Solvation structures fundamentally control the ion-transport dynamics and mechanical properties of polymer electrolytes.However,there is a lack of strategies to rationally regulate the solvation structures and fundame...Solvation structures fundamentally control the ion-transport dynamics and mechanical properties of polymer electrolytes.However,there is a lack of strategies to rationally regulate the solvation structures and fundamental understanding on how they control the electrochemical performances.Herein,by harnessing the electrostatic adsorption of one-dimensional nanofiller(i.e.,surface-charged halloysite nanotubes,d-HNTs),we successfully fabricate a high-performance polymer nanocomposite electrolyte enabled by strong surface adsorption,referred as adsorption-state polymer electrolyte(ASPE).This ASPE shows fast ion transport(0.71±0.05 mS cm^(-1)at room temperature),high mechanical strength and toughness(10.3±0.05 MPa;15.73 MJ m^(-3)),improved lithium-ion transference number,and long cycle life with lithium metal anode,in comparison with the sample without the d-HNT adsorption effect.To fundamentally understand these high performances,an anion-rich asymmetric solvent structure model is further proposed and evidenced by both experiments and simulation studies.Results show that the electrostatic adsorption among the d-HNT,ionic liquid electrolyte,and polymer chain generates a nano filler-supported fast ion-conduction pathway with asymmetric Li+-coordination microenvironment.Meanwhile,the anion-rich asymmetric solvent structure model of ASPE also generates a fast de-solvation and anion-derived stable solid-electrolyte interphase for lithium metal anode.The high performance and understanding of the mechanism for ASPE provide a promising path to develop advanced polymer electrolytes.展开更多
Amorphous Ga_(2)O_(3)(a-Ga_(2)O_(3))thin films were prepared on flexible polyimide,rigid quartz glass,and Si substrates via radio frequency magnetron sputtering at room temperature.The effect of oxygen/Ar flow rate ra...Amorphous Ga_(2)O_(3)(a-Ga_(2)O_(3))thin films were prepared on flexible polyimide,rigid quartz glass,and Si substrates via radio frequency magnetron sputtering at room temperature.The effect of oxygen/Ar flow rate ratio on the structure,optical property,surface morphology,and chemical bonding properties of the a-Ga_(2)O_(3) films was investigated.Results show that the average optical transmittance of the a-Ga_(2)O_(3) films is over 80%within the wavelength range of 300-2000 nm.The extracted optical band gap of the a-Ga_(2)O_(3) films is increased from 4.97 eV to 5.13 eV with the increase in O_(2)/Ar flow rate ratio from 0 to 0.25,due to the decrease in concentration of oxygen vacancy defects in the film.Furthermore,the optical refractive index and surface roughness of the a-Ga_(2)O_(3) films are optimized when the O_(2)/Ar flow rate ratio reaches 0.25.X-ray photoelectron spectroscopy analysis also shows that the proportion of oxygen vacancies(VO)and Ga-O chemical bonds in the O 1s peak is gradually decreased with the increase in O_(2)/Ar flow rate ratio from 0 to 0.25,proving that increasing the O_(2)/Ar flow rate ratio during film growth can reduce the concentration of oxygen vacancy defects in a-Ga_(2)O_(3) films.In this case,a-Ga_(2)O_(3) with optimal properties can be obtained.This work provides a research basis for high-performance flexible and rigid deep ultraviolet solar-blind detection devices based on a-Ga_(2)O_(3) films.展开更多
This study comprehensively studied the precipitation ofαlaths and formation of inducedγnanotwins in a cast Ti-48Al-3Nb-1.5Ta(at.%)alloy tempered at theα+γphase region.The evolution of the microstruc-ture and its c...This study comprehensively studied the precipitation ofαlaths and formation of inducedγnanotwins in a cast Ti-48Al-3Nb-1.5Ta(at.%)alloy tempered at theα+γphase region.The evolution of the microstruc-ture and its corresponding atomic mechanisms were investigated by transmission electron microscopy.The results show thatαphase precipitates as intersected laths,nucleates at stacking faults,and grows by a diffusion-controlled ledge-kink-terrace mechanism.The precipitation ofαlath introduces high stress concentrations at theγ/αinterface,produces dislocations and stacking faults,and induces the formation ofγnanotwins.Theγnanotwins nucleate at stacking faults emitted from theγ/αinterface and grow by Frank partials climbing,Schockley partials gliding,and several new mechanisms related to non-planar reactions of dislocations and annihilation of antiphase boundaries.Theγnanotwins are limited to sub-microns due to the lack of driving force.High temperatures promote the formation ofγnanotwins by activating non-planar reactions of dislocations and atom diffusion.In addition,Nb and Ta can promoteαlath precipitation andγnanotwin formation by reducing the stacking fault energy and preferring stacking fault emission.In summary,these findings provide new insights intoαlath precipitation andγtwinning mechanisms,which are relevant as theoretical bases for microstructure control and refinement of castγ-TiAl alloys.展开更多
How to describe the austenite reverse transformation(ART)has always been considered as a key problem of controlling microstructures and mechanical properties in high-strength steels.So far,numerous studies have been c...How to describe the austenite reverse transformation(ART)has always been considered as a key problem of controlling microstructures and mechanical properties in high-strength steels.So far,numerous studies have been conducted,unfortunately,without fully considering diffusion of elements,interface migration,and interaction between trans-interface diffusion and interface migration,as well as synergy of thermodynamic and kinetic for interfacial migration.A more flexible modeling for the ART is herein developed using thermodynamic extremal principle,where the concept of trans-interface diffusion in two steps,i.e.,from the parent phase to the interface and from the interface to the product phase,as well as the Gibbs energy balance approach,was introduced to predict the behavior of interface migration and element trans-interface diffusion within the migrating interface.Subsequently,the thermodynamic driving force ΔG and the effective kinetic energy barrier Q_(eff) for the ART were also analytically performed,as well as a unified expression for so-called generalized stability(GS).It is demonstrated that the higher driving force in the ART generally results in the increased yield strength,while the larger GS tends to yield improved uniform elongation,thus forming a correspondence between the thermo-kinetics trade-off and the strength-ductility trade-off.Applying a proposed criterion of high ΔG-high GS,the present model can be adopted to design the ART,which will produce the austenite microstructure with high strength and high plasticity,as evidenced by the current experiments.展开更多
Enantiomer identification is of paramount industrial value and physiological significance.Construction of sensitive chiral sensors with high enantiomeric discrimination ability is highly desirable.In this work,a chira...Enantiomer identification is of paramount industrial value and physiological significance.Construction of sensitive chiral sensors with high enantiomeric discrimination ability is highly desirable.In this work,a chiral covalent organic framework/anodic aluminum oxide(c-COF/AAO)membrane was prepared for electrochemical enantioselective recognition and sensing.Benefiting from the remarkable asymmetry,the asprepared nanofluidic c-COF/AAO presents a distinct ion current rectification(ICR)characteristic,enabling sensitive bioanalysis.In addition,owing to the large surface area,high chemical stability and perfect ion selectivity of chiral COF,the prepared c-COF/AAO membrane presents exceptionally selective mass transport and thereby enables excellent chiral discrimination for S-/R-Naproxen(S-/R-Npx)enantiomers.It is especially noteworthy that the detection limit is achieved as low as 3.88 pmol/L.These results raise the possibility for a facile,stable and low-cost method to carry out sensitive enantioselective recognition and detection.展开更多
