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
To elucidate the deformation mechanisms ofγ-TiAl,the nanoindentation experiments and crystal plasticity finite element(CPFE)simulation were employed to investigate the effects of crystal orientations and GBs on the m...To elucidate the deformation mechanisms ofγ-TiAl,the nanoindentation experiments and crystal plasticity finite element(CPFE)simulation were employed to investigate the effects of crystal orientations and GBs on the mechanical properties ofγ-TiAl alloys.A crystal plasticity constitutive model was developed,and load-displacement curves,hardness,and Young's modulus were obtained for both single grains and GBs inγ-TiAl alloys.Based on the aforementioned model,this study investigated the distribution patterns of surface morphology around the indentation sites of individual grain and GBs.It also analyzed the cumulative shear strain distribution,slip system activation,and the interaction between GBs and dislocation slip for various crystal orientations.The results indicate that the mechanical response and pileup behavior exhibit significant anisotropy due to the interplay among the indenter geometry,material slip systems,and cumulative shear strain distribution.Moreover,the interaction between GBs and dislocation slip substantially alters dislocation distribution,thereby influencing material flow and playing a critical role in the mechanical response and plastic deformation of the material.展开更多
The deformation behavior of GH4169 superalloy under room-temperature uniaxial tension was investigated through synchronized mesoscopic digital image correlation(DIC)and electron backscatter diffraction(EBSD)in-situ ch...The deformation behavior of GH4169 superalloy under room-temperature uniaxial tension was investigated through synchronized mesoscopic digital image correlation(DIC)and electron backscatter diffraction(EBSD)in-situ characterization techniques.Results show that in the field of grain deflection dynamics,through quantitative analysis using the independently developed M-DIC software,during uniaxial tension with significant bidirectional rotation along the tensile axis and the stress level of 1100 MPa,oscillatory rotation of±0.6°can be obtained,and microvoids are generated at the grain boundaries with 45°to the stress axis.EBSD crystallographic analysis demonstrates the load-dependent slip system evolution:in the initial stage,the soft-oriented systems with high Schmid factor(>0.4)is activated and then transformed into hard-oriented systems during cross-slip,generating parallel slip bands and dislocation pile-ups at grain boundaries.During the uniaxial tensile process,the characteristic of strain energy accumulation is observed,which follows a two-stage accumulation pattern:initial grain boundary localization(Stage I)and intragranular propagation(Stage II).Ultimately,the intergranular cracks are initiated at triple junctions,and the twin boundaries exhibit superior mechanical stability compared with the large-angle grain boundaries.Deformation texture characteristics indicate the copper-type components,including C{112}<111¯>,S{123}<634¯>,and B{110}<11¯0>.The complete deformation sequence is as follows:cross-slip of soft-oriented slip systems→initiation of dislocation slip→strain partitioning through grain rotation→intergranular stress concentration→damage dominated by boundary cracking.The cross-scale deformation mechanism revealed in this study provides critical guidance for the crystal boundary engineering to optimize nickel-based superalloys.展开更多
Using multi-directional forging temperature as the independent variable and adopting the dual-mode phase field crystal model,the nucleation modes,reaction mechanisms,and interactions between grain boundaries and dislo...Using multi-directional forging temperature as the independent variable and adopting the dual-mode phase field crystal model,the nucleation modes,reaction mechanisms,and interactions between grain boundaries and dislocations at different temperatures were investigated.Results show that a mapping relationship between process parameters and grain refinement/coarsening is established,and the optimal processing temperature coefficient is 0.23.Compared with the cases with processing temperature coefficient of 0.19,0.20,0.21,0.25,and 0.27,the refinement effect increases by 256.0%,146.0%,113.0%,6.7%,and 52.4%,respectively.Excessively high temperatures lead to grain coarsening due to dislocation annihilation,and the application of strain can reduce the actual melting point of materials.Even if the processing temperature does not exceed the theoretical melting point,remelting and crystallization may still occur,resulting in an overburning phenomenon that reduces internal defects and increases overall grain size.This research is of great significance for the actual forging process design.展开更多
The effect of trace addition of 0.1wt%Y on the grain refinement and mechanical properties of Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc alloys at as-cast and heat-treated states was investigated.Results show that the additi...The effect of trace addition of 0.1wt%Y on the grain refinement and mechanical properties of Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc alloys at as-cast and heat-treated states was investigated.Results show that the addition of 0.1wt%Y into the Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc alloys can elevate the nucleation temperature of the Al_(3)(Sc,Zr)phase,leading to the preferential precipitation of the Al_(3)(Sc,Zr)phase and increasing the amount of Al_(3)(Sc,Zr)phase in the matrix.Al_(3)(Sc,Zr)phase can also act as a heterogeneous nucleation site in theα-Al matrix to promote nucleation and refine grains.The addition of element Y changes the precipitation phase characteristics at the grain boundaries in the as-cast alloy,which changes the distribution characteristics of secondary phases from initially continuous and coarse strip-like distribution at grain boundaries into the discontinuous dot-like and rod-like distribution.Besides,the size of secondary phases becomes smaller and their amount increases.Under the combined effects of grain refinement strengthening and precipitation strengthening,the Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc-0.1Y alloy after 175℃/10 h aging treatment achieves an ultimate tensile strength of 412 MPa and an elongation of 6.3%.Compared with those of the alloy without Y addition,the ultimate tensile strength and elongation of the added alloy increase by 16.1%and 53.7%,respectively.展开更多
Combining the phase-field method and the moving boundary method,a three-dimensional phase-field simulation was conducted for the growth and grain evolution of Ti films deposited by physical vapor deposition under diff...Combining the phase-field method and the moving boundary method,a three-dimensional phase-field simulation was conducted for the growth and grain evolution of Ti films deposited by physical vapor deposition under different deposition rates and grain orientations.The evolution of grain morphology and grain orientation was also taken into consideration.Simulation results show that at lower deposition rates,the surface of the formed Ti film exhibits a distinct oriented texture structure.The surface roughness of the Ti film is positively correlated with the grain misorientation.Moreover,the surface roughness obtained from the simulation is in good agreement with the experiment results.展开更多
