The simulation of a large number of particles requires unacceptable computational time that is the most criticalproblem existing in the industrial application of the DEM. Coarse graining is a promising approach to fac...The simulation of a large number of particles requires unacceptable computational time that is the most criticalproblem existing in the industrial application of the DEM. Coarse graining is a promising approach to facilitatethe application of DEM to industrial problems. While the current coarse graining framework is often developedin an ad-hoc manner, leading to different formulations and different solution accuracy and efficiency. Therefore,in this paper, existing coarse graining techniques have been carefully analysed by the exact scaling law which canprovide the theory basis for the upscaling method. A proper scaling rule for the size of particles and samples as wellas interaction laws have been proposed. The scaling rule is applied to a series simulations of biaxial compressiontests with different scale factors to investigate the precision of the coarse graining system. The error between theoriginal system and the coarse system shows a growing tendency as the scale factor increases. It can be concludedthat the precision of the coarse graining system is accepted when applying scaling rules based on the exact scalinglaws.展开更多
Coarse graining of complex networks is an important method to study large-scale complex networks, and is also in the focus of network science today. This paper tries to develop a new coarse-graining method for complex...Coarse graining of complex networks is an important method to study large-scale complex networks, and is also in the focus of network science today. This paper tries to develop a new coarse-graining method for complex networks, which is based on the node similarity index. From the information structure of the network node similarity, the coarse-grained network is extracted by defining the local similarity and the global similarity index of nodes. A large number of simulation experiments show that the proposed method can effectively reduce the size of the network, while maintaining some statistical properties of the original network to some extent. Moreover, the proposed method has low computational complexity and allows people to freely choose the size of the reduced networks.展开更多
The scratching mechanism of polycrystallineγ-TiAl alloy was investigated at the atomic scale using the molecular dynamics method,with a focus on the influence of different grain sizes.The analysis encompassed tribolo...The scratching mechanism of polycrystallineγ-TiAl alloy was investigated at the atomic scale using the molecular dynamics method,with a focus on the influence of different grain sizes.The analysis encompassed tribological characteristics,scratch morphology,subsurface defect distribution,temperature variations,and stress states during the scratching process.The findings indicate that the scratch force,number of recovered atoms,and pile-up height exhibit abrupt changes when the critical size is 9.41 nm due to the influence of the inverse Hall-Petch effect.Variations in the number of grain boundaries and randomness of grain orientation result in different accumulation patterns on the scratch surface.Notably,single crystal materials and those with 3.73 nm in grain size display more regular surface morphology.Furthermore,smaller grain size leads to an increase in average coefficient of friction,removed atoms number,and wear rate.While it also causes higher temperatures with a larger range of distributions.Due to the barrier effect of grain boundaries,smaller grains exhibit reduced microscopic defects.Additionally,average von Mises stress and hydrostatic compressive stress at the indenter tip decrease as grain size decreases owing to grain boundary obstruction.展开更多
As-forged WSTi6421 titanium alloy billet afterβannealing was investigated.Abnormally coarse grains larger than adjacent grains could be observed in the microstructures,forming abnormal grain structures with uneven si...As-forged WSTi6421 titanium alloy billet afterβannealing was investigated.Abnormally coarse grains larger than adjacent grains could be observed in the microstructures,forming abnormal grain structures with uneven size distribution.Through electron backscattered diffraction(EBSD),the forged microstructure at various locations of as-forged WSTi6421 titanium alloy billet was analyzed,revealing that the strength of theβphase cubic texture generated by forging significantly influences the grain size afterβannealing.Heat treatment experiments were conducted within the temperature range from T_(β)−50°C to T_(β)+10°C to observe the macro-and micro-morphologies.Results show that the cubic texture ofβphase caused by forging impacts the texture of the secondaryαphase,which subsequently influences theβphase formed during the post-βannealing process.Moreover,the pinning effect of the residual primaryαphase plays a crucial role in the growth ofβgrains during theβannealing process.EBSD analysis results suggest that the strength ofβphase with cubic texture formed during forging process impacts the orientation distribution differences ofβgrains afterβannealing.Additionally,the development of grains with large orientations within the cubic texture shows a certain degree of selectivity duringβannealing,which is affected by various factors,including the pinning effect of the primaryαphase,the strength of the matrix cubic texture,and the orientation relationship betweenβgrain and matrix.Comprehensively,the stronger the texture in a certain region,the less likely the large misoriented grains suffering secondary growth,thereby aggregating the difference in microstructure and grain orientation distribution across different regions afterβannealing.展开更多
Low-angle grain boundaries(LAGBs)are one of the solidification defects in single-crystal nickel-based superalloys and are detrimental to the mechanical properties.The formation of LAGBs is related to dendrite deformat...Low-angle grain boundaries(LAGBs)are one of the solidification defects in single-crystal nickel-based superalloys and are detrimental to the mechanical properties.The formation of LAGBs is related to dendrite deformation,while the mechanism has not been fully understood at the mesoscale.In this work,a model coupling dendrite growth,thermal-solutal-fluid flow,thermal stress and flow-induced dendrite deformation via cellular automaton-finite volume method and finite element method is developed to study the formation of LAGBs in single crystal superalloys.Results reveal that the bending of dendrites is primarily attributed to the thermal-solutal convection-induced dendrite deformation.The mechanical stress of dendrite deformation develops and stabilises as solidification proceeds.As the width of the mushy zone gets stable,stresses are built up and then dendritic elastoplastic bending occurs at some thin primary dendrites with the wider inter-dendritic space.There are three characteristic zones of stress distribution along the solidification direction:(i)no stress concentration in the fully solidified regions;(ii)stress developing in the primary dendrite bridging region,and(iii)stress decrease in the inter-dendritic uncontacted zone.The stresses reach maximum near the initial dendrite bridging position.The lower temperature gradients,the finer primary dendritic trunks and sudden reductions in local dendritic trunk radius jointly promote the elastoplastic deformation of the dendrites.Corresponding measures are suggested to reduce LAGBs.展开更多
Agricultural practices significantly contribute to greenhouse gas(GHG)emissions,necessitating cleaner production technologies to reduce environmental pressure and achieve sustainable maize production.Plastic film mulc...Agricultural practices significantly contribute to greenhouse gas(GHG)emissions,necessitating cleaner production technologies to reduce environmental pressure and achieve sustainable maize production.Plastic film mulching is commonly used in the Loess Plateau region.Incorporating slow-release fertilizers as a replacement for urea within this practice can reduce nitrogen losses and enhance crop productivity.Combining these techniques represents a novel agricultural approach in semi-arid areas.However,the impact of this integration on soil carbon storage(SOCS),carbon footprint(CF),and economic benefits has received limited research attention.Therefore,we conducted an eight-year study(2015-2022)in the semi-arid northwestern region to quantify the effects of four treatments[urea supplied without plastic film mulching(CK-U),slow-release fertilizer supplied without plastic film mulching(CK-S),urea supplied with plastic film mulching(PM-U),and slow-release fertilizer supplied with plastic film mulching(PM-S)]on soil fertility,economic and environmental benefits.The results revealed that nitrogen fertilizer was the primary contributor to total GHG emissions(≥71.97%).Compared to other treatments,PM-S increased average grain yield by 12.01%-37.89%,water use efficiency by 9.19%-23.33%,nitrogen accumulation by 27.07%-66.19%,and net return by 6.21%-29.57%.Furthermore,PM-S decreased CF by 12.87%-44.31%and CF per net return by 14.25%-41.16%.After eight years,PM-S increased SOCS(0-40 cm)by 2.46%,while PM-U decreased it by 7.09%.These findings highlight the positive effects of PM-S on surface soil fertility,economic gains,and environmental benefits in spring maize production on the Loess Plateau,underscoring its potential for widespread adoption and application.展开更多