As emerging pollutants,microplastics have recently received considerable attention owing to detection in various organisms and environments.Mass production and widespread use of plastic products increase their potenti...As emerging pollutants,microplastics have recently received considerable attention owing to detection in various organisms and environments.Mass production and widespread use of plastic products increase their potential risks to humans owing to their persistent,mobile,and toxic properties.Numerous methods have been used to identify and quantify the various forms of microplastics,however,unified standards do not exist.In this review,we systematically summarize the sources,migration,transformation,and analytical methods for microplastics in diverse ecosystems,particularly the most recent sampling and identification techniques.Additionally,the environmental effects and health hazards of microplastics on aquatic and terrestrial systems,as well as human beings are discussed.We also present management strategies for reducing microplastics in a broader social and policy context.This review aims to provide an overview of the migration,transformation,sampling,analysis,and environmental effects of microplastics,which addresses knowledge gaps in microplastic pollution and provides proposals for key research gaps.展开更多
Despite the promising prospects of body-centered cubic iron(BCC Fe)in aerospace,energy transportation,and nuclear applications,the effects of extreme environments on its mechanical behaviors and deformation mechanisms...Despite the promising prospects of body-centered cubic iron(BCC Fe)in aerospace,energy transportation,and nuclear applications,the effects of extreme environments on its mechanical behaviors and deformation mechanisms remain elusive to date.In this work,the mechanical responses and deformation behaviors of BCC Fe single crystals under extreme loading conditions are investigated by performing the three-dimensional discrete dislocation dynamics simulations.It turns out that the yield strength(oy)of BCC Fe can be enhanced by increasing the strain rate()and/or decreasing the deformation temperature(T).With the strain rate increasing from=10^(2)s^(-1)to 106 s^(-1),the yield strength at 300 K rises fromσy=51.14 MPa to 1114.57 MPa.When the strain rate exceeds 10^(3)s^(-1),an elastic overshoot phenomenon appears because the applied stress and the low initial dislocation density at the early tensile stage cannot drive the plastic deformation immediately.With the temperature increasing from T=100 K to 800 K,the yield strength atσ_(y)=10^(3)3 s^(-1)decreases fromσε=64.97 MPa to 59.50 MPa.Such temperature and strain rate sensitivity of deformation behaviors are clarified from variations in the configurations of dislocation evolution and dislocation density fluxes.It is demonstrated that at low strain rate(ε≤10^(3)s^(-1))conditions,the deformation behaviors of BCC Fe are dominated by the dislocation multi-slip mechanism.With increasing strain rate to e.g.,>10^(3)s^(-1),the deformation behaviors are governed by the dislocation single-slip.Our investigation on the temperature and strain rate sensitivity of deformation behaviors provides insightful guidance for optimizing the mechanical performances of BCC Fe based ferritic steels.展开更多
Catalytic oxidation plays a crucial role in chemical industry,in which the utilization of abundant and environmental-friendly oxygen(O_(2))as oxidant aligns with sustainable development principles in green chemistry.H...Catalytic oxidation plays a crucial role in chemical industry,in which the utilization of abundant and environmental-friendly oxygen(O_(2))as oxidant aligns with sustainable development principles in green chemistry.However,the intrinsic inertness of ground-state O_(2) molecule poses a long-standing challenge in developing an efficient non-noble metal-based catalyst.Herein,inspired by the electron transfer process in respiratory chain,we engineered long-range N_(V) to mediate Fe_(1) center for O_(2) activation in aerobic oxidation.Combined in/quasi-situ spectroscopic characterizations and control experiments suggest the Fe_(1) site efficiently adsorbs O_(2),and the N_(V) site facilitates electron delocalization to adjacent Fe_(1),providing efficient transformation of O_(2) to reactive oxygen species that boost oxidation reactions mildly.This Fe_(1)--N_(V) single-atom catalyst demonstrates outstanding catalytic performance in aerobic oxidations of alkanes,N-heterocycles,alcohols,and amines under relatively mild conditions.Our findings offer a new perspective for designing high-efficiency heterogeneous catalysts in aerobic oxidations,promising various potential applications.展开更多
Although platinum-based materials are regarded as the state-of-the-art electro-catalysts for hydrogen evolution reaction(HER),high cost and quantity scarcity hamper their scale-up utilization in industrial deployment....Although platinum-based materials are regarded as the state-of-the-art electro-catalysts for hydrogen evolution reaction(HER),high cost and quantity scarcity hamper their scale-up utilization in industrial deployment.Herein,a one-step strategy was developed to synthesize multi-walled carbon nanotubes and reduced graphene oxide supported Pt nanoparticle hydrogel(PtNP/rGO-MWCNT),in which only ascorbic acid was used as the reductant for one-pot reduction of both GO and chloroplatinic acid.The hydrogel can be directly used as a flexible binder-free catalytic electrode to achieve high performance of HER.Compared to conventional strategies,the current strategy not only significantly reduces the Pt loading to 3.48 wt%,simplifies the synthesis process,but also eliminates the use of any polymer binders,thus decreasing the series resistance and improving catalytic activity.An overpotential of only 11 mV was achieved on as-prepared PtNP/rGO-MWCNT to drive a geometrical current density of 10 mA/cm2 in0.5 mol/L H2 SO4,with its catalytic activity being kept over 15 h.In acidic medium,the HER activity of the PtNP/rGO-MWCNT catalyst exceeds most of the reported Pt-based electro-catalysts and is 3-fold higher than that obtained on commercial Pt/C electrode.展开更多
Although several strategies(including grain refinement,texture adjustment,precipitation hardening,etc.)have been verified to effectively improve the mechanical properties of lightweight magnesium(Mg)alloys,considerabl...Although several strategies(including grain refinement,texture adjustment,precipitation hardening,etc.)have been verified to effectively improve the mechanical properties of lightweight magnesium(Mg)alloys,considerable efforts are still needed to be made to comprehensively understand the potential mechanisms controlling complex microstructures and deformation behaviors exhibited by the hexagonal close-packed host lattice of Mg,thus assisting the rational design of materials at a more physical level.As the cornerstone of this review,a universal rule,the so-called synergy of thermodynamics and kinetics(i.e.,thermo-kinetic diversity,correlation and connectivity),including a recently proposed theory of generalized stability(GS),is introduced to deepen our understanding on common behaviors in Mg alloys(i.e.,deformations(slip and twining modes),phase transformations(especially for precipitations)and interactions in between)at a new perspective.Guided by the GS theory,typical cases for Mg alloys design are qualitatively evaluated to reemphasize the traditional strengthening and toughening strategies mentioned above and to illuminate their exquisite coordination for breaking through the trade-off relationship between strength and ductility,corresponding to a typical thermo-kinetic pair(i.e.,high driving force(ΔG)-high GS).To produce the Mg alloys with superior strength-ductility balances,the potential capacity of this GS theory for guiding processing path design is discussed,finally。展开更多