Gradient microstructures strengthened by serrated Grain Boundaries(GBs)were achieved through a combination of Gradient Strain Deformation(GSD)and Serration Heat Treatment(SHT),with particular focus on microstructural ...Gradient microstructures strengthened by serrated Grain Boundaries(GBs)were achieved through a combination of Gradient Strain Deformation(GSD)and Serration Heat Treatment(SHT),with particular focus on microstructural evolution,underlying mechanisms,and the critical influencing factors.Dynamic recrystallization governed the microstructural evolution in the fine-grained and transition regions during GSD,where multiple nucleation mechanisms were active.Plastic deformation facilitated the dissolution ofγ'phase in fine-grained regions,ultimately resulting in its morphological transformation.During the subsequent SHT,serrated GBs formed within the gradient microstructures produced by prior GSD without disrupting the grain size gradient,thereby enhancing creep resistance.Two distinct mechanisms associated withγ'gbparticles governed the formation of the serrations at GBs.Owing to the stronger dragging effect of grain boundary junctions in fine-grained regions,the amplitude and wavelength of serrations in these regions were smaller than those in coarse-grained regions.Moreover,the formation of serrations exhibited a strong dependence on the inherent properties of the GBs.The random high-angle grain boundaries(HAGBs)with misorientation angles in the range of 30-59°tended to become serrated more easily during SHT due to their high mobility and the accelerated precipitation ofγ'gbparticles at them.Low-ΣHAGBs and low-angle GBs were not prone to form serrations.In particular,serration formation was completely inhibited atΣ3 twin boundaries due to their extremely low mobility and the absence ofγ'gbparticles.展开更多
Gas-solid flows are ubiquitous in industrial systems.The coupled model of the discrete element method(DEM)and computational fluid dynamics(CFD)is one of the techniques for the simulation of the gas-solid flows.To enha...Gas-solid flows are ubiquitous in industrial systems.The coupled model of the discrete element method(DEM)and computational fluid dynamics(CFD)is one of the techniques for the simulation of the gas-solid flows.To enhance the applicability of the DEM-CFD method,the coarse graining DEM has been developed to simulate large-scale powder systems.The coarse graining DEM is a scaling law model and hence can simulate large-scale systems using a smaller number of particles than the actual one.Although the coarse graining DEM enables to effectively simulate large-scale powder systems on a single PC,visualized image is lack of reality due to reduced spatial resolution.Here a novel visualization method is developed to produce realistic images.In the proposed technique,the virtual particles are located by considering the motion and location of the coarse grain particles.To show the adequacy of the proposed method,two types of visualization based on the computational results are made:a blow-up of powder due to injected gas flow and a spouted bed.In these systems,the visualized images are shown to be improved by the proposed visualization technique.The effectiveness of the proposed method is proved by the agreement of the images based on the calculation results between the standard DEM-CFD method and coarse graining DEM.展开更多
Highlights OsCAX2 is localized to tonoplast,and cadmium induces its expression.OsCAX2 overexpression reduces cadmium concentration in indica rice grains by 49.1%.Cadmium(Cd)exposure poses significant health risks to h...Highlights OsCAX2 is localized to tonoplast,and cadmium induces its expression.OsCAX2 overexpression reduces cadmium concentration in indica rice grains by 49.1%.Cadmium(Cd)exposure poses significant health risks to humans,and the International Agency for Research on Cancer has classified it as a Group I carcinogen.Cadmium undergoes minimal metabolism in the human body;consequently,prolonged Cd^(2+)exposure can cause severe damage to multiple organs including the liver,kidneys,lungs,bones,and immune system(Shao et al.2024).Rice,one of the three global staple crops,and Cd exposure in humans primarily occurs the consumption of contaminated rice grains.The contribution of rice to the total dietary Cd intake is over 50% for non-smoking Asian populations(Chen et al.2018;Shi et al.2020).展开更多
CR Dhan 310(CRD310),a biofortified rice variety,contains a significantly higher level of grain protein compared with its recurrent parent Naveen(NV),as well as most adapted high-yielding rice varieties in India.Althou...CR Dhan 310(CRD310),a biofortified rice variety,contains a significantly higher level of grain protein compared with its recurrent parent Naveen(NV),as well as most adapted high-yielding rice varieties in India.Although a limited investigation depicted that CRD310 contained higher levels of glutelin and some essential amino acids,detailed biochemical,molecular,and cellular mechanisms remain to be studied.As one of the means to identify the proteins and understand the underlying mechanism of higher proteins accumulation in grains of CRD310,the comparative proteomics was undertaken on grains of CRD310 and NV at the yellow ripening stage.展开更多
A comprehensive assessment of grain supply,demand,and ecosystem service flows is essential for identifying grain movement pathways,ensuring regional grain security,and guiding sustainable management strategies.However...A comprehensive assessment of grain supply,demand,and ecosystem service flows is essential for identifying grain movement pathways,ensuring regional grain security,and guiding sustainable management strategies.However,current studies primarily focus on short-term grain provision services while neglecting the spatiotemporal variations in grain flows across different scales.This gap limits the identification of dynamic matching relationships and the formulation of optimization strategies for balancing grain flows.This study examined the spatiotemporal evolution of grain supply and demand in the Beijing-Tianjin-Hebei(BTH)region from 1980 to 2020.Using the Enhanced TwoStep Floating Catchment Area method,the grain provision ecosystem service flows were quantified,the changes in supply–demand matching under different grain flow scenarios were analyzed and the optimal distance threshold for grain flows was investigated.The results revealed that grain production follows a spatial distribution pattern characterized by high levels in the southeast and low levels in the northwest.A significant mismatch exists between supply and demand,and it shows a scale effect.Deficit areas are mainly concentrated in the northwest,while surplus areas are mainly located in the central and southern regions.As the spatial scale increases,the ecosystem service supply–demand ratio(SDR)classification becomes more clustered,while it exhibits greater spatial SDR heterogeneity at smaller scales.This study examined two distinct scenarios of grain provision ecosystem service flow dynamics based on 100 and 200 km distance thresholds.The flow increased significantly,from 2.17 to 11.81million tons in the first