Composite structures consisting of two-dimensional(2D)materials deposited on elastic substrates have a wide range of potential applications in flexible electronics.For such devices,robust 2D film/substrate interfacial...Composite structures consisting of two-dimensional(2D)materials deposited on elastic substrates have a wide range of potential applications in flexible electronics.For such devices,robust 2D film/substrate interfacial adhesion is essential for their reliable performance when subjected to external thermal and mechanical loads.To better understand the strength and failure behavior of the 2D film/substrate interfaces,two types of graphene/polymer samples with distinct interfacial adhesion properties are fabricated and tested by uniaxially stretching the substrates.Depending on the interfacial adhesion,two drastically different debonding rates are observed,i.e.,rapid snap-through debonding and more progressive crack propagation.Motivated by the experimental observation,we propose an improved shear-lag model with a trapezoidal-shaped cohesive zone to derive an analytical solution for the decohesion behavior.The theoretical model reveals that the decohesion behavior of the frictional adhesive interface is governed by three dimensionless parameters.Particularly,the dimensionless length of the film essentially determines the decohesion rate;while the other two parameters affect the critical substrate strain to initiate debonding.By fitting the experimental data with the theoretical model,the intrinsic adhesion properties of the two samples are obtained with physically meaningful values.This work offers an analytical solution to describing the decohesion behavior of general thin film/substrate systems with a frictional adhesive interface,which is beneficial for characterizing and optimizing the mechanical properties of various thin film/polymer devices.展开更多
Solids in nano-scales hold the promise to exhibit extreme strength and elasticity due to the absence of interior defects and the designability of micro-arrangements.A nano-scaled bulk sample can be produced by diamond...Solids in nano-scales hold the promise to exhibit extreme strength and elasticity due to the absence of interior defects and the designability of micro-arrangements.A nano-scaled bulk sample can be produced by diamond,ice,metallic twins,high entropy alloy(HEA),or cubic boron nitride(cBN).A loading stage capable of 4-DoF movements was designed and built to achieve multi-axial mechanical loading inside a transmission electronic microscope chamber with sub-nanometer loading precision.For single crystal diamond in the shape of nano-needles,we were able to achieve an extreme bending strength of 125 GPa at the tensile side,approaching the theoretical strength of diamond.For ice fibers of sub-micron radius,an extreme elastic strain of 10.9%was acquired,far exceeding the previous record of 0.3%for the elastic strain achievable by ice.For metallic twin specimens made by nano-welding,a shear strain as large as 364%was recorded parallel to the twin boundary.Cyclic shear loading aligned with the twin boundary would drive an up-and-down sweeping movement of the low-angle grain boundary,as composed by an array of dislocations.The sweep of the grain boundary effectively cleanses the lattice defects and creates a feasible scenario of unlimited cyclic endurance.For a HEA dog-bone specimen in nano-scale,an extreme elastic strain of about 10%was achieved.At this level of mechanical straining,stretch-induced melting for crystalline metals,as envisaged by Lindemann a century ago,was realized.For cBN crystals,a fracture path inclined to the stacking hexagon planes would result in a new failure mechanism of layered decohesion,triggered by the extremely large elastic strain(>7%)along the edge of the submicron-scaled specimen.These results indicate ample room for upgrading the mechanical behaviour of solids in nano-scales.展开更多
The variations of Debye temperature and lattice parameter of Ti-30Mo alloy with different hydrogen contents were measured by means of X-ray diffraction.It was found that as the hydrogen content increases,the Debye tem...The variations of Debye temperature and lattice parameter of Ti-30Mo alloy with different hydrogen contents were measured by means of X-ray diffraction.It was found that as the hydrogen content increases,the Debye temperature decreases,but the lattice parameter of the aUoy increases.The above results experimentally support the decohesion theory that the in- crease of hydrogen in metals will weaken the cohesive force between the atoms and make met- als brittle.展开更多