A novel three-dimension separable and recyclable r GH-PANI/BiOI photocatalyst with the synergism of adsorption-enrichment and photocatalytic-degradation was successfully prepared via a facile three-step hydrothermal m...A novel three-dimension separable and recyclable r GH-PANI/BiOI photocatalyst with the synergism of adsorption-enrichment and photocatalytic-degradation was successfully prepared via a facile three-step hydrothermal method.The three-dimension reduced graphene oxide hydrogel(rGH)in with flower-like BiOI photocatalyst uniformly distributed not only possesses excellent adsorption and electron transport properties,but also is easy to be separated from water for recycling.In addition,polyphenylamine(PANI)provides superior hole transport ability due to its delocalizedл-лconjugate structure.The cooperation of rGH and PANI greatly enhances the separation efficiency of photogenerated carriers,and finally improves the photocatalytic degradation behaviors.The removal rates of Rhodamine B(RhB)by rGH-PANI/BiOI-70%composite under visible light respectively reach 100%and 50.13%in static and dynamic systems,which are 12.85 and 3.58 times of BiOI,respectively.The removal rate does not show decrease after 5 recycles indicating the excellent separable and recyclable property of rGH-PANI/BiOI photocatalyst.The work provides an essential reference for designing and constructing hydrogel-based ternary composite photocatalysts with excellent synergism of adsorption and photocatalysis,which shows great potential in the treatment of water pollution.展开更多
In this work, the structures of a pair of isomers were identified. And we showed the ability of the selective 1D version, performed the most common NMR experiments including the 1D-HMBC and GOESY experiments, to deter...In this work, the structures of a pair of isomers were identified. And we showed the ability of the selective 1D version, performed the most common NMR experiments including the 1D-HMBC and GOESY experiments, to determine the isom^ric composition that were found in the production process of roflumilast. The experimental results proved that this method would be even more time saving and could get more reliable results.展开更多
The irreversible motion of magnetic domain walls in ferromagnets can dissipate a large portion of the elastic energy,and the associated damping capacity is proportional to the magnetostriction constant.In contrast,her...The irreversible motion of magnetic domain walls in ferromagnets can dissipate a large portion of the elastic energy,and the associated damping capacity is proportional to the magnetostriction constant.In contrast,here we found that the damping capacity of the large magnetostriction Fe-Ga alloys can be enhanced by 2-3 times through introducing structural defects including interfacial dislocations and stacking faults,despite that these defects deteriorate the magnetostriction.These structural defects were introduced by aging the BCC(body-centered-cubic)solution-treated precursor,for which the formation of mechanically harder FCT(face-centered-tetragonal)and/or FCC(face-centered-cubic)phases can result in high-density partial dislocations at the semi-coherent phase interfaces and quasi-periodically stacked nano-layer substructure inside the FCC variants.The structural defects act as extra damping sources besides the magnetic domain walls because the structural accommodation of the semi-coherent phase interfaces between BCC and FCT/FCC nanoprecipitates with different elastic moduli and the nano-layer substructure towards long-range ordered periodical stacking can dissipate a large portion of mechanical energy.These findings suggest that introducing structural defects provides fresh freedom to design high damping ferromagnetic materials.展开更多
A good combination of ultimate tensile strength(UTS)up to 1365 MPa and total strain to failure(StF)to 15.5%has been achieved due to deformable martensite in the invented vanadium-microalloyed dual-phase(DP)steel,which...A good combination of ultimate tensile strength(UTS)up to 1365 MPa and total strain to failure(StF)to 15.5%has been achieved due to deformable martensite in the invented vanadium-microalloyed dual-phase(DP)steel,which was manufactured by two-stage annealing of cold rolled steel strip.The employed extensive characterizations revealed that the ductile martensitic phase in this DP steel differentiated from ordinarily low-carbon martensitic lath in both morphology and lattice structure.Complex coherent orientation relationships between ferrite,reverse austenite,martensitic phase and vanadium carbide(VC)do exist,leading to a new martensitic transformation mechanism and resultant dual-phase microstructure.Besides,a detailed characterization including essential phase transformation analysis in combination with in situ TEM observation,shows that,all the essential processing including recrystallization,reverse austenitic and martensitic transformation,in debt to the particular effects of VC,can be recognized as phase transformations with higher thermodynamic driving force and higher kinetic energy barrier as compared to previously common processing,which actually changes the microstructure and,indirectly leads to higher strength and higher ductility.This synergy of thermodynamics and kinetics can be generalized to improve mechanical properties of present steels.展开更多
Upon non-equilibrium solidifications, dendrite growth, generally as precursor of as-solidified structures,has severe effects on subsequent phase transformations. Considering synergy of thermodynamics and kinetics cont...Upon non-equilibrium solidifications, dendrite growth, generally as precursor of as-solidified structures,has severe effects on subsequent phase transformations. Considering synergy of thermodynamics and kinetics controlling interface migration and following conservation of heat flux in solid temperature field, a more flexible modeling for the dendrite growth is herein developed for multi-component alloys,where, two inherent problems, i.e. correlation between thermodynamics and kinetics(i.e. the thermokinetic correlation), and theoretical connection between dendrite growth model and practical processing,have been successfully solved. Accordingly, both the thermodynamic driving force G and the effective kinetic energy barrier Qeffhave been found to control quantitatively the dendrite growth(i.e. especially the growth velocity, V), as reflected by the thermo-kinetic trade-off. Compared with previous models, it is the thermo-kinetic correlation that guarantees quantitative connection between the practical processing parameters and the current theoretical framework, as well as more reasonable description for kinetic behaviors involved. Applied to the vertical twin-roll casting(VTC), the present model, realizes a good prediction for kissing points, which influences significantly alloy design and processing optimization.This work deduces quantitatively the thermo-kinetic correlation controlling the dendrite growth, and by proposing the parameter-triplets(i.e. G-Qeff-V), further opens a new beginning for connecting solidification theories with industrial applications, such as the VTC.展开更多
Designing structured materials with optimized mechanical properties generally focuses on engineering microstructures,which are closely determined by the processing routes,such as phase transformations(PTs)and plastic ...Designing structured materials with optimized mechanical properties generally focuses on engineering microstructures,which are closely determined by the processing routes,such as phase transformations(PTs)and plastic deformations(PDs).Both PTs and PDs follow inherent trade-off relation between thermodynamic driving force ΔG and kinetic energy barrier Q,i.e.,so-called thermo-kinetic correlation.By analyzing nucleation and growth and proposing a conception of negative driving force integrating strain energy,interface energy and any kind of energy that equivalently inhibits the PT itself,ΔG^(S),unified expressions for the thermo-kinetic correlation and generalized stability(GS)were derived for three kinds of PTs,i.e.,diffusive PTs with simultaneously decreasedΔG and increased Q,diffusive PTs with simultaneously increasedΔG and decreased Q,and displacive PTs with simultaneously increased ΔG and decreased Q.This leads to so-called thermo-kinetic connectivity by integrating the thermo-kinetic correlation and the GS,where,by application in typical PTs,it was clearly shown,a criterion of high ΔG-high GS can be predicted by modulating chemical driving force,negative driving force and kinetic energy barrier for diffusion or nucleation.Following thermo-kinetic connectivity,analogous procedure for dislocation evolution upon PDs was performed,and materials design in terms of the highΔG-high GS criterion was discussed and prospected.展开更多
