Asymmetric tilt boundaries on conventional twin boundaries(TBs)are significant for understanding the role of twins on coordinating plastic deformation in many metallic alloys.However,the formation modes of many asymme...Asymmetric tilt boundaries on conventional twin boundaries(TBs)are significant for understanding the role of twins on coordinating plastic deformation in many metallic alloys.However,the formation modes of many asymmetric tilt boundaries are hard to be accounted for based on traditional theoretical models,and the corresponding solute segregation is complex.Herein,atomic structures of a specific asymmetric boundary on{1012}TBs were reveled using aberration-corrected high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),molecular dynamics(MD)and density functional theory(DFT)simulations.Reaction between<a60>M dislocations and the{1012}TB can generate a~61°/25°asymmetric tilt boundary.The segregation of Gd and Zn atoms is closely related to the aggregateddislocations and the interfacial interstices of the asymmetric tilt boundary,which is energetically favorable in reducing the total system energy.展开更多
Deformation twinning in a WE43 alloy subjected to uniaxial compression at room temperature is in-vestigated.Active{1121}and{1012}extension twinning is observed.The activation of{1121}twinning in a certain grain is inf...Deformation twinning in a WE43 alloy subjected to uniaxial compression at room temperature is in-vestigated.Active{1121}and{1012}extension twinning is observed.The activation of{1121}twinning in a certain grain is influenced not only by its own Schmid factor,but also by that of the basal slip.Twin-twin interactions of the co-zone{1121}twin variants are commonly observed and systematically studied,including the crystallographic characteristics of the four typically observed twin-twin junctions(TTJs)and the associated twin-twin boundaries.Unlike the quilted-looking TTJs formed by the interaction of co-zone{1012}twin variants,crossing-like TTJs of co-zone{1121}twin variants are observed and their formation mechanisms are discussed.Crossing-like TTJs are also formed by the interaction of{1121}and{10¯12}twins.The morphology and thickening rate of{1121}and{1012}twins vary markedly due to the difference in twinning shear.The needle-like{1121}twins thicken more slowly than the lenticular{1012}twins.Twin nucleation is observed on the previously formed{1121}twin boundary due to the relatively large strain concentration on such interface,while twin nucleation on{1012}twin boundary is rarely observed.展开更多
Tension-compression asymmetry is a critical concern for magnesium(Mg)alloys,particularly in automo-tive crash structures.This study systematically examines the tension-compression asymmetry of a cast Mg-Gd-Y alloy at ...Tension-compression asymmetry is a critical concern for magnesium(Mg)alloys,particularly in automo-tive crash structures.This study systematically examines the tension-compression asymmetry of a cast Mg-Gd-Y alloy at various strain rates.Experimental results indicate symmetric yielding stress under both tension and compression at all strain rates,along with a reduction in the tension-compression asym-metry of ultimate stress and plastic strain as the strain rate increases.This trend arises from an unusual strain rate-dependent tension-compression asymmetry,characterized by strain rate toughening in tension and negligible strain rate effect in compression.The differing behavior is linked to the distinct twinning mechanisms under tension and compression.The suppression of twinning under tension contributes to the positive strain rate dependence of pyramidal slip,whereas the activation of abundant twins during compression means that pyramidal slip is unnecessary to accommodate c-axis strain,leading to the ab-sence of a strain rate effect in compression.Abundant twins nucleate consistently from yielding to 2%strain,but only after basal and prismaticslip have mediated microplasticity,suggesting that these slip systems reduce the nucleation stress for twinning during compression,resulting in a lower activation stress for twinning compared to tension.This study provides new insights into micromechanisms of the tension-compression asymmetry in cast Mg-Gd-Y alloys and offers practical guidance for the application of these materials in critical components that must endure both tension and compression under varying strain rates.展开更多
1.Introduction.Twinning is a fundamental mechanism for plastic deformation in many face-centered cubic(FCC)metals having low stacking fault energies(SFEs)[1,2].In particular,twinning-induced plasticity(TWIP)alloys hav...1.Introduction.Twinning is a fundamental mechanism for plastic deformation in many face-centered cubic(FCC)metals having low stacking fault energies(SFEs)[1,2].In particular,twinning-induced plasticity(TWIP)alloys have excellent tensile properties as a result of the intensive twinning activity[3-5].The twin boundaries also have been proven to contribute to an improved strengthening-toughening effect,mechanical stability and even fatigue performance,relative to high-angle grain boundaries and low-angle grain boundaries[6-11].Therefore,it is of major interest to clarify the twinning mechanism and thereby improve the mechanical properties of metallic materials.展开更多
A strong basal texture is typically developed in magnesium alloy sheets that have been subjected to the rolling process.Consequently,their mechanical properties and formability are significantly impaired,which in turn...A strong basal texture is typically developed in magnesium alloy sheets that have been subjected to the rolling process.Consequently,their mechanical properties and formability are significantly impaired,which in turn restricts potential applications.In this study,an innovative texture-altering technique,which involves in-plane free compression and width-constrained rolling(FCWR),is used for AZ31 alloy sheets in order to manufacture magnesium alloy sheets with both high strength and high ductility.During FCWR deformation process,a substantial number of tensile twins and a small quantity of(1012)-(01¯12)twin-twin boundaries are induced to coordinate plastic deformation.It is precisely the presence of such crossed twins that impedes the detwinning of partial twins under low-stress conditions.The retained twins hinder the motion of dislocation,thereby enhancing the strength.Specifically,the yield strength of preset crossed twins sample along rolling direction,45°and transverse direction has increased by 105%,16.8%and 23%,respectively.Additionally,the ultimate tensile strength along these three directions has increased by 42.7%,25.5%and 34.8%,respectively.The twin boundaries in FCWR sample consist of steps,which correspond to basal-prismatic(BP/PB)boundaries that connect straight terraces which are parallel to theoretical{10¯12}twin boundaries.Furthermore,as the number of processing passes increases,the step features become more pronounced.Compared with the as-received sample,the YS enhancement in the sample prepared via the second pass of the FCWR process is attributed to two primary mechanisms:grain refinement strengthening contributes 61 MPa,while dislocation strengthening accounts for 90 MPa.展开更多