Dislocations and disclinations are fundamental topological defects within crystals,which determine the mechanical properties of metals and alloys.Despite their important roles in multiple physical mechanisms,e.g.,dyna...Dislocations and disclinations are fundamental topological defects within crystals,which determine the mechanical properties of metals and alloys.Despite their important roles in multiple physical mechanisms,e.g.,dynamic recovery and grain boundary mediated plasticity,the intrinsic coupling and correlation between disclinations and dislocations,and their impacts on the deformation behavior of metallic materials still remain obscure,partially due to the lack of a theoretical tool to capture the rotational nature of disclinations.By using a Lie-algebra-based theoretical framework,we obtain a general equation to quantify the intrinsic coupling of disclinations and dislocations.Through quasi in-situ electron backscatter diffraction characterizations and disclination/dislocation density analyses in Mg alloys,the generation,coevolution and reactions of disclinations and dislocations during dynamic recovery and superplastic deformation have been quantitatively analyzed.It has been demonstrated that the obtained governing equation can capture multiple physical processes associated with mechanical deformation of metals,e.g.,grain rotation and grain boundary migration,at both room temperature and high temperature.By establishing the disclination-dislocation coupling equation within a Lie algebra description,our work provides new insights for exploring the coevolution and reaction of disclinations/dislocations,with profound implications for elucidating the microstructure-property relationship and underlying deformation mechanisms in metallic materials.展开更多
The increase in soil temperature associated with climate change has introduced considerable challenges to crop production.Split nitrogen application(SN)represents a potential strategy for improving crop nitrogen use e...The increase in soil temperature associated with climate change has introduced considerable challenges to crop production.Split nitrogen application(SN)represents a potential strategy for improving crop nitrogen use efficiency and enhancing crop stress resistance.Nevertheless,the precise interaction between soil warming(SW)and SN remains unclear.In order to ascertain the impact of SW on maize growth and whether SN can improve the tolerance of maize to SW,a two-year field experiment was conducted(2022-2023).The aim was to examine the influence of two SW ranges(MT,warming 1.40℃;HT,warming 2.75℃)and two nitrogen application methods(N1,one-time basal application of nitrogen fertilizer;N2,one third of base nitrogen fertilizer+two thirds of jointing stage supplemental nitrogen fertilizer)on maize root growth,photosynthetic characteristics,nitrogen use efficiency,and yield.The results demonstrated that SW impeded root growth and precipitated the premature aging of maize leaves following anthesis,particularly in the HT,which led to a notable reduction in maize yield.In comparison to N1,SN has been shown to increase root length density by 8.54%,root bleeding rate by 8.57%,and enhance root distribution ratio in the middle soil layers(20-60 cm).The interaction between SW and SN had a notable impact on maize growth and yield.The SN improved the absorption and utilization efficiency of nitrogen by promoting root development and downward canopy growth,thus improving the tolerance of maize to SW at the later stage of growth.In particular,the N2HT resulted in a 14.51%increase in the photosynthetic rate,a 18.58%increase in nitrogen absorption efficiency,and a 18.32%increase in maize yield compared with N1HT.It can be posited that the SN represents a viable nitrogen management measure with the potential to enhance maize tolerance to soil high-temperature stress.展开更多
Rice is a poor source of folate,an essential micronutrient for the body.Biofortification offers an effective way to enhance the folate content of rice and alleviate folate deficiencies in humans.In this study,we confi...Rice is a poor source of folate,an essential micronutrient for the body.Biofortification offers an effective way to enhance the folate content of rice and alleviate folate deficiencies in humans.In this study,we confirmed that OsADCS and OsGTPCHI,encoding the initial enzymes necessary for folate synthesis,positively regulate folate accumulation in knockout mutants of both japonica and indica rice backgrounds.The folate content in the low-folate japonica variety was slightly increased by the expression of the indica alleles driven by the endosperm-specific promoter.We further obtained co-expression lines by stacking OsADCS and OsGTPCHI genes;the folate accumulation in brown rice and polished rice reached 5.65μg/g and 2.95μg/g,respectively,representing 37.9-fold and 26.5-fold increases compared with the wild type.Transcriptomic analysis of rice grains from six transgenic lines showed that folate changes affected biological pathways involved in the synthesis and metabolism of rice seed storage substances,while the expression of other folate synthesis genes was weakly regulated.In addition,we identified Aus rice as a high-folate germplasm carrying superior haplotypes of OsADCS and OsGTPCHI through natural variation.This study provides an alternative and effective complementary strategy for rice biofortification,promoting the rational combination of metabolic engineering and conventional breeding to breed high-folate varieties.展开更多
Low temperature(LT)in spring has become one of the principal abiotic stresses that restrict the growth and development of wheat.Diverse analyses were performed to investigate the mechanism underlying the response of w...Low temperature(LT)in spring has become one of the principal abiotic stresses that restrict the growth and development of wheat.Diverse analyses were performed to investigate the mechanism underlying the response of wheat grain development to LT stress during booting.These included morphological observation,measurements of starch synthase activity,and determination of amylose and amylopectin content of wheat grain after exposure to treatment with LT during booting.Additionally,proteomic analysis was performed using tandem mass tags(TMT).Results showed that the plumpness of wheat grains decreased after LT stress.Moreover,the activities of sucrose synthase(SuS,EC 2.4.1.13)and ADP-glucose pyrophosphorylase(AGPase,EC 2.7.7.27)exhibited a significant reduction,leading to a significant reduction in the contents of amylose and amylopectin.A total of 509 differentially expressed proteins(DEPs)were identified by proteomics analysis.The Gene Ontology(GO)enrichment analysis showed that the protein difference multiple in the nutritional repository activity was the largest among the molecular functions,and the up-regulated seed storage protein(ssP)played an active role in the response of grains to LT stress and subsequent damage.The Kyoto Encyclopedia of Genes and Genomes(KEGG)enrichment analysis showed that LT stress reduced the expression of DEPs such as sucrose phosphate synthase(SPS),glucose-1-phosphate adenylyltransferase(glgC),andβ-fructofuranosidase(FFase)in sucrose and starch metabolic pathways,thus affecting the synthesis of grain starch.In addition,many heat shock proteins(HsPs)were found in the protein processing in endoplasmic reticulum pathways,which can resist some damage caused by LT stress.These findings provide a new theoretical foundation for elucidating the underlying mechanism governing wheat yield developmentafterexposuretoLTstress inspring.展开更多