Dynamic recrystallization(DRX)plays significant roles in manipulating of microstructures during hot deformation and the result mechanical properties;however,the underling mechanism leading to multi scale-microstructur...Dynamic recrystallization(DRX)plays significant roles in manipulating of microstructures during hot deformation and the result mechanical properties;however,the underling mechanism leading to multi scale-microstructures remains poorly understood.Here,the DRX mechanism under wide processing conditions(i.e.950-1200°C,0.001-10 s-1)in Incoloy 028 alloy was investigated,where the relationships among flow stress,Z parameter and grain size,as well as the evolution of characteristic microstructures(grain size,sub-grain boundaries,and high angle grain boundaries),are established.As the values of Z parameters decrease(corresponding to decreased flow stresses),three typical softening mechanisms successively occur,ranging from continuous DRX controlled by dislocation glide,discontinuous DRX dominated by dislocation motion(climb and cross/multiple slip)and grain boundary migration,to dynamic normal/abnormal grain growth resulting from grain boundary migration,with transition regions where two adjacent mechanisms occur simultaneously.Correspondingly,these above three softening mechanisms result in ultrafine,fine and coarse grains,respectively.The present findings demonstrate a comprehensive understanding of DRX mechanism over a wide range of processing conditions,and further provide a new guideline for preparing single crystals.展开更多
Grain-boundary(GB)precipitation has a significant adverse effect on plasticity of alloys,which easily leads to catastrophic intergranular failure in safety-critical applications under high external loading.Herein,we r...Grain-boundary(GB)precipitation has a significant adverse effect on plasticity of alloys,which easily leads to catastrophic intergranular failure in safety-critical applications under high external loading.Herein,we report a novel strategy that uses the local stress concentration induced by GB precipitates as a driving force to trigger phase transformation of preset non-equiatomic high-entropy solid-solution phase at GBs.This in situ deformation-induced phase transformation at GBs introduces a well-known effect:transformation-induced plasticity(TRIP),which enables an exceptional elongation to fracture(above 38%)at a high strength(above 1.5 GPa)in a GB precipitation-hardened high-entropy alloy(HEA).The present strategy in terms of"local stress concentration-induced phase transformations at GBs"may provide a fundamental approach by taking advantage of(rather than avoiding)the GB precipitation to gain a superior combination of high strength and high ductility in HEAs.展开更多
1.Introduction,Understanding and predicting microstructure and its relationship with the mechanical properties of metallic materials require detailed knowledge of phase transformations(PTs)and plastic deformations(PDs...1.Introduction,Understanding and predicting microstructure and its relationship with the mechanical properties of metallic materials require detailed knowledge of phase transformations(PTs)and plastic deformations(PDs).These two processes,as central topics in material science,can be fundamentally described to a large extent by a framework of thermodynamic and kinetics(thermo-kinetics).The situation of PTs arises when the microstructure is losing phase stability,whereas the issue of PDs corresponds to the break of mechanical stability,all of which can be uniformly defined as the so-called loss of thermodynamic stability(TS).In this context,the higher TS will lead to the higher driving force G essentially required for the PT and/or PD forming and/or changing the microstructure.In the case of PTs,extensive examples showing the high TS can be found,such as martensite transformations(MTs)upon continuous cooling or strain[1,2],coherent precipitation[3,4],so-called Schwarz crystal[5],etc.展开更多
Using dislocation-based constitutive modeling in three-dimension crystal plasticity finite element(3D CPFE)simulations,co-deformation and instability of hetero-phase interface in different material systems were herein...Using dislocation-based constitutive modeling in three-dimension crystal plasticity finite element(3D CPFE)simulations,co-deformation and instability of hetero-phase interface in different material systems were herein studied for polycrystalline metal matrix composites(MMCs).Local stress and strain fields in two types of 3layer MMCs such as fcc/fcc Cu-Ag and fcc/bcc Cu-Nb have been predicted under simple compressive deformations.Accordingly,more severe strain-induced interface instability can be observed in the fcc/bcc systems than in the fcc/fcc systems upon refining to metallic nanolayered composites(MNCs).By detailed analysis of stress and strain localization,it has been demonstrated that the interface instability is always accompanied by high-stress concentration,i.e.,thermodynamic characteristics,or high strain prevention i.e.,kinetic characteristics,at the hetero-phase interface.It then follows that the thermodynamic driving forceG and the kinetic energy barrier Q during dislocation and shear banding can be adopted to classify the deformation modes,following the so-called thermo-kinetic correlation.Then by inserting a high density of high-energy interfaces into the Cu-Nb composites,such thermo-kinetic integration at the hetero-phase interface allows a successful establishment of MMCs with the high△G-high Q deformation mode,which ensures high hardening and uniform strain distri-bution,thus efficiently suppressing the shear band,stabilizing the hetero-phase interface,and obtaining an exceptional combination in strength and ductility.Such hetero-phase interface chosen by a couple of thermodynamics and kinetics can be defined as breaking the thermo-kinetic correlation and has been proposed for artificially designing MNCs.展开更多
基金financial support from the National Natural Science Foundation of China(52203123)the Sichuan Science and Technology Program(2023NSFSC0991)+2 种基金the State Key Laboratory of Polymer Materials Engineering(sklpme 2023-1-05 and sklpme 2024-2-04)the Fundamental Research Funds for the Central Universitiespartially sponsored by the Double First-Class Construction Funds of Sichuan University。
文摘Solvation structures fundamentally control the ion-transport dynamics and mechanical properties of polymer electrolytes.However,there is a lack of strategies to rationally regulate the solvation structures and fundamental understanding on how they control the electrochemical performances.Herein,by harnessing the electrostatic adsorption of one-dimensional nanofiller(i.e.,surface-charged halloysite nanotubes,d-HNTs),we successfully fabricate a high-performance polymer nanocomposite electrolyte enabled by strong surface adsorption,referred as adsorption-state polymer electrolyte(ASPE).This ASPE shows fast ion transport(0.71±0.05 mS cm^(-1)at room temperature),high mechanical strength and toughness(10.3±0.05 MPa;15.73 MJ m^(-3)),improved lithium-ion transference number,and long cycle life with lithium metal anode,in comparison with the sample without the d-HNT adsorption effect.To fundamentally understand these high performances,an anion-rich asymmetric solvent structure model is further proposed and evidenced by both experiments and simulation studies.Results show that the electrostatic adsorption among the d-HNT,ionic liquid electrolyte,and polymer chain generates a nano filler-supported fast ion-conduction pathway with asymmetric Li+-coordination microenvironment.Meanwhile,the anion-rich asymmetric solvent structure model of ASPE also generates a fast de-solvation and anion-derived stable solid-electrolyte interphase for lithium metal anode.The high performance and understanding of the mechanism for ASPE provide a promising path to develop advanced polymer electrolytes.