This study investigates the influence of initial crystallographic texture on the deformation mechanisms during three-point bending of AZ31 Mg alloy sheets.Three distinct orientations are examined by using the followin...This study investigates the influence of initial crystallographic texture on the deformation mechanisms during three-point bending of AZ31 Mg alloy sheets.Three distinct orientations are examined by using the following bending specimens:(i)the normal direction(ND)sample,where the c-axes are predominantly aligned along the specimen thickness,(ii)the rolling direction(RD)sample,where the c-axes are mostly aligned along the longitudinal direction,and(iii)the 45 sample,where the c-axes are tilted at approximately 45°from both the thickness and longitudinal directions.The bending properties vary significantly depending on the initial texture,thereby affecting the strain accommodation and dominant deformation modes.The ND sample exhibits the lowest bendability due to its unfavorable orientation for{10–12}extension twinning and basal slip,which results in poor strain accommodation and early crack initiation in the outer tensile side.By comparison,the RD sample demonstrates an approximately 22.1%improvement,with extensive{10–12}extension twinning in the outer tensile zone.Meanwhile,the 45 sample exhibits the highest bendability(approximately 75.7%greater than that of the ND sample)due to sustained activation of both basal slip and{10–12}extension twinning,promoting uniform strain distribution and delaying fracture.Detailed electron backscatter diffraction analysis reveals that the 45 sample retains favorable crystallographic orientations for basal slip throughout bending,minimizing strain localization and enhancing the bendability.These findings highlight the importance of tailoring the initial texture in order to optimize the bending properties of Mg alloy sheets,and provide valuable insights for improving the manufacturability of Mg-based structural components.展开更多
Theoretically,a twinning dislocation must stay on the twinning plane which is the first invariant plane of a twinning mode,because the glide of twinning dislocation linearly transforms the parent lattice to the twin l...Theoretically,a twinning dislocation must stay on the twinning plane which is the first invariant plane of a twinning mode,because the glide of twinning dislocation linearly transforms the parent lattice to the twin lattice.However,recent experimental observations showed that a{1011}{1012}twin variant could cross another variant during twin-twin interaction.It is well known that{1011}twinning is mediated by zonal twinning dislocations.Thus,how the zonal twinning dislocations transmute during twin-twin interaction is of great interest but not well understood.In this work,atomistic simulation is performed to investigate interaction between{1011}twin variants.Our results show that when an incoming twin variant impinges on the other which acts as a barrier,surprisingly,the barrier twin can grow at the expense of the incoming twin.Eventually one variant consumes the other.Structural analysis shows that the twinning dislocations of the barrier variant are able to penetrate the zone of twin-twin intersection,by plowing through the lattice of one variant and transform its lattice into the lattice of the other.Careful lattice correspondence analysis reveals that,the lattice transformation from one variant to the other is close to{1012}{1011}twinning,but the orientation relationship deviates by a minor lattice rotation.This deviation presents a significant energy barrier to the lattice transformation,and thus it is expected such a twin-twin interaction will increase the stress for twin growth.展开更多
In this study,the typical Mg-14Gd-0.3Zr alloy was rolled at the high-temperature range of 450–500℃.The rolled Mg alloy plate with thickness of 30 mm exhibits an ultra-high ultimate tensile strength of 428 MPa and el...In this study,the typical Mg-14Gd-0.3Zr alloy was rolled at the high-temperature range of 450–500℃.The rolled Mg alloy plate with thickness of 30 mm exhibits an ultra-high ultimate tensile strength of 428 MPa and elongation of 3.4%,which has rarely been reported,and the strong fiber texture played a critical role in strengthening.The mechanisms underlying the evolution of texture during rolling were systematically investigated.At the early stage of rolling,alloys(450℃and 475℃)exhibited a[10.10]texture due to twinning assisted by Prismaticslipping.At 500℃,the alloy underwent nearly complete dynamic recrystallization(DRX)process.With increasing the rolling reduction,the DRX occurred in the whole temperature range,exhibiting the typical[10.10]–[11.20]double fiber texture.For continuous DRX,Prismaticdislocations accumulate to form grains with 30°[0001]grain boundaries,which exhibit a[10.10]fiber texture.During discontinuous DRX,Prismaticslip induced grain rotation around the[0001]axis,stabilizing either the<10.10>//RD(rolling direction)or<11.20>//RD orientations,leading to the formation of[10.10]–[11.20]double fiber texture.TEM observations confirmed that Prismaticdislocations can accumulate to form sub-grain lamellae,which gradually transform into high-angle grain boundaries by absorbing more Prismaticdislocations.First-principle calculation demonstrated that with increasing Gd content,the unstable stacking fault energy of prismatic slipping significantly decreases,promoting the activation of Prismaticslipping.These findings elucidate the critical role of twinning and Prismaticdislocations in texture evolution and the DRX process during thick plate rolling of the high-Gd content Mg-Gd-Zr alloy.展开更多
The evolution of microstructure and texture in Mg-3Al-1Zn-1Ca alloy sheets subjected to in-plane shear(IPS)loading was investigated using experimental techniques and viscoplastic self-consistent(VPSC)modeling.The spec...The evolution of microstructure and texture in Mg-3Al-1Zn-1Ca alloy sheets subjected to in-plane shear(IPS)loading was investigated using experimental techniques and viscoplastic self-consistent(VPSC)modeling.The specimens were deformed under varying degrees of IPS strain(γ12=0.05,0.10,and 0.15)using a customized jig.Electron backscatter diffraction(EBSD)observations revealed profuse tensile twinning(TTW)even at an IPS strain of 0.05,with its intensity continuously increased as the IPS strain increased.The TTWs progressively engulfed parent grains with increasing shear strain,evolving into an unusual deformation twin morphology.Furthermore,VPSC model predictions confirmed basal slip as the dominant deformation mode at low IPS strains,transitioning to prismatic slip dominance at higher IPS strains.The activity of the TTW mode was significantly higher during the initial stages of IPS strain and saturated to lower values at higher strains.VPSC simulation results also indicated preferential shear accumulation on a single twin system,explaining the phenomenon of a single twin variant engulfing a parent grain.Additionally,the influence of individual slip and twin modes on texture evolution was evaluated through orientation tracking of representative grains at various shear strain increments using VPSC simulation.The simulation results quantitatively highlighted the activities of basal slip,prismatic slip,and tensile twinning,establishing a correlation between texture evolution and the underlying deformation mechanisms.展开更多
The effects of varying strain rates and deformation temperatures on the microstructure evolution of the FGH4113A alloy were investigated through hot compression experiments.During hot deformation,grain evolution is pr...The effects of varying strain rates and deformation temperatures on the microstructure evolution of the FGH4113A alloy were investigated through hot compression experiments.During hot deformation,grain evolution is primarily governed by dynamic recrystallization(DRX)and twinning primarily.Furthermore,the pinning effect of the primaryγ'phase(γ'p phase)plays a crucial role in grain refinement.Lower strain rates or higher temperatures facilitate DRX,twinning,and the dissolution of theγ'p phase.At 1140℃,significant dissolution of theγ'p phase and the subsequent loss of its pinning effect reduce twinning activity.A unique twinning mechanism,termed“pinning twinning”,is identified,occurring exclusively under the influence of the pinning effect.When grain boundary migration fails to accommodate dislocations due to the pinning effect,grains preferentially eliminate dislocations via twinning,thereby reducing local strain energy.The grain size prediction model is improved by considering the pinning effect.展开更多