Hydrogen embrittlement(HE)remains a critical challenge in the reliability and safety of metallic components across a range of engineering applications,from aerospace to energy infrastructure.This review comprehensivel...Hydrogen embrittlement(HE)remains a critical challenge in the reliability and safety of metallic components across a range of engineering applications,from aerospace to energy infrastructure.This review comprehensively explores the fundamental mechanisms underlying HE-including hydrogen-enhanced decohesion(HEDE),hydrogen-enhanced localized plasticity(HELP),and hydride-induced embrittlement-across various metal systems.Emphasis is placed on advanced characterization techniques such as thermal desorption spectroscopy,atom probe tomography,and in-situ mechanical testing,which provide multi-scale insights into hydrogen transport,trapping,and damage evolution.The study further evaluates key factors influencing HE susceptibility,including alloy composition,microstructural features,environmental conditions,and applied stress states.Mitigation strategies are systematically discussed,focusing on alloy design,microstructural engineering,surface treatments,and thermal processing.By integrating mechanistic understanding with practical prevention methods,this work provides a comprehensive framework for the design and maintenance of hydrogen-tolerant metallic materials in modern engineering systems.展开更多
The low damage resistance and fracture toughness hinder the widespread application of ultrahighstrength dual phase(DP)steels.In this work,we propose a novel strategy to improve the fracture toughness of ultrahigh-stre...The low damage resistance and fracture toughness hinder the widespread application of ultrahighstrength dual phase(DP)steels.In this work,we propose a novel strategy to improve the fracture toughness of ultrahigh-strength DP steels by an order of magnitude without sacrificing the tensile strength.Six ultrahigh-strength DP steels with varying microstructure but comparable tensile strength(>1400 MPa)were prepared via tailoring the heat treatment process after cold rolling.Additionally,finite element(FE)method incorporated with Gurson-Tvergaad-Needleman(GTN)model and cohesive zone model(CZM)is established to simulate the fracture behavior of DP steel.Twelve model DP steels with different ferrite sizes and F/M strength differences are constructed.The combined experiment and simulation results demonstrate that(i)ferrite/martensite(F/M)interface decohesion prevails in all steels,(ii)the ferrite morphology has a strong influence on the fracture toughness of ultrahigh-strength DP steels,(iii)the effects of matrix type,ferrite size,and F/M hardness difference on the fracture toughness are relatively weak,(iv)the exceptional high fracture toughness of plate-like DP steel can be attributed to the crack deflection,crack divider and crack arrester mechanisms induced by F/M interface decohesion.展开更多
基金the National Natural Science Foundation of China(Nos.12025203,11921002,and 11890671)the National Key R&D Program of China(No.2022YFF0706100)the Initiative Program of State Key Laboratory of Tribology in Advanced Equipment(No.SKLT2022A01).
文摘Composite structures consisting of two-dimensional(2D)materials deposited on elastic substrates have a wide range of potential applications in flexible electronics.For such devices,robust 2D film/substrate interfacial adhesion is essential for their reliable performance when subjected to external thermal and mechanical loads.To better understand the strength and failure behavior of the 2D film/substrate interfaces,two types of graphene/polymer samples with distinct interfacial adhesion properties are fabricated and tested by uniaxially stretching the substrates.Depending on the interfacial adhesion,two drastically different debonding rates are observed,i.e.,rapid snap-through debonding and more progressive crack propagation.Motivated by the experimental observation,we propose an improved shear-lag model with a trapezoidal-shaped cohesive zone to derive an analytical solution for the decohesion behavior.The theoretical model reveals that the decohesion behavior of the frictional adhesive interface is governed by three dimensionless parameters.Particularly,the dimensionless length of the film essentially determines the decohesion rate;while the other two parameters affect the critical substrate strain to initiate debonding.By fitting the experimental data with the theoretical model,the intrinsic adhesion properties of the two samples are obtained with physically meaningful values.This work offers an analytical solution to describing the decohesion behavior of general thin film/substrate systems with a frictional adhesive interface,which is beneficial for characterizing and optimizing the mechanical properties of various thin film/polymer devices.