scenario and from 2.41 to 12.37 million tons in the second scenario over nearly 40 years,forming a spatial movement pattern from the central and southern regions to the surrounding areas.Large flows were mainly concentrated in the interior of urban centers,with significant outflows between cities such as Baoding,Shijiazhuang,Xingtai,and Hengshui.At the county scale,supply–demand matching patterns remained consistent between the grain flows in the two scenarios.Notably,incorporating grain flow dynamics significantly reduced the number of grain-deficit areas compared to scenarios without grain flow.In 2020,grain-deficit counties decreased by28.79 and 37.88%,and cities by 12.50 and 25.0%under the two scenarios,respectively.Furthermore,the distance threshold for achieving optimal supply and demand matching at the county scale was longer than at the city scale in both grain flow scenarios.This study provides valuable insights into the dynamic relationships and heterogeneous patterns of grain matching,and expands the research perspective on grain and ecosystem service flows across various spatiotemporal scales.展开更多
THE mechanical response and deformation mechanisms of pure nickel under nanoindentation were systematically investigated using molecular dynamics(MD)simulations,with a particular focus on the novel interplay between c...THE mechanical response and deformation mechanisms of pure nickel under nanoindentation were systematically investigated using molecular dynamics(MD)simulations,with a particular focus on the novel interplay between crystallographic orientation,grain boundary(GB)proximity,and pore characteristics(size/location).This study compares single-crystal nickel models along[100],[110],and[111]orientations with equiaxed polycrystalline models containing 0,1,and 2.5 nm pores in surface and subsurface configurations.Our results reveal that crystallographic anisotropy manifests as a 24.4%higher elastic modulus and 22.2%greater hardness in[111]-oriented single crystals compared to[100].Pore-GB synergistic effects are found to dominate the deformation behavior:2.5 nm subsurface pores reduce hardness by 25.2%through stress concentration and dislocation annihilation at GBs,whereas surface pores enable mechanical recovery via accelerated dislocation generation post-collapse.Additionally,size-dependent deformation regimes were identified,with 1 nm pores inducing negligible perturbation due to rapid atomic rearrangement,in contrast with persistent softening in 2.5 nm pores.These findings establish atomic-scale design principles for defect engineering in nickel-based aerospace components,demonstrating how crystallographic orientation,pore configuration,and GB interactions collectively govern nanoindentation behavior.展开更多
Mixed halide perovskites exhibit great potential as materials for the future generation of photovoltaic devices.Yet,their reaction to moisture remains uncertain,necessitating further exploration.While prolonged exposu...Mixed halide perovskites exhibit great potential as materials for the future generation of photovoltaic devices.Yet,their reaction to moisture remains uncertain,necessitating further exploration.While prolonged exposure to moisture can lead to degradation,it can also passivate traps at an optimal moisture level.Here,we use scanning probe microscopy to perform nanoscale moisture-dependent photovoltaic characterizations of open and compressed grain boundary(GB)structures of wide bandgap(FAPbI_(3))_(0.3)(FAPbBr_(3))_(0.7) perovskites.The investigation reveals a decrease in the potential barrier at compact GBs with increasing moisture levels,contrasting with the behavior observed in open GBs.Moreover,the photocurrent distribution over both samples proportionally increases when relative humidity(RH)is raised from 10%to 60%.Notably,following a 24-h exposure at RH 60%,the compact-GB sample demonstrates:i)a reduction in the density of charged trap states at GBs,ii)higher photocurrent,accompanied by a noticeable decrease in current hysteresis compared to the open GB sample,and iii)further enhancement in device efficiency and crystallinity compared to devices with open GBs.These findings suggest that optimizing humidity conditions in engineering the GB chemistry can enhance the optoelectrical properties of GBs,ultimately leading to improved device performance.展开更多
A deep-undercooling rapid-solidification technique combining cyclic superheating and molten glass purification was employed to successfully prepare Cu60Ni40 and Cu65Ni35 alloys at various undercooling levels.Furthermo...A deep-undercooling rapid-solidification technique combining cyclic superheating and molten glass purification was employed to successfully prepare Cu60Ni40 and Cu65Ni35 alloys at various undercooling levels.Furthermore,through precise compositional regulation by adjusting the Cu content and introducing Co,the Cu60Ni35Co5 alloy was obtained.The morphological evolution of the solidification front and the variation in solidification rate with undercooling were systematically investigated.By combining metallographic analysis,the BCT model,electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM),the microstructural evolution and grain refinement mechanisms of the undercooled alloys were revealed.This work aims to establish the intrinsic relationship among undercooling,solidification behavior,and microstructure,thereby provides both experimental and theoretical foundations for a deeper understanding of the deep undercooling solidification mechanism and microstructural control.展开更多
The optimization of microstructure represents a significant methodology for enhancing coercivity(Hcj).This paper concentrates on optimizing the microstructure of magnets through the manipulation of the composition of ...The optimization of microstructure represents a significant methodology for enhancing coercivity(Hcj).This paper concentrates on optimizing the microstructure of magnets through the manipulation of the composition of low-melting-point and high-melting-point elements,thereby achieving the objective of augmenting the comprehensive magnetic properties of magnets.The present study is concerned with the microstructure of magnets comprising three distinct Ga and B contents,and the associated changes in their magnetic properties.The findings indicate that when the Ga content is 0.5 wt%and the B content is 0.88 wt%,the coercivity of the magnets is markedly enhanced.This is evidenced by an increase in coercivity from 8.51 to 14.83 kOe,representing a 74.26%rise.Concurrently,the residual magnetization strength of the magnet remains unaltered.This finding provides a crucial foundation for optimizing the overall magnetic properties of the magnets.The microstructural analysis indicates that a reduction in B content coupled with an increase in Ga content leads to the melting of sharp angles on the surface of the main-phase grains,facilitated by low-melting-point rare-earth-rich phases.This process results in the migration of Fe from the grain boundaries(GBs)to the triple junction phases(TJPs),while Nd migrates from the TJPs to the GBs.This migration results in a reduction in the agglomeration of rare-earth-rich elements within the TJPs,thereby increasing the Nd content in the GBs.This increase enhances the wettability of the GBs,while the reduction of Fe content in this phase mitigates the exchange-coupling effect between the main-phase GBs.Consequently,the GBs become more smooth,more homogeneous and more continuous,which ultimately results in an enhancement of the coercivity of the magnets.展开更多