基金Research Project of Shenzhen Science and Technology Innovation Committee(JCYJ20180306170801080)。
文摘Amorphous Ga_(2)O_(3)(a-Ga_(2)O_(3))thin films were prepared on flexible polyimide,rigid quartz glass,and Si substrates via radio frequency magnetron sputtering at room temperature.The effect of oxygen/Ar flow rate ratio on the structure,optical property,surface morphology,and chemical bonding properties of the a-Ga_(2)O_(3) films was investigated.Results show that the average optical transmittance of the a-Ga_(2)O_(3) films is over 80%within the wavelength range of 300-2000 nm.The extracted optical band gap of the a-Ga_(2)O_(3) films is increased from 4.97 eV to 5.13 eV with the increase in O_(2)/Ar flow rate ratio from 0 to 0.25,due to the decrease in concentration of oxygen vacancy defects in the film.Furthermore,the optical refractive index and surface roughness of the a-Ga_(2)O_(3) films are optimized when the O_(2)/Ar flow rate ratio reaches 0.25.X-ray photoelectron spectroscopy analysis also shows that the proportion of oxygen vacancies(VO)and Ga-O chemical bonds in the O 1s peak is gradually decreased with the increase in O_(2)/Ar flow rate ratio from 0 to 0.25,proving that increasing the O_(2)/Ar flow rate ratio during film growth can reduce the concentration of oxygen vacancy defects in a-Ga_(2)O_(3) films.In this case,a-Ga_(2)O_(3) with optimal properties can be obtained.This work provides a research basis for high-performance flexible and rigid deep ultraviolet solar-blind detection devices based on a-Ga_(2)O_(3) films.
基金financially supported by the National Natural Science Foundation of China(No.51971176)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(No.CX2022036).
文摘This study comprehensively studied the precipitation ofαlaths and formation of inducedγnanotwins in a cast Ti-48Al-3Nb-1.5Ta(at.%)alloy tempered at theα+γphase region.The evolution of the microstruc-ture and its corresponding atomic mechanisms were investigated by transmission electron microscopy.The results show thatαphase precipitates as intersected laths,nucleates at stacking faults,and grows by a diffusion-controlled ledge-kink-terrace mechanism.The precipitation ofαlath introduces high stress concentrations at theγ/αinterface,produces dislocations and stacking faults,and induces the formation ofγnanotwins.Theγnanotwins nucleate at stacking faults emitted from theγ/αinterface and grow by Frank partials climbing,Schockley partials gliding,and several new mechanisms related to non-planar reactions of dislocations and annihilation of antiphase boundaries.Theγnanotwins are limited to sub-microns due to the lack of driving force.High temperatures promote the formation ofγnanotwins by activating non-planar reactions of dislocations and atom diffusion.In addition,Nb and Ta can promoteαlath precipitation andγnanotwin formation by reducing the stacking fault energy and preferring stacking fault emission.In summary,these findings provide new insights intoαlath precipitation andγtwinning mechanisms,which are relevant as theoretical bases for microstructure control and refinement of castγ-TiAl alloys.
基金supported by the National Natural Science Foundation of China(Nos.52130110,52271116,52431002)the Fundamental Research Funds for the Central Universities(No.D5000220052)the Aeronautical Science Foundation of China(2023Z053053003).
文摘How to describe the austenite reverse transformation(ART)has always been considered as a key problem of controlling microstructures and mechanical properties in high-strength steels.So far,numerous studies have been conducted,unfortunately,without fully considering diffusion of elements,interface migration,and interaction between trans-interface diffusion and interface migration,as well as synergy of thermodynamic and kinetic for interfacial migration.A more flexible modeling for the ART is herein developed using thermodynamic extremal principle,where the concept of trans-interface diffusion in two steps,i.e.,from the parent phase to the interface and from the interface to the product phase,as well as the Gibbs energy balance approach,was introduced to predict the behavior of interface migration and element trans-interface diffusion within the migrating interface.Subsequently,the thermodynamic driving force ΔG and the effective kinetic energy barrier Q_(eff) for the ART were also analytically performed,as well as a unified expression for so-called generalized stability(GS).It is demonstrated that the higher driving force in the ART generally results in the increased yield strength,while the larger GS tends to yield improved uniform elongation,thus forming a correspondence between the thermo-kinetics trade-off and the strength-ductility trade-off.Applying a proposed criterion of high ΔG-high GS,the present model can be adopted to design the ART,which will produce the austenite microstructure with high strength and high plasticity,as evidenced by the current experiments.
基金supported by grants from the National Natural Science Foundation of China(Nos.22274076,22304084)the Primary Research&Development Plan of Jiangsu Province(No.BE2022793)+1 种基金the Natural Science Foundation of Jiangsu Province of China(No.BK20230377)Jiangsu Provincial Department of Education(No.211090B52303)。
文摘Enantiomer identification is of paramount industrial value and physiological significance.Construction of sensitive chiral sensors with high enantiomeric discrimination ability is highly desirable.In this work,a chiral covalent organic framework/anodic aluminum oxide(c-COF/AAO)membrane was prepared for electrochemical enantioselective recognition and sensing.Benefiting from the remarkable asymmetry,the asprepared nanofluidic c-COF/AAO presents a distinct ion current rectification(ICR)characteristic,enabling sensitive bioanalysis.In addition,owing to the large surface area,high chemical stability and perfect ion selectivity of chiral COF,the prepared c-COF/AAO membrane presents exceptionally selective mass transport and thereby enables excellent chiral discrimination for S-/R-Naproxen(S-/R-Npx)enantiomers.It is especially noteworthy that the detection limit is achieved as low as 3.88 pmol/L.These results raise the possibility for a facile,stable and low-cost method to carry out sensitive enantioselective recognition and detection.