Nanopowder consolidation under high strain rate shock compression is a potential method for synthesizing and processing bulk nanomaterials,and a thorough investigation of the deformation and its underlying mechanisms ...Nanopowder consolidation under high strain rate shock compression is a potential method for synthesizing and processing bulk nanomaterials,and a thorough investigation of the deformation and its underlying mechanisms in consolidation is of great engineering significance.We conduct non-equilibrium molecular dynamics(NEMD)simulation and X-ray diffraction(XRD)simulation to systematically study shock-induced deformation and the corresponding mechanisms during the consolidation of nanopowdered Mg(NP-Mg).Two different deformation modes govern the shock consolidation in NP-Mg,i.e.,deformation twinning at up≤1.5 km s^(-1)and structural disordering,at up≥2.0 km s^(-1).They accelerate the collapse of nanopores and void compaction,giving rise to the final consolidation of NP-Mg.Three types of deformation twinning are emitted in NP-Mg,i.e.,the extension twinning for{1121}(1126),and{1102}〈1101>,and the compression{1122}(1123)twinning.They are prompted via coupling atomic shuffles and slips.Deformation twinning prefers to occur within the grains as shock along<1120>or its approaching direction(A-and B-type grains),originated from the high-angle grain boundaries(HAGB)at compression stage.They are inhibited within the ones as shocking along<0001>and the approaching ones(C-and D-type grains).The release and tension loading facilitates the reversible and irreversible detwinning,for the extension and compression twinning,respectively,within the A-and B-type grains.It also contributes to a compression-tension asymmetry for twinning,i.e.,release and tension induced extension twinning within the C-and D-type grains.The subsequent spallation is mediated by GB sliding and GB-induced stacking faults at up≤1.5 km s^(-1),and structural disordering at up≥2.0 km s^(-1).展开更多
In the study,three 16Cr-25.5Ni-4.2Mo superaustenitic stainless steel weld metals with C contents of 0.082 wt%,0.075 wt%,and 0.045 wt%,were prepared to investigate the microstructural evolution and its effect on mechan...In the study,three 16Cr-25.5Ni-4.2Mo superaustenitic stainless steel weld metals with C contents of 0.082 wt%,0.075 wt%,and 0.045 wt%,were prepared to investigate the microstructural evolution and its effect on mechanical behavior.At a C content of 0.082 wt%,the microstructure of weld metal consisted of austenite,M_(6)C,and M_(23)C_(6),where M_(6)C was the main carbide.The number and average size of the M_(6)C carbides significantly decreased as the C content decreased.At a C content of 0.045 wt%,only a very small number of M_(6)C carbides were observed in the weld metal.For the tensile process,the number of deformation twins increased as the C content decreased,which introduced a stronger dynamic Hall-Petch effect,resulting in only a small decrease in the ultimate tensile strength of the weld metal.Meanwhile,the increase in deformation twins significantly enhanced the elongation of the weld metals.For the impact process,the impact energy increased from 204 to 241 J as the C content decreased.The crack initiation resistance was improved due to the reduction in M_(6)C carbide,which inhibited cracking at the interface of M_(6)C/matrix.Additionally,the crack propagation resistance was enhanced due to the increase in deformation twins,which consumed more impact energy.展开更多
In this study,the twinning-detwinning behavior and slip behavior of rolled AZ31 magnesium-alloy plates during a three-step intermittent dynamic compression process along the rolling direction(RD)and normal direction(N...In this study,the twinning-detwinning behavior and slip behavior of rolled AZ31 magnesium-alloy plates during a three-step intermittent dynamic compression process along the rolling direction(RD)and normal direction(ND),are investigated via quasi-in situ electron backscatter diffraction,and the causes of the twinning and detwinning behavior are explained according to Schmid law,local strain coordination,and slip trajectories.It is found that the twins are first nucleated and grow at a compressive strain of 3%along the RD.In addition to the Schmid factor(SF),the strain coordination factor(m’)also influences the selection of the twin variants during the twinning process,resulting in the nucleation of twins with a low SF.During the second and third steps of the application of continuous compressive strains with magnitudes and directions of 3%RD+3%ND and 3%RD+3%ND+2.5%ND,detwinning occurs to different extents.The observation of the detwinning behavior reveals that the order in which multiple twins within the same grain undergo complete detwinning is related to Schmid law and the strain concentration,with a low SF and a high strain concentration promoting complete detwinning.The interaction between slip dislocations and twin boundaries in the deformed grains as well as the pinning of dislocations at the tips of the {1012} tensile twins with a special structure result in incomplete detwinning.Understanding the microstructural evolution and twinning behavior of magnesium alloys under different deformation geometries is important for the development of high-strength and high-toughness magnesium alloys.展开更多
Magnesium is distinguished by its highly anisotropic inelastic deformation involving a profuse activity of deformation twinning.Instrumented micro/nano-indentation technique has been widely applied to characterize the...Magnesium is distinguished by its highly anisotropic inelastic deformation involving a profuse activity of deformation twinning.Instrumented micro/nano-indentation technique has been widely applied to characterize the mechanical properties of magnesium,typically through the analysis of the indentation load-depth response,surface topography,and less commonly,the post-mortem microstructure within the bulk material.However,experimental limitations prevent the real-time observation of the evolving microstructure.To bridge this gap,we employ a recently-developed finite-strain model that couples the phase-field method and conventional crystal plasticity to simulate the evolution of the indentation-induced twin microstructure and its interaction with plastic slip in a magnesium single-crystal.Particular emphasis is placed on two aspects:orientation-dependent inelastic deformation and indentation size effects.Several outcomes of our 2D computational study are consistent with prior experimental observations.Chief among them is the intricate morphology of twin microstructure obtained at large spatial scales,which,to our knowledge,represents a level of detail that has not been captured in previous modeling studies.To further elucidate on size effects,we extend the model by incorporating gradient-enhanced crystal plasticity,and re-examine the notion of‘smaller is stronger’.The corresponding results underscore the dominant influence of gradient plasticity over the interfacial energy of twin boundaries in governing the size-dependent mechanical response.展开更多
Heterogeneous structure exhibits superiority in improving mechanical properties,whereas their effects on fatigue damage properties have rarely been studied.In this work,we employed a high-throughput gradient heat trea...Heterogeneous structure exhibits superiority in improving mechanical properties,whereas their effects on fatigue damage properties have rarely been studied.In this work,we employed a high-throughput gradient heat treatment method(757−857℃)to rapidly acquire the solution microstructure of the Ti-6554 alloy with different recrystallization degrees(0%,40%and 100%),followed by the same aging treatment.The results showed that theβ-hetero structure exhibited a yield strength(σ_(YS))of 1403 MPa,an increase of 6.7%,and a remarkable improvement in uniform elongation(UE)of 109.7%,reaching 6.5%,compared to the homogeneous structure.Interestingly,introducing a heterogeneous structure not only overcame the traditional trade-off between strength and ductility but also enhanced fatigue crack propagation(FCP)performance.During FCP process,β-hetero structure,through hetero-deformation induced(HDI)strengthening effects,promoted the accumulation of geometric necessary dislocations(GNDs)within coarseα_(S) phase,enabling faster attainment of the critical shear stress of twinning and increasing twinning density.This facilitated stress relief,improved plastic deformation in the crack tip zone,and increased the critical fast fracture threshold from 30.4 to 36.0 MPa·m^(1/2)showing an enlarged steady state propagation region.This study provides valuable insights on tailoring fatigue damage tolerance through heterogeneous structure for titanium alloys.展开更多
