Currently,the enhancement in electromagnetic interference(EMI)performance of polymeric composite generally relies on either improving electrical conductivity(σ)for stronger electromagnetic(EM)reflections or tailoring...Currently,the enhancement in electromagnetic interference(EMI)performance of polymeric composite generally relies on either improving electrical conductivity(σ)for stronger electromagnetic(EM)reflections or tailoring structure for higher EM resonances.Herein,we proposed a novel technique called cyclic pulsating pressure enhanced segregating structuration(CPP-SS),which can reinforce these two factors simultaneously.The structural information was supplied by optical microscopy(OM)and scanning electron microscopy(SEM),both of which confirmed the formation and evolution of segregate structured ultra-high molecular weight polyethylene(UHMWPE)/graphene composites.Then,the result showed that CPP-SS can significantly improve theσof samples.Ultimately,advanced specific EMI shielding efficiency of 31.1 d B/mm was achieved for UHMWPE/graphene composite at 1-mm thickness and a low graphene loading of 5 wt%.Meanwhile,it also confirmed that the intrinsic disadvantage of poor mechanical properties of conventional segregated structure composites can be surpassed.This work is believed to provide a fundamental understanding of the structural and performance evolutions of segregated structured composites prepared under CPPSS,and to bring us a simple and efficient approach for fabricating high-performance,strong and light-weight polymeric EMI shields.展开更多
Salt tolerance of segregating progenies of a cross between a domesticated salt sensitive tomato cultivar (CA4) and a natural salt-tolerant wild-type tomato species (LA1606) was characterized. The F1 plants from this c...Salt tolerance of segregating progenies of a cross between a domesticated salt sensitive tomato cultivar (CA4) and a natural salt-tolerant wild-type tomato species (LA1606) was characterized. The F1 plants from this cross were selfed and 120 F2 segregating progenies from the resulting population along with parental CA4 and LA1606 plants were evaluated for salt tolerance. These plants were irrigated everyday with 185 mM NaCl for 82 days and quantitative traits were quantified including number of flowers, fruit number, fruit weight, fruit length, fruit width, fruit set percentage, and total yield. The two parental lines were evaluated for the presence of 27 seven independent RAPD markers and 7 markers were found to be polymorphic for the two genotypes. Bulk Segregant (BSA) analyses consisting of pooling 10 “most tolerant” and 10 “most sensitive” F2 segregating plants showed association of two RAPD polymorphic markers with higher salt tolerance. Two DNA markers that exhibit co-segregation with salt tolerance were identified and characterized. RAPD marker OPX-17 and MRTOMR-022 exhibited 2 positive molecule markers (polymorphism) which were found only in the resistant parent (LA1606) and resistant F2 bulk.展开更多
It is pointed out in the modern theory of micro-nonhomogeneity in solid solution that solute atoms will present a short-range order distribntion following a certain pattern when the binding force between different ato...It is pointed out in the modern theory of micro-nonhomogeneity in solid solution that solute atoms will present a short-range order distribntion following a certain pattern when the binding force between different atoms AB is stronger than that between the same ones AA展开更多
In response to the urgent demand for lightweight,magnesium(Mg)alloys have garnered considerable attention owing to their low density.Nonetheless,the intrinsic poor room-temperature formability of Mg alloys remains a m...In response to the urgent demand for lightweight,magnesium(Mg)alloys have garnered considerable attention owing to their low density.Nonetheless,the intrinsic poor room-temperature formability of Mg alloys remains a major obstacle in shaping precise complex components,necessitating the development of superplastic Mg alloys.Excellent superplasticity is usually acquired in high-alloyed Mg alloys with enhanced microstructural thermal stability facilitated by abundant optimized second-phase particles.While for cost-effective low-alloyed Mg alloys lacking particles,regulating solute segregation has emerged as a promising approach to achieve superplasticity recently.Moreover,the potential of bimodal-grained Mg alloys for superplastic deformation has been revealed,expanding the options for designing superplastic materials beyond the conventional approach of fine-grained microstructures.This study reviews significant developments in superplastic Mg alloys from the view of alloying strategies,grain structure control and deformation mechanisms,with potential implications for future research and industrial applications of superplastic Mg alloys.展开更多
Asymmetric tilt boundaries on conventional twin boundaries(TBs)are significant for understanding the role of twins on coordinating plastic deformation in many metallic alloys.However,the formation modes of many asymme...Asymmetric tilt boundaries on conventional twin boundaries(TBs)are significant for understanding the role of twins on coordinating plastic deformation in many metallic alloys.However,the formation modes of many asymmetric tilt boundaries are hard to be accounted for based on traditional theoretical models,and the corresponding solute segregation is complex.Herein,atomic structures of a specific asymmetric boundary on{1012}TBs were reveled using aberration-corrected high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),molecular dynamics(MD)and density functional theory(DFT)simulations.Reaction between<a60>M dislocations and the{1012}TB can generate a~61°/25°asymmetric tilt boundary.The segregation of Gd and Zn atoms is closely related to the aggregateddislocations and the interfacial interstices of the asymmetric tilt boundary,which is energetically favorable in reducing the total system energy.展开更多
The impact of heavy reduction on dendritic morphology was explored by combining experimental research and numerical simulation in metallurgy,including a detailed three-dimensional(3D)analysis and reconstruction of den...The impact of heavy reduction on dendritic morphology was explored by combining experimental research and numerical simulation in metallurgy,including a detailed three-dimensional(3D)analysis and reconstruction of dendritic solidification structures.Combining scanning electron microscopy and energy-dispersive scanning analysis and ANSYS simulation,the high-precision image processing software Mimics Research was utilized to conduct the extraction of dendritic morphologies.Reverse engineering software NX Imageware was employed for the 3D reconstruction of two-dimensional dendritic morphologies,restoring the dendritic characteristics in three-dimensional space.The results demonstrate that in a two-dimensional plane,dendrites connect with each other to form irregularly shaped“ring-like”structures.These dendrites have a thickness greater than 0.1 mm along the Z-axis direction,leading to the envelopment of molten steel by dendrites in a 3D space of at least 0.1 mm.This results in obstructed flow,confirming the“bridging”of dendrites in three-dimensional space,resulting in a tendency for central segregation.Dense and dispersed tiny dendrites,under the influence of heat flow direction,interconnect and continuously grow,gradually forming primary and secondary dendrites in three-dimensional space.After the completion of dendritic solidification and growth,these microdendrites appear dense and dispersed on the two-dimensional plane,providing the nuclei for the formation of new dendrites.When reduction occurs at a solid fraction of 0.46,there is a noticeable decrease in dendritic spacing,resulting in improved central segregation.展开更多