Conventional rolled Mg-Al alloy sheets typically exhibit strong basal textures that remain and may even strengthen after recrystallization annealing due to the preferential growth of basal-oriented grains,resulting in...Conventional rolled Mg-Al alloy sheets typically exhibit strong basal textures that remain and may even strengthen after recrystallization annealing due to the preferential growth of basal-oriented grains,resulting in poor formability at room temperature.Therefore,the knowledge of recrystallization and grain growth is critical for modifying textures of Mg-Al alloy sheets.The static recrystallization and texture evolution in a cold-rolled dilute Mg-1Al(wt.%)alloy during various annealed temperatures ranging from 300℃ to 450℃,have been investigated using the quasi in-situ electron backscatter diffraction(EBSD)method.The as-rolled Mg-1Al alloy shows a dominant basal texture,which weakens and broadens in the rolling direction(RD)during the subsequent annealing,accompanied by the formation of{1010}texture component.Particularly,the {1010} texture component is more pronounced after annealing at high temperatures.The quasi in-situ EBSD results show that recrystallized grains are mainly induced by shear bands,which exhibit a wide spectrum of orientations with c-axis tilt angles ranging 20°-45°from the normal direction(ND).Orientations of shear band-induced recrystallized grains are retained during the entire recrystallization process,resulting in a reduction in the texture intensity.Moreover,recrystallized grains belonging to the {1010}texture component grow preferentially compared to those with other orientations,which is attributed to low energy grain boundaries,especially grain boundaries with∼30°misorientation angles.Furthermore,the high temperature annealing facilitates the rapid growth of grain boundaries having a 30°misorientation angle,leading to the occurrence of distinct {1010} texture after annealing at 450℃ for 1 h.The results provide insights for texture modification of rare earth-free low-alloyed Mg alloys by controlling annealing parameters.展开更多
Increasing the grain yield(GY) and water use efficiency(WUE) of winter wheat in the Huaibei Plain(HP), China are essential. However, the effects of micro-sprinkler irrigation and topsoil compaction after wheat seed so...Increasing the grain yield(GY) and water use efficiency(WUE) of winter wheat in the Huaibei Plain(HP), China are essential. However, the effects of micro-sprinkler irrigation and topsoil compaction after wheat seed sowing on the GY and WUE are unclear. Therefore, a two-year field experiment was conducted during the 2021–2023 winter wheat growing seasons with a total six treatments: rain-fed(RF), conventional irrigation(CI) and micro-sprinkler irrigation(MI), as well as topsoil compaction after seed sowing under these three irrigation methods(RFC, CIC, and MIC). The results in the two years indicated that MI significantly increased GY compared to CI and RF, by averages of 17.9 and 42.1%, respectively. The increase in GY of MI was due to its significant increases in the number of spikes, kernels per spike, and grain weight. The chlorophyll concentration in flag leaves of MI after the anthesis stage maintained higher levels than with CI and RF, and was the lowest in RF. This was due to the dramatically enhanced catalase and peroxidase activities and lower malondialdehyde content under MI. Compared with RF and CI, MI significantly promoted dry matter remobilization and production after anthesis, as well as its contribution to GY. In addition, MI significantly boosted root growth, and root activity during the grain-filling stage was remarkably enhanced compared to CI and RF. In 2021–2022, there was no significant difference in WUE between MI and RF, but the WUE of RF was significantly lower than that of MI in 2022–2023. However, the WUE in MI was significantly improved compared to CI, and it increased by averages of 15.1 and 17.6% for the two years. Topsoil compaction significantly increased GY and WUE under rain-fed conditions due to improved spike numbers and dry matter production. Overall, topsoil compaction is advisable for enhancing GY and WUE in rain-fed conditions, whereas micro-sprinkler irrigation can be adopted to simultaneously achieve high GY and WUE in the HP.展开更多
It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size...It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size(grain size,GS)or the external size(geometric size).The coupled effect of GS and geometric size on the functional properties has not been clearly understood yet.In this work,the super-elasticity,one-way,and stress-assisted two-way shape memory effects of the polycrystalline NiTi SMAs with different aspect ratios(length/width for the gauge section)and different GSs are investigated based on the phase field method.The coupled effect of the aspect ratio and GS on the functional properties is adequately revealed.The simulated results indicate that when the aspect ratio is lower than about 4:1,the stress biaxiality and stress heterogeneity in the gauge section of the sample become more and more obvious with decreasing the aspect ratio,which can significantly influence the microstructure evolution in the process involving external stress.Therefore,the corresponding functional property is strongly dependent on the aspect ratio.With decreasing the GS and the aspect ratio(to be lower than 4:1),both the aspect ratio and GS can affect the MT or martensite reorientation in each grain and the interaction among grains.Thus,due to the strong internal constraint(i.e.,the constraint of grain boundary)and the external constraint(i.e.,the constraint of geometric boundary),the capabilities of the functional properties of NiTi SMAs are gradually weakened and highly dependent on these two factors.展开更多
To effectively regulate the grain boundary infiltration in CoCrFeMnNi high-entropy alloy(Cantor alloys,HEA)caused by the violent atomic interdiffusion,the higher configuration entropy on Cantor alloys surface was desi...To effectively regulate the grain boundary infiltration in CoCrFeMnNi high-entropy alloy(Cantor alloys,HEA)caused by the violent atomic interdiffusion,the higher configuration entropy on Cantor alloys surface was designed and realized via eutectic high-entropy(EHEA)transformation.Meanwhile,to effectively alleviate the residual stress caused by the notable difference in the thermal expansion coefficient(CTE)between Cantor alloys and Zr-3 alloys,a cladding layer was applied to the HEA surface using laser cladding technology of Nb,followed by brazing to Zr-3 alloys with Zr63.2Cu filler.The cladding layer’s microstructure comprised Nbss and FCC+(Co,Ni)_(2) Nb eutectic structure,resulting from an in-situ reaction between Cantor alloys and Nb.The Nbss and FCC demonstrated good plasticity,and the(Co,Ni)_(2) Nb Laves phase provided increased strength,endowing both good plastic deformation ability and strength of the cladding layer.Notably,the existence of EHEA in the laser cladding layer made the Cantor alloy entropy from 1.61 R to 1.77 R,greatly enhancing its thermal stability and suppressing the grave grain boundary infiltration.Joints produced via laser cladding with Nb-assisted brazing exhibited a complex microstructure(HEA/Nbss+FCC+(Co,Ni)_(2)Nb/(Zr,Nb)(Cr,Mn)_(2)+(Zr,Nb)ss/(Zr,Nb)_(2)(Cu,Ni,Co,Fe)+(Zr,Nb)(Cr,Mn)_(2)+(Zr,Nb)ss/Zr-3) and a significantly improved shear strength of 242.8 MPa at 1010℃ for 10 min,42.4%higher than that of directly brazed joints.This improvement was attributed to reduced grain boundary infiltration,alleviated residual stress due to CTE disparity,and eliminated micro-cracks in the brazing seam.This study presents an effective solution for reducing residual stresses and achieving reliable bonding between Cantor alloys and Zr-3 alloys,with potential applications in brazing CoCrFeNi-based HEA and Zr-3 due to the beneficial eutectic reaction between CoCrFeNi and Nb.展开更多
Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can res...Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can result in solidification defects and reduced mechanical properties.In this work,a novel welding wire containing MgO particles has been developed to promote columnar-to-equiaxed transition(CET)in the FZ of TIG-welded AZ31 alloy.The results show the achievement of a fully equiaxed grain structure in the FZ,with a significant 71.9%reduction in grain size to 41 μm from the original coarse columnar dendrites.Furthermore,the combination of using MgO-containing welding wire and pulse current can further refine the grain size to 25.6 μm.Microstructural analyses reveal the homogeneous distribution of MgO particles in the FZ.The application of pulse current results in an increase in the number density of MgO(1-2 μm)from 5.16 × 10^(4) m^(-3) to 6.18 × 10^(4) m^(-3).The good crystallographic matching relationship between MgO and α-Mg matrix,characterized by the orientation relationship of[11(2)0]α-Mg//[0(1)1]MgO and(0002)_(α-Mg)//(111)_(MgO),indicates that the MgO particles can act as effective nucleation sites for α-Mg to reduce nucleation undercooling.According to the Hunt criteria,the critical temperature gradient for CET is greatly enhanced due to the significantly increased number density of MgO nucleation sites.In addition,the correlation with the thermal simulation results reveals a transition in the solidification conditions within the welding pool from the columnar grain zone to the equiaxed grain zone in the CET map,leading to the realization of CET.The exceptional grain refinement has contributed to a simultaneous improvement in the strength and plasticity of welded joints.This study presents a novel strategy for controlling equiaxed microstructure and optimizing mechanical properties in fusion welding or wire and arc additive manufacturing of Mg alloy components.展开更多