Grain boundary(GB)deformation and twinning behavior have been recognized as important contributors to the plasticity of polycrystalline materials.However,a comprehensive understanding of dynamic interplay between GB d...Grain boundary(GB)deformation and twinning behavior have been recognized as important contributors to the plasticity of polycrystalline materials.However,a comprehensive understanding of dynamic interplay between GB deformation and twinning behavior remains largely elusive.Using in situ nanomechanical testing,we reveal that GB plasticity and twinning plasticity can be strongly coupled in the context of various deformation characteristics,including lamellae-type twinning from GBs,GB splitting-induced twinning,twinning from triple junctions(TJs),and GB-mediated hierarchical twinning.These GB/TJ-associated twinning modes often arise from the combined effect of macroscopic(geometry-dominated)and microscopic(excess volume-dominated)degrees of freedom of GBs/TJs as an effective way to alleviate local stress concentration,which in turn provides a chance of adjusting GB mobility and enhancing the coordinated evolution of entire interface network in three-dimensional space.Such coupling between GB plasticity and twinning plasticity should represent a general deformation mode in different metallic materials,holding important implications for preventing premature GB cracking and enhancing material ductility.展开更多
The evolution of cities into digitally managed environments requires computational systems that can operate in real time while supporting predictive and adaptive infrastructure management.Earlier approaches have often...The evolution of cities into digitally managed environments requires computational systems that can operate in real time while supporting predictive and adaptive infrastructure management.Earlier approaches have often advanced one dimension—such as Internet of Things(IoT)-based data acquisition,Artificial Intelligence(AI)-driven analytics,or digital twin visualization—without fully integrating these strands into a single operational loop.As a result,many existing solutions encounter bottlenecks in responsiveness,interoperability,and scalability,while also leaving concerns about data privacy unresolved.This research introduces a hybrid AI–IoT–Digital Twin framework that combines continuous sensing,distributed intelligence,and simulation-based decision support.The design incorporates multi-source sensor data,lightweight edge inference through Convolutional Neural Networks(CNN)and Long ShortTerm Memory(LSTM)models,and federated learning enhanced with secure aggregation and differential privacy to maintain confidentiality.A digital twin layer extends these capabilities by simulating city assets such as traffic flows and water networks,generating what-if scenarios,and issuing actionable control signals.Complementary modules,including model compression and synchronization protocols,are embedded to ensure reliability in bandwidth-constrained and heterogeneous urban environments.The framework is validated in two urban domains:traffic management,where it adapts signal cycles based on real-time congestion patterns,and pipeline monitoring,where it anticipates leaks through pressure and vibration data.Experimental results show a 28%reduction in response time,a 35%decrease in maintenance costs,and a marked reduction in false positives relative to conventional baselines.The architecture also demonstrates stability across 50+edge devices under federated training and resilience to uneven node participation.The proposed system provides a scalable and privacy-aware foundation for predictive urban infrastructure management.By closing the loop between sensing,learning,and control,it reduces operator dependence,enhances resource efficiency,and supports transparent governance models for emerging smart cities.展开更多
Industry pure zirconium sheets with a strong c-axis fiber texture were rolled to different strains at 77 K to investigate the twinning behavior and deformation mechanism. The microstructure and texture of the rolled s...Industry pure zirconium sheets with a strong c-axis fiber texture were rolled to different strains at 77 K to investigate the twinning behavior and deformation mechanism. The microstructure and texture of the rolled specimens were characterized by scanning electron microscopy （SEM） together with electron backscatter diffraction （EBSD） techniques. The results show that the {1022} （1123） compression twinning mode is the dominant deformation twin at low strains loaded along the c-axis, and the {1012} （ 10]- 1 ） tensile twinning generates as the second twin in {1022} （ 1123 ） twins. The selection of twinning modes is governed by Schmid factor （SF） due to the calculating of SF and the EBSD simulating of twinning distribution. The evolution of texture during rolling affected by twins with increase of the strain was explained.展开更多
The morphology and orientation of the growth twins formed in the cast Mg-Zn-Cu-Zr alloys aged at 100 ＆#176;C were characterized using optical microscopy and transmission electron microscopy. It was found that twins w...The morphology and orientation of the growth twins formed in the cast Mg-Zn-Cu-Zr alloys aged at 100 ＆#176;C were characterized using optical microscopy and transmission electron microscopy. It was found that twins were invisible in the as-cast or solutionized Mg-Zn-Cu-Zr alloys while {10 12} twins were exclusively formed in the aged condition. The twinning behavior was significantly affected by two factors, namely, the Zn content and the heat treatment process. A possible formation mechanism of such growth twins was discussed using the viewpoint of vacancy.展开更多
Deformation twinning, i.e., twin nucleation and twin growth （or twin boundary migration, TBM） activated by impinged basal slip at a symmetrical tilt grain boundary in HCP Mg, was examined with molecular dynamics （M...Deformation twinning, i.e., twin nucleation and twin growth （or twin boundary migration, TBM） activated by impinged basal slip at a symmetrical tilt grain boundary in HCP Mg, was examined with molecular dynamics （MD） simulations. The results show that the {1^-1^-21}-type twinning acts as the most preferential mode of twinning. Once such twins are formed, they are almost ready to grow. The TBM of such twins is led by pure atomic shuffling events. A secondary mode of twinning can also occur in our simulations. The {112^-2} twinning is observed at 10 K as the secondary twin. This secondary mode of twinning shows different energy barriers for nucleation as well as for growth compared with the {1^-1^-21}-type twining. In particular, TBMs in this case is triggered intrinsically by pyramidal slip at its twin boundary.展开更多
基金supported by the Scientific and Technological Developing Scheme of Jilin Province under grants no.YDZJ202301ZYTS538the Chinese Academy of Sciences Youth Innovation Promotion Association under grants number 2023234+3 种基金the National Natural Science Foundation of China under grants number U21A20323the Scientific and Technological Developing Scheme of Jilin Province under grants no.SKL202302038the Major Scientific and Technological Projects of Hebei Province under grants No.23291001Zthe Scientific and Technology Project of Hanjiang District.