A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped C...A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped CrCoNi MEAs at similar yield strength levels.P segregation at grain boundaries(GBs)and dissolution inside grain interiors,together with the related lower stacking fault energy(SFE)are found in the P-doped CrCoNi MEA.Higher hetero-deformation-induced(HDI)hardening rate is observed in the P-doped CrCoNi MEA due to the grain-to-grain plastic deformation and the dynamic structural refinement by high-density stacking fault-walls(SFWs).The enhanced yield strength in the P-doped CoCrNi MEA can be attributed to the strong substitutional solid-solution strengthening by severer lattice distortion and the GB strengthening by phosphorus segregation at GBs.During the tensile deformation,the multiple SFW frames inundated with massive multi-orientational tiny planar stacking faults(SFs)between them,rather than deformation twins,are observed to induce dynamic structural refinement for forming par-allelepiped domains in the P-doped CoCrNi MEA,due to the lower SFE and even lower atomically-local SFE.These nano-sized domains with domain boundary spacing at tens of nanometers can block disloca-tion movement for strengthening on one hand,and can accumulate defects in the interiors of domains for exceptionally high hardening rate on the other hand.展开更多
Solute atoms and precipitates significantly influence the mechanical properties of Mg alloys.Previous studies have mainly focused on the segregation behaviors of Mg alloys after annealing.In this study,we investigated...Solute atoms and precipitates significantly influence the mechanical properties of Mg alloys.Previous studies have mainly focused on the segregation behaviors of Mg alloys after annealing.In this study,we investigated the segregation behaviors of an Mg-RE alloy under deformation.We found that the enrichment of solute atoms occurred in{101^(-)1}compressive twin boundaries under compression at 298 K without any annealing in an Mg-RE alloy by scanning transmission electron microscopy and energy-dispersive X-ray analysis.The segregated solutes and precipitates impeded the twin growth,partially contributing to the formation of small-sized{101^(-)1}compressive twins.This research indicates the twin boundaries can be strengthened by segregated solutes and precipitates formed under deformation at room temperature.展开更多
This study aims to clarify the mechanisms for the grain boundary(GB)segregation through investigating the absorption of excess solute atoms at GBs in Al−Cu alloys by using the hybrid molecular dynamics/Monte Carlo sim...This study aims to clarify the mechanisms for the grain boundary(GB)segregation through investigating the absorption of excess solute atoms at GBs in Al−Cu alloys by using the hybrid molecular dynamics/Monte Carlo simulations.Two segregation mechanisms,substitutional and interstitial mechanisms,are observed.The intergranular defects,including dislocations,steps and vacancies,and the intervals in structural units are conductive to the prevalence of interstitial mechanism.And substitutional mechanism is favored by the highly ordered twin GBs.Furthermore,the two mechanisms affect the GB structure differently.It is quantified that interstitial mechanism is less destructive to GB structure than substitutional one,and often leads to a segregation level being up to about 6 times higher than the latter.These findings contribute to atomic scale insights into the microscopic mechanisms about how solute atoms are absorbed by GB structures,and clarify the correlation among intergranular structures,segregation mechanisms and kinetics.展开更多
First-principles theory calculations were used to investigate the segregation behavior of P and Mg as well as the interactions between Mg and P atα-FeΣ3(111)[11¯0]symmetrical tilt grain boundary(GB).Results dem...First-principles theory calculations were used to investigate the segregation behavior of P and Mg as well as the interactions between Mg and P atα-FeΣ3(111)[11¯0]symmetrical tilt grain boundary(GB).Results demonstrate that both P and Mg are segregated at GB,and P has a stronger segregation potency.Mg prefers to substitute at grain boundary plane with the largest absorbable vacancy,whereas P inclines to substitute at the sites near Fe atoms to form strong covalent Fe-P bonds.When Mg exists at GB,the segregation behavior of P may be greatly inhibited by the decrease in possible solution sites and the increase in segregation energy.P has stronger interactions with Mg at GB,forming a lower energy hybridization peak.These results can be used to explain why the addition of a small amount of Mg can ameliorate the temper embrittlement phenomenon.展开更多
Grain boundary segregation(GBS)of solutes influences the grain size,texture,and strength of Mg wrought alloys.So far,solutes'GBS in Mg has mostly been investigated by qualitative experimental observations.In this ...Grain boundary segregation(GBS)of solutes influences the grain size,texture,and strength of Mg wrought alloys.So far,solutes'GBS in Mg has mostly been investigated by qualitative experimental observations.In this work,we develop a quantitative model to compute the grain boundary segregation energy(ΔE_(seg))in binary Mg based alloys that takes the relative atomic density of GB into account.The model is utilized to computeΔE_(seg)of Al,Zn,Ca,Sn,Y,Gd,and Nd solutes in Mg.The result suggests that rare earth elements and Ca are more prone to GBS than Al,Zn,and Sn.Segregation of Gd solutes can explain the smaller grain size and slower grain growth in Mg-Gd extruded alloys than Mg-Al and Mg-Zn counterparts.It also provides an explanation for the weak extrusion texture in Mg-Gd.展开更多
Elements(As,Bi)and(Cu,Fe)exhibiting two typical segregation behavior in liquid Sb alloys were selected as solute atoms for analysis.Ab initio molecular dynamics(AIMD)simulations were employed to study the molten Sb al...Elements(As,Bi)and(Cu,Fe)exhibiting two typical segregation behavior in liquid Sb alloys were selected as solute atoms for analysis.Ab initio molecular dynamics(AIMD)simulations were employed to study the molten Sb alloy at different temperatures.By analyzing its pair correlation function(PCF),bond pairs,bond angle distribution function(BADF),and Voronoi polyhedron(VP),the short-range order(SRO)of the alloy was investigated.In the Sb melt,the solute atoms Cu and Fe,which have smaller distribution coefficients,exhibit a stronger affinity for Sb than the solute atoms As and Bi,which have larger distribution coefficients.The BADF of As and Bi with larger distribution coefficients shows a lower probability of small-angle peaks compared to large-angle peaks,whereas the BADF of Cu and Fe with smaller distribution coefficients exhibits the opposite trend.The BADF reveals that Sb-As and Sb-Bi approach pure Sb melt,while Sb-Cu and Sb-Fe deviate significantly.Compared to Sb-Cu and Sb-Fe,the Sb-As and Sb-Bi systems exhibit more low-index bonds,suggesting weaker interactions and more disorder.The VP fractions around As and Bi atoms are lower than those around Cu and Fe,and the VP face distributions around As and Bi are more complex.There are differences in the VP around different solute atoms,primarily due to the varying bond pair fractions associated with each solute atom.Fe has the smallest diffusion coefficient,primarily due to its compact local structure.展开更多