The influences of silicon addition to commercially pure magnesium(CP Mg)and cooling rate during solidification on the as-cast microstructure and shear mechanical properties of Mg-Si alloys were systematically investig...The influences of silicon addition to commercially pure magnesium(CP Mg)and cooling rate during solidification on the as-cast microstructure and shear mechanical properties of Mg-Si alloys were systematically investigated.For this purpose,the Mg-0.6Si,Mg-1.34Si,and Mg-3Si(wt%)alloys were considered as hypoeutectic,eutectic,and hypereutectic alloys,respectively.By decreasing the geometrical modulus of the solidifying section(increasing cooling rate),remarkable grain refinement,refining the dendrite arm spacing(DAS),and modification of Mg_(2)Si particles were achieved.Moreover,the grain size was refined via Si addition in the hypoeutectic range,while coarsening of grain size at high Si concentrations was observed.The results of shear punch testing and hardness measurements demonstrated that the ultimate shear strength(USS)and hardness increased by increasing the cooling rate during solidification.Moreover,Si addition generally improved hardness,while the highest USS level was achieved for the eutectic alloy due to the fine grain size and strengthening effect of the eutectic constituent.However,regarding the hypereutectic Mg-3Si alloy that exhibited high hardness,the shear properties were inferior due to the detrimental effect of the primary Mg_(2)Si particles.Finally,the results were discussed with consideration of the relationship between strength and hardness,for which the critical effect of Si was clarified.展开更多
Understanding the temperature dependent deformation behavior of Mg alloys is crucial for their expanding use in the aerospace sector.This study investigates the deformation mechanisms of hot-rolled AZ61 Mg alloy under...Understanding the temperature dependent deformation behavior of Mg alloys is crucial for their expanding use in the aerospace sector.This study investigates the deformation mechanisms of hot-rolled AZ61 Mg alloy under uniaxial tension along rolling direction(RD)and transverse direction(TD)at-50,25,50,and 150℃.Results reveal a transition from high strength with limited elongation at-50℃ to significant softening and maximum ductility at 150℃.TD samples consistently showed 2%-6%higher strength than RD;however,this yield anisotropy diminished at 150℃ due to the shift from twinning to thermally activated slip and recovery.Fractography indicated a change from semi-brittle to fully ductile fracture with increasing temperature.Electron backscattered diffraction(EBSD)analysis confirmed twinning-driven grain refinement at low temperatures,while deformation at high temperatures involved grain elongation along shear zones,enabling greater strain accommodation before material failure.展开更多
Texture and grain structure evolution during annealing and their effects on tensile strength and anisotropy were studied using XRD,DSC,SEM,EBSD and TEM.The results indicate that elevated rolling temperatures reduce th...Texture and grain structure evolution during annealing and their effects on tensile strength and anisotropy were studied using XRD,DSC,SEM,EBSD and TEM.The results indicate that elevated rolling temperatures reduce the f(g)_(max(Copper))/f(g)_(max(Brass))ratio,increase S-Brass fine bands,and promote S-dispersoid precipitation,leading to finer recrystallized grains.Dominant recrystallization textures transform from Goss+P to Goss and then to Goss+Cube with increasing rolling temperature.Annealing at 350℃shows four tensile strength response stages:fast softening I,rapid strengthening II,slow strengthening III,and slow softening IV.The transition from Stages I to II is driven by the formation of strong Goss and P textures,and Stage IV is linked to enhanced Cube texture.Plates with Goss+Cube textures and fine equiaxed grains exhibit the lowest YS/UTS ratio and minimal anisotropy.展开更多
High-performance magnesium alloys are in great demand to meet the lightweight design requirements of aircraft.Grain size has long been recognized as a key factor influencing the mechanical properties of alloys.This st...High-performance magnesium alloys are in great demand to meet the lightweight design requirements of aircraft.Grain size has long been recognized as a key factor influencing the mechanical properties of alloys.This study investigates the effect of grain size,controlled by Zr addition,on the fatigue behavior of a recently developed low-cost Mg-2.6Nd-0.35Zn alloy,through systematic characterization and analysis of stress-life(S-N)curves,fatigue crack propagation,fracture surface morphology,stress intensity factor,and crack propagation threshold.The results show that after heat treatment(solution at 525±5℃ for 8 h and water quenching at 60-80℃,followed by aging at 250±5℃for 14 h and then air cooling),coarse-grained specimens(average grain size approximately 596μm)containing 0.12wt.%Zr exhibit greater resistance to fatigue crack propagation than fine-grained specimens(average grain size approximately 94μm)containing 0.46wt.%Zr.Coarse grains promote intergranular fracture,while fine grains favor transgranular fracture.In addition,coarse grains reduce the sensitivity of the crack tip to stress concentration.Furthermore,fine-grained samples demonstrate a longer total fatigue life,owing to their superior resistance to crack initiation,which significantly prolongs the crack initiation stage.These findings highlight the importance of optimizing grain size to achieve the best possible fatigue resistance in Mg-Nd-Zn-Zr alloys for practical engineering applications.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(23JRRA760,24JRRA175,25JRRA060)+1 种基金Hongliu Outstanding Youth Foundation of Lanzhou University of TechnologyLeading Innovative Talents Project of Changzhou(CQ20210111)。
文摘To elucidate the deformation mechanisms ofγ-TiAl,the nanoindentation experiments and crystal plasticity finite element(CPFE)simulation were employed to investigate the effects of crystal orientations and GBs on the mechanical properties ofγ-TiAl alloys.A crystal plasticity constitutive model was developed,and load-displacement curves,hardness,and Young's modulus were obtained for both single grains and GBs inγ-TiAl alloys.Based on the aforementioned model,this study investigated the distribution patterns of surface morphology around the indentation sites of individual grain and GBs.It also analyzed the cumulative shear strain distribution,slip system activation,and the interaction between GBs and dislocation slip for various crystal orientations.The results indicate that the mechanical response and pileup behavior exhibit significant anisotropy due to the interplay among the indenter geometry,material slip systems,and cumulative shear strain distribution.Moreover,the interaction between GBs and dislocation slip substantially alters dislocation distribution,thereby influencing material flow and playing a critical role in the mechanical response and plastic deformation of the material.