文摘Asymmetric tilt boundaries on conventional twin boundaries(TBs)are significant for understanding the role of twins on coordinating plastic deformation in many metallic alloys.However,the formation modes of many asymmetric tilt boundaries are hard to be accounted for based on traditional theoretical models,and the corresponding solute segregation is complex.Herein,atomic structures of a specific asymmetric boundary on{1012}TBs were reveled using aberration-corrected high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),molecular dynamics(MD)and density functional theory(DFT)simulations.Reaction between<a60>M dislocations and the{1012}TB can generate a~61°/25°asymmetric tilt boundary.The segregation of Gd and Zn atoms is closely related to the aggregateddislocations and the interfacial interstices of the asymmetric tilt boundary,which is energetically favorable in reducing the total system energy.
基金sponsored in part by the National Natural Sci-ence Foundation of China (No.52101150)the Sichuan Science and Technology Program (No.2022YFG0287)the Fundamental Re-search Funds for the Central Universities (No.2682021CX114).
文摘Deformation twinning in a WE43 alloy subjected to uniaxial compression at room temperature is in-vestigated.Active{1121}and{1012}extension twinning is observed.The activation of{1121}twinning in a certain grain is influenced not only by its own Schmid factor,but also by that of the basal slip.Twin-twin interactions of the co-zone{1121}twin variants are commonly observed and systematically studied,including the crystallographic characteristics of the four typically observed twin-twin junctions(TTJs)and the associated twin-twin boundaries.Unlike the quilted-looking TTJs formed by the interaction of co-zone{1012}twin variants,crossing-like TTJs of co-zone{1121}twin variants are observed and their formation mechanisms are discussed.Crossing-like TTJs are also formed by the interaction of{1121}and{10¯12}twins.The morphology and thickening rate of{1121}and{1012}twins vary markedly due to the difference in twinning shear.The needle-like{1121}twins thicken more slowly than the lenticular{1012}twins.Twin nucleation is observed on the previously formed{1121}twin boundary due to the relatively large strain concentration on such interface,while twin nucleation on{1012}twin boundary is rarely observed.
基金the National Natural Science Foundation of China(grant Nos.11988102,52301146,51301173,51531002,52171055,52371037,51601193)the National Key Research and Development Program of China(grant No.2016YFB0301104)+1 种基金the Fundamental Research Funds for the Central Universities(grant No.2023JG007)China Postdoctoral Science Foundation(grant No.8206300226).
文摘Tension-compression asymmetry is a critical concern for magnesium(Mg)alloys,particularly in automo-tive crash structures.This study systematically examines the tension-compression asymmetry of a cast Mg-Gd-Y alloy at various strain rates.Experimental results indicate symmetric yielding stress under both tension and compression at all strain rates,along with a reduction in the tension-compression asym-metry of ultimate stress and plastic strain as the strain rate increases.This trend arises from an unusual strain rate-dependent tension-compression asymmetry,characterized by strain rate toughening in tension and negligible strain rate effect in compression.The differing behavior is linked to the distinct twinning mechanisms under tension and compression.The suppression of twinning under tension contributes to the positive strain rate dependence of pyramidal slip,whereas the activation of abundant twins during compression means that pyramidal slip is unnecessary to accommodate c-axis strain,leading to the ab-sence of a strain rate effect in compression.Abundant twins nucleate consistently from yielding to 2%strain,but only after basal and prismaticslip have mediated microplasticity,suggesting that these slip systems reduce the nucleation stress for twinning during compression,resulting in a lower activation stress for twinning compared to tension.This study provides new insights into micromechanisms of the tension-compression asymmetry in cast Mg-Gd-Y alloys and offers practical guidance for the application of these materials in critical components that must endure both tension and compression under varying strain rates.
基金supported by the National Natural Science Foundation of China(Nos.52001153,52322105,52271121,52130002 and 52321001)the Youth Innovation Promotion Association CAS(No.202119)+2 种基金the IMR Innovation Fund(No.2023-ZD01)the KC Wong Education Foundation(No.GJTD-2020-09)One of the authors was supported by the European Research Council under grant agreement No.267464-SPDMETALS(TGL).
文摘1.Introduction.Twinning is a fundamental mechanism for plastic deformation in many face-centered cubic(FCC)metals having low stacking fault energies(SFEs)[1,2].In particular,twinning-induced plasticity(TWIP)alloys have excellent tensile properties as a result of the intensive twinning activity[3-5].The twin boundaries also have been proven to contribute to an improved strengthening-toughening effect,mechanical stability and even fatigue performance,relative to high-angle grain boundaries and low-angle grain boundaries[6-11].Therefore,it is of major interest to clarify the twinning mechanism and thereby improve the mechanical properties of metallic materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1810208 and 52401162)Shanxi province science and technology major projects,China(Grant No.20181101008).
文摘A strong basal texture is typically developed in magnesium alloy sheets that have been subjected to the rolling process.Consequently,their mechanical properties and formability are significantly impaired,which in turn restricts potential applications.In this study,an innovative texture-altering technique,which involves in-plane free compression and width-constrained rolling(FCWR),is used for AZ31 alloy sheets in order to manufacture magnesium alloy sheets with both high strength and high ductility.During FCWR deformation process,a substantial number of tensile twins and a small quantity of(1012)-(01¯12)twin-twin boundaries are induced to coordinate plastic deformation.It is precisely the presence of such crossed twins that impedes the detwinning of partial twins under low-stress conditions.The retained twins hinder the motion of dislocation,thereby enhancing the strength.Specifically,the yield strength of preset crossed twins sample along rolling direction,45°and transverse direction has increased by 105%,16.8%and 23%,respectively.Additionally,the ultimate tensile strength along these three directions has increased by 42.7%,25.5%and 34.8%,respectively.The twin boundaries in FCWR sample consist of steps,which correspond to basal-prismatic(BP/PB)boundaries that connect straight terraces which are parallel to theoretical{10¯12}twin boundaries.Furthermore,as the number of processing passes increases,the step features become more pronounced.Compared with the as-received sample,the YS enhancement in the sample prepared via the second pass of the FCWR process is attributed to two primary mechanisms:grain refinement strengthening contributes 61 MPa,while dislocation strengthening accounts for 90 MPa.
基金supported by the National Research Foundation of Korea(NRF)grants funded by the Korea government(MSIT)(nos.RS-2024-00351052 and 202300212657).
