Developing alloys with exceptional strength-ductility combinations across a broad temperature range is crucial for advanced structural applications.The emerging face-centered cubic medium-entropy alloys(MEAs)demonstra...Developing alloys with exceptional strength-ductility combinations across a broad temperature range is crucial for advanced structural applications.The emerging face-centered cubic medium-entropy alloys(MEAs)demonstrate outstanding mechanical properties at both ambient and cryogenic temperatures.They are anticipated to extend their applicability to elevated temperatures,owing to their inherent advantages in leveraging multiple strengthening and deformation mechanisms.Here,a dual heterostructure,comprising of heterogeneous grain structure with heterogeneous distribution of the micro-scale Nb-rich Laves phases,is introduced in a CrCoNi-based MEA through thermo-mechanical processing.Additionally,a high-density nano-coherentγ’phase is introduced within the grains through isothermal aging treatments.The superior thermal stability of the heterogeneously distributed precipitates enables the dual heterostructure to persist at temperatures up to 1073 K,allowing the MEA to maintain excellent mechanical properties across a wide temperature range.The yield strength of the dual-heterogeneous-structured MEA reaches up to 1.2 GPa,1.1 GPa,0.8 GPa,and 0.6 GPa,coupled with total elongation values of 28.6%,28.4%,12.6%,and 6.1%at 93 K,298 K,873 K,and 1073 K,respectively.The high yield strength primar-ily stems from precipitation strengthening and hetero-deformation-induced strengthening.The high flow stress and low stacking fault energy of the dual-heterogeneous-structured MEA promote the formation of high-density stacking faults and nanotwins during deformation from 93 K to 1073 K,and their density increase with decreasing deformation temperature.This greatly contributes to the enhanced strainhardening capability and ductility across a wide temperature range.This study offers a practical solution for designing dual-heterogeneous-structured MEAs with both high yield strength and large ductility across a wide temperature range.展开更多
In this work,a heterogeneous structure(HS)with an alternating distribution of coarse and fineαlamella is fabricated in bimodal Ti6242 alloy via insufficient diffusion of alloying elements induced by fast heat-ing tre...In this work,a heterogeneous structure(HS)with an alternating distribution of coarse and fineαlamella is fabricated in bimodal Ti6242 alloy via insufficient diffusion of alloying elements induced by fast heat-ing treatment.Instead of a distinct interface between the primaryα_(p)hase(α_(p))andβ_(t)ransformation microstructure(β_(t))in the equiaxed microstructure(EM),allα_(p)/β_(t)interfaces are eliminated in the HS,and the largeα_(p)phases are replaced by coarseαlamella.Compared to the EM alloy,the heterostruc-tured alloy exhibits a superior strength-ductility combination.The enhanced strength is predominantly attributed to the increased interfaces ofα/βplates and hetero-deformation induced(HDI)strengthening caused by back stress.Meanwhile,good ductility is ascribed to its uniform distribution of coarse and fineαlamella,which effectively inhibits strain localization and generates an extra HDI hardening.This can be evidenced by the accumulated geometrically necessary dislocations(GNDs)induced by strain partitioning of the heterostructure.Significantly,the HDI causes extra<c+a>dislocations piling up in the coarseαlamella,which generates an extra strain hardening to further improve the ductility.Such hetero-interface coordinated deformation mechanism sheds light on a new perspective for tailoring bimodal titanium al-loys with excellent mechanical properties.展开更多
In recent years,a new class of metallic materials featuring heterogeneous structures has emerged.These materials consist of distinct soft and hard domains with significant differences in mechanical properties,allowing...In recent years,a new class of metallic materials featuring heterogeneous structures has emerged.These materials consist of distinct soft and hard domains with significant differences in mechanical properties,allowing them to maintain high strength while offering superior ductility.Magnesium(Mg)alloys,renowned for their low density,high specific strength,exceptional vibration damping,and electromagnetic shielding properties,exhibit tremendous potential as lightweight and functional materials.Despite their advantageous properties,high-strength Mg alloys often suffer from limited ductility.However,the emergence of heterogeneous materials provides a fresh perspective for the development of Mg alloys with both high strength and ductility.This article provided a fundamental overview of heterostructured materials and systematically reviewed the recent research progress in the design of Mg alloys with strength-ductility balance based on heterostructure principles.The review encompassed various aspects,including preparation methods,formation mechanisms of diverse heterostructures,and mechanical properties,both within domestic and international contexts.On this basis,the article discussed the challenges encountered in the design and fabrication of heterostructured Mg alloys,as well as the urgent issues that require attention and resolution in the future.展开更多