基金National Natural Science Foundation of China(2022YFF0609300)。
文摘The deformation behavior of GH4169 superalloy under room-temperature uniaxial tension was investigated through synchronized mesoscopic digital image correlation(DIC)and electron backscatter diffraction(EBSD)in-situ characterization techniques.Results show that in the field of grain deflection dynamics,through quantitative analysis using the independently developed M-DIC software,during uniaxial tension with significant bidirectional rotation along the tensile axis and the stress level of 1100 MPa,oscillatory rotation of±0.6°can be obtained,and microvoids are generated at the grain boundaries with 45°to the stress axis.EBSD crystallographic analysis demonstrates the load-dependent slip system evolution:in the initial stage,the soft-oriented systems with high Schmid factor(>0.4)is activated and then transformed into hard-oriented systems during cross-slip,generating parallel slip bands and dislocation pile-ups at grain boundaries.During the uniaxial tensile process,the characteristic of strain energy accumulation is observed,which follows a two-stage accumulation pattern:initial grain boundary localization(Stage I)and intragranular propagation(Stage II).Ultimately,the intergranular cracks are initiated at triple junctions,and the twin boundaries exhibit superior mechanical stability compared with the large-angle grain boundaries.Deformation texture characteristics indicate the copper-type components,including C{112}<111¯>,S{123}<634¯>,and B{110}<11¯0>.The complete deformation sequence is as follows:cross-slip of soft-oriented slip systems→initiation of dislocation slip→strain partitioning through grain rotation→intergranular stress concentration→damage dominated by boundary cracking.The cross-scale deformation mechanism revealed in this study provides critical guidance for the crystal boundary engineering to optimize nickel-based superalloys.
基金National Natural Science Foundation of China(52375394,52275390,U23A20628,52305429)Major Project of Science and Technology in Shanxi(202301050201004)Natural Science Foundation of Shanxi Province(202403021222132)。
文摘Using multi-directional forging temperature as the independent variable and adopting the dual-mode phase field crystal model,the nucleation modes,reaction mechanisms,and interactions between grain boundaries and dislocations at different temperatures were investigated.Results show that a mapping relationship between process parameters and grain refinement/coarsening is established,and the optimal processing temperature coefficient is 0.23.Compared with the cases with processing temperature coefficient of 0.19,0.20,0.21,0.25,and 0.27,the refinement effect increases by 256.0%,146.0%,113.0%,6.7%,and 52.4%,respectively.Excessively high temperatures lead to grain coarsening due to dislocation annihilation,and the application of strain can reduce the actual melting point of materials.Even if the processing temperature does not exceed the theoretical melting point,remelting and crystallization may still occur,resulting in an overburning phenomenon that reduces internal defects and increases overall grain size.This research is of great significance for the actual forging process design.
基金National Natural Science Foundation of China(52071065)Fundamental Research Funds for the Central Universities(N2007007)+2 种基金Joint Fund of Henan Province Science and Technology R&D Program(N225200810040)High-Level Talent Research Start-Up Project Funding of Henan Academy of Sciences(N242017003)Liaoning Provincial Department of Education Basic Research Projects for Colleges and Universities(LJ212410142093)。
文摘The effect of trace addition of 0.1wt%Y on the grain refinement and mechanical properties of Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc alloys at as-cast and heat-treated states was investigated.Results show that the addition of 0.1wt%Y into the Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc alloys can elevate the nucleation temperature of the Al_(3)(Sc,Zr)phase,leading to the preferential precipitation of the Al_(3)(Sc,Zr)phase and increasing the amount of Al_(3)(Sc,Zr)phase in the matrix.Al_(3)(Sc,Zr)phase can also act as a heterogeneous nucleation site in theα-Al matrix to promote nucleation and refine grains.The addition of element Y changes the precipitation phase characteristics at the grain boundaries in the as-cast alloy,which changes the distribution characteristics of secondary phases from initially continuous and coarse strip-like distribution at grain boundaries into the discontinuous dot-like and rod-like distribution.Besides,the size of secondary phases becomes smaller and their amount increases.Under the combined effects of grain refinement strengthening and precipitation strengthening,the Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc-0.1Y alloy after 175℃/10 h aging treatment achieves an ultimate tensile strength of 412 MPa and an elongation of 6.3%.Compared with those of the alloy without Y addition,the ultimate tensile strength and elongation of the added alloy increase by 16.1%and 53.7%,respectively.
基金National MCF Energy R&D Program of China(2018YFE0306100)Natural Science Foundation of Hunan Province for Distinguished Young Scholars(2021JJ10062)+1 种基金National Natural Science Foundation of China(52101028)China Postdoctoral Science Foundation(2021M703628)。
文摘Combining the phase-field method and the moving boundary method,a three-dimensional phase-field simulation was conducted for the growth and grain evolution of Ti films deposited by physical vapor deposition under different deposition rates and grain orientations.The evolution of grain morphology and grain orientation was also taken into consideration.Simulation results show that at lower deposition rates,the surface of the formed Ti film exhibits a distinct oriented texture structure.The surface roughness of the Ti film is positively correlated with the grain misorientation.Moreover,the surface roughness obtained from the simulation is in good agreement with the experiment results.