文摘This study investigates the influence of initial crystallographic texture on the deformation mechanisms during three-point bending of AZ31 Mg alloy sheets.Three distinct orientations are examined by using the following bending specimens:(i)the normal direction(ND)sample,where the c-axes are predominantly aligned along the specimen thickness,(ii)the rolling direction(RD)sample,where the c-axes are mostly aligned along the longitudinal direction,and(iii)the 45 sample,where the c-axes are tilted at approximately 45°from both the thickness and longitudinal directions.The bending properties vary significantly depending on the initial texture,thereby affecting the strain accommodation and dominant deformation modes.The ND sample exhibits the lowest bendability due to its unfavorable orientation for{10–12}extension twinning and basal slip,which results in poor strain accommodation and early crack initiation in the outer tensile side.By comparison,the RD sample demonstrates an approximately 22.1%improvement,with extensive{10–12}extension twinning in the outer tensile zone.Meanwhile,the 45 sample exhibits the highest bendability(approximately 75.7%greater than that of the ND sample)due to sustained activation of both basal slip and{10–12}extension twinning,promoting uniform strain distribution and delaying fracture.Detailed electron backscatter diffraction analysis reveals that the 45 sample retains favorable crystallographic orientations for basal slip throughout bending,minimizing strain localization and enhancing the bendability.These findings highlight the importance of tailoring the initial texture in order to optimize the bending properties of Mg alloy sheets,and provide valuable insights for improving the manufacturability of Mg-based structural components.
基金support from U.S.National Science Foundation(NSF)(CMMI-2016263,2032483).
文摘Theoretically,a twinning dislocation must stay on the twinning plane which is the first invariant plane of a twinning mode,because the glide of twinning dislocation linearly transforms the parent lattice to the twin lattice.However,recent experimental observations showed that a{1011}{1012}twin variant could cross another variant during twin-twin interaction.It is well known that{1011}twinning is mediated by zonal twinning dislocations.Thus,how the zonal twinning dislocations transmute during twin-twin interaction is of great interest but not well understood.In this work,atomistic simulation is performed to investigate interaction between{1011}twin variants.Our results show that when an incoming twin variant impinges on the other which acts as a barrier,surprisingly,the barrier twin can grow at the expense of the incoming twin.Eventually one variant consumes the other.Structural analysis shows that the twinning dislocations of the barrier variant are able to penetrate the zone of twin-twin intersection,by plowing through the lattice of one variant and transform its lattice into the lattice of the other.Careful lattice correspondence analysis reveals that,the lattice transformation from one variant to the other is close to{1012}{1011}twinning,but the orientation relationship deviates by a minor lattice rotation.This deviation presents a significant energy barrier to the lattice transformation,and thus it is expected such a twin-twin interaction will increase the stress for twin growth.
基金the National Key Research and Development Program(2023YFB3710903)the National Natural Science Foundation of China(U2167213)+1 种基金the Fundamental Research Funds for the Central Universities(N25GFZ006)the Xingliao Talent Plan Program(XLYC2203202).
文摘In this study,the typical Mg-14Gd-0.3Zr alloy was rolled at the high-temperature range of 450–500℃.The rolled Mg alloy plate with thickness of 30 mm exhibits an ultra-high ultimate tensile strength of 428 MPa and elongation of 3.4%,which has rarely been reported,and the strong fiber texture played a critical role in strengthening.The mechanisms underlying the evolution of texture during rolling were systematically investigated.At the early stage of rolling,alloys(450℃and 475℃)exhibited a[10.10]texture due to twinning assisted by Prismaticslipping.At 500℃,the alloy underwent nearly complete dynamic recrystallization(DRX)process.With increasing the rolling reduction,the DRX occurred in the whole temperature range,exhibiting the typical[10.10]–[11.20]double fiber texture.For continuous DRX,Prismaticdislocations accumulate to form grains with 30°[0001]grain boundaries,which exhibit a[10.10]fiber texture.During discontinuous DRX,Prismaticslip induced grain rotation around the[0001]axis,stabilizing either the<10.10>//RD(rolling direction)or<11.20>//RD orientations,leading to the formation of[10.10]–[11.20]double fiber texture.TEM observations confirmed that Prismaticdislocations can accumulate to form sub-grain lamellae,which gradually transform into high-angle grain boundaries by absorbing more Prismaticdislocations.First-principle calculation demonstrated that with increasing Gd content,the unstable stacking fault energy of prismatic slipping significantly decreases,promoting the activation of Prismaticslipping.These findings elucidate the critical role of twinning and Prismaticdislocations in texture evolution and the DRX process during thick plate rolling of the high-Gd content Mg-Gd-Zr alloy.
文摘The evolution of microstructure and texture in Mg-3Al-1Zn-1Ca alloy sheets subjected to in-plane shear(IPS)loading was investigated using experimental techniques and viscoplastic self-consistent(VPSC)modeling.The specimens were deformed under varying degrees of IPS strain(γ12=0.05,0.10,and 0.15)using a customized jig.Electron backscatter diffraction(EBSD)observations revealed profuse tensile twinning(TTW)even at an IPS strain of 0.05,with its intensity continuously increased as the IPS strain increased.The TTWs progressively engulfed parent grains with increasing shear strain,evolving into an unusual deformation twin morphology.Furthermore,VPSC model predictions confirmed basal slip as the dominant deformation mode at low IPS strains,transitioning to prismatic slip dominance at higher IPS strains.The activity of the TTW mode was significantly higher during the initial stages of IPS strain and saturated to lower values at higher strains.VPSC simulation results also indicated preferential shear accumulation on a single twin system,explaining the phenomenon of a single twin variant engulfing a parent grain.Additionally,the influence of individual slip and twin modes on texture evolution was evaluated through orientation tracking of representative grains at various shear strain increments using VPSC simulation.The simulation results quantitatively highlighted the activities of basal slip,prismatic slip,and tensile twinning,establishing a correlation between texture evolution and the underlying deformation mechanisms.
基金supported by the National Key Research and Development Program of China(No.2022YFB3706902)Innovation Project for Graduate Students of Hunan Province+1 种基金China(No.1053320212786)supported in part by the High Performance Computing Center of Central South University,China。
文摘The effects of varying strain rates and deformation temperatures on the microstructure evolution of the FGH4113A alloy were investigated through hot compression experiments.During hot deformation,grain evolution is primarily governed by dynamic recrystallization(DRX)and twinning primarily.Furthermore,the pinning effect of the primaryγ'phase(γ'p phase)plays a crucial role in grain refinement.Lower strain rates or higher temperatures facilitate DRX,twinning,and the dissolution of theγ'p phase.At 1140℃,significant dissolution of theγ'p phase and the subsequent loss of its pinning effect reduce twinning activity.A unique twinning mechanism,termed“pinning twinning”,is identified,occurring exclusively under the influence of the pinning effect.When grain boundary migration fails to accommodate dislocations due to the pinning effect,grains preferentially eliminate dislocations via twinning,thereby reducing local strain energy.The grain size prediction model is improved by considering the pinning effect.