In this work,a good balance of strength and ductility(a yield strength of 185 MPa and a uniform elongation of 20%)has been obtained in a dilute Mg-1.8Zn-0.3Y-0.3Ca-0.3Zr(wt.%)alloy using hard plate rolling(HPR)followe...In this work,a good balance of strength and ductility(a yield strength of 185 MPa and a uniform elongation of 20%)has been obtained in a dilute Mg-1.8Zn-0.3Y-0.3Ca-0.3Zr(wt.%)alloy using hard plate rolling(HPR)followed by annealing,with a low anisotropy in mechanical properties.More importantly,the HPR-annealed alloy shows an excellent formability at the same time,i.e.,the index Erichsen(I.E.)value reaches 7.9 mm(the Erichsen cupping test)at room temperature,which is higher compared with the Mg-1.8Zn-0.3Y-0.3Ca0.3Zr alloy produced by conventional multi-pass rolling(CR)followed by annealing.The excellent synergy of strength and formability of the HPR-annealed alloy is mainly attributed to a weak elliptical ring texture,as well as finer and denser Zn_(2)Zr_(3)precipitates.The formation of weak elliptical ring texture is related to the preferential co-segregation of Zn and Ca elements at boundaries of basal grains with smal misorientation angles during annealing,which inhibits the growth of basal grains and promotes the preferential growth of non-basal grains At the same time,in comparison with the CR-annealed alloy,the HPR-annealed alloy contains finer and denser Zn_(2)Zr_(3)precipitates that ar less likely to become sources of cracks,leading to the higher strength and formability of the HPR-annealed alloy.The results in this work can provide reference for the development of high strength Mg alloy sheets with excellent room temperature formability,which also shed light on mitigating planar anisotropy in mechanical properties for Mg alloy sheets.展开更多
Through thermodynamic calculations and microstructural characterization,the effect of niobium(Nb)content on the solidifica-tion characteristics of Alloy 625 Plus was systematically investigated.Subsequently,the effect...Through thermodynamic calculations and microstructural characterization,the effect of niobium(Nb)content on the solidifica-tion characteristics of Alloy 625 Plus was systematically investigated.Subsequently,the effect of Nb content on hot deformation behaviorwas examined through hot compression experiments.The results indicated that increasing the Nb content lowers the liquidus temperatureof the alloy by 51℃,producing a denser solidification microstructure.The secondary dendrite arm spacing(SDAS)of the alloy decreasesfrom 39.09 to 22.61μm.Increasing the Nb content alleviates element segregation but increases interdendritic precipitates,increasing theirarea fraction from 0.15% to 5.82%.These precipitates are primarily composed of large Laves,δ,η,and γ″phases,and trace amounts of Nb C.The shapes of these precipitates change from small chunks to large elongated forms.No significant change in the type or amount ofinclusions within the alloy is detected.The inclusions are predominantly individual Al_(2)O_(3) and TiN,as well as Al_(2)O_(3)/Ti N composite inclu-sions.Samples with varying Nb contents underwent hot compression deformation at a true strain of 0.69,a strain rate of 0.5 s^(-1),and a de-formation temperature of 1150℃.Increasing the Nb content also elevates the peak stress observed in the flow curves.However,alloyswith higher Nb content exhibit more pronounced recrystallization softening effects.The Laves phase precipitates do not completely redis-solve during hot deformation and are stretched to elongated shapes.The high-strain energy storage increases the recrystallization fractionfrom 32.4% to 95.5%,significantly enhancing the degree of recrystallization and producing a more uniform deformation microstructure.This effect is primarily attributed to the addition of Nb,which refines the initial grains of the alloy,enhances the solid solution strengthen-ing of the matrix,and improves the induction of particle-stimulated nucleation.展开更多
The limited creep resistance of wrought Mg-Al alloys restricts their lightweight applications at intermediate temperatures due to the softening effect of discontinuous precipitation(DP)on the dislocation-controlled cr...The limited creep resistance of wrought Mg-Al alloys restricts their lightweight applications at intermediate temperatures due to the softening effect of discontinuous precipitation(DP)on the dislocation-controlled creep.Here,we developed a creep-resistant wrought Mg-Al alloy through microalloying of Y and Ca.The resulting alloy exhibited an order of magnitude enhancement in the creep resistance at 125℃/50±100 MPa.In contrast to the grain boundary instabilities by DP in the previously reported wrought Mg-Al alloys,we show that the addition of 0.21Y+0.15Ca wt%produces a(Zn+Ca)co-segregation at the grain boundaries as a result of their segregation energy and the activation energy of grain boundary migration,thereby stabilizing the grain boundaries.The(Zn+Ca)co-segregation inhibits the dynamic DP and promotes the formation of intragranular Al-enriched clusters,which favorthe formation of Al_(2)Y,Mg_(17)Al_(12)nano precipitates,thereby impeding intragranular dislocation motion during creep.Furthermore,the addition of 0.21Y+0.15Ca wt%facilitates the formation of a fine and uniform recrystallization structure in the microalloyed alloys compared to AZ80 due to the high activation energy of mobility for the(Zn+Ca)segregated grain boundary.Therefore,the microalloyed alloys exhibit good tensile properties with 380 MPa tensile strength and 18%elongation.Our constitutive analysis revealed that the(Y+Ca)microalloying decreased the creep stress exponent by 29%and increased the creep resistance in the medium to high-stress range.Microalloying provides a promising way to develop low-cost creep-resistant wrought Mg-Al alloys.展开更多
A microscopic understanding of the complex solute-defect interaction is pivotal for optimizing the alloy’s macroscopic mechanical properties.Simulating solute segregation in a plastically deformed crystalline system ...A microscopic understanding of the complex solute-defect interaction is pivotal for optimizing the alloy’s macroscopic mechanical properties.Simulating solute segregation in a plastically deformed crystalline system at atomic resolution remains challenging.The objective is to efficiently model and predict a phys-ically informed segregated solute distribution rather than simulating a series of diffusion kinetics.To ad-dress this objective,we coupled molecular dynamics(MD)and Monte Carlo(MC)methods using a novel method based on virtual atoms technique.We applied our MD-MC coupling approach to model off-lattice carbon(C)solute segregation in nanoindented Fe-C samples containing complex dislocation networks.Our coupling framework yielded the final configuration through efficient parallelization and localized en-ergy computations,showing C Cottrell atmospheres near dislocations.Different initial C concentrations resulted in a consistent trend of C atoms migrating from less crystalline distortion to high crystalline distortion regions.Besides unraveling the strong spatial correlation between local C concentration and defect regions,our results revealed two crucial aspects of solute segregation preferences:(1)defect ener-getics hierarchy and(2)tensile strain fields near dislocations.The proposed approach is generic and can be applied to other material systems as well.展开更多