基金co-supported by the National Natural Science Foundation of China(Nos.52305421 and 52175363)the General Research Fund of Hong Kong,China(No.15223520)the projects from the Hong Kong Polytechnic University,China(Nos.4-W418,1-ZE1W,4-WZ4W and 1-CD4H)。
文摘Gradient microstructures strengthened by serrated Grain Boundaries(GBs)were achieved through a combination of Gradient Strain Deformation(GSD)and Serration Heat Treatment(SHT),with particular focus on microstructural evolution,underlying mechanisms,and the critical influencing factors.Dynamic recrystallization governed the microstructural evolution in the fine-grained and transition regions during GSD,where multiple nucleation mechanisms were active.Plastic deformation facilitated the dissolution ofγ'phase in fine-grained regions,ultimately resulting in its morphological transformation.During the subsequent SHT,serrated GBs formed within the gradient microstructures produced by prior GSD without disrupting the grain size gradient,thereby enhancing creep resistance.Two distinct mechanisms associated withγ'gbparticles governed the formation of the serrations at GBs.Owing to the stronger dragging effect of grain boundary junctions in fine-grained regions,the amplitude and wavelength of serrations in these regions were smaller than those in coarse-grained regions.Moreover,the formation of serrations exhibited a strong dependence on the inherent properties of the GBs.The random high-angle grain boundaries(HAGBs)with misorientation angles in the range of 30-59°tended to become serrated more easily during SHT due to their high mobility and the accelerated precipitation ofγ'gbparticles at them.Low-ΣHAGBs and low-angle GBs were not prone to form serrations.In particular,serration formation was completely inhibited atΣ3 twin boundaries due to their extremely low mobility and the absence ofγ'gbparticles.
基金supported by JSPS KAKENH1 Grant Number 19J22534.
文摘Gas-solid flows are ubiquitous in industrial systems.The coupled model of the discrete element method(DEM)and computational fluid dynamics(CFD)is one of the techniques for the simulation of the gas-solid flows.To enhance the applicability of the DEM-CFD method,the coarse graining DEM has been developed to simulate large-scale powder systems.The coarse graining DEM is a scaling law model and hence can simulate large-scale systems using a smaller number of particles than the actual one.Although the coarse graining DEM enables to effectively simulate large-scale powder systems on a single PC,visualized image is lack of reality due to reduced spatial resolution.Here a novel visualization method is developed to produce realistic images.In the proposed technique,the virtual particles are located by considering the motion and location of the coarse grain particles.To show the adequacy of the proposed method,two types of visualization based on the computational results are made:a blow-up of powder due to injected gas flow and a spouted bed.In these systems,the visualized images are shown to be improved by the proposed visualization technique.The effectiveness of the proposed method is proved by the agreement of the images based on the calculation results between the standard DEM-CFD method and coarse graining DEM.
基金financially supported by the National Key R&D Program of China(2024YFD1200800)the Guangdong Basic and Applied Basic Research Foundation,China(2024A1515030094)。
文摘Highlights OsCAX2 is localized to tonoplast,and cadmium induces its expression.OsCAX2 overexpression reduces cadmium concentration in indica rice grains by 49.1%.Cadmium(Cd)exposure poses significant health risks to humans,and the International Agency for Research on Cancer has classified it as a Group I carcinogen.Cadmium undergoes minimal metabolism in the human body;consequently,prolonged Cd^(2+)exposure can cause severe damage to multiple organs including the liver,kidneys,lungs,bones,and immune system(Shao et al.2024).Rice,one of the three global staple crops,and Cd exposure in humans primarily occurs the consumption of contaminated rice grains.The contribution of rice to the total dietary Cd intake is over 50% for non-smoking Asian populations(Chen et al.2018;Shi et al.2020).
基金supported by the director of Indian Council of Agricultural Research and International Rice Research Institute (ICAR-CRRI), Cuttack, Indiathe coordinator of the ICAR-sponsored project ‘C-reactive protein (CRP) in Biofortification in Selected Crops’, India
文摘CR Dhan 310(CRD310),a biofortified rice variety,contains a significantly higher level of grain protein compared with its recurrent parent Naveen(NV),as well as most adapted high-yielding rice varieties in India.Although a limited investigation depicted that CRD310 contained higher levels of glutelin and some essential amino acids,detailed biochemical,molecular,and cellular mechanisms remain to be studied.As one of the means to identify the proteins and understand the underlying mechanism of higher proteins accumulation in grains of CRD310,the comparative proteomics was undertaken on grains of CRD310 and NV at the yellow ripening stage.