The application of single-phase face-centered cubic(FCC)medium entropy alloys(MEAs)in the engi-neering industry is often hindered by the challenge of insufficient strength.In this study,a novel non-equiatomic ratio Ni...The application of single-phase face-centered cubic(FCC)medium entropy alloys(MEAs)in the engi-neering industry is often hindered by the challenge of insufficient strength.In this study,a novel non-equiatomic ratio Ni_(40)Co_(30)Cr_(20)Al_(5)Ti_(5)MEA was successfully fabricated.Through the well-designed mechan-ical heat treatment processing,we introduced a heterogeneous grain structure comprising 67.4%fine grain and 32.6%coarse grain.Additionally,heterogeneous size L12 phases consisting of 18.7%submicron precip-itates and 11.7%nano-sized precipitates,were incorporated into the alloy.Tensile tests conducted at room temperature revealed that the double heterogeneous structure alloy demonstrated remarkable strength–ductility synergy.It exhibited a yield strength of 1200 MPa,an ultimate tensile strength of 1560 MPa and a total elongation of 33.6%.The exceptional strength of the alloy can be primarily attributed to heteroge-neous deformation induced strengthening,grain boundary strengthening and precipitation strengthening.The excellent ductility is mainly attributed to the high-density stacking faults and Lomer–Cottrell locks.This study not only contributes to the clarification of the strengthening and deformation mechanism of double heterogeneous structure alloys but also provides an effective strategy for the development of high-performance alloys with high strength and ductility.展开更多
Although refractory high-entropy alloys(RHEAs)possess excellent softening resistance and thermal sta-bility at high temperatures,their practical application is often limited due to room temperature(RT)brit-tleness.In ...Although refractory high-entropy alloys(RHEAs)possess excellent softening resistance and thermal sta-bility at high temperatures,their practical application is often limited due to room temperature(RT)brit-tleness.In this work,we successfully achieved RT plasticization in a brittle(TaMoTi)_(92)Al_(8)RHEA via in situ forming heterogeneous structure(HS)with the doping of Zr.Different from the mainstream design con-cept of“soft solid solution matrices with hard intermetallic phases”proposed in the literature,the newly developed TaMoZrTiAl RHEA is featured by a hard disordered BCC phase embedded into a soft intermetal-lic B2 matrix.Such an HS leads to the remarkable strength-plasticity synergy in this alloy at RT,showing a large plasticity of>20%,associated with a high strength of>2380 MPa.It was found that solid solu-tion strengthening and heterodeformation-induced strengthening caused by dislocation pile-ups at phase boundaries are responsible for the enhancement in the yield strength,while deformation-induced strain partition and the frequent operation of dislocation cross-slip substantially improve the work hardening capacity of alloy,thus enabling the high strength and good RT plasticity.In short,the current work not only reveals the micromechanisms of the influence of heterogeneous dual-phase structure on the RT me-chanical behaviour in RHEAs but also provides a useful strategy for plasticizing brittle RHEAs.展开更多
Developing high-ductility magnesium(Mg)alloys has become an imminent issue for their wide appli-cation.In this work,a new Mg-Sn-Zn-Zr alloy with ultra-high ductility(elongation,El.over 40%)and high ultimate tensile st...Developing high-ductility magnesium(Mg)alloys has become an imminent issue for their wide appli-cation.In this work,a new Mg-Sn-Zn-Zr alloy with ultra-high ductility(elongation,El.over 40%)and high ultimate tensile strength(UTS,~309-354 MPa)was prepared by a novel differential thermal equal-channel angular pressing(DT-ECAP).Heterogeneous structures,including bimodal grain structures and in-homogeneous distribution of second phases composed of banded structure and particle free