High-purity antimony(Sb)is essential for industries like semiconductors and photovoltaics,driving research on its production.This review summarizes research advances in production and preparation techniques for high-p...High-purity antimony(Sb)is essential for industries like semiconductors and photovoltaics,driving research on its production.This review summarizes research advances in production and preparation techniques for high-purity Sb.Three process flowcharts to produce high-purity Sb are described according to different raw materials.Various process parameters of vacuum distillation,zone refining purification techniques and research progress in the field of high-purity Sb are discussed.Numerical simulation,atomic scale simulation,and research progress of alloying elements in the field of high-purity Sb are highlighted.It is shown that for the difficult removal of As element in Sb,the addition of Al makes the regional refining process more effective in reducing the arsenic content.Finally,the purification of high-purity Sb is summarized,providing insights into achieving efficient and environmentally friendly high-purity Sb production and outlining future directions.展开更多
As a rare earth solute element in Mg alloys,Y has the beneficial effects of increasing both the strength and the ductility as well as weakening the crystallographic texture.To achieve a more fundamental understanding ...As a rare earth solute element in Mg alloys,Y has the beneficial effects of increasing both the strength and the ductility as well as weakening the crystallographic texture.To achieve a more fundamental understanding on how Y addition affects the microstructural evolution and mechanical properties,the Y segregation behavior at grain boundaries was investigated in Mg-1wt.%Y and Mg-7wt.%Y alloys at different conditions.The segregation intensity and its dependence on the grain boundary misorientation angle were experimentally characterized and computationally predicted.Strong segregation at grain boundaries was observed in both low and high Y-containing alloys.Y segregation was found to remain in alloy Mg-7Y after high-temperature annealing heat treatment at 540℃.No direct correlation between the Y segregation intensity and the grain boundary misorientation angle could be established based on either the experimental characterization or the atomistic simulation with a spectral model.We thus conclude that grain boundary segregation of Y is independent of grain boundary misorientation angle.展开更多
N6-methyladenosine(m6A)plays a key role in mammalian early embryonic development and cell lineage differentiation.However,the role and mechanisms of 18S ribosomal RNA(rRNA)m6A methyltransferase METTL5 in early embryon...N6-methyladenosine(m6A)plays a key role in mammalian early embryonic development and cell lineage differentiation.However,the role and mechanisms of 18S ribosomal RNA(rRNA)m6A methyltransferase METTL5 in early embryonic development remain unclear.Here,we found that 18S rRNA m6A methyltransferase METTL5 plays an important role in porcine early embryonic development.METTL5 knockdown and overexpression significantly reduced the developmental efficiency of porcine early embryos and impaired cell lineage allocation.METTL5 knockdown apparently decreased the global translation efficiency in blastocyst,while METTL5 overexpression increased the global translation efficiency.Furthermore,METTL5 knockdown did not affect the abundance of CDX2 mRNA,but resulted in a significant reduction in CDX2 protein levels.Moreover,the low developmental efficiency and abnormal lineage distribution of METTL5 knockdown embryos could be rescued by CDX2 overexpression.Collectively,our results demonstrated that 18S rRNA methyltransferase METTL5 regulates porcine early embryonic development via modulating the translation of CDX2.展开更多
Four powder metallurgy(PM)Ni-based superalloys with different Hf and Ta contents were creep-tested at 650℃ and 970 MPa,700℃ and 770 MPa,and 750℃ and 580 MPa,respectively.The effect of Hf and Ta on creep deformation...Four powder metallurgy(PM)Ni-based superalloys with different Hf and Ta contents were creep-tested at 650℃ and 970 MPa,700℃ and 770 MPa,and 750℃ and 580 MPa,respectively.The effect of Hf and Ta on creep deformation behaviors of the superalloys was studied from multiple scales by SEM,electron backscatter diffraction(EBSD),and aberration-corrected scanning transmission electron microscope(AC-STEM).The results showed that Hf and Ta suppressed the intergranular fracture and initiation of cracks during the acceleration creep stage,which prolonged the creep rupture time.Hf and Ta inhibited the stacking faults extending and the dislocation climbing and promoted the Suzuki segregation of W during the steady-state creep stage,which reduced the minimum creep rate and delayed the start time of the acceleration creep stage.The Suzuki segregation of Co,Cr,Mo,Ti,Nb,W,and Ta along stacking faults was observed after Hf and Ta addition,leading to the localized phase transformation in the γ′phase,and the stacking fault phase was chemically disordered.This study provided ideas for the composition design of novel PM Ni-based superalloys and theoretical foundations for the combined addition of Hf and Ta.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0302300)the China Postdoctoral Science Foundation(No.2019M652883)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2020A1515110467)the financial support from the opening project of Guangdong provincial key laboratory of technique and equipment for macromolecular advanced manufacturing,South China University of Technology,China。
文摘Currently,the enhancement in electromagnetic interference(EMI)performance of polymeric composite generally relies on either improving electrical conductivity(σ)for stronger electromagnetic(EM)reflections or tailoring structure for higher EM resonances.Herein,we proposed a novel technique called cyclic pulsating pressure enhanced segregating structuration(CPP-SS),which can reinforce these two factors simultaneously.The structural information was supplied by optical microscopy(OM)and scanning electron microscopy(SEM),both of which confirmed the formation and evolution of segregate structured ultra-high molecular weight polyethylene(UHMWPE)/graphene composites.Then,the result showed that CPP-SS can significantly improve theσof samples.Ultimately,advanced specific EMI shielding efficiency of 31.1 d B/mm was achieved for UHMWPE/graphene composite at 1-mm thickness and a low graphene loading of 5 wt%.Meanwhile,it also confirmed that the intrinsic disadvantage of poor mechanical properties of conventional segregated structure composites can be surpassed.This work is believed to provide a fundamental understanding of the structural and performance evolutions of segregated structured composites prepared under CPPSS,and to bring us a simple and efficient approach for fabricating high-performance,strong and light-weight polymeric EMI shields.
