foundation of China(NSFC),No.52222507)the Natural Science Foundation of Ningbo City(No.2022J304).
文摘Pourbaix diagrams are calculated to describe electrochemical processes for alloys in aqueous solution.With the multi-component differentiation of alloy systems,the construction of Pourbaix diagrams is fac-ing challenges,especially for non-single-phase alloy systems.In this study,the simultaneous construction of phase diagrams and Pourbaix diagrams were implemented for predicting the evolution of the phases in the immune and passive regions.The CALPHAD(CALculation of PHAse Diagram)approach was used to quickly access the Gibbs free energies of various phases and the chemical potential of the elements in the phases from the thermodynamic database of the Ni-Si-Al-Y system.The corrosion behavior of two typical Ni-Al-Si and Ni-Al-Y systems was investigated.Si and Y were added to Ni-based alloys to produce the solid solutions L12-Ni_(3)(Al,Si)and L12-Ni_(3)Al+Ni_(5)Y,respectively.Calculations showed that NiO and Al_(2)O_(3)make up the passive area of the Ni_(3)Al 1 alloy.The introduction of SiO_(2)and Y(OH)3 in the passive region separately helped to minimize the alloys’susceptibility to corrosion.However,Si reduced the thermody-namical possibility of NiO for mation in the passive film,and the addition of Y caused extreme galvanic corrosion.Experiments on Ni-based alloys validated the results through electrochemical corrosion.It was also discovered that the presence of Ni_(5)Y produced galvanic corrosion and that Si reduced the oxide in the passive film,causing pitting corrosion.The corrosion prediction of the quaternary alloys indicates that the solid solution of Si in Ni_(5)Y reduces the galvanic corrosion effect and the dissolution of passive film.The current work demonstrates that phase diagrams and Pourbaix diagrams may be efficiently and accurately predicted using a well-constructed thermodynamic database,which has major implications for future studies on the corrosion behavior of multi-component alloys.
基金the National Natural Science Foundation of China(Nos.52101026 and 52222507)the Natural Science Foundation of Zhejiang Province(No.LQ20E010004)+2 种基金the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(No.2022C01017)the National Natural Science Foundation of China(52101108)the Ningbo 3315 Innovation Team(Nos.2019A-18-C and 2020A-03-C)is gratefully acknowledged.
文摘Rare-earth(RE)elements,known as“industrial vitamins”,have permeated modern lives,especially in high-tech applications.Although the RE elements possess close chemical similarities and have been treated as“one element”in the periodic table,their characteristics differ from each other.The RE microalloying effect is the crux to ameliorate the physicomechanical and thermochemical properties of materials,thereby the study of RE-related phase diagrams becomes indispensable to the design and optimization of RE-containing materials.However,in reality,the knowledge base in this area is considerably scarce compared with that of other commonly-used elements.In this work,the phase equilibria,phase diagrams,phase transformations,and some recent examples of RE-containing materials design are summarized,with which one can predict the RE solubilities,the RE precipitates,as well as the corresponding service behaviors.The attainment of enhanced materials’properties suggests that the thermodynamic rules extracted from the phase diagrams could serve as fundamental criteria for the successful development of novel RE-containing materials.
基金Financial supports from National Natural Science Foundation of China(grant no.U21A20127,52101026&52101108)Hubei Provincial Natural Science Foundation of China(grant no.2024AFB455)CAS PIFI program are greatly acknowledged.
文摘Graphene-metal(G-M)composites have attracted tremendous interests due to their promising applications in electronics,optics,energy-storage devices and nano-electromechanical systems.Especially,phase formations of graphene combined with different metals are considered valuable for discovering and designing advanced G-M composites.However,the phase formations in G-M systems have rarely been systematically described since graphene wasfirst extracted from graphite in 2004.Here,we propose a data-driven approach to predict the phase formations in G-M systems leveraging G-M binary phase diagrams,which were established using the calculation of phase diagrams method.Phase relationships obtained from G-M phase diagrams of 34 systems and formation enthalpies of corresponding carbides were employed as the training dataset in a machine learning model to further predict the phase formations in additional 13 G-M systems.Phase formation predictions achieved an accuracy of 87.5%in the test dataset.Three distinct phase formations were characterised in G-M systems.Finally,we propose a general phase formation rule in the G-M systems:metals with smaller atomic numbers in the same period are more likely to form secondary solutions with graphene.
基金Financial support from the National Natural Science Foundation of China(52142501 and 52101026)the National Key R&D Program of China(2018YFA0703400)+4 种基金Natural Science Foundation of Zhejiang Province(LQ20E010004)China Postdoctoral Science Foundation(2021M693250)Ningbo 3315 Innovation Team(2019A-18-C)CAS PIFI program(2022VEA0005)CAS Pioneer Hundred Talents Program are greatly acknowledged。
文摘Réfractory high/medium entropy nitrides(HENs/MENs)exhibit comprehensive application prospects as protective films on mechanical parts,particularly those subjected to sliding contacts at elevated temperatures.In this study,a new MEN system TiNbWN,forming a single fc solution,is designed and its wear performance at temperatures ranging from 25 to 750℃is explored.The wear mechanisms can be rationalized by examining the subsurface microstructural evolutions using the transmission electron microscopy as well as calculating the phase diagrams and interfacial adhesion behavior employing calculation of phase diagram(CALPHAD)and density functional theory(DFT).To be specific,increased wear losses occur in a temperature range of 25-600℃,being predominantly caused by the thermally-induced hardness degradation;whereas at the ultimate temperature(750℃),the wear loss is refrained due to the formation of nanocrystalline oxides(WnO_(3n-2r)TiO_(2),and TiOx),as synergistically revealed by microscopy and CALPHAD,which not only enhance the mechanical properties of the pristine nitride film,but also act as solid lubricants,reducing the interfacial adhesion.Thus,our work delineates the role of the in situ formed nanocrystalline oxides in the wear mechanism transition of TiNbWN thin films,which could shed light on the high-temperature wear behavior of refractory HEN/MENfilms.