zone(PFZ),were induced by DT-ECAP process.Based on the results of electron backscatter diffraction(EBSD),trans-mission electron microscopy(TEM),high-resolution TEM(HRTEM),and selected area electron diffraction(SAED),the bimodal grain structure originated from incomplete dynamic recrystallization(DRX)domi-nated by Zener pinning,strain-induced grain boundary migration(SIBM)and the limitation of polycrys-tallization due to lower dislocation density.Meanwhile,the bimodal distribution of second phases was highly associated with the defect density and initial structure.More importantly,the enhanced strength of DT-ECAPed alloys can be primarily attributed to hetero-deformation induced(HDI)strengthening,grain boundary strengthening,and precipitation strengthening.Moreover,HDI hardening,texture weakening or randomizing activation of non-basal slip,high density of dislocations in sub-structures,and twining in-duced superior work-hardening effect,which was highly responsible for the ultra-high ductility in sixth pass(6P)alloy.The current work provides a novel DT-ECAP process for inducing heterogeneous structure and offers beneficial insight into the development of ultra-high ductility and high strength for rare-earth-free Mg alloys via a combination of HDI strengthening and hardening and other vital mechanisms.展开更多
The coarsening-grained single-phase face-centered cubic(fcc)medium-entropy alloys(MEAs)normally exhibit insufficient strength for some engineering applications.Here,superior mechanical properties with ultimate tensile...The coarsening-grained single-phase face-centered cubic(fcc)medium-entropy alloys(MEAs)normally exhibit insufficient strength for some engineering applications.Here,superior mechanical properties with ultimate tensile strength of 1.6 GPa and fracture strain of 13.1%at ambient temperature have been achieved in a(CoCrNi)_(94)Ti_(3)Al_(3)MEA by carefully architecting the multi-scale heterogeneous structures.Electron microscopy characterization indicates that the superior mechanical properties mainly originated from the favorable heterogeneous fcc matrix(1-40μm)and the coherent sphericalγ’precipitates(10-100 nm),together with a high number density of crystalline defects(2-10 nm),including dislocations,small stacking faults,Lomer-Cottrell locks,and ultrafine deformation twins.展开更多
In order to mimic the natural heterogeneity of native tissue and provide a better microenvironment for cell culturing,multi-material bioprinting has become a common solution to construct tissue models in vitro.With th...In order to mimic the natural heterogeneity of native tissue and provide a better microenvironment for cell culturing,multi-material bioprinting has become a common solution to construct tissue models in vitro.With the embedded printing method,complex 3D structure can be printed using soft biomaterials with reasonable shape fidelity.However,the current sequential multi-material embedded printing method faces a major challenge,which is the inevitable trade-off between the printed structural integrity and printing precision.Here,we propose a simultaneous multi-material embedded printing method.With this method,we can easily print firmly attached and high-precision multilayer structures.With multiple individually controlled nozzles,different biomaterials can be precisely deposited into a single crevasse,minimizing uncontrolled squeezing and guarantees no contamination of embedding medium within the structure.We analyse the dynamics of the extruded bioink in the embedding medium both analytically and experimentally,and quantitatively evaluate the effects of printing parameters including printing speed and rheology of embedding medium,on the 3D morphology of the printed filament.We demonstrate the printing of double-layer thin-walled structures,each layer less than 200μm,as well as intestine and liver models with 5%gelatin methacryloyl that are crosslinked and extracted from the embedding medium without significant impairment or delamination.The peeling test further proves that the proposed method offers better structural integrity than conventional sequential printing methods.The proposed simultaneous multi-material embedded printing method can serve as a powerful tool to support the complex heterogeneous structure fabrication and open unique prospects for personalized medicine.展开更多