基金financially supported by the Natural Science Foundation(NSF)of China(Nos.11802092 and U2230401)NSF of Hunan Province(Nos.2019JJ50221,2019JJ40127,2020JJ5260,and 2020JJ4375)+5 种基金the Funding of the Hunan Education Department Project(Nos.20A248 and 22B0225)the Double first-class construction project of Hunan Agricultural University(No.SYL2019063)the Postgraduate Scientific Research Innovation Project of Hunan Province(No.CX20230682)the Postgraduate Scientific Research Innovation Project of Hunan Province(No.CX20230682)the Postgraduate Scientific Research Innovation Project of Hunan Agricultural University(No.2023XC019)We also acknowledge the support of the computation platform of the National Super Computer Center in Changsha(NSCC).
文摘Nanopowder consolidation under high strain rate shock compression is a potential method for synthesizing and processing bulk nanomaterials,and a thorough investigation of the deformation and its underlying mechanisms in consolidation is of great engineering significance.We conduct non-equilibrium molecular dynamics(NEMD)simulation and X-ray diffraction(XRD)simulation to systematically study shock-induced deformation and the corresponding mechanisms during the consolidation of nanopowdered Mg(NP-Mg).Two different deformation modes govern the shock consolidation in NP-Mg,i.e.,deformation twinning at up≤1.5 km s^(-1)and structural disordering,at up≥2.0 km s^(-1).They accelerate the collapse of nanopores and void compaction,giving rise to the final consolidation of NP-Mg.Three types of deformation twinning are emitted in NP-Mg,i.e.,the extension twinning for{1121}(1126),and{1102}〈1101>,and the compression{1122}(1123)twinning.They are prompted via coupling atomic shuffles and slips.Deformation twinning prefers to occur within the grains as shock along<1120>or its approaching direction(A-and B-type grains),originated from the high-angle grain boundaries(HAGB)at compression stage.They are inhibited within the ones as shocking along<0001>and the approaching ones(C-and D-type grains).The release and tension loading facilitates the reversible and irreversible detwinning,for the extension and compression twinning,respectively,within the A-and B-type grains.It also contributes to a compression-tension asymmetry for twinning,i.e.,release and tension induced extension twinning within the C-and D-type grains.The subsequent spallation is mediated by GB sliding and GB-induced stacking faults at up≤1.5 km s^(-1),and structural disordering at up≥2.0 km s^(-1).
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA0410201)the Natural Science Foundation of Heilongjiang Province(No.TD2021E006)+1 种基金the Liaoning Provincial Doctoral Initiation Fund Project(No.2022-BS-008)the China Postdoctoral Science Foundation(No.2023T160654).
文摘In the study,three 16Cr-25.5Ni-4.2Mo superaustenitic stainless steel weld metals with C contents of 0.082 wt%,0.075 wt%,and 0.045 wt%,were prepared to investigate the microstructural evolution and its effect on mechanical behavior.At a C content of 0.082 wt%,the microstructure of weld metal consisted of austenite,M_(6)C,and M_(23)C_(6),where M_(6)C was the main carbide.The number and average size of the M_(6)C carbides significantly decreased as the C content decreased.At a C content of 0.045 wt%,only a very small number of M_(6)C carbides were observed in the weld metal.For the tensile process,the number of deformation twins increased as the C content decreased,which introduced a stronger dynamic Hall-Petch effect,resulting in only a small decrease in the ultimate tensile strength of the weld metal.Meanwhile,the increase in deformation twins significantly enhanced the elongation of the weld metals.For the impact process,the impact energy increased from 204 to 241 J as the C content decreased.The crack initiation resistance was improved due to the reduction in M_(6)C carbide,which inhibited cracking at the interface of M_(6)C/matrix.Additionally,the crack propagation resistance was enhanced due to the increase in deformation twins,which consumed more impact energy.
基金supported by the General Project of Liaoning Provincial Department of Education(NO:JYTMS20231199)Project of Liaoning Education Department(No:LKMZ20220462 and No:LJKMZ20220467)+1 种基金Basic scientific research project of Liaoning Provincial Department of Education(key research project)(No:JYTZD2023108)Liaoning Nature Fund Guidance Plan(No:42022-BS.179)。
文摘In this study,the twinning-detwinning behavior and slip behavior of rolled AZ31 magnesium-alloy plates during a three-step intermittent dynamic compression process along the rolling direction(RD)and normal direction(ND),are investigated via quasi-in situ electron backscatter diffraction,and the causes of the twinning and detwinning behavior are explained according to Schmid law,local strain coordination,and slip trajectories.It is found that the twins are first nucleated and grow at a compressive strain of 3%along the RD.In addition to the Schmid factor(SF),the strain coordination factor(m’)also influences the selection of the twin variants during the twinning process,resulting in the nucleation of twins with a low SF.During the second and third steps of the application of continuous compressive strains with magnitudes and directions of 3%RD+3%ND and 3%RD+3%ND+2.5%ND,detwinning occurs to different extents.The observation of the detwinning behavior reveals that the order in which multiple twins within the same grain undergo complete detwinning is related to Schmid law and the strain concentration,with a low SF and a high strain concentration promoting complete detwinning.The interaction between slip dislocations and twin boundaries in the deformed grains as well as the pinning of dislocations at the tips of the {1012} tensile twins with a special structure result in incomplete detwinning.Understanding the microstructural evolution and twinning behavior of magnesium alloys under different deformation geometries is important for the development of high-strength and high-toughness magnesium alloys.
文摘Magnesium is distinguished by its highly anisotropic inelastic deformation involving a profuse activity of deformation twinning.Instrumented micro/nano-indentation technique has been widely applied to characterize the mechanical properties of magnesium,typically through the analysis of the indentation load-depth response,surface topography,and less commonly,the post-mortem microstructure within the bulk material.However,experimental limitations prevent the real-time observation of the evolving microstructure.To bridge this gap,we employ a recently-developed finite-strain model that couples the phase-field method and conventional crystal plasticity to simulate the evolution of the indentation-induced twin microstructure and its interaction with plastic slip in a magnesium single-crystal.Particular emphasis is placed on two aspects:orientation-dependent inelastic deformation and indentation size effects.Several outcomes of our 2D computational study are consistent with prior experimental observations.Chief among them is the intricate morphology of twin microstructure obtained at large spatial scales,which,to our knowledge,represents a level of detail that has not been captured in previous modeling studies.To further elucidate on size effects,we extend the model by incorporating gradient-enhanced crystal plasticity,and re-examine the notion of‘smaller is stronger’.The corresponding results underscore the dominant influence of gradient plasticity over the interfacial energy of twin boundaries in governing the size-dependent mechanical response.