基金supported by the National Natural Science Foundation of China(Nos.21906179 and 22074098)Sichuan Science and Technology Program(No.2021ZYD0047)the Fundamental Research Funds for the Central Universities.
文摘As emerging pollutants,microplastics have recently received considerable attention owing to detection in various organisms and environments.Mass production and widespread use of plastic products increase their potential risks to humans owing to their persistent,mobile,and toxic properties.Numerous methods have been used to identify and quantify the various forms of microplastics,however,unified standards do not exist.In this review,we systematically summarize the sources,migration,transformation,and analytical methods for microplastics in diverse ecosystems,particularly the most recent sampling and identification techniques.Additionally,the environmental effects and health hazards of microplastics on aquatic and terrestrial systems,as well as human beings are discussed.We also present management strategies for reducing microplastics in a broader social and policy context.This review aims to provide an overview of the migration,transformation,sampling,analysis,and environmental effects of microplastics,which addresses knowledge gaps in microplastic pollution and provides proposals for key research gaps.
基金supported by the National Natural Science Foundation of China(Grant Nos.52171013 and 52130110)the Key Research and Development Program of Shaanxi(Grant No.2025CY-YBXM-127)+1 种基金the Natural Science Foundation of Chongqing(Grant No.CSTB2022NSCQ-MSX0369)the Research Fund of the State Key Laboratory of Solidification Processing(NPU)China(Grant No.2023-QZ-03)。
文摘Despite the promising prospects of body-centered cubic iron(BCC Fe)in aerospace,energy transportation,and nuclear applications,the effects of extreme environments on its mechanical behaviors and deformation mechanisms remain elusive to date.In this work,the mechanical responses and deformation behaviors of BCC Fe single crystals under extreme loading conditions are investigated by performing the three-dimensional discrete dislocation dynamics simulations.It turns out that the yield strength(oy)of BCC Fe can be enhanced by increasing the strain rate()and/or decreasing the deformation temperature(T).With the strain rate increasing from=10^(2)s^(-1)to 106 s^(-1),the yield strength at 300 K rises fromσy=51.14 MPa to 1114.57 MPa.When the strain rate exceeds 10^(3)s^(-1),an elastic overshoot phenomenon appears because the applied stress and the low initial dislocation density at the early tensile stage cannot drive the plastic deformation immediately.With the temperature increasing from T=100 K to 800 K,the yield strength atσ_(y)=10^(3)3 s^(-1)decreases fromσε=64.97 MPa to 59.50 MPa.Such temperature and strain rate sensitivity of deformation behaviors are clarified from variations in the configurations of dislocation evolution and dislocation density fluxes.It is demonstrated that at low strain rate(ε≤10^(3)s^(-1))conditions,the deformation behaviors of BCC Fe are dominated by the dislocation multi-slip mechanism.With increasing strain rate to e.g.,>10^(3)s^(-1),the deformation behaviors are governed by the dislocation single-slip.Our investigation on the temperature and strain rate sensitivity of deformation behaviors provides insightful guidance for optimizing the mechanical performances of BCC Fe based ferritic steels.
文摘Catalytic oxidation plays a crucial role in chemical industry,in which the utilization of abundant and environmental-friendly oxygen(O_(2))as oxidant aligns with sustainable development principles in green chemistry.However,the intrinsic inertness of ground-state O_(2) molecule poses a long-standing challenge in developing an efficient non-noble metal-based catalyst.Herein,inspired by the electron transfer process in respiratory chain,we engineered long-range N_(V) to mediate Fe_(1) center for O_(2) activation in aerobic oxidation.Combined in/quasi-situ spectroscopic characterizations and control experiments suggest the Fe_(1) site efficiently adsorbs O_(2),and the N_(V) site facilitates electron delocalization to adjacent Fe_(1),providing efficient transformation of O_(2) to reactive oxygen species that boost oxidation reactions mildly.This Fe_(1)--N_(V) single-atom catalyst demonstrates outstanding catalytic performance in aerobic oxidations of alkanes,N-heterocycles,alcohols,and amines under relatively mild conditions.Our findings offer a new perspective for designing high-efficiency heterogeneous catalysts in aerobic oxidations,promising various potential applications.
基金fund support from the National Natural Science Foundation of China(Nos.21575092,21622508)the 111 project(No.B17030)。
文摘Although platinum-based materials are regarded as the state-of-the-art electro-catalysts for hydrogen evolution reaction(HER),high cost and quantity scarcity hamper their scale-up utilization in industrial deployment.Herein,a one-step strategy was developed to synthesize multi-walled carbon nanotubes and reduced graphene oxide supported Pt nanoparticle hydrogel(PtNP/rGO-MWCNT),in which only ascorbic acid was used as the reductant for one-pot reduction of both GO and chloroplatinic acid.The hydrogel can be directly used as a flexible binder-free catalytic electrode to achieve high performance of HER.Compared to conventional strategies,the current strategy not only significantly reduces the Pt loading to 3.48 wt%,simplifies the synthesis process,but also eliminates the use of any polymer binders,thus decreasing the series resistance and improving catalytic activity.An overpotential of only 11 mV was achieved on as-prepared PtNP/rGO-MWCNT to drive a geometrical current density of 10 mA/cm2 in0.5 mol/L H2 SO4,with its catalytic activity being kept over 15 h.In acidic medium,the HER activity of the PtNP/rGO-MWCNT catalyst exceeds most of the reported Pt-based electro-catalysts and is 3-fold higher than that obtained on commercial Pt/C electrode.
基金the Natural Science Foundation of China(Nos.52130110,52171013 and 51790481)the Research Fund of the State Key Laboratory of Solidification Processing(Nos.2019-TZ-01 and 2019-BJ-02)+1 种基金the Fundamental Research Funds for the Central Universities(No.3102020QD0412)“2020-2022 Youth Talent Promotion Project”of China Association for Science and Technology.