A carbon-containing CoCrFeNi high entropy alloy(HEA)with heterogeneous structures was obtained through thermomechanical treatments,which induced concurrent recrystallization and carbide precipitation in the alloy.A co...A carbon-containing CoCrFeNi high entropy alloy(HEA)with heterogeneous structures was obtained through thermomechanical treatments,which induced concurrent recrystallization and carbide precipitation in the alloy.A combination of high yield strength(556 MPa)and large uniform elongation(45%)was achieved in the investigated alloy.The enhancement of the strength is attributed to the combined effects of grain refinement,precipitation strengthening and microstructural heterogeneity.Our work demonstrated that the heterogeneity design could be realized by thermomechanical processes,which provided a practical strategy for producing HEAs with high performance.展开更多
High-/medium-entropy stainless alloys(HESAs/MESAs)are a new kind of alloys with great potential to combine excellent properties from high-/medium-entropy alloys(HEAs/MEAs)and stainless steels.A CrFeNi MESA was chosen ...High-/medium-entropy stainless alloys(HESAs/MESAs)are a new kind of alloys with great potential to combine excellent properties from high-/medium-entropy alloys(HEAs/MEAs)and stainless steels.A CrFeNi MESA was chosen to investigate its microstructures and mechanical behaviors.After homogenization,the strength and ductility of CrFeNi MESAs with single-phase face-centered-cubic(fcc)structure were higher compared with those of Fe_(100−x-y)Cr_(x)Ni_(y)austenitic stainless steels.Cr-rich body-centered-cubic(bcc)precipitates and heterogeneous structure were introduced by cold rolling and annealing at 800℃.Rolling at 700℃ results in higher dislocation density and the occurrence of lamellar Cr-rich bcc precipitates.High-density dislocations and fcc grains with heterogeneous structure,together with Cr-rich bcc precipitates,contribute to a yield strength improvement of about 50 MPa,and appreciable tensile yield strength of~540 MPa and fracture strain of~20%are obtained.It reveals that not only compositional variations but also grain size and phase structure tuning can be utilized for achieving desired mechanical properties.展开更多
In present work,we successfully fabricated a novel Co-free non-equiatomic Ni_(46)Cr_(23)Fe_(23)Al_(4)Ti_(4)mediumentropy alloy with dual heterogeneous structures,i.e.three-levels grain structures and heterogeneous L1;...In present work,we successfully fabricated a novel Co-free non-equiatomic Ni_(46)Cr_(23)Fe_(23)Al_(4)Ti_(4)mediumentropy alloy with dual heterogeneous structures,i.e.three-levels grain structures and heterogeneous L1;precipitates.Experimental results revealed the dual heterogeneous structures lead to remarkable strength-ductility synergy properties in this Co-free medium-entropy alloy,showing high yield strength and ultimate tensile strength of~1203 MPa and~1633 MPa,respectively,remaining an excellent ductility of~28.7%.Further analyses about strengthening and deformation mechanisms indicated precipitation hardening and hetero-deformation induced hardening contribute the majority strength enhancement,meanwhile deformation-induced hierarchical stacking-faults networks,high density Lomer-Cottrell locks and microstructure features of heterogeneous grains and precipitates substantially facilitate the high work-hardening capacity and excellent tensile ductility.This work not only offers fundamental understanding of the strength and deformation mechanisms of the dual heterogeneous structural material,but also provides useful strength design strategy for low-price high performance high/medium-entropy alloys.展开更多
Metastable β titanium alloy is an ideal material for lightweight and high strength due to its excellent comprehensive mechanical properties.However,overcoming the trade-off relation between strength and ductility rem...Metastable β titanium alloy is an ideal material for lightweight and high strength due to its excellent comprehensive mechanical properties.However,overcoming the trade-off relation between strength and ductility remains a significant challenge.In this study,the mechanical properties of Ti-38644 alloy were optimized by introducing a heterogeneous bi-grain bi-lamella(BG-BL)structure through a well-designed combination of rolling,drawing and heat treatment.The results demonstrate that the present BG-BL Ti-38644 alloy shows a tensile strength of~1500 MPa and a total elongation of 18%.In particular,the high strength-elongation combination of the BG-BL Ti-38644 alloy breakthroughs the trade-off relation in all the titanium alloys available.The recrystallized grains with low dislocation enhance the ductility of the Ti-38644 alloy,while the highly distorted elongated grains mainly contribute to the high strength.The present study provides a new principle for designing Ti alloys with superior strength and ductility.展开更多
