The deformation characteristics and activation mechanisms of kink bands in refractory multi-principal element alloys with local chemical fluctuations(LCFs)were systematically studied.These alloys were fabricated using...The deformation characteristics and activation mechanisms of kink bands in refractory multi-principal element alloys with local chemical fluctuations(LCFs)were systematically studied.These alloys were fabricated using laser-directed energy deposition technology and characterized by room-temperature compression testing,electron backscatter diffraction(EBSD),transmission electron microscopy(TEM),and high-angle annular dark-field(HAADF)imaging.The results reveal that kinking is a gradual rotational diffusion process,during which the misorientation difference between the kink and the matrix varies.A low Schmid factor is a prerequisite for kink excitation.The slip system closest to the loading axis is passively activated by the applied external force,leading to the accumulation of geometrically necessary dislocations(GNDs)required for lattice rotation.The widespread LCFs within the matrix reduce the migration rate of edge dislocations,promoting GND accumulation and enhancing the propensity for kink band formation.During deformation,the occurrence of kinking enables continuous lattice rotation to accommodate the exceptionally high strain in the vicinity,when the stress concentration in the primary kink cannot be fully released,double kinks are activated to reduce strain energy.展开更多
Titanium alloys engineered in structural applications achieve ultrahigh strength primarily through precipitation strengthening of secondary α-phase(αs)during aging,while they often experience compromised ductility a...Titanium alloys engineered in structural applications achieve ultrahigh strength primarily through precipitation strengthening of secondary α-phase(αs)during aging,while they often experience compromised ductility and toughness due to traditional strength-toughness tradeoff.In this study,we propose a novel strategy to address this conflict by introducing deformation kinks prior to conventional cold rolling(CR)and aging processes.These kinks are produced by cold forging(CF)to create macroscopic lamellar structures in β-grains,which alter strain partitioning during subsequent CR and ultimately tailor α_(s)-precipitation upon aging.As a result,an ultrafine duplex(αe+β)-structure is formed within kink interi-ors,while hierarchicalαs-precipitates are generated in the external β-matrix.This unique microstructure effectively enhances dislocation activity,promotes uniform plastic strain distribution and impedes crack propagation.Consequently,a simple Ti-V binary titanium alloy exhibits exceptional properties with ultra-high strength∼1636 MPa,decent ductility∼5.4% and appreciable fracture toughness∼36.1 MPa m^(1/2).The synergetic properties surpass those obtained through traditional CR and aging processes for the alloy and even outperform numerous multielement engineering titanium alloys reported in literature.Our findings open up a new avenue for overcoming the strength-toughness tradeoffof ultrahigh-strength titanium alloys,and also offer a facile production route towards structural materials for advanced performance.展开更多
The Mg-Y-Zn magnesium alloy system is known for the presence of Long-Period Stacking Ordered(LPSO)phases that improves strength and ductility with minimal amounts of alloying elements.Even better improvements are asso...The Mg-Y-Zn magnesium alloy system is known for the presence of Long-Period Stacking Ordered(LPSO)phases that improves strength and ductility with minimal amounts of alloying elements.Even better improvements are associated with the specific microstructure known as the Mille-Feuille(MF)structure that can occur in this alloy as well after proper heat treatment.This study systematically compares the traditional ingot metallurgy method with the Bridgman method(slow cooling),coupled with diverse heat treatments and extrusion process.Microscopic analyses reveal variations in the presence of LPSO phases,MF structure,and especially grain size,leading to divergent mechanical and corrosion properties.The Bridgman approach surprisingly stands out,ensuring superior mechanical properties due to kink and texture strengthening.展开更多
Kinked rebar is a special type of steel material,which is installed in beam column nodes and frame beams.It effectively enhances the blast resilience,seismic collapse resistance,and progressive collapse resistance of ...Kinked rebar is a special type of steel material,which is installed in beam column nodes and frame beams.It effectively enhances the blast resilience,seismic collapse resistance,and progressive collapse resistance of reinforced concrete(RC)structures without imposing substantial cost burdens,thereby emerging as a focal point of recent research endeavors.On the basis of explaining the working principle of kinked rebars,this paper reviews the research status of kinked rebars at home and abroad from three core domains:the tensile mechanical properties of kinked rebars,beam column nodes with kinked rebars,and concrete frame structures with kinked rebars.The analysis underscores that the straightening process of kinked rebars does not compromise their ultimate strength but significantly bolsters structural ductility and enhances energy dissipation capabilities.In beam-column joints,the incorporation of kinked rebars facilitates the seamless transfer of plastic hinges,adhering to the design principle of“strong columns and weak beams.”In addition,kinked rebars can greatly improve the resistance of the beam;The seismic resistance,internal explosion resistance,and progressive collapse resistance of reinforced concrete frame structures with kinked rebar have significantly improved.Beyond its primary application,the principle of kinked rebar was extended to other applications of kinked materials such as corrugated steel plates and origami structures,and the stress characteristics of related components and structures were studied.Intriguingly,this paper also proposes the application of kinked rebars in bridge engineering,aiming to address the challenges of localized damage concentration and excessive residual displacement in RC bridge piers.The introduction of kinked rebars in piers is envisioned to mitigate these issues,with the paper outlining its advantages and feasibility,thereby offering valuable insights for future research on kinked reinforcement and seismic design strategies for bridges.展开更多