The trade-offbetween strength and ductility remains a persistent obstacle in the development of advanced structural materials.In the present study,a novel dual-heterogeneous structure with a bimodal grain distribution...The trade-offbetween strength and ductility remains a persistent obstacle in the development of advanced structural materials.In the present study,a novel dual-heterogeneous structure with a bimodal grain distribution in both ferrite and austenite phases was fabricated via cold rolling and partial recrystallization annealing on solution-treated 2205 duplex stainless steel(DSS).The processed steel exhibited superior mechanical properties,with the yield strength increasing from 586 MPa to 903 MPa,and the ultimate tensile strength from 796 MPa to 1082 MPa,while maintaining a high total elongation of 35.3%.Based on in-situ electron backscatter diffraction(EBSD)and scanning electron microscope(SEM)analyses,the microstructural deformation behavior and strengthening mechanisms of the dual-heterostructured 2205 DSS were elucidated.The outstanding combination of strength and ductility was ascribed to the synergistic effects of grain refinement,dislocation strengthening,and hetero-deformation induced(HDI)strengthening.Moreover,the high ductility in DSS was attributed to the coactivation of cross-slip systems in ferrite{110}and{112}along with the single-slip systems in austenite{111}.These findings provide a new strategy for the design and development of high-strength and ultra-high-strength DSSs.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
Grain boundary engineering plays a significant role in the improvement of strength and plasticity of alloys. However, in refractory high-entropy alloys, the susceptibility of grain boundaries to oxygen presents a bott...Grain boundary engineering plays a significant role in the improvement of strength and plasticity of alloys. However, in refractory high-entropy alloys, the susceptibility of grain boundaries to oxygen presents a bottleneck in achieving high mechanical performance. Creating a large number of clean grain boundaries in refractory high-entropy alloys is a challenge. In this study, an ultrafine-grained (UFG) NbMoTaW alloy with high grain-boundary cohesion was prepared by powder metallurgy, taking advantages of rapid hot-pressing sintering and full-process inert atmosphere protection from powder synthesis to sintering. By oxygen control and an increase in the proportion of grain boundaries, the segregation of oxygen and formation of oxides at grain boundaries were strongly mitigated, thus the intrinsic high cohesion of the interfaces was preserved. Compared to the coarse-grained alloys prepared by arc-melting and those sintered by traditional powder metallurgy methods, the UFG NbMoTaW alloy demonstrated simultaneously increased strength and plasticity at ambient temperature. The highly cohesive grain boundaries not only reduce brittle fractures effectively but also promote intragranular deformation. Consequently, the UFG NbMoTaW alloy achieved a high yield strength even at elevated temperatures, with a remarkable performance of 1117 MPa at 1200 ℃. This work provides a feasible solution for producing refractory high-entropy alloys with low impurity content, refined microstructure, and excellent mechanical performance.展开更多
1.Introduction.Cold Spray(CS)is a highly advanced solid-state metal depo-sition process that was first developed in the 1980s.This innovative technique involves the high-speed(300-1200 m/s)impact deposition of micron-...1.Introduction.Cold Spray(CS)is a highly advanced solid-state metal depo-sition process that was first developed in the 1980s.This innovative technique involves the high-speed(300-1200 m/s)impact deposition of micron-sized particles(5-50μm)to fabricate coatings[1-3].CS has been extensively used in a variety of coating applications,such as aerospace,automotive,energy,medical,marine,and others,to provide protection against high temperatures,corrosion,erosion,oxidation,and chemicals[4,5].Nowadays,the technical interest in CS is twofold:(i)as a repair process for damaged components,and(ii)as a solid-state additive manufacturing process.Compared to other fusion-based additive manufacturing(AM)technologies,Cold Spray Additive Manufacturing(CSAM)is a new member of the AM family that can enable the fabrication of deposits without undergoing melting.The chemical composition has been largely preserved from the powder to the deposit due to the minimal oxidation.The significant advantages of CSAM over other additive manufacturing processes include a high production rate,unlimited deposition size,high flexibility,and suitability for repairing damaged parts.展开更多
In this study,two wheat-derived cadmium(Cd)-immobilizing endophytic Pseudomonas paralactis M14 and Priestia megaterium R27 were evaluated for their effects on wheat tissue Cd uptake under hydroponic conditions.Then,th...In this study,two wheat-derived cadmium(Cd)-immobilizing endophytic Pseudomonas paralactis M14 and Priestia megaterium R27 were evaluated for their effects on wheat tissue Cd uptake under hydroponic conditions.Then,the impacts of the biochar(BC),M14+R27(MR),and BC+MR treatments on wheat Cd uptake and the mechanisms involved were investigated at the jointing,heading,and mature stages of wheat plants under field-plot conditions.A hydroponic experiment showed that the MR treatment significantly decreased the above-ground tissue Cd content compared with theM14 or R27 treatment.The BC+MRtreatment reduced the grain Cd content by 51.5%-67.7%and Cd translocation factor at the mature stage of wheat plants and increased the organic matter-bound Cd content by 31%-75%in the rhizosphere soils compared with the BC or MR treatment.Compared with the BC or MR treatment,the relative abundances of the biomarkers associated with Gemmatimonas,Altererythrobacter,Gammaproteobacteria,Xanthomonadaceae,Phenylobacterium,and Nocardioides in the BC+MR-treated rhizosphere microbiome decreased and negatively correlated with the organic matter-bound Cd contents.In the BC+MR-treated root interior microbiome,the relative abundance of the biomarker belonging to Exiguobacterium increased and negatively correlated with the Cd translocation factor,while the relative abundance of the biomarker belonging to Pseudonocardiaceae decreased and positively correlated with the Cd translocation factor.Our findings suggested that the BC+MR treatment reduced Cd availability and Cd transfer through affecting the abundances of these specific biomarkers in the rhizosphere soil and root interior microbiomes,leading to decreased wheat grain Cd uptake in the contaminated soil.展开更多
基金This work is partially supported by National Natural Science Foundation of China under Grant No.12072217.The support is gratefully acknowledged.
文摘The simulation of a large number of particles requires unacceptable computational time that is the most criticalproblem existing in the industrial application of the DEM. Coarse graining is a promising approach to facilitatethe application of DEM to industrial problems. While the current coarse graining framework is often developedin an ad-hoc manner, leading to different formulations and different solution accuracy and efficiency. Therefore,in this paper, existing coarse graining techniques have been carefully analysed by the exact scaling law which canprovide the theory basis for the upscaling method. A proper scaling rule for the size of particles and samples as wellas interaction laws have been proposed. The scaling rule is applied to a series simulations of biaxial compressiontests with different scale factors to investigate the precision of the coarse graining system. The error between theoriginal system and the coarse system shows a growing tendency as the scale factor increases. It can be concludedthat the precision of the coarse graining system is accepted when applying scaling rules based on the exact scalinglaws.