文摘Salt tolerance of segregating progenies of a cross between a domesticated salt sensitive tomato cultivar (CA4) and a natural salt-tolerant wild-type tomato species (LA1606) was characterized. The F1 plants from this cross were selfed and 120 F2 segregating progenies from the resulting population along with parental CA4 and LA1606 plants were evaluated for salt tolerance. These plants were irrigated everyday with 185 mM NaCl for 82 days and quantitative traits were quantified including number of flowers, fruit number, fruit weight, fruit length, fruit width, fruit set percentage, and total yield. The two parental lines were evaluated for the presence of 27 seven independent RAPD markers and 7 markers were found to be polymorphic for the two genotypes. Bulk Segregant (BSA) analyses consisting of pooling 10 “most tolerant” and 10 “most sensitive” F2 segregating plants showed association of two RAPD polymorphic markers with higher salt tolerance. Two DNA markers that exhibit co-segregation with salt tolerance were identified and characterized. RAPD marker OPX-17 and MRTOMR-022 exhibited 2 positive molecule markers (polymorphism) which were found only in the resistant parent (LA1606) and resistant F2 bulk.
文摘It is pointed out in the modern theory of micro-nonhomogeneity in solid solution that solute atoms will present a short-range order distribntion following a certain pattern when the binding force between different atoms AB is stronger than that between the same ones AA
基金primarily supported by The National Natural Science Foundation of China(under Nos.52234009 and 52271103)Partial financial support came from the Program for the Central University Youth Innovation Team(No.419021423505)the Fundamental Research Funds for the Central Universities,JLU.
文摘In response to the urgent demand for lightweight,magnesium(Mg)alloys have garnered considerable attention owing to their low density.Nonetheless,the intrinsic poor room-temperature formability of Mg alloys remains a major obstacle in shaping precise complex components,necessitating the development of superplastic Mg alloys.Excellent superplasticity is usually acquired in high-alloyed Mg alloys with enhanced microstructural thermal stability facilitated by abundant optimized second-phase particles.While for cost-effective low-alloyed Mg alloys lacking particles,regulating solute segregation has emerged as a promising approach to achieve superplasticity recently.Moreover,the potential of bimodal-grained Mg alloys for superplastic deformation has been revealed,expanding the options for designing superplastic materials beyond the conventional approach of fine-grained microstructures.This study reviews significant developments in superplastic Mg alloys from the view of alloying strategies,grain structure control and deformation mechanisms,with potential implications for future research and industrial applications of superplastic Mg alloys.
基金supported by the Scientific and Technological Developing Scheme of Jilin Province under grants no.YDZJ202301ZYTS538the Chinese Academy of Sciences Youth Innovation Promotion Association under grants number 2023234+3 种基金the National Natural Science Foundation of China under grants number U21A20323the Scientific and Technological Developing Scheme of Jilin Province under grants no.SKL202302038the Major Scientific and Technological Projects of Hebei Province under grants No.23291001Zthe Scientific and Technology Project of Hanjiang District.
文摘Asymmetric tilt boundaries on conventional twin boundaries(TBs)are significant for understanding the role of twins on coordinating plastic deformation in many metallic alloys.However,the formation modes of many asymmetric tilt boundaries are hard to be accounted for based on traditional theoretical models,and the corresponding solute segregation is complex.Herein,atomic structures of a specific asymmetric boundary on{1012}TBs were reveled using aberration-corrected high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),molecular dynamics(MD)and density functional theory(DFT)simulations.Reaction between<a60>M dislocations and the{1012}TB can generate a~61°/25°asymmetric tilt boundary.The segregation of Gd and Zn atoms is closely related to the aggregateddislocations and the interfacial interstices of the asymmetric tilt boundary,which is energetically favorable in reducing the total system energy.
基金supported by Open Foundation of the State Key Laboratory of Refractories and Metallurgy(No.G201711)the National Natural Science Foundation of China(Nos.52104317 and 51874001).
文摘The impact of heavy reduction on dendritic morphology was explored by combining experimental research and numerical simulation in metallurgy,including a detailed three-dimensional(3D)analysis and reconstruction of dendritic solidification structures.Combining scanning electron microscopy and energy-dispersive scanning analysis and ANSYS simulation,the high-precision image processing software Mimics Research was utilized to conduct the extraction of dendritic morphologies.Reverse engineering software NX Imageware was employed for the 3D reconstruction of two-dimensional dendritic morphologies,restoring the dendritic characteristics in three-dimensional space.The results demonstrate that in a two-dimensional plane,dendrites connect with each other to form irregularly shaped“ring-like”structures.These dendrites have a thickness greater than 0.1 mm along the Z-axis direction,leading to the envelopment of molten steel by dendrites in a 3D space of at least 0.1 mm.This results in obstructed flow,confirming the“bridging”of dendrites in three-dimensional space,resulting in a tendency for central segregation.Dense and dispersed tiny dendrites,under the influence of heat flow direction,interconnect and continuously grow,gradually forming primary and secondary dendrites in three-dimensional space.After the completion of dendritic solidification and growth,these microdendrites appear dense and dispersed on the two-dimensional plane,providing the nuclei for the formation of new dendrites.When reduction occurs at a solid fraction of 0.46,there is a noticeable decrease in dendritic spacing,resulting in improved central segregation.