基金Project(2021YFB3700801)supported by the National Key Research and Development Program of ChinaProject(2023JJ30683)supported by the Natural Science Foundation of Hunan Province,ChinaProject supported by the State Key Laboratory of Powder Metallurgy(Central South University),China。
文摘Heterogeneous structure exhibits superiority in improving mechanical properties,whereas their effects on fatigue damage properties have rarely been studied.In this work,we employed a high-throughput gradient heat treatment method(757−857℃)to rapidly acquire the solution microstructure of the Ti-6554 alloy with different recrystallization degrees(0%,40%and 100%),followed by the same aging treatment.The results showed that theβ-hetero structure exhibited a yield strength(σ_(YS))of 1403 MPa,an increase of 6.7%,and a remarkable improvement in uniform elongation(UE)of 109.7%,reaching 6.5%,compared to the homogeneous structure.Interestingly,introducing a heterogeneous structure not only overcame the traditional trade-off between strength and ductility but also enhanced fatigue crack propagation(FCP)performance.During FCP process,β-hetero structure,through hetero-deformation induced(HDI)strengthening effects,promoted the accumulation of geometric necessary dislocations(GNDs)within coarseα_(S) phase,enabling faster attainment of the critical shear stress of twinning and increasing twinning density.This facilitated stress relief,improved plastic deformation in the crack tip zone,and increased the critical fast fracture threshold from 30.4 to 36.0 MPa·m^(1/2)showing an enlarged steady state propagation region.This study provides valuable insights on tailoring fatigue damage tolerance through heterogeneous structure for titanium alloys.
基金financially supported by the National Key R&D Program of China(No.2021YFA1200201)the National Natural Science Foundation of China(No.52071284)the Zhejiang Provincial Natural Science Foundation of China(No.LR24E010002).
文摘Grain boundary(GB)deformation and twinning behavior have been recognized as important contributors to the plasticity of polycrystalline materials.However,a comprehensive understanding of dynamic interplay between GB deformation and twinning behavior remains largely elusive.Using in situ nanomechanical testing,we reveal that GB plasticity and twinning plasticity can be strongly coupled in the context of various deformation characteristics,including lamellae-type twinning from GBs,GB splitting-induced twinning,twinning from triple junctions(TJs),and GB-mediated hierarchical twinning.These GB/TJ-associated twinning modes often arise from the combined effect of macroscopic(geometry-dominated)and microscopic(excess volume-dominated)degrees of freedom of GBs/TJs as an effective way to alleviate local stress concentration,which in turn provides a chance of adjusting GB mobility and enhancing the coordinated evolution of entire interface network in three-dimensional space.Such coupling between GB plasticity and twinning plasticity should represent a general deformation mode in different metallic materials,holding important implications for preventing premature GB cracking and enhancing material ductility.
基金The researchers would like to thank the Deanship of Graduate Studies and Scientific Research at Qassim University for financial support(QU-APC-2025)。
文摘The evolution of cities into digitally managed environments requires computational systems that can operate in real time while supporting predictive and adaptive infrastructure management.Earlier approaches have often advanced one dimension—such as Internet of Things(IoT)-based data acquisition,Artificial Intelligence(AI)-driven analytics,or digital twin visualization—without fully integrating these strands into a single operational loop.As a result,many existing solutions encounter bottlenecks in responsiveness,interoperability,and scalability,while also leaving concerns about data privacy unresolved.This research introduces a hybrid AI–IoT–Digital Twin framework that combines continuous sensing,distributed intelligence,and simulation-based decision support.The design incorporates multi-source sensor data,lightweight edge inference through Convolutional Neural Networks(CNN)and Long ShortTerm Memory(LSTM)models,and federated learning enhanced with secure aggregation and differential privacy to maintain confidentiality.A digital twin layer extends these capabilities by simulating city assets such as traffic flows and water networks,generating what-if scenarios,and issuing actionable control signals.Complementary modules,including model compression and synchronization protocols,are embedded to ensure reliability in bandwidth-constrained and heterogeneous urban environments.The framework is validated in two urban domains:traffic management,where it adapts signal cycles based on real-time congestion patterns,and pipeline monitoring,where it anticipates leaks through pressure and vibration data.Experimental results show a 28%reduction in response time,a 35%decrease in maintenance costs,and a marked reduction in false positives relative to conventional baselines.The architecture also demonstrates stability across 50+edge devices under federated training and resilience to uneven node participation.The proposed system provides a scalable and privacy-aware foundation for predictive urban infrastructure management.By closing the loop between sensing,learning,and control,it reduces operator dependence,enhances resource efficiency,and supports transparent governance models for emerging smart cities.
基金Project(51171213)supported by the National Natural Science Foundation of ChinaProject(NCET-08-0606)supported by New Century Excellent Talents in University,China
文摘Industry pure zirconium sheets with a strong c-axis fiber texture were rolled to different strains at 77 K to investigate the twinning behavior and deformation mechanism. The microstructure and texture of the rolled specimens were characterized by scanning electron microscopy （SEM） together with electron backscatter diffraction （EBSD） techniques. The results show that the {1022} （1123） compression twinning mode is the dominant deformation twin at low strains loaded along the c-axis, and the {1012} （ 10]- 1 ） tensile twinning generates as the second twin in {1022} （ 1123 ） twins. The selection of twinning modes is governed by Schmid factor （SF） due to the calculating of SF and the EBSD simulating of twinning distribution. The evolution of texture during rolling affected by twins with increase of the strain was explained.
基金Project(51201088)supported by the National Natural Science Foundation of ChinaProject(12C0324)supported by the Research Foundation of Education Bureau of Hunan Province,China+1 种基金Project(2011XQD26)supported by Doctoral Scientific Research Foundation of the University of South,ChinaProject([2011]76)supported by the Construct Program of the Key Discipline in Hunan Province,China
文摘The morphology and orientation of the growth twins formed in the cast Mg-Zn-Cu-Zr alloys aged at 100 ＆#176;C were characterized using optical microscopy and transmission electron microscopy. It was found that twins were invisible in the as-cast or solutionized Mg-Zn-Cu-Zr alloys while {10 12} twins were exclusively formed in the aged condition. The twinning behavior was significantly affected by two factors, namely, the Zn content and the heat treatment process. A possible formation mechanism of such growth twins was discussed using the viewpoint of vacancy.
基金Project(2012CB932202)supported by the National Basic Research Program of ChinaProjects(50890174,50971088)supported by the National Natural Science Foundation of China
文摘Deformation twinning, i.e., twin nucleation and twin growth （or twin boundary migration, TBM） activated by impinged basal slip at a symmetrical tilt grain boundary in HCP Mg, was examined with molecular dynamics （MD） simulations. The results show that the {1^-1^-21}-type twinning acts as the most preferential mode of twinning. Once such twins are formed, they are almost ready to grow. The TBM of such twins is led by pure atomic shuffling events. A secondary mode of twinning can also occur in our simulations. The {112^-2} twinning is observed at 10 K as the secondary twin. This secondary mode of twinning shows different energy barriers for nucleation as well as for growth compared with the {1^-1^-21}-type twining. In particular, TBMs in this case is triggered intrinsically by pyramidal slip at its twin boundary.