文摘Coarse graining of complex networks is an important method to study large-scale complex networks, and is also in the focus of network science today. This paper tries to develop a new coarse-graining method for complex networks, which is based on the node similarity index. From the information structure of the network node similarity, the coarse-grained network is extracted by defining the local similarity and the global similarity index of nodes. A large number of simulation experiments show that the proposed method can effectively reduce the size of the network, while maintaining some statistical properties of the original network to some extent. Moreover, the proposed method has low computational complexity and allows people to freely choose the size of the reduced networks.
基金National Natural Science Foundation of China(52065036,52365018)Natural Science Foundation of Gansu(23JRRA760)+1 种基金Hongliu Outstanding Youth Foundation of Lanzhou University of TechnologyChina Postdoctoral Science Foundation(2023M733583)。
文摘The scratching mechanism of polycrystallineγ-TiAl alloy was investigated at the atomic scale using the molecular dynamics method,with a focus on the influence of different grain sizes.The analysis encompassed tribological characteristics,scratch morphology,subsurface defect distribution,temperature variations,and stress states during the scratching process.The findings indicate that the scratch force,number of recovered atoms,and pile-up height exhibit abrupt changes when the critical size is 9.41 nm due to the influence of the inverse Hall-Petch effect.Variations in the number of grain boundaries and randomness of grain orientation result in different accumulation patterns on the scratch surface.Notably,single crystal materials and those with 3.73 nm in grain size display more regular surface morphology.Furthermore,smaller grain size leads to an increase in average coefficient of friction,removed atoms number,and wear rate.While it also causes higher temperatures with a larger range of distributions.Due to the barrier effect of grain boundaries,smaller grains exhibit reduced microscopic defects.Additionally,average von Mises stress and hydrostatic compressive stress at the indenter tip decrease as grain size decreases owing to grain boundary obstruction.
基金Key Research and Development Plan of Shaanxi Province(2023-YBGY-493)。
文摘As-forged WSTi6421 titanium alloy billet afterβannealing was investigated.Abnormally coarse grains larger than adjacent grains could be observed in the microstructures,forming abnormal grain structures with uneven size distribution.Through electron backscattered diffraction(EBSD),the forged microstructure at various locations of as-forged WSTi6421 titanium alloy billet was analyzed,revealing that the strength of theβphase cubic texture generated by forging significantly influences the grain size afterβannealing.Heat treatment experiments were conducted within the temperature range from T_(β)−50°C to T_(β)+10°C to observe the macro-and micro-morphologies.Results show that the cubic texture ofβphase caused by forging impacts the texture of the secondaryαphase,which subsequently influences theβphase formed during the post-βannealing process.Moreover,the pinning effect of the residual primaryαphase plays a crucial role in the growth ofβgrains during theβannealing process.EBSD analysis results suggest that the strength ofβphase with cubic texture formed during forging process impacts the orientation distribution differences ofβgrains afterβannealing.Additionally,the development of grains with large orientations within the cubic texture shows a certain degree of selectivity duringβannealing,which is affected by various factors,including the pinning effect of the primaryαphase,the strength of the matrix cubic texture,and the orientation relationship betweenβgrain and matrix.Comprehensively,the stronger the texture in a certain region,the less likely the large misoriented grains suffering secondary growth,thereby aggregating the difference in microstructure and grain orientation distribution across different regions afterβannealing.
基金sponsored by the National Natural Science Foundation of China(Grant Nos.52074182,52304406 and U23A20612)the Natural Science Foundation of Shanghai(Grant Nos.22ZR1430700 and 23TS1401900)+1 种基金the National Science and Technology Major Project(No.2017-VII-0008-0102)Neng Ren acknowledges the Startup Fund for Young Faculty at SJTU.
文摘Low-angle grain boundaries(LAGBs)are one of the solidification defects in single-crystal nickel-based superalloys and are detrimental to the mechanical properties.The formation of LAGBs is related to dendrite deformation,while the mechanism has not been fully understood at the mesoscale.In this work,a model coupling dendrite growth,thermal-solutal-fluid flow,thermal stress and flow-induced dendrite deformation via cellular automaton-finite volume method and finite element method is developed to study the formation of LAGBs in single crystal superalloys.Results reveal that the bending of dendrites is primarily attributed to the thermal-solutal convection-induced dendrite deformation.The mechanical stress of dendrite deformation develops and stabilises as solidification proceeds.As the width of the mushy zone gets stable,stresses are built up and then dendritic elastoplastic bending occurs at some thin primary dendrites with the wider inter-dendritic space.There are three characteristic zones of stress distribution along the solidification direction:(i)no stress concentration in the fully solidified regions;(ii)stress developing in the primary dendrite bridging region,and(iii)stress decrease in the inter-dendritic uncontacted zone.The stresses reach maximum near the initial dendrite bridging position.The lower temperature gradients,the finer primary dendritic trunks and sudden reductions in local dendritic trunk radius jointly promote the elastoplastic deformation of the dendrites.Corresponding measures are suggested to reduce LAGBs.
基金supported by the National Natural Science Foundation of China(No.32071980)the Key Projects of Shaanxi Agricultural Collaborative Innovation and Extension Alliance(No.LMZD202201)+1 种基金the Key R&D Project in Shaanxi Province(No.2021LLRH-07)Shaanxi Natural Scientific Basic Research Program project(No.2022JQ-157).
文摘Agricultural practices significantly contribute to greenhouse gas(GHG)emissions,necessitating cleaner production technologies to reduce environmental pressure and achieve sustainable maize production.Plastic film mulching is commonly used in the Loess Plateau region.Incorporating slow-release fertilizers as a replacement for urea within this practice can reduce nitrogen losses and enhance crop productivity.Combining these techniques represents a novel agricultural approach in semi-arid areas.However,the impact of this integration on soil carbon storage(SOCS),carbon footprint(CF),and economic benefits has received limited research attention.Therefore,we conducted an eight-year study(2015-2022)in the semi-arid northwestern region to quantify the effects of four treatments[urea supplied without plastic film mulching(CK-U),slow-release fertilizer supplied without plastic film mulching(CK-S),urea supplied with plastic film mulching(PM-U),and slow-release fertilizer supplied with plastic film mulching(PM-S)]on soil fertility,economic and environmental benefits.The results revealed that nitrogen fertilizer was the primary contributor to total GHG emissions(≥71.97%).Compared to other treatments,PM-S increased average grain yield by 12.01%-37.89%,water use efficiency by 9.19%-23.33%,nitrogen accumulation by 27.07%-66.19%,and net return by 6.21%-29.57%.Furthermore,PM-S decreased CF by 12.87%-44.31%and CF per net return by 14.25%-41.16%.After eight years,PM-S increased SOCS(0-40 cm)by 2.46%,while PM-U decreased it by 7.09%.These findings highlight the positive effects of PM-S on surface soil fertility,economic gains,and environmental benefits in spring maize production on the Loess Plateau,underscoring its potential for widespread adoption and application.