The growth of dendrites in Li/Na metal batteries is a multifaceted process that is controlled by several factors such as electric field,ion transportation,temperature,and pressure.Rational design of battery components...The growth of dendrites in Li/Na metal batteries is a multifaceted process that is controlled by several factors such as electric field,ion transportation,temperature,and pressure.Rational design of battery components has become a viable approach to address this challenge.Among the various design strategies,heterogeneous structures have been demonstrated to be effective in mitigating uneven metal deposition by reducing the local current density and regulating the deposition sites.In this review,we discuss comprehensively the underlying principles and factors that influence dendrite growth,as well as the synthesis approaches for heterogeneous structures.Furthermore,we provide an overview of the diverse applications of heterogeneous structures in battery components.Finally,we highlight existing challenges and future directions for the use of heterogeneous structures in regulating metal deposition.展开更多
1.Introduction The strength-ductility trade-offdilemma has long been a per-sistent challenge in Al matrix composites(AMCs)[1,2].This is-sue primarily arises from the agglomeration of reinforcements at the grain bounda...1.Introduction The strength-ductility trade-offdilemma has long been a per-sistent challenge in Al matrix composites(AMCs)[1,2].This is-sue primarily arises from the agglomeration of reinforcements at the grain boundaries(GBs),which restricts local plastic flow dur-ing the plastic deformation and leads to stress concentration[3,4].Recently,the development of concepts aimed at achieving hetero-geneous grain has emerged as a promising approach for enhanc-ing comprehensive mechanical properties[5,6].展开更多
Lead-free dielectric relaxor ferroelectric(RFE)ceramics are one of the promising materials for dielectric energy storage applications.However,the contradiction between high polarization and low hysteresis leads to int...Lead-free dielectric relaxor ferroelectric(RFE)ceramics are one of the promising materials for dielectric energy storage applications.However,the contradiction between high polarization and low hysteresis leads to interior energy storage performance,which greatly limits their applications in high/pulsed power systems.Here,we propose an effective strategy to significantly improve the energy storage properties of 0.94Bi_(0.5)Na_(0.5)TiO_(3)-0.06BaTiO_(3)(0.94BNT-0.06BT)with a morphotropic phase boundary(MPB)composition by constructing multiscale polymorphic domains and local heterogeneous structures.The introduction of Nd(Mg_(1/2)Hf_(1/2))O_(3)(NMH)facilitates the formation of short-range ordered polar nanoregions(PNRs).Moreover,small amounts of nanodomains with high polarization are resulted from local heterogeneous structures with Bi-and Ti-rich regions.Multiscale polymorphic domains with the coexistence of rhombohedral/tetragonal(R+T)nanodomains and PNRs ensure both high polarization and low hysteresis,which is crucial for improving the energy storage performance.Furthermore,the excellent electrical insulation is resulted from the high insulation resistivity,grain size at the submicron scale and a wide band gap by NMH doping.Therefore,a high recoverable energy density(Wrec)of 7.82 J/cm^(3) with an ultrahigh efficiency(η)of 93.1%is realized in the designed BNT-BT-NMH ternary system because of both a largeΔP and high Eb.These findings,together with good temperature/frequency/cycling stability,indicate that the optimum composition ceramics are very promising materials for energy storage applications in high/pulsed power systems.展开更多
Poly(_(L)-lactide)(PLLA),a leading biodegradable polyester,has demonstrated potential as a sustainable alternative,owing to its excellent biodegradability and rigidity.However,their slow crystallization kinetics and p...Poly(_(L)-lactide)(PLLA),a leading biodegradable polyester,has demonstrated potential as a sustainable alternative,owing to its excellent biodegradability and rigidity.However,their slow crystallization kinetics and poor heat resistance limit their application scope.Recent advances have highlighted that the combination of extensional flow and thermal fields can achieve toughness–stiffness balance,high transparency,and good heat resistance.However,the effect of extensional flow on the post-non-isothermal crystallization of PLLA during heating and the resulting crystalline texture remains unclear.In this study,PLLA with a heterogeneous amorphous structure and oriented polymorph was prepared by extensional flow.The effect of heterogeneous amorphous structures