基金supported by the National Natural Science Foundation of China(42471336,52379021 and 42201278)the Hebei Province Backbone Talent Program,China(Returnee Platform for Overseas Study)(A20240028)+2 种基金the Hebei Province Statistical Science Research Project,China(2024HZ04)the Hebei Province Graduate Education and Teaching Reform Research Project,China(YJG2024046)the Innovation Ability Training Program for Postgraduate Students of Hebei Provincial Department of Education,China(CXZZSS2025048)。
文摘A comprehensive assessment of grain supply,demand,and ecosystem service flows is essential for identifying grain movement pathways,ensuring regional grain security,and guiding sustainable management strategies.However,current studies primarily focus on short-term grain provision services while neglecting the spatiotemporal variations in grain flows across different scales.This gap limits the identification of dynamic matching relationships and the formulation of optimization strategies for balancing grain flows.This study examined the spatiotemporal evolution of grain supply and demand in the Beijing-Tianjin-Hebei(BTH)region from 1980 to 2020.Using the Enhanced TwoStep Floating Catchment Area method,the grain provision ecosystem service flows were quantified,the changes in supply–demand matching under different grain flow scenarios were analyzed and the optimal distance threshold for grain flows was investigated.The results revealed that grain production follows a spatial distribution pattern characterized by high levels in the southeast and low levels in the northwest.A significant mismatch exists between supply and demand,and it shows a scale effect.Deficit areas are mainly concentrated in the northwest,while surplus areas are mainly located in the central and southern regions.As the spatial scale increases,the ecosystem service supply–demand ratio(SDR)classification becomes more clustered,while it exhibits greater spatial SDR heterogeneity at smaller scales.This study examined two distinct scenarios of grain provision ecosystem service flow dynamics based on 100 and 200 km distance thresholds.The flow increased significantly,from 2.17 to 11.81million tons in the first scenario and from 2.41 to 12.37 million tons in the second scenario over nearly 40 years,forming a spatial movement pattern from the central and southern regions to the surrounding areas.Large flows were mainly concentrated in the interior of urban centers,with significant outflows between cities such as Baoding,Shijiazhuang,Xingtai,and Hengshui.At the county scale,supply–demand matching patterns remained consistent between the grain flows in the two scenarios.Notably,incorporating grain flow dynamics significantly reduced the number of grain-deficit areas compared to scenarios without grain flow.In 2020,grain-deficit counties decreased by28.79 and 37.88%,and cities by 12.50 and 25.0%under the two scenarios,respectively.Furthermore,the distance threshold for achieving optimal supply and demand matching at the county scale was longer than at the city scale in both grain flow scenarios.This study provides valuable insights into the dynamic relationships and heterogeneous patterns of grain matching,and expands the research perspective on grain and ecosystem service flows across various spatiotemporal scales.
基金The National Natural Science Foundation of China(Grant No.12462006)Beijing Institute of Structure and Environment Engineering Joint Innovation Fund(No.BQJJ202414).
文摘THE mechanical response and deformation mechanisms of pure nickel under nanoindentation were systematically investigated using molecular dynamics(MD)simulations,with a particular focus on the novel interplay between crystallographic orientation,grain boundary(GB)proximity,and pore characteristics(size/location).This study compares single-crystal nickel models along[100],[110],and[111]orientations with equiaxed polycrystalline models containing 0,1,and 2.5 nm pores in surface and subsurface configurations.Our results reveal that crystallographic anisotropy manifests as a 24.4%higher elastic modulus and 22.2%greater hardness in[111]-oriented single crystals compared to[100].Pore-GB synergistic effects are found to dominate the deformation behavior:2.5 nm subsurface pores reduce hardness by 25.2%through stress concentration and dislocation annihilation at GBs,whereas surface pores enable mechanical recovery via accelerated dislocation generation post-collapse.Additionally,size-dependent deformation regimes were identified,with 1 nm pores inducing negligible perturbation due to rapid atomic rearrangement,in contrast with persistent softening in 2.5 nm pores.These findings establish atomic-scale design principles for defect engineering in nickel-based aerospace components,demonstrating how crystallographic orientation,pore configuration,and GB interactions collectively govern nanoindentation behavior.
基金support from the Australian Research Council through Discovery Grants and the ARC Centre of Excellence in Future Low-Energy Electronics Technologies(FLEET)supported by the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(NRF-2021K1A4A7A03093851)+1 种基金J.S.Y.acknowledges the Royal Society research grant(RGS/R1/221369)the support by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MEST)(RS-2023-00257494 and 2022H1D3A2A01082324).
文摘Mixed halide perovskites exhibit great potential as materials for the future generation of photovoltaic devices.Yet,their reaction to moisture remains uncertain,necessitating further exploration.While prolonged exposure to moisture can lead to degradation,it can also passivate traps at an optimal moisture level.Here,we use scanning probe microscopy to perform nanoscale moisture-dependent photovoltaic characterizations of open and compressed grain boundary(GB)structures of wide bandgap(FAPbI_(3))_(0.3)(FAPbBr_(3))_(0.7) perovskites.The investigation reveals a decrease in the potential barrier at compact GBs with increasing moisture levels,contrasting with the behavior observed in open GBs.Moreover,the photocurrent distribution over both samples proportionally increases when relative humidity(RH)is raised from 10%to 60%.Notably,following a 24-h exposure at RH 60%,the compact-GB sample demonstrates:i)a reduction in the density of charged trap states at GBs,ii)higher photocurrent,accompanied by a noticeable decrease in current hysteresis compared to the open GB sample,and iii)further enhancement in device efficiency and crystallinity compared to devices with open GBs.These findings suggest that optimizing humidity conditions in engineering the GB chemistry can enhance the optoelectrical properties of GBs,ultimately leading to improved device performance.
基金Funded by the Central Government-Guided Local Development Fund Project(No.YDZJSX2025D042)the Key R&D Program of Shanxi Province(No.202202150401018)+1 种基金the Basic Research Program of Shanxi Province(No.202503021211112)the State Key Laboratory of CAD/CG of Zhejiang University(No.A2325)。
文摘A deep-undercooling rapid-solidification technique combining cyclic superheating and molten glass purification was employed to successfully prepare Cu60Ni40 and Cu65Ni35 alloys at various undercooling levels.Furthermore,through precise compositional regulation by adjusting the Cu content and introducing Co,the Cu60Ni35Co5 alloy was obtained.The morphological evolution of the solidification front and the variation in solidification rate with undercooling were systematically investigated.By combining metallographic analysis,the BCT model,electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM),the microstructural evolution and grain refinement mechanisms of the undercooled alloys were revealed.This work aims to establish the intrinsic relationship among undercooling,solidification behavior,and microstructure,thereby provides both experimental and theoretical foundations for a deeper understanding of the deep undercooling solidification mechanism and microstructural control.