基金supported by the National Key R&D Program of China(No.2019YFA0209902)the Natural Science Foundation of China(Nos.52071326,52192593,51601204)+1 种基金the NSFC Basic Science Center Program for Multiscale Problems in Nonlinear Mechanics(No.11988102)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040503).
文摘A newly developed P-doped CrCoNi medium-entropy alloy(MEA)provides both higher yield strength and larger uniform elongation than the conventional CrCoNi MEA,even superior tensile ductility to the other-element-doped CrCoNi MEAs at similar yield strength levels.P segregation at grain boundaries(GBs)and dissolution inside grain interiors,together with the related lower stacking fault energy(SFE)are found in the P-doped CrCoNi MEA.Higher hetero-deformation-induced(HDI)hardening rate is observed in the P-doped CrCoNi MEA due to the grain-to-grain plastic deformation and the dynamic structural refinement by high-density stacking fault-walls(SFWs).The enhanced yield strength in the P-doped CoCrNi MEA can be attributed to the strong substitutional solid-solution strengthening by severer lattice distortion and the GB strengthening by phosphorus segregation at GBs.During the tensile deformation,the multiple SFW frames inundated with massive multi-orientational tiny planar stacking faults(SFs)between them,rather than deformation twins,are observed to induce dynamic structural refinement for forming par-allelepiped domains in the P-doped CoCrNi MEA,due to the lower SFE and even lower atomically-local SFE.These nano-sized domains with domain boundary spacing at tens of nanometers can block disloca-tion movement for strengthening on one hand,and can accumulate defects in the interiors of domains for exceptionally high hardening rate on the other hand.
基金support from Interdisciplinary Research Project for Young Teachers of USTB Fundamental Research Funds for the Central Universities(Grant no.FRF-IDRY-23-030).
文摘Solute atoms and precipitates significantly influence the mechanical properties of Mg alloys.Previous studies have mainly focused on the segregation behaviors of Mg alloys after annealing.In this study,we investigated the segregation behaviors of an Mg-RE alloy under deformation.We found that the enrichment of solute atoms occurred in{101^(-)1}compressive twin boundaries under compression at 298 K without any annealing in an Mg-RE alloy by scanning transmission electron microscopy and energy-dispersive X-ray analysis.The segregated solutes and precipitates impeded the twin growth,partially contributing to the formation of small-sized{101^(-)1}compressive twins.This research indicates the twin boundaries can be strengthened by segregated solutes and precipitates formed under deformation at room temperature.
基金supported by grants from the National Natural Science Foundation of China(Nos.52031017,51801237)the National Key Laboratory of Science and Technology on High-strength Structural Materials in Central South University,China(No.6142912200106).
文摘This study aims to clarify the mechanisms for the grain boundary(GB)segregation through investigating the absorption of excess solute atoms at GBs in Al−Cu alloys by using the hybrid molecular dynamics/Monte Carlo simulations.Two segregation mechanisms,substitutional and interstitial mechanisms,are observed.The intergranular defects,including dislocations,steps and vacancies,and the intervals in structural units are conductive to the prevalence of interstitial mechanism.And substitutional mechanism is favored by the highly ordered twin GBs.Furthermore,the two mechanisms affect the GB structure differently.It is quantified that interstitial mechanism is less destructive to GB structure than substitutional one,and often leads to a segregation level being up to about 6 times higher than the latter.These findings contribute to atomic scale insights into the microscopic mechanisms about how solute atoms are absorbed by GB structures,and clarify the correlation among intergranular structures,segregation mechanisms and kinetics.
文摘First-principles theory calculations were used to investigate the segregation behavior of P and Mg as well as the interactions between Mg and P atα-FeΣ3(111)[11¯0]symmetrical tilt grain boundary(GB).Results demonstrate that both P and Mg are segregated at GB,and P has a stronger segregation potency.Mg prefers to substitute at grain boundary plane with the largest absorbable vacancy,whereas P inclines to substitute at the sites near Fe atoms to form strong covalent Fe-P bonds.When Mg exists at GB,the segregation behavior of P may be greatly inhibited by the decrease in possible solution sites and the increase in segregation energy.P has stronger interactions with Mg at GB,forming a lower energy hybridization peak.These results can be used to explain why the addition of a small amount of Mg can ameliorate the temper embrittlement phenomenon.
基金supported by the National Key Research and Development Program of China(No.2021YFB3702602)the National Natural Science Foundation of China(Nos.51825101,52425101)。
文摘Grain boundary segregation(GBS)of solutes influences the grain size,texture,and strength of Mg wrought alloys.So far,solutes'GBS in Mg has mostly been investigated by qualitative experimental observations.In this work,we develop a quantitative model to compute the grain boundary segregation energy(ΔE_(seg))in binary Mg based alloys that takes the relative atomic density of GB into account.The model is utilized to computeΔE_(seg)of Al,Zn,Ca,Sn,Y,Gd,and Nd solutes in Mg.The result suggests that rare earth elements and Ca are more prone to GBS than Al,Zn,and Sn.Segregation of Gd solutes can explain the smaller grain size and slower grain growth in Mg-Gd extruded alloys than Mg-Al and Mg-Zn counterparts.It also provides an explanation for the weak extrusion texture in Mg-Gd.
文摘Elements(As,Bi)and(Cu,Fe)exhibiting two typical segregation behavior in liquid Sb alloys were selected as solute atoms for analysis.Ab initio molecular dynamics(AIMD)simulations were employed to study the molten Sb alloy at different temperatures.By analyzing its pair correlation function(PCF),bond pairs,bond angle distribution function(BADF),and Voronoi polyhedron(VP),the short-range order(SRO)of the alloy was investigated.In the Sb melt,the solute atoms Cu and Fe,which have smaller distribution coefficients,exhibit a stronger affinity for Sb than the solute atoms As and Bi,which have larger distribution coefficients.The BADF of As and Bi with larger distribution coefficients shows a lower probability of small-angle peaks compared to large-angle peaks,whereas the BADF of Cu and Fe with smaller distribution coefficients exhibits the opposite trend.The BADF reveals that Sb-As and Sb-Bi approach pure Sb melt,while Sb-Cu and Sb-Fe deviate significantly.Compared to Sb-Cu and Sb-Fe,the Sb-As and Sb-Bi systems exhibit more low-index bonds,suggesting weaker interactions and more disorder.The VP fractions around As and Bi atoms are lower than those around Cu and Fe,and the VP face distributions around As and Bi are more complex.There are differences in the VP around different solute atoms,primarily due to the varying bond pair fractions associated with each solute atom.Fe has the smallest diffusion coefficient,primarily due to its compact local structure.