文摘Although several strategies(including grain refinement,texture adjustment,precipitation hardening,etc.)have been verified to effectively improve the mechanical properties of lightweight magnesium(Mg)alloys,considerable efforts are still needed to be made to comprehensively understand the potential mechanisms controlling complex microstructures and deformation behaviors exhibited by the hexagonal close-packed host lattice of Mg,thus assisting the rational design of materials at a more physical level.As the cornerstone of this review,a universal rule,the so-called synergy of thermodynamics and kinetics(i.e.,thermo-kinetic diversity,correlation and connectivity),including a recently proposed theory of generalized stability(GS),is introduced to deepen our understanding on common behaviors in Mg alloys(i.e.,deformations(slip and twining modes),phase transformations(especially for precipitations)and interactions in between)at a new perspective.Guided by the GS theory,typical cases for Mg alloys design are qualitatively evaluated to reemphasize the traditional strengthening and toughening strategies mentioned above and to illuminate their exquisite coordination for breaking through the trade-off relationship between strength and ductility,corresponding to a typical thermo-kinetic pair(i.e.,high driving force(ΔG)-high GS).To produce the Mg alloys with superior strength-ductility balances,the potential capacity of this GS theory for guiding processing path design is discussed,finally。
基金the National Natural Science Foundation of China(No.21706091)Science and Technology Program of Guangzhou(No.201804010400)Fundamental Research Funds for the Central Universities(No.21617426)。
文摘A novel three-dimension separable and recyclable r GH-PANI/BiOI photocatalyst with the synergism of adsorption-enrichment and photocatalytic-degradation was successfully prepared via a facile three-step hydrothermal method.The three-dimension reduced graphene oxide hydrogel(rGH)in with flower-like BiOI photocatalyst uniformly distributed not only possesses excellent adsorption and electron transport properties,but also is easy to be separated from water for recycling.In addition,polyphenylamine(PANI)provides superior hole transport ability due to its delocalizedл-лconjugate structure.The cooperation of rGH and PANI greatly enhances the separation efficiency of photogenerated carriers,and finally improves the photocatalytic degradation behaviors.The removal rates of Rhodamine B(RhB)by rGH-PANI/BiOI-70%composite under visible light respectively reach 100%and 50.13%in static and dynamic systems,which are 12.85 and 3.58 times of BiOI,respectively.The removal rate does not show decrease after 5 recycles indicating the excellent separable and recyclable property of rGH-PANI/BiOI photocatalyst.The work provides an essential reference for designing and constructing hydrogel-based ternary composite photocatalysts with excellent synergism of adsorption and photocatalysis,which shows great potential in the treatment of water pollution.
文摘In this work, the structures of a pair of isomers were identified. And we showed the ability of the selective 1D version, performed the most common NMR experiments including the 1D-HMBC and GOESY experiments, to determine the isom^ric composition that were found in the production process of roflumilast. The experimental results proved that this method would be even more time saving and could get more reliable results.
基金supported by the National Natural Science Foundation of China(Nos.51871174,52071256,and 51831006)the State Key Laboratory of Solidification Processing in NPU(No.SKLSP202003)the State Key Laboratory for Mechanical Behavior of Materials(No.2019016)。
文摘The irreversible motion of magnetic domain walls in ferromagnets can dissipate a large portion of the elastic energy,and the associated damping capacity is proportional to the magnetostriction constant.In contrast,here we found that the damping capacity of the large magnetostriction Fe-Ga alloys can be enhanced by 2-3 times through introducing structural defects including interfacial dislocations and stacking faults,despite that these defects deteriorate the magnetostriction.These structural defects were introduced by aging the BCC(body-centered-cubic)solution-treated precursor,for which the formation of mechanically harder FCT(face-centered-tetragonal)and/or FCC(face-centered-cubic)phases can result in high-density partial dislocations at the semi-coherent phase interfaces and quasi-periodically stacked nano-layer substructure inside the FCC variants.The structural defects act as extra damping sources besides the magnetic domain walls because the structural accommodation of the semi-coherent phase interfaces between BCC and FCT/FCC nanoprecipitates with different elastic moduli and the nano-layer substructure towards long-range ordered periodical stacking can dissipate a large portion of mechanical energy.These findings suggest that introducing structural defects provides fresh freedom to design high damping ferromagnetic materials.
基金the financial support from the National Key R&D Program of China(Nos.2017YFB0703001,2017YFB0305100)the National Natural Science Foundation of China(Nos.51134011,51431008)the financial support from the National Natural Science Foundation of China(Nos.51861135302,51831002 and U1460203)。
文摘A good combination of ultimate tensile strength(UTS)up to 1365 MPa and total strain to failure(StF)to 15.5%has been achieved due to deformable martensite in the invented vanadium-microalloyed dual-phase(DP)steel,which was manufactured by two-stage annealing of cold rolled steel strip.The employed extensive characterizations revealed that the ductile martensitic phase in this DP steel differentiated from ordinarily low-carbon martensitic lath in both morphology and lattice structure.Complex coherent orientation relationships between ferrite,reverse austenite,martensitic phase and vanadium carbide(VC)do exist,leading to a new martensitic transformation mechanism and resultant dual-phase microstructure.Besides,a detailed characterization including essential phase transformation analysis in combination with in situ TEM observation,shows that,all the essential processing including recrystallization,reverse austenitic and martensitic transformation,in debt to the particular effects of VC,can be recognized as phase transformations with higher thermodynamic driving force and higher kinetic energy barrier as compared to previously common processing,which actually changes the microstructure and,indirectly leads to higher strength and higher ductility.This synergy of thermodynamics and kinetics can be generalized to improve mechanical properties of present steels.
基金supported financially by the National Key R&D Program of China (Nos. 2017YFB0703001 and 2017YFB0305100)the Natural Science Foundation of China (Nos. 51790483,51790481,51134011,51431008 and 51671075)+3 种基金the Fundamental Research Funds for the Central Universities (No. 3102017jc01002)the Research Fund of the State Key Laboratory of Solidification Processing (Nos. 2019-TZ-01 and 2019-BJ-02)the China Postdoctoral Science Foundation (No. 2018M643729and 2019T120942)the Natural Science Basic Research Plan in Shaanxi Province of China(No. 2019JQ-091)
文摘Upon non-equilibrium solidifications, dendrite growth, generally as precursor of as-solidified structures,has severe effects on subsequent phase transformations. Considering synergy of thermodynamics and kinetics controlling interface migration and following conservation of heat flux in solid temperature field, a more flexible modeling for the dendrite growth is herein developed for multi-component alloys,where, two inherent problems, i.e. correlation between thermodynamics and kinetics(i.e. the thermokinetic correlation), and theoretical connection between dendrite growth model and practical processing,have been successfully solved. Accordingly, both the thermodynamic driving force G and the effective kinetic energy barrier Qeffhave been found to control quantitatively the dendrite growth(i.e. especially the growth velocity, V), as reflected by the thermo-kinetic trade-off. Compared with previous models, it is the thermo-kinetic correlation that guarantees quantitative connection between the practical processing parameters and the current theoretical framework, as well as more reasonable description for kinetic behaviors involved. Applied to the vertical twin-roll casting(VTC), the present model, realizes a good prediction for kissing points, which influences significantly alloy design and processing optimization.This work deduces quantitatively the thermo-kinetic correlation controlling the dendrite growth, and by proposing the parameter-triplets(i.e. G-Qeff-V), further opens a new beginning for connecting solidification theories with industrial applications, such as the VTC.