基金Financial supports from the National Natural Science Foundation of China(Nos.52171116,U22A20109,52334010 and T2325013)are greatly acknowledgedPartial financial support came from The Program for the Central University Youth Innovation Team,and the Fundamental Research Funds for the Central Universities,JLU.
文摘Dislocations and disclinations are fundamental topological defects within crystals,which determine the mechanical properties of metals and alloys.Despite their important roles in multiple physical mechanisms,e.g.,dynamic recovery and grain boundary mediated plasticity,the intrinsic coupling and correlation between disclinations and dislocations,and their impacts on the deformation behavior of metallic materials still remain obscure,partially due to the lack of a theoretical tool to capture the rotational nature of disclinations.By using a Lie-algebra-based theoretical framework,we obtain a general equation to quantify the intrinsic coupling of disclinations and dislocations.Through quasi in-situ electron backscatter diffraction characterizations and disclination/dislocation density analyses in Mg alloys,the generation,coevolution and reactions of disclinations and dislocations during dynamic recovery and superplastic deformation have been quantitatively analyzed.It has been demonstrated that the obtained governing equation can capture multiple physical processes associated with mechanical deformation of metals,e.g.,grain rotation and grain boundary migration,at both room temperature and high temperature.By establishing the disclination-dislocation coupling equation within a Lie algebra description,our work provides new insights for exploring the coevolution and reaction of disclinations/dislocations,with profound implications for elucidating the microstructure-property relationship and underlying deformation mechanisms in metallic materials.
基金supported by the Natural Science Fund of China(31771724)the Key Research and Development Project of Shaanxi Province(2024NC-ZDCYL-01-10).
文摘The increase in soil temperature associated with climate change has introduced considerable challenges to crop production.Split nitrogen application(SN)represents a potential strategy for improving crop nitrogen use efficiency and enhancing crop stress resistance.Nevertheless,the precise interaction between soil warming(SW)and SN remains unclear.In order to ascertain the impact of SW on maize growth and whether SN can improve the tolerance of maize to SW,a two-year field experiment was conducted(2022-2023).The aim was to examine the influence of two SW ranges(MT,warming 1.40℃;HT,warming 2.75℃)and two nitrogen application methods(N1,one-time basal application of nitrogen fertilizer;N2,one third of base nitrogen fertilizer+two thirds of jointing stage supplemental nitrogen fertilizer)on maize root growth,photosynthetic characteristics,nitrogen use efficiency,and yield.The results demonstrated that SW impeded root growth and precipitated the premature aging of maize leaves following anthesis,particularly in the HT,which led to a notable reduction in maize yield.In comparison to N1,SN has been shown to increase root length density by 8.54%,root bleeding rate by 8.57%,and enhance root distribution ratio in the middle soil layers(20-60 cm).The interaction between SW and SN had a notable impact on maize growth and yield.The SN improved the absorption and utilization efficiency of nitrogen by promoting root development and downward canopy growth,thus improving the tolerance of maize to SW at the later stage of growth.In particular,the N2HT resulted in a 14.51%increase in the photosynthetic rate,a 18.58%increase in nitrogen absorption efficiency,and a 18.32%increase in maize yield compared with N1HT.It can be posited that the SN represents a viable nitrogen management measure with the potential to enhance maize tolerance to soil high-temperature stress.
基金supported by the Central Public-Interest Scientific Institution Basal Research Fund,China(Grant No.CPSIBRF-CNRRI-202403)。
文摘Rice is a poor source of folate,an essential micronutrient for the body.Biofortification offers an effective way to enhance the folate content of rice and alleviate folate deficiencies in humans.In this study,we confirmed that OsADCS and OsGTPCHI,encoding the initial enzymes necessary for folate synthesis,positively regulate folate accumulation in knockout mutants of both japonica and indica rice backgrounds.The folate content in the low-folate japonica variety was slightly increased by the expression of the indica alleles driven by the endosperm-specific promoter.We further obtained co-expression lines by stacking OsADCS and OsGTPCHI genes;the folate accumulation in brown rice and polished rice reached 5.65μg/g and 2.95μg/g,respectively,representing 37.9-fold and 26.5-fold increases compared with the wild type.Transcriptomic analysis of rice grains from six transgenic lines showed that folate changes affected biological pathways involved in the synthesis and metabolism of rice seed storage substances,while the expression of other folate synthesis genes was weakly regulated.In addition,we identified Aus rice as a high-folate germplasm carrying superior haplotypes of OsADCS and OsGTPCHI through natural variation.This study provides an alternative and effective complementary strategy for rice biofortification,promoting the rational combination of metabolic engineering and conventional breeding to breed high-folate varieties.
基金supported by the National Natural Science Foundation of China(32372223)the National Key Research and Development Program of China(2022YFD2301404)+1 种基金the College Students'Innovationand Entrepreneurship Training Program of Anhui Province,China(S202210364136)the Natural Science Research Project of Anhui Educational Committee,China(2023AH040133).
文摘Low temperature(LT)in spring has become one of the principal abiotic stresses that restrict the growth and development of wheat.Diverse analyses were performed to investigate the mechanism underlying the response of wheat grain development to LT stress during booting.These included morphological observation,measurements of starch synthase activity,and determination of amylose and amylopectin content of wheat grain after exposure to treatment with LT during booting.Additionally,proteomic analysis was performed using tandem mass tags(TMT).Results showed that the plumpness of wheat grains decreased after LT stress.Moreover,the activities of sucrose synthase(SuS,EC 2.4.1.13)and ADP-glucose pyrophosphorylase(AGPase,EC 2.7.7.27)exhibited a significant reduction,leading to a significant reduction in the contents of amylose and amylopectin.A total of 509 differentially expressed proteins(DEPs)were identified by proteomics analysis.The Gene Ontology(GO)enrichment analysis showed that the protein difference multiple in the nutritional repository activity was the largest among the molecular functions,and the up-regulated seed storage protein(ssP)played an active role in the response of grains to LT stress and subsequent damage.The Kyoto Encyclopedia of Genes and Genomes(KEGG)enrichment analysis showed that LT stress reduced the expression of DEPs such as sucrose phosphate synthase(SPS),glucose-1-phosphate adenylyltransferase(glgC),andβ-fructofuranosidase(FFase)in sucrose and starch metabolic pathways,thus affecting the synthesis of grain starch.In addition,many heat shock proteins(HsPs)were found in the protein processing in endoplasmic reticulum pathways,which can resist some damage caused by LT stress.These findings provide a new theoretical foundation for elucidating the underlying mechanism governing wheat yield developmentafterexposuretoLTstress inspring.
基金by National Natural Science Foundation of China(Nos.52271103,52334010 and 52271031)Jilin Scientific and Technological Development Program(Nos.20220301026GX,20210201115GX and 20210301041GX).