基金Tral Science Foundation of China(Nos.52271103,52334010and 52271031)Partial financial support came from JilinScientific and Technological Development Program(No.20220301026GX)Program for the Central UniversityYouth Innovation Team。
文摘In this work,a good balance of strength and ductility(a yield strength of 185 MPa and a uniform elongation of 20%)has been obtained in a dilute Mg-1.8Zn-0.3Y-0.3Ca-0.3Zr(wt.%)alloy using hard plate rolling(HPR)followed by annealing,with a low anisotropy in mechanical properties.More importantly,the HPR-annealed alloy shows an excellent formability at the same time,i.e.,the index Erichsen(I.E.)value reaches 7.9 mm(the Erichsen cupping test)at room temperature,which is higher compared with the Mg-1.8Zn-0.3Y-0.3Ca0.3Zr alloy produced by conventional multi-pass rolling(CR)followed by annealing.The excellent synergy of strength and formability of the HPR-annealed alloy is mainly attributed to a weak elliptical ring texture,as well as finer and denser Zn_(2)Zr_(3)precipitates.The formation of weak elliptical ring texture is related to the preferential co-segregation of Zn and Ca elements at boundaries of basal grains with smal misorientation angles during annealing,which inhibits the growth of basal grains and promotes the preferential growth of non-basal grains At the same time,in comparison with the CR-annealed alloy,the HPR-annealed alloy contains finer and denser Zn_(2)Zr_(3)precipitates that ar less likely to become sources of cracks,leading to the higher strength and formability of the HPR-annealed alloy.The results in this work can provide reference for the development of high strength Mg alloy sheets with excellent room temperature formability,which also shed light on mitigating planar anisotropy in mechanical properties for Mg alloy sheets.
基金the financial support from the National Natural Science Foundation of China(No.52174303)the Program of Introducing Talents of Disciplineto Universities,China(No.B21001)the Joint Program of Science and Technology Plans in Liaoning Province,China(No.2023JH2/101700302t)。
文摘Through thermodynamic calculations and microstructural characterization,the effect of niobium(Nb)content on the solidifica-tion characteristics of Alloy 625 Plus was systematically investigated.Subsequently,the effect of Nb content on hot deformation behaviorwas examined through hot compression experiments.The results indicated that increasing the Nb content lowers the liquidus temperatureof the alloy by 51℃,producing a denser solidification microstructure.The secondary dendrite arm spacing(SDAS)of the alloy decreasesfrom 39.09 to 22.61μm.Increasing the Nb content alleviates element segregation but increases interdendritic precipitates,increasing theirarea fraction from 0.15% to 5.82%.These precipitates are primarily composed of large Laves,δ,η,and γ″phases,and trace amounts of Nb C.The shapes of these precipitates change from small chunks to large elongated forms.No significant change in the type or amount ofinclusions within the alloy is detected.The inclusions are predominantly individual Al_(2)O_(3) and TiN,as well as Al_(2)O_(3)/Ti N composite inclu-sions.Samples with varying Nb contents underwent hot compression deformation at a true strain of 0.69,a strain rate of 0.5 s^(-1),and a de-formation temperature of 1150℃.Increasing the Nb content also elevates the peak stress observed in the flow curves.However,alloyswith higher Nb content exhibit more pronounced recrystallization softening effects.The Laves phase precipitates do not completely redis-solve during hot deformation and are stretched to elongated shapes.The high-strain energy storage increases the recrystallization fractionfrom 32.4% to 95.5%,significantly enhancing the degree of recrystallization and producing a more uniform deformation microstructure.This effect is primarily attributed to the addition of Nb,which refines the initial grains of the alloy,enhances the solid solution strengthen-ing of the matrix,and improves the induction of particle-stimulated nucleation.
基金financial support from the National Natural Science Foundation of China(No:52061040,No:52371121,No:52031011)China Postdoctoral Science Foundation(No:2021M692512)the 2020 open projects(No:KLATM202003)of Key Laboratory of Advanced Technologies of Materials,Ministry of Education China,Southwest Jiaotong University。
文摘The limited creep resistance of wrought Mg-Al alloys restricts their lightweight applications at intermediate temperatures due to the softening effect of discontinuous precipitation(DP)on the dislocation-controlled creep.Here,we developed a creep-resistant wrought Mg-Al alloy through microalloying of Y and Ca.The resulting alloy exhibited an order of magnitude enhancement in the creep resistance at 125℃/50±100 MPa.In contrast to the grain boundary instabilities by DP in the previously reported wrought Mg-Al alloys,we show that the addition of 0.21Y+0.15Ca wt%produces a(Zn+Ca)co-segregation at the grain boundaries as a result of their segregation energy and the activation energy of grain boundary migration,thereby stabilizing the grain boundaries.The(Zn+Ca)co-segregation inhibits the dynamic DP and promotes the formation of intragranular Al-enriched clusters,which favorthe formation of Al_(2)Y,Mg_(17)Al_(12)nano precipitates,thereby impeding intragranular dislocation motion during creep.Furthermore,the addition of 0.21Y+0.15Ca wt%facilitates the formation of a fine and uniform recrystallization structure in the microalloyed alloys compared to AZ80 due to the high activation energy of mobility for the(Zn+Ca)segregated grain boundary.Therefore,the microalloyed alloys exhibit good tensile properties with 380 MPa tensile strength and 18%elongation.Our constitutive analysis revealed that the(Y+Ca)microalloying decreased the creep stress exponent by 29%and increased the creep resistance in the medium to high-stress range.Microalloying provides a promising way to develop low-cost creep-resistant wrought Mg-Al alloys.