基金the National Key R&D Program of China(No.2017YFB0703001)the National Natural Science Foundation of China(Nos.52130110,51790481,51901182 and 51901185)the Natural Science Foundation of Shaanxi Province(Nos.2020JQ-157 and 2020JQ-153)。
文摘Designing structured materials with optimized mechanical properties generally focuses on engineering microstructures,which are closely determined by the processing routes,such as phase transformations(PTs)and plastic deformations(PDs).Both PTs and PDs follow inherent trade-off relation between thermodynamic driving force ΔG and kinetic energy barrier Q,i.e.,so-called thermo-kinetic correlation.By analyzing nucleation and growth and proposing a conception of negative driving force integrating strain energy,interface energy and any kind of energy that equivalently inhibits the PT itself,ΔG^(S),unified expressions for the thermo-kinetic correlation and generalized stability(GS)were derived for three kinds of PTs,i.e.,diffusive PTs with simultaneously decreasedΔG and increased Q,diffusive PTs with simultaneously increasedΔG and decreased Q,and displacive PTs with simultaneously increased ΔG and decreased Q.This leads to so-called thermo-kinetic connectivity by integrating the thermo-kinetic correlation and the GS,where,by application in typical PTs,it was clearly shown,a criterion of high ΔG-high GS can be predicted by modulating chemical driving force,negative driving force and kinetic energy barrier for diffusion or nucleation.Following thermo-kinetic connectivity,analogous procedure for dislocation evolution upon PDs was performed,and materials design in terms of the highΔG-high GS criterion was discussed and prospected.
基金This work was supported by the National Key R&D Program of China(grant numbers 2017YFB0703001,2017YFB0305100)the Natural Science Foundation of China(grant numbers 51431008,51790481,51804336,51901185)+1 种基金the Research Fund of the State Key Laboratory of Solidification Processing(grant numbers 2019-BJ-04,2019-TZ-01)and the Natural Science Basic Research Plan in Shaanxi Province of China(grant number 2019JM-132).We would like to thank the Analytical&Testing Center of Northwestern Polytechnical University for EBSD and TEM experiments.
文摘Dynamic recrystallization(DRX)plays significant roles in manipulating of microstructures during hot deformation and the result mechanical properties;however,the underling mechanism leading to multi scale-microstructures remains poorly understood.Here,the DRX mechanism under wide processing conditions(i.e.950-1200°C,0.001-10 s-1)in Incoloy 028 alloy was investigated,where the relationships among flow stress,Z parameter and grain size,as well as the evolution of characteristic microstructures(grain size,sub-grain boundaries,and high angle grain boundaries),are established.As the values of Z parameters decrease(corresponding to decreased flow stresses),three typical softening mechanisms successively occur,ranging from continuous DRX controlled by dislocation glide,discontinuous DRX dominated by dislocation motion(climb and cross/multiple slip)and grain boundary migration,to dynamic normal/abnormal grain growth resulting from grain boundary migration,with transition regions where two adjacent mechanisms occur simultaneously.Correspondingly,these above three softening mechanisms result in ultrafine,fine and coarse grains,respectively.The present findings demonstrate a comprehensive understanding of DRX mechanism over a wide range of processing conditions,and further provide a new guideline for preparing single crystals.
基金supported financially by the National Natural Science Foundation of China(No.51871178)。
文摘Grain-boundary(GB)precipitation has a significant adverse effect on plasticity of alloys,which easily leads to catastrophic intergranular failure in safety-critical applications under high external loading.Herein,we report a novel strategy that uses the local stress concentration induced by GB precipitates as a driving force to trigger phase transformation of preset non-equiatomic high-entropy solid-solution phase at GBs.This in situ deformation-induced phase transformation at GBs introduces a well-known effect:transformation-induced plasticity(TRIP),which enables an exceptional elongation to fracture(above 38%)at a high strength(above 1.5 GPa)in a GB precipitation-hardened high-entropy alloy(HEA).The present strategy in terms of"local stress concentration-induced phase transformations at GBs"may provide a fundamental approach by taking advantage of(rather than avoiding)the GB precipitation to gain a superior combination of high strength and high ductility in HEAs.
基金the financial support of the Natural Science Foundation of China(Nos.52130110,51790480,52271116,and 51901185)the Fundamental Research Funds for the Central Universities(No.D5000220052).
文摘1.Introduction,Understanding and predicting microstructure and its relationship with the mechanical properties of metallic materials require detailed knowledge of phase transformations(PTs)and plastic deformations(PDs).These two processes,as central topics in material science,can be fundamentally described to a large extent by a framework of thermodynamic and kinetics(thermo-kinetics).The situation of PTs arises when the microstructure is losing phase stability,whereas the issue of PDs corresponds to the break of mechanical stability,all of which can be uniformly defined as the so-called loss of thermodynamic stability(TS).In this context,the higher TS will lead to the higher driving force G essentially required for the PT and/or PD forming and/or changing the microstructure.In the case of PTs,extensive examples showing the high TS can be found,such as martensite transformations(MTs)upon continuous cooling or strain[1,2],coherent precipitation[3,4],so-called Schwarz crystal[5],etc.
基金support of the National Natural Science Foundation of China(No.52130110 and 51901182)the Research Fund of the State Key Laboratory of Solidification Process-ing(No.2022-TS-01).
文摘Using dislocation-based constitutive modeling in three-dimension crystal plasticity finite element(3D CPFE)simulations,co-deformation and instability of hetero-phase interface in different material systems were herein studied for polycrystalline metal matrix composites(MMCs).Local stress and strain fields in two types of 3layer MMCs such as fcc/fcc Cu-Ag and fcc/bcc Cu-Nb have been predicted under simple compressive deformations.Accordingly,more severe strain-induced interface instability can be observed in the fcc/bcc systems than in the fcc/fcc systems upon refining to metallic nanolayered composites(MNCs).By detailed analysis of stress and strain localization,it has been demonstrated that the interface instability is always accompanied by high-stress concentration,i.e.,thermodynamic characteristics,or high strain prevention i.e.,kinetic characteristics,at the hetero-phase interface.It then follows that the thermodynamic driving forceG and the kinetic energy barrier Q during dislocation and shear banding can be adopted to classify the deformation modes,following the so-called thermo-kinetic correlation.Then by inserting a high density of high-energy interfaces into the Cu-Nb composites,such thermo-kinetic integration at the hetero-phase interface allows a successful establishment of MMCs with the high△G-high Q deformation mode,which ensures high hardening and uniform strain distri-bution,thus efficiently suppressing the shear band,stabilizing the hetero-phase interface,and obtaining an exceptional combination in strength and ductility.Such hetero-phase interface chosen by a couple of thermodynamics and kinetics can be defined as breaking the thermo-kinetic correlation and has been proposed for artificially designing MNCs.