on non-isothermal crystallization kinetics during the heating process was studied by thermal analysis,polarized optical microscopy,infrared spectroscopy,and ex situ/in situ X-ray characterization.These results clearly illustrate that extensional flow enhances the formation of oriented crystalline structures,accelerates non-isothermal crystallization,and modulates the polymorphic composition of PLLA.Moreover,an unexpected dual cold-crystallization behavior is identified in ordered PLLA samples upon extensional flow,which is from the extensional flow-induced heterogeneous amorphous phase into α' phase(low-temperature peak)and the pristine amorphous phase intoαphase(high-temperature peak).The extensional flow primarily promotes the formation of the more perfectαandα'phases,but has a negative effect on the final content ofαphase formed after cold crystallization andα'-to-αphase transformation.The findings of this work advance the understanding of PLLA non-isothermal crystallization after extensional flow and offer valuable guidance for high-performance PLLA upon heat treatment in practical processing.展开更多
1060/7050 Al/Al laminated metal composites(LMCs)with heterogeneous lamellar structures were prepared by accumulative roll bonding(ARB),cold rolling and subsequent annealing treatment.The strengthening mechanism was in...1060/7050 Al/Al laminated metal composites(LMCs)with heterogeneous lamellar structures were prepared by accumulative roll bonding(ARB),cold rolling and subsequent annealing treatment.The strengthening mechanism was investigated by microstructural characterization,mechanical property tests and in-situ fracture morphology observations.The results show that microstructural differences between the constituent layers are present in the Al/Al LMCs after various numbers of ARB cycles.Compared with rolled 2560-layered Al/Al LMCs with 37.5%and 50.0%rolling reductions,those with 62.5%rolling reductions allow for more effective improvements in the mechanical properties after annealing treatment due to their relatively high mechanical incompatibility across the interface.During tensile deformation,with the increased magnitude of incompatibility in the 2560-layered Al/Al LMC with a heterogeneous lamellar structure,the densities of the geometrically necessary dislocations(GNDs)increase to accommodate the relatively large strain gradient,resulting in considerable back stress strengthening and improved mechanical properties.展开更多
Integrating a heterogeneous structure can significantly enhance the strength-ductility synergy of composites.However,the relationship between hetero-deformation induced(HDI)strain hardening and dislocation activity ca...Integrating a heterogeneous structure can significantly enhance the strength-ductility synergy of composites.However,the relationship between hetero-deformation induced(HDI)strain hardening and dislocation activity caused by heterogeneous structures in the magnesium matrix composite remains unclear.In this study,a dual-heterogeneous TiC/AZ61 composite exhibits significantly improved plastic elongation(PEL)by nearly one time compared to uniform FG composite,meanwhile maintaining a high strength(UTS:417 MPa).This is because more severe deformation inhomogeneity in heterogeneous structure leads to more geometrically necessary dislocations(GNDs)accumulation and stronger HDI stress,resulting in higher HDI hardening compared to FG and CG composites.During the early stage of plastic deformation,the pile-up types of GND in the FG zone and CG zone are significantly different.GNDs tend to form substructures in the FG zone instead of the CG zone.They only accumulate at grain boundaries of the CG region,thereby leading to obviously increased back stress in the CG region.In the late deformation stage,the elevated HDI stress activates the new〈c+a〉dislocations in the CG region,resulting in dislocation entanglements and even the formation of substructures,further driving the high hardening in the heterogeneous composite.However,For CG composite,〈c+a〉dislocations are not activated even under large plastic strains,and only〈a〉dislocations pile up at grain boundaries and twin boundaries.Our work provides an in-depth understanding of dislocation variation and HDI hardening in heterogeneous magnesium-based composites.展开更多
A multi-phase heterogeneous FeCoNi-based high-entropy alloy is developed to overcome the trade-off between strength and ductility.By alloying with a small amount of Cu and employing a rapid recrystalliza-tion process,...A multi-phase heterogeneous FeCoNi-based high-entropy alloy is developed to overcome the trade-off between strength and ductility