In this paper,the mutual influence of plastic behaviors between kinked macro-crack and kinked micro-crack is analyzed based on the distributed dislocation technique and the dislocation-free zone model.A novel theoreti...In this paper,the mutual influence of plastic behaviors between kinked macro-crack and kinked micro-crack is analyzed based on the distributed dislocation technique and the dislocation-free zone model.A novel theoretical model for the size of the plastic zone is proposed,where the length of the dislocation array calculated in a specific direction is utilized to characterize the size of the plastic zone at the crack tip.The results demonstrate that,compared with the length of the dislocation array distributed along the crack direction,the length of the dislocation array distributed at a certain specific angle can more accurately characterize the plastic zone at the crack tip.When compared with the results of finite element analysis,the relative error is within 0.2%.Within the theoretical framework of this paper,it is considered that when the dislocation array is set at the crack tip and forms an angle of approximately 25°with respect to the horizontal direction,the calculated length of the dislocation array can effectively characterize the size of the plastic zone.The dislocation density increases with the decrease of the kinking angle of the crack.These results are conducive to predicting the plastic and fracture behaviors of materials containing kinked cracks.展开更多
Combining the continuously distributed dislocation technique(DDT)and the von Mises yield criterion,new double-crack and multi-crack models were established.The influences of multi-segment kinked micro-cracks and group...Combining the continuously distributed dislocation technique(DDT)and the von Mises yield criterion,new double-crack and multi-crack models were established.The influences of multi-segment kinked micro-cracks and groups of kinked micro-cracks on the plastic behavior of the macro-crack were investigated.The results show that a smaller kinking angle of the micro-crack enhances its influence on the plastic deformation of the macro-crack,potentially leading to plastic zone fusion.Meanwhile,micro-cracks with smaller kinking angles exert a stronger attracting force on macro-crack growth,facilitating convergence between them.Furthermore,annularly distributed micro-crack groups demonstrate a more pronounced attraction on macro-crack propagation compared to linearly distributed micro-crack groups.The double-crack and multi-crack models established in this paper offer a theoretical framework for analyzing the plastic fracture behavior of metallic materials containing complex kinked cracks.展开更多
多晶硅薄膜晶体管(P-Si TFTs)技术在SOP(system on panel)显示应用中发挥着越来越重要的作用。随着尺寸的不断缩小,P-Si TFT的Kink效应越来越明显,对有源液晶显示矩阵和驱动电路的性能影响很大。对发生Kink效应的物理机制、二维数值仿...多晶硅薄膜晶体管(P-Si TFTs)技术在SOP(system on panel)显示应用中发挥着越来越重要的作用。随着尺寸的不断缩小,P-Si TFT的Kink效应越来越明显,对有源液晶显示矩阵和驱动电路的性能影响很大。对发生Kink效应的物理机制、二维数值仿真及其一维解析模型进行了分析,讨论了晶粒边界、沟道长度与Kink效应的关系,提出建立适合电路仿真的一维解析模型的关键与展望。展开更多
A semi-analytical method is introduced to study kink instability in cylindrical plasma with line-tied boundary conditions. The method is based on an expansion for magnetohydrodynamics （MHD） equations in one-dimensio...A semi-analytical method is introduced to study kink instability in cylindrical plasma with line-tied boundary conditions. The method is based on an expansion for magnetohydrodynamics （MHD） equations in one-dimensional （1D） radial eigenvalue problems by using Fourier transforms. The MHD equations then become an ordinary differential equation. This method is applicable to both ideal and non-ideal MHD problem. The effect of plasma pressure （P0） on kink instability is studied in a cylindrical geometry. Complex discrete spectra are pre- sented. Two-dimensional （2D） eigenfunctions with the line-tied boundary conditions are obtained. The growth rate and radial eigenfunctions are different in the two cases of P0 = 0 and P0 ≠ 0, which indicate that the effect of plasma pressure can not be ignored if it is large enough. This method allows us to understand the role of individual radial eigenfunctions, and is also computationally efficient compared to direct solutions of the MHD equations by the finite difference method.展开更多
文摘The deformation characteristics and activation mechanisms of kink bands in refractory multi-principal element alloys with local chemical fluctuations(LCFs)were systematically studied.These alloys were fabricated using laser-directed energy deposition technology and characterized by room-temperature compression testing,electron backscatter diffraction(EBSD),transmission electron microscopy(TEM),and high-angle annular dark-field(HAADF)imaging.The results reveal that kinking is a gradual rotational diffusion process,during which the misorientation difference between the kink and the matrix varies.A low Schmid factor is a prerequisite for kink excitation.The slip system closest to the loading axis is passively activated by the applied external force,leading to the accumulation of geometrically necessary dislocations(GNDs)required for lattice rotation.The widespread LCFs within the matrix reduce the migration rate of edge dislocations,promoting GND accumulation and enhancing the propensity for kink band formation.During deformation,the occurrence of kinking enables continuous lattice rotation to accommodate the exceptionally high strain in the vicinity,when the stress concentration in the primary kink cannot be fully released,double kinks are activated to reduce strain energy.