文摘Solids in nano-scales hold the promise to exhibit extreme strength and elasticity due to the absence of interior defects and the designability of micro-arrangements.A nano-scaled bulk sample can be produced by diamond,ice,metallic twins,high entropy alloy(HEA),or cubic boron nitride(cBN).A loading stage capable of 4-DoF movements was designed and built to achieve multi-axial mechanical loading inside a transmission electronic microscope chamber with sub-nanometer loading precision.For single crystal diamond in the shape of nano-needles,we were able to achieve an extreme bending strength of 125 GPa at the tensile side,approaching the theoretical strength of diamond.For ice fibers of sub-micron radius,an extreme elastic strain of 10.9%was acquired,far exceeding the previous record of 0.3%for the elastic strain achievable by ice.For metallic twin specimens made by nano-welding,a shear strain as large as 364%was recorded parallel to the twin boundary.Cyclic shear loading aligned with the twin boundary would drive an up-and-down sweeping movement of the low-angle grain boundary,as composed by an array of dislocations.The sweep of the grain boundary effectively cleanses the lattice defects and creates a feasible scenario of unlimited cyclic endurance.For a HEA dog-bone specimen in nano-scale,an extreme elastic strain of about 10%was achieved.At this level of mechanical straining,stretch-induced melting for crystalline metals,as envisaged by Lindemann a century ago,was realized.For cBN crystals,a fracture path inclined to the stacking hexagon planes would result in a new failure mechanism of layered decohesion,triggered by the extremely large elastic strain(>7%)along the edge of the submicron-scaled specimen.These results indicate ample room for upgrading the mechanical behaviour of solids in nano-scales.
文摘The variations of Debye temperature and lattice parameter of Ti-30Mo alloy with different hydrogen contents were measured by means of X-ray diffraction.It was found that as the hydrogen content increases,the Debye temperature decreases,but the lattice parameter of the aUoy increases.The above results experimentally support the decohesion theory that the in- crease of hydrogen in metals will weaken the cohesive force between the atoms and make met- als brittle.
文摘Hydrogen embrittlement(HE)remains a critical challenge in the reliability and safety of metallic components across a range of engineering applications,from aerospace to energy infrastructure.This review comprehensively explores the fundamental mechanisms underlying HE-including hydrogen-enhanced decohesion(HEDE),hydrogen-enhanced localized plasticity(HELP),and hydride-induced embrittlement-across various metal systems.Emphasis is placed on advanced characterization techniques such as thermal desorption spectroscopy,atom probe tomography,and in-situ mechanical testing,which provide multi-scale insights into hydrogen transport,trapping,and damage evolution.The study further evaluates key factors influencing HE susceptibility,including alloy composition,microstructural features,environmental conditions,and applied stress states.Mitigation strategies are systematically discussed,focusing on alloy design,microstructural engineering,surface treatments,and thermal processing.By integrating mechanistic understanding with practical prevention methods,this work provides a comprehensive framework for the design and maintenance of hydrogen-tolerant metallic materials in modern engineering systems.
基金financially supported by the National Key R&D program(no.2022YFB3707501)GDAS’Project of Sci-ence and Technology(no.2021GDASYL-20210102002)+1 种基金Guangdong Provincial Project(nos.2022A0505050053,2021B1515120071,and 2020B1515130007)National Natural Science Foundation of China(no.52130102).
文摘The low damage resistance and fracture toughness hinder the widespread application of ultrahighstrength dual phase(DP)steels.In this work,we propose a novel strategy to improve the fracture toughness of ultrahigh-strength DP steels by an order of magnitude without sacrificing the tensile strength.Six ultrahigh-strength DP steels with varying microstructure but comparable tensile strength(>1400 MPa)were prepared via tailoring the heat treatment process after cold rolling.Additionally,finite element(FE)method incorporated with Gurson-Tvergaad-Needleman(GTN)model and cohesive zone model(CZM)is established to simulate the fracture behavior of DP steel.Twelve model DP steels with different ferrite sizes and F/M strength differences are constructed.The combined experiment and simulation results demonstrate that(i)ferrite/martensite(F/M)interface decohesion prevails in all steels,(ii)the ferrite morphology has a strong influence on the fracture toughness of ultrahigh-strength DP steels,(iii)the effects of matrix type,ferrite size,and F/M hardness difference on the fracture toughness are relatively weak,(iv)the exceptional high fracture toughness of plate-like DP steel can be attributed to the crack deflection,crack divider and crack arrester mechanisms induced by F/M interface decohesion.