文摘Conventional rolled Mg-Al alloy sheets typically exhibit strong basal textures that remain and may even strengthen after recrystallization annealing due to the preferential growth of basal-oriented grains,resulting in poor formability at room temperature.Therefore,the knowledge of recrystallization and grain growth is critical for modifying textures of Mg-Al alloy sheets.The static recrystallization and texture evolution in a cold-rolled dilute Mg-1Al(wt.%)alloy during various annealed temperatures ranging from 300℃ to 450℃,have been investigated using the quasi in-situ electron backscatter diffraction(EBSD)method.The as-rolled Mg-1Al alloy shows a dominant basal texture,which weakens and broadens in the rolling direction(RD)during the subsequent annealing,accompanied by the formation of{1010}texture component.Particularly,the {1010} texture component is more pronounced after annealing at high temperatures.The quasi in-situ EBSD results show that recrystallized grains are mainly induced by shear bands,which exhibit a wide spectrum of orientations with c-axis tilt angles ranging 20°-45°from the normal direction(ND).Orientations of shear band-induced recrystallized grains are retained during the entire recrystallization process,resulting in a reduction in the texture intensity.Moreover,recrystallized grains belonging to the {1010}texture component grow preferentially compared to those with other orientations,which is attributed to low energy grain boundaries,especially grain boundaries with∼30°misorientation angles.Furthermore,the high temperature annealing facilitates the rapid growth of grain boundaries having a 30°misorientation angle,leading to the occurrence of distinct {1010} texture after annealing at 450℃ for 1 h.The results provide insights for texture modification of rare earth-free low-alloyed Mg alloys by controlling annealing parameters.
基金funding from the Scientific Research Program of the Higher Educational Institutions in Anhui Province, China (2023AH050986)the Natural Science Foundation of Anhui Province, China (240805MC063)+1 种基金the National Natural Science Foundation of China (32172119)the Talent Introduction Project of Anhui Agricultural University, China (rc312212 and yj2019-01)。
文摘Increasing the grain yield(GY) and water use efficiency(WUE) of winter wheat in the Huaibei Plain(HP), China are essential. However, the effects of micro-sprinkler irrigation and topsoil compaction after wheat seed sowing on the GY and WUE are unclear. Therefore, a two-year field experiment was conducted during the 2021–2023 winter wheat growing seasons with a total six treatments: rain-fed(RF), conventional irrigation(CI) and micro-sprinkler irrigation(MI), as well as topsoil compaction after seed sowing under these three irrigation methods(RFC, CIC, and MIC). The results in the two years indicated that MI significantly increased GY compared to CI and RF, by averages of 17.9 and 42.1%, respectively. The increase in GY of MI was due to its significant increases in the number of spikes, kernels per spike, and grain weight. The chlorophyll concentration in flag leaves of MI after the anthesis stage maintained higher levels than with CI and RF, and was the lowest in RF. This was due to the dramatically enhanced catalase and peroxidase activities and lower malondialdehyde content under MI. Compared with RF and CI, MI significantly promoted dry matter remobilization and production after anthesis, as well as its contribution to GY. In addition, MI significantly boosted root growth, and root activity during the grain-filling stage was remarkably enhanced compared to CI and RF. In 2021–2022, there was no significant difference in WUE between MI and RF, but the WUE of RF was significantly lower than that of MI in 2022–2023. However, the WUE in MI was significantly improved compared to CI, and it increased by averages of 15.1 and 17.6% for the two years. Topsoil compaction significantly increased GY and WUE under rain-fed conditions due to improved spike numbers and dry matter production. Overall, topsoil compaction is advisable for enhancing GY and WUE in rain-fed conditions, whereas micro-sprinkler irrigation can be adopted to simultaneously achieve high GY and WUE in the HP.
基金supported by the National Natural Science Foundation of China (Grant Nos.12202294 and 12022208)the Project funded by China Postdoctoral Science Foundation (Grant No.2022M712243)the Fundamental Research Funds for the Central Universities (Grant No.2023SCU12098).
文摘It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size(grain size,GS)or the external size(geometric size).The coupled effect of GS and geometric size on the functional properties has not been clearly understood yet.In this work,the super-elasticity,one-way,and stress-assisted two-way shape memory effects of the polycrystalline NiTi SMAs with different aspect ratios(length/width for the gauge section)and different GSs are investigated based on the phase field method.The coupled effect of the aspect ratio and GS on the functional properties is adequately revealed.The simulated results indicate that when the aspect ratio is lower than about 4:1,the stress biaxiality and stress heterogeneity in the gauge section of the sample become more and more obvious with decreasing the aspect ratio,which can significantly influence the microstructure evolution in the process involving external stress.Therefore,the corresponding functional property is strongly dependent on the aspect ratio.With decreasing the GS and the aspect ratio(to be lower than 4:1),both the aspect ratio and GS can affect the MT or martensite reorientation in each grain and the interaction among grains.Thus,due to the strong internal constraint(i.e.,the constraint of grain boundary)and the external constraint(i.e.,the constraint of geometric boundary),the capabilities of the functional properties of NiTi SMAs are gradually weakened and highly dependent on these two factors.
基金supported by the National Natural Science Foundation of China(Grant Nos.52275321 and 52205348)the Shandong Natural Science Foundation(Grant No.ZR2023JQ021)+3 种基金the Taishan Scholars Foundation of Shandong Province(No.tsqn 201812128)the Innovation Scientists and Technicians Troop Projects of Henan Province(No.204200510031)the Heilongjiang Touyan Innovation Team Program(No.HITTY-20190013)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(Nos.NRF-2021R1A2C3006662 and NRF-2022R1A5A1030054).
文摘To effectively regulate the grain boundary infiltration in CoCrFeMnNi high-entropy alloy(Cantor alloys,HEA)caused by the violent atomic interdiffusion,the higher configuration entropy on Cantor alloys surface was designed and realized via eutectic high-entropy(EHEA)transformation.Meanwhile,to effectively alleviate the residual stress caused by the notable difference in the thermal expansion coefficient(CTE)between Cantor alloys and Zr-3 alloys,a cladding layer was applied to the HEA surface using laser cladding technology of Nb,followed by brazing to Zr-3 alloys with Zr63.2Cu filler.The cladding layer’s microstructure comprised Nbss and FCC+(Co,Ni)_(2) Nb eutectic structure,resulting from an in-situ reaction between Cantor alloys and Nb.The Nbss and FCC demonstrated good plasticity,and the(Co,Ni)_(2) Nb Laves phase provided increased strength,endowing both good plastic deformation ability and strength of the cladding layer.Notably,the existence of EHEA in the laser cladding layer made the Cantor alloy entropy from 1.61 R to 1.77 R,greatly enhancing its thermal stability and suppressing the grave grain boundary infiltration.Joints produced via laser cladding with Nb-assisted brazing exhibited a complex microstructure(HEA/Nbss+FCC+(Co,Ni)_(2)Nb/(Zr,Nb)(Cr,Mn)_(2)+(Zr,Nb)ss/(Zr,Nb)_(2)(Cu,Ni,Co,Fe)+(Zr,Nb)(Cr,Mn)_(2)+(Zr,Nb)ss/Zr-3) and a significantly improved shear strength of 242.8 MPa at 1010℃ for 10 min,42.4%higher than that of directly brazed joints.This improvement was attributed to reduced grain boundary infiltration,alleviated residual stress due to CTE disparity,and eliminated micro-cracks in the brazing seam.This study presents an effective solution for reducing residual stresses and achieving reliable bonding between Cantor alloys and Zr-3 alloys,with potential applications in brazing CoCrFeNi-based HEA and Zr-3 due to the beneficial eutectic reaction between CoCrFeNi and Nb.
基金supported by the National Natural Science Foundation of China(No.51871155).