基金Project supported by the National Key Research and Development Program of China(2022YFB3503302)the Major Projects in Inner Mongolia Autonomous Region(20212D0035)the High-quality Development Special Funds Program Ministry of Industry Technology(TC220H06G)。
文摘The optimization of microstructure represents a significant methodology for enhancing coercivity(Hcj).This paper concentrates on optimizing the microstructure of magnets through the manipulation of the composition of low-melting-point and high-melting-point elements,thereby achieving the objective of augmenting the comprehensive magnetic properties of magnets.The present study is concerned with the microstructure of magnets comprising three distinct Ga and B contents,and the associated changes in their magnetic properties.The findings indicate that when the Ga content is 0.5 wt%and the B content is 0.88 wt%,the coercivity of the magnets is markedly enhanced.This is evidenced by an increase in coercivity from 8.51 to 14.83 kOe,representing a 74.26%rise.Concurrently,the residual magnetization strength of the magnet remains unaltered.This finding provides a crucial foundation for optimizing the overall magnetic properties of the magnets.The microstructural analysis indicates that a reduction in B content coupled with an increase in Ga content leads to the melting of sharp angles on the surface of the main-phase grains,facilitated by low-melting-point rare-earth-rich phases.This process results in the migration of Fe from the grain boundaries(GBs)to the triple junction phases(TJPs),while Nd migrates from the TJPs to the GBs.This migration results in a reduction in the agglomeration of rare-earth-rich elements within the TJPs,thereby increasing the Nd content in the GBs.This increase enhances the wettability of the GBs,while the reduction of Fe content in this phase mitigates the exchange-coupling effect between the main-phase GBs.Consequently,the GBs become more smooth,more homogeneous and more continuous,which ultimately results in an enhancement of the coercivity of the magnets.
文摘The influences of silicon addition to commercially pure magnesium(CP Mg)and cooling rate during solidification on the as-cast microstructure and shear mechanical properties of Mg-Si alloys were systematically investigated.For this purpose,the Mg-0.6Si,Mg-1.34Si,and Mg-3Si(wt%)alloys were considered as hypoeutectic,eutectic,and hypereutectic alloys,respectively.By decreasing the geometrical modulus of the solidifying section(increasing cooling rate),remarkable grain refinement,refining the dendrite arm spacing(DAS),and modification of Mg_(2)Si particles were achieved.Moreover,the grain size was refined via Si addition in the hypoeutectic range,while coarsening of grain size at high Si concentrations was observed.The results of shear punch testing and hardness measurements demonstrated that the ultimate shear strength(USS)and hardness increased by increasing the cooling rate during solidification.Moreover,Si addition generally improved hardness,while the highest USS level was achieved for the eutectic alloy due to the fine grain size and strengthening effect of the eutectic constituent.However,regarding the hypereutectic Mg-3Si alloy that exhibited high hardness,the shear properties were inferior due to the detrimental effect of the primary Mg_(2)Si particles.Finally,the results were discussed with consideration of the relationship between strength and hardness,for which the critical effect of Si was clarified.
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea Program(No.RS-2025-02603127,Innovation Research Center for Zero-carbon Fuel Gas Turbine Design,Manufacture,and Safety)。
文摘Understanding the temperature dependent deformation behavior of Mg alloys is crucial for their expanding use in the aerospace sector.This study investigates the deformation mechanisms of hot-rolled AZ61 Mg alloy under uniaxial tension along rolling direction(RD)and transverse direction(TD)at-50,25,50,and 150℃.Results reveal a transition from high strength with limited elongation at-50℃ to significant softening and maximum ductility at 150℃.TD samples consistently showed 2%-6%higher strength than RD;however,this yield anisotropy diminished at 150℃ due to the shift from twinning to thermally activated slip and recovery.Fractography indicated a change from semi-brittle to fully ductile fracture with increasing temperature.Electron backscattered diffraction(EBSD)analysis confirmed twinning-driven grain refinement at low temperatures,while deformation at high temperatures involved grain elongation along shear zones,enabling greater strain accommodation before material failure.
基金financial support from the National Key Research and Development Program of China(No.2016YFB0300900)the National Key Fundamental Research Project of China(No.2012CB619506-3)the National Natural Science Foundation of China(No.51171209)。
文摘Texture and grain structure evolution during annealing and their effects on tensile strength and anisotropy were studied using XRD,DSC,SEM,EBSD and TEM.The results indicate that elevated rolling temperatures reduce the f(g)_(max(Copper))/f(g)_(max(Brass))ratio,increase S-Brass fine bands,and promote S-dispersoid precipitation,leading to finer recrystallized grains.Dominant recrystallization textures transform from Goss+P to Goss and then to Goss+Cube with increasing rolling temperature.Annealing at 350℃shows four tensile strength response stages:fast softening I,rapid strengthening II,slow strengthening III,and slow softening IV.The transition from Stages I to II is driven by the formation of strong Goss and P textures,and Stage IV is linked to enhanced Cube texture.Plates with Goss+Cube textures and fine equiaxed grains exhibit the lowest YS/UTS ratio and minimal anisotropy.
文摘High-performance magnesium alloys are in great demand to meet the lightweight design requirements of aircraft.Grain size has long been recognized as a key factor influencing the mechanical properties of alloys.This study investigates the effect of grain size,controlled by Zr addition,on the fatigue behavior of a recently developed low-cost Mg-2.6Nd-0.35Zn alloy,through systematic characterization and analysis of stress-life(S-N)curves,fatigue crack propagation,fracture surface morphology,stress intensity factor,and crack propagation threshold.The results show that after heat treatment(solution at 525±5℃ for 8 h and water quenching at 60-80℃,followed by aging at 250±5℃for 14 h and then air cooling),coarse-grained specimens(average grain size approximately 596μm)containing 0.12wt.%Zr exhibit greater resistance to fatigue crack propagation than fine-grained specimens(average grain size approximately 94μm)containing 0.46wt.%Zr.Coarse grains promote intergranular fracture,while fine grains favor transgranular fracture.In addition,coarse grains reduce the sensitivity of the crack tip to stress concentration.Furthermore,fine-grained samples demonstrate a longer total fatigue life,owing to their superior resistance to crack initiation,which significantly prolongs the crack initiation stage.These findings highlight the importance of optimizing grain size to achieve the best possible fatigue resistance in Mg-Nd-Zn-Zr alloys for practical engineering applications.