基金supported by the National Natural Science Foundation of China(Nos.52271113,92163201)Jinyu Zhang is grateful for the Shaanxi Province Youth Innovation Team(No.22JP042)Shaanxi Province Innovation Team Project(2024RS-CXTD-58).
文摘Titanium alloys engineered in structural applications achieve ultrahigh strength primarily through precipitation strengthening of secondary α-phase(αs)during aging,while they often experience compromised ductility and toughness due to traditional strength-toughness tradeoff.In this study,we propose a novel strategy to address this conflict by introducing deformation kinks prior to conventional cold rolling(CR)and aging processes.These kinks are produced by cold forging(CF)to create macroscopic lamellar structures in β-grains,which alter strain partitioning during subsequent CR and ultimately tailor α_(s)-precipitation upon aging.As a result,an ultrafine duplex(αe+β)-structure is formed within kink interi-ors,while hierarchicalαs-precipitates are generated in the external β-matrix.This unique microstructure effectively enhances dislocation activity,promotes uniform plastic strain distribution and impedes crack propagation.Consequently,a simple Ti-V binary titanium alloy exhibits exceptional properties with ultra-high strength∼1636 MPa,decent ductility∼5.4% and appreciable fracture toughness∼36.1 MPa m^(1/2).The synergetic properties surpass those obtained through traditional CR and aging processes for the alloy and even outperform numerous multielement engineering titanium alloys reported in literature.Our findings open up a new avenue for overcoming the strength-toughness tradeoffof ultrahigh-strength titanium alloys,and also offer a facile production route towards structural materials for advanced performance.
基金supported by Japan Society for the Promotion of Science(KAKENHI Grant-in-Aid for Scientific Research,18H05475,18H05476 and JP20H00312)MRC International Collaborative Research Grant+4 种基金The authors would like to thank the Czech Science Foundation(Project No.22-22248S)specific university research(A1_FCHT_2024_007)for financial supportsupported by the Ministry of Education,Youth,and Sports of the Czech Republic.Project No.CZ.02.01.01/00/22_008/0004591co-funded by the European UnionCzechNanoLab project LM2023051 funded by MEYS CR is gratefully acknowledged for the financial support of the measurements/sample fabrication at LNSM Research Infrastructure。
文摘The Mg-Y-Zn magnesium alloy system is known for the presence of Long-Period Stacking Ordered(LPSO)phases that improves strength and ductility with minimal amounts of alloying elements.Even better improvements are associated with the specific microstructure known as the Mille-Feuille(MF)structure that can occur in this alloy as well after proper heat treatment.This study systematically compares the traditional ingot metallurgy method with the Bridgman method(slow cooling),coupled with diverse heat treatments and extrusion process.Microscopic analyses reveal variations in the presence of LPSO phases,MF structure,and especially grain size,leading to divergent mechanical and corrosion properties.The Bridgman approach surprisingly stands out,ensuring superior mechanical properties due to kink and texture strengthening.
基金supported by the Zhejiang Provincial Natural Science Foundation of China under Grant No.LTGG23E080001Zhejiang Engineering Research Center of Intelligent Urban Infrastructure under Grant No.IUI2022-ZD-01.