文摘Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can result in solidification defects and reduced mechanical properties.In this work,a novel welding wire containing MgO particles has been developed to promote columnar-to-equiaxed transition(CET)in the FZ of TIG-welded AZ31 alloy.The results show the achievement of a fully equiaxed grain structure in the FZ,with a significant 71.9%reduction in grain size to 41 μm from the original coarse columnar dendrites.Furthermore,the combination of using MgO-containing welding wire and pulse current can further refine the grain size to 25.6 μm.Microstructural analyses reveal the homogeneous distribution of MgO particles in the FZ.The application of pulse current results in an increase in the number density of MgO(1-2 μm)from 5.16 × 10^(4) m^(-3) to 6.18 × 10^(4) m^(-3).The good crystallographic matching relationship between MgO and α-Mg matrix,characterized by the orientation relationship of[11(2)0]α-Mg//[0(1)1]MgO and(0002)_(α-Mg)//(111)_(MgO),indicates that the MgO particles can act as effective nucleation sites for α-Mg to reduce nucleation undercooling.According to the Hunt criteria,the critical temperature gradient for CET is greatly enhanced due to the significantly increased number density of MgO nucleation sites.In addition,the correlation with the thermal simulation results reveals a transition in the solidification conditions within the welding pool from the columnar grain zone to the equiaxed grain zone in the CET map,leading to the realization of CET.The exceptional grain refinement has contributed to a simultaneous improvement in the strength and plasticity of welded joints.This study presents a novel strategy for controlling equiaxed microstructure and optimizing mechanical properties in fusion welding or wire and arc additive manufacturing of Mg alloy components.
基金supported by the National Natural Science Foundation of China(Nos.U1960115 and U21A20116)the Fundamental Research Funds for the Central Universities(No.N232405-10)Special thanks are due to the instrumental and data analysis from Analytical and Testing Center,Northeastern University.
文摘The trade-offbetween strength and ductility remains a persistent obstacle in the development of advanced structural materials.In the present study,a novel dual-heterogeneous structure with a bimodal grain distribution in both ferrite and austenite phases was fabricated via cold rolling and partial recrystallization annealing on solution-treated 2205 duplex stainless steel(DSS).The processed steel exhibited superior mechanical properties,with the yield strength increasing from 586 MPa to 903 MPa,and the ultimate tensile strength from 796 MPa to 1082 MPa,while maintaining a high total elongation of 35.3%.Based on in-situ electron backscatter diffraction(EBSD)and scanning electron microscope(SEM)analyses,the microstructural deformation behavior and strengthening mechanisms of the dual-heterostructured 2205 DSS were elucidated.The outstanding combination of strength and ductility was ascribed to the synergistic effects of grain refinement,dislocation strengthening,and hetero-deformation induced(HDI)strengthening.Moreover,the high ductility in DSS was attributed to the coactivation of cross-slip systems in ferrite{110}and{112}along with the single-slip systems in austenite{111}.These findings provide a new strategy for the design and development of high-strength and ultra-high-strength DSSs.
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supported by the National Natural Science Foundation of China(Nos.52371128,52304378,52101031 and 92163107).
文摘Grain boundary engineering plays a significant role in the improvement of strength and plasticity of alloys. However, in refractory high-entropy alloys, the susceptibility of grain boundaries to oxygen presents a bottleneck in achieving high mechanical performance. Creating a large number of clean grain boundaries in refractory high-entropy alloys is a challenge. In this study, an ultrafine-grained (UFG) NbMoTaW alloy with high grain-boundary cohesion was prepared by powder metallurgy, taking advantages of rapid hot-pressing sintering and full-process inert atmosphere protection from powder synthesis to sintering. By oxygen control and an increase in the proportion of grain boundaries, the segregation of oxygen and formation of oxides at grain boundaries were strongly mitigated, thus the intrinsic high cohesion of the interfaces was preserved. Compared to the coarse-grained alloys prepared by arc-melting and those sintered by traditional powder metallurgy methods, the UFG NbMoTaW alloy demonstrated simultaneously increased strength and plasticity at ambient temperature. The highly cohesive grain boundaries not only reduce brittle fractures effectively but also promote intragranular deformation. Consequently, the UFG NbMoTaW alloy achieved a high yield strength even at elevated temperatures, with a remarkable performance of 1117 MPa at 1200 ℃. This work provides a feasible solution for producing refractory high-entropy alloys with low impurity content, refined microstructure, and excellent mechanical performance.
基金supported by the National Natural Science Foundation of China(No.52061135101 and 52001078)the German Research Foundation(DFG,No.448318292)+3 种基金the Technology Innovation Guidance Special Foundation of Shaanxi Province(No.2023GXLH-085)the Fundamental Research Funds for the Central Universities(No.D5000240161)the Project of Key areas of innovation team in Shaanxi Province(No.2024RS-CXTD-20)The author Yingchun Xie thanks the support from the National Key R&D Program(No.2023YFE0108000).
文摘1.Introduction.Cold Spray(CS)is a highly advanced solid-state metal depo-sition process that was first developed in the 1980s.This innovative technique involves the high-speed(300-1200 m/s)impact deposition of micron-sized particles(5-50μm)to fabricate coatings[1-3].CS has been extensively used in a variety of coating applications,such as aerospace,automotive,energy,medical,marine,and others,to provide protection against high temperatures,corrosion,erosion,oxidation,and chemicals[4,5].Nowadays,the technical interest in CS is twofold:(i)as a repair process for damaged components,and(ii)as a solid-state additive manufacturing process.Compared to other fusion-based additive manufacturing(AM)technologies,Cold Spray Additive Manufacturing(CSAM)is a new member of the AM family that can enable the fabrication of deposits without undergoing melting.The chemical composition has been largely preserved from the powder to the deposit due to the minimal oxidation.The significant advantages of CSAM over other additive manufacturing processes include a high production rate,unlimited deposition size,high flexibility,and suitability for repairing damaged parts.
基金supported by the National Natural Science Foundation of China(No.41977199).
文摘In this study,two wheat-derived cadmium(Cd)-immobilizing endophytic Pseudomonas paralactis M14 and Priestia megaterium R27 were evaluated for their effects on wheat tissue Cd uptake under hydroponic conditions.Then,the impacts of the biochar(BC),M14+R27(MR),and BC+MR treatments on wheat Cd uptake and the mechanisms involved were investigated at the jointing,heading,and mature stages of wheat plants under field-plot conditions.A hydroponic experiment showed that the MR treatment significantly decreased the above-ground tissue Cd content compared with theM14 or R27 treatment.The BC+MRtreatment reduced the grain Cd content by 51.5%-67.7%and Cd translocation factor at the mature stage of wheat plants and increased the organic matter-bound Cd content by 31%-75%in the rhizosphere soils compared with the BC or MR treatment.Compared with the BC or MR treatment,the relative abundances of the biomarkers associated with Gemmatimonas,Altererythrobacter,Gammaproteobacteria,Xanthomonadaceae,Phenylobacterium,and Nocardioides in the BC+MR-treated rhizosphere microbiome decreased and negatively correlated with the organic matter-bound Cd contents.In the BC+MR-treated root interior microbiome,the relative abundance of the biomarker belonging to Exiguobacterium increased and negatively correlated with the Cd translocation factor,while the relative abundance of the biomarker belonging to Pseudonocardiaceae decreased and positively correlated with the Cd translocation factor.Our findings suggested that the BC+MR treatment reduced Cd availability and Cd transfer through affecting the abundances of these specific biomarkers in the rhizosphere soil and root interior microbiomes,leading to decreased wheat grain Cd uptake in the contaminated soil.