基金the funding from the Ger-man Research Foundation(DFG)-BE 5360/1-1 and ThyssenKrupp Europe.
文摘A microscopic understanding of the complex solute-defect interaction is pivotal for optimizing the alloy’s macroscopic mechanical properties.Simulating solute segregation in a plastically deformed crystalline system at atomic resolution remains challenging.The objective is to efficiently model and predict a phys-ically informed segregated solute distribution rather than simulating a series of diffusion kinetics.To ad-dress this objective,we coupled molecular dynamics(MD)and Monte Carlo(MC)methods using a novel method based on virtual atoms technique.We applied our MD-MC coupling approach to model off-lattice carbon(C)solute segregation in nanoindented Fe-C samples containing complex dislocation networks.Our coupling framework yielded the final configuration through efficient parallelization and localized en-ergy computations,showing C Cottrell atmospheres near dislocations.Different initial C concentrations resulted in a consistent trend of C atoms migrating from less crystalline distortion to high crystalline distortion regions.Besides unraveling the strong spatial correlation between local C concentration and defect regions,our results revealed two crucial aspects of solute segregation preferences:(1)defect ener-getics hierarchy and(2)tensile strain fields near dislocations.The proposed approach is generic and can be applied to other material systems as well.
文摘High-purity antimony(Sb)is essential for industries like semiconductors and photovoltaics,driving research on its production.This review summarizes research advances in production and preparation techniques for high-purity Sb.Three process flowcharts to produce high-purity Sb are described according to different raw materials.Various process parameters of vacuum distillation,zone refining purification techniques and research progress in the field of high-purity Sb are discussed.Numerical simulation,atomic scale simulation,and research progress of alloying elements in the field of high-purity Sb are highlighted.It is shown that for the difficult removal of As element in Sb,the addition of Al makes the regional refining process more effective in reducing the arsenic content.Finally,the purification of high-purity Sb is summarized,providing insights into achieving efficient and environmentally friendly high-purity Sb production and outlining future directions.
基金supported by PRISMS(PRedictive Integrated Structural Materials Science)center which is located at University of Michigan and funded by U.S.Department of Energy,Office of Basic Energy Science,Division of Materials Science and Engineering(Grant award number DE-SC0008637)support from Michigan Center for Materials Characterization(MC2)at University of Michigan and Canmet MATERIALS,Natural Resources Canada+1 种基金the Extreme Science and Engineering Discovery Environment(XSEDE)Stampede2 at the TACC through allocation TG-MSS160003the National Energy Research Scientific Computing Center(NERSC),a U.S.Department of Energy Office of Science User Facility operated under Contract No.DE-AC02-05CH11231。
文摘As a rare earth solute element in Mg alloys,Y has the beneficial effects of increasing both the strength and the ductility as well as weakening the crystallographic texture.To achieve a more fundamental understanding on how Y addition affects the microstructural evolution and mechanical properties,the Y segregation behavior at grain boundaries was investigated in Mg-1wt.%Y and Mg-7wt.%Y alloys at different conditions.The segregation intensity and its dependence on the grain boundary misorientation angle were experimentally characterized and computationally predicted.Strong segregation at grain boundaries was observed in both low and high Y-containing alloys.Y segregation was found to remain in alloy Mg-7Y after high-temperature annealing heat treatment at 540℃.No direct correlation between the Y segregation intensity and the grain boundary misorientation angle could be established based on either the experimental characterization or the atomistic simulation with a spectral model.We thus conclude that grain boundary segregation of Y is independent of grain boundary misorientation angle.
基金supported by grants from the Sub-project of National Key Research and Development Program of China(2021YFA0805905-1)the Special Fund for Anhui Agriculture Research System,China(AHCYJSTX-04)+2 种基金the Joint Research Project on the Anhui Local Pigs Breeding and Utilization,China(340000211260001000431)the Open Project of Key Laboratory of Embryo Development and Reproductive Regulation of Anhui Province,China(FSKFKT004)the Major Special Science And Technology Project of Anhui Province,China(202103a06020013)。
文摘N6-methyladenosine(m6A)plays a key role in mammalian early embryonic development and cell lineage differentiation.However,the role and mechanisms of 18S ribosomal RNA(rRNA)m6A methyltransferase METTL5 in early embryonic development remain unclear.Here,we found that 18S rRNA m6A methyltransferase METTL5 plays an important role in porcine early embryonic development.METTL5 knockdown and overexpression significantly reduced the developmental efficiency of porcine early embryos and impaired cell lineage allocation.METTL5 knockdown apparently decreased the global translation efficiency in blastocyst,while METTL5 overexpression increased the global translation efficiency.Furthermore,METTL5 knockdown did not affect the abundance of CDX2 mRNA,but resulted in a significant reduction in CDX2 protein levels.Moreover,the low developmental efficiency and abnormal lineage distribution of METTL5 knockdown embryos could be rescued by CDX2 overexpression.Collectively,our results demonstrated that 18S rRNA methyltransferase METTL5 regulates porcine early embryonic development via modulating the translation of CDX2.
基金financially supported by the National Science and Technology Major Project of China(No.2017-Ⅵ-0008-0078)。
文摘Four powder metallurgy(PM)Ni-based superalloys with different Hf and Ta contents were creep-tested at 650℃ and 970 MPa,700℃ and 770 MPa,and 750℃ and 580 MPa,respectively.The effect of Hf and Ta on creep deformation behaviors of the superalloys was studied from multiple scales by SEM,electron backscatter diffraction(EBSD),and aberration-corrected scanning transmission electron microscope(AC-STEM).The results showed that Hf and Ta suppressed the intergranular fracture and initiation of cracks during the acceleration creep stage,which prolonged the creep rupture time.Hf and Ta inhibited the stacking faults extending and the dislocation climbing and promoted the Suzuki segregation of W during the steady-state creep stage,which reduced the minimum creep rate and delayed the start time of the acceleration creep stage.The Suzuki segregation of Co,Cr,Mo,Ti,Nb,W,and Ta along stacking faults was observed after Hf and Ta addition,leading to the localized phase transformation in the γ′phase,and the stacking fault phase was chemically disordered.This study provided ideas for the composition design of novel PM Ni-based superalloys and theoretical foundations for the combined addition of Hf and Ta.