文摘Kinked rebar is a special type of steel material,which is installed in beam column nodes and frame beams.It effectively enhances the blast resilience,seismic collapse resistance,and progressive collapse resistance of reinforced concrete(RC)structures without imposing substantial cost burdens,thereby emerging as a focal point of recent research endeavors.On the basis of explaining the working principle of kinked rebars,this paper reviews the research status of kinked rebars at home and abroad from three core domains:the tensile mechanical properties of kinked rebars,beam column nodes with kinked rebars,and concrete frame structures with kinked rebars.The analysis underscores that the straightening process of kinked rebars does not compromise their ultimate strength but significantly bolsters structural ductility and enhances energy dissipation capabilities.In beam-column joints,the incorporation of kinked rebars facilitates the seamless transfer of plastic hinges,adhering to the design principle of“strong columns and weak beams.”In addition,kinked rebars can greatly improve the resistance of the beam;The seismic resistance,internal explosion resistance,and progressive collapse resistance of reinforced concrete frame structures with kinked rebar have significantly improved.Beyond its primary application,the principle of kinked rebar was extended to other applications of kinked materials such as corrugated steel plates and origami structures,and the stress characteristics of related components and structures were studied.Intriguingly,this paper also proposes the application of kinked rebars in bridge engineering,aiming to address the challenges of localized damage concentration and excessive residual displacement in RC bridge piers.The introduction of kinked rebars in piers is envisioned to mitigate these issues,with the paper outlining its advantages and feasibility,thereby offering valuable insights for future research on kinked reinforcement and seismic design strategies for bridges.
基金supported by the National Natural Science Foundation of China(Grant No.12393782).
文摘In this paper,the mutual influence of plastic behaviors between kinked macro-crack and kinked micro-crack is analyzed based on the distributed dislocation technique and the dislocation-free zone model.A novel theoretical model for the size of the plastic zone is proposed,where the length of the dislocation array calculated in a specific direction is utilized to characterize the size of the plastic zone at the crack tip.The results demonstrate that,compared with the length of the dislocation array distributed along the crack direction,the length of the dislocation array distributed at a certain specific angle can more accurately characterize the plastic zone at the crack tip.When compared with the results of finite element analysis,the relative error is within 0.2%.Within the theoretical framework of this paper,it is considered that when the dislocation array is set at the crack tip and forms an angle of approximately 25°with respect to the horizontal direction,the calculated length of the dislocation array can effectively characterize the size of the plastic zone.The dislocation density increases with the decrease of the kinking angle of the crack.These results are conducive to predicting the plastic and fracture behaviors of materials containing kinked cracks.
基金supported by the National Natural Science Foundation of China(Grant No.12393782).
文摘Combining the continuously distributed dislocation technique(DDT)and the von Mises yield criterion,new double-crack and multi-crack models were established.The influences of multi-segment kinked micro-cracks and groups of kinked micro-cracks on the plastic behavior of the macro-crack were investigated.The results show that a smaller kinking angle of the micro-crack enhances its influence on the plastic deformation of the macro-crack,potentially leading to plastic zone fusion.Meanwhile,micro-cracks with smaller kinking angles exert a stronger attracting force on macro-crack growth,facilitating convergence between them.Furthermore,annularly distributed micro-crack groups demonstrate a more pronounced attraction on macro-crack propagation compared to linearly distributed micro-crack groups.The double-crack and multi-crack models established in this paper offer a theoretical framework for analyzing the plastic fracture behavior of metallic materials containing complex kinked cracks.
文摘多晶硅薄膜晶体管(P-Si TFTs)技术在SOP(system on panel)显示应用中发挥着越来越重要的作用。随着尺寸的不断缩小,P-Si TFT的Kink效应越来越明显,对有源液晶显示矩阵和驱动电路的性能影响很大。对发生Kink效应的物理机制、二维数值仿真及其一维解析模型进行了分析,讨论了晶粒边界、沟道长度与Kink效应的关系,提出建立适合电路仿真的一维解析模型的关键与展望。
基金supported by National Basic Research Program of China (No.2008CB717801)National Natural Science Foundation of China (No.10875024)Laboratory of College and University Program of Liaoning Province of China (No.2008S059)
文摘A semi-analytical method is introduced to study kink instability in cylindrical plasma with line-tied boundary conditions. The method is based on an expansion for magnetohydrodynamics （MHD） equations in one-dimensional （1D） radial eigenvalue problems by using Fourier transforms. The MHD equations then become an ordinary differential equation. This method is applicable to both ideal and non-ideal MHD problem. The effect of plasma pressure （P0） on kink instability is studied in a cylindrical geometry. Complex discrete spectra are pre- sented. Two-dimensional （2D） eigenfunctions with the line-tied boundary conditions are obtained. The growth rate and radial eigenfunctions are different in the two cases of P0 = 0 and P0 ≠ 0, which indicate that the effect of plasma pressure can not be ignored if it is large enough. This method allows us to understand the role of individual radial eigenfunctions, and is also computationally efficient compared to direct solutions of the MHD equations by the finite difference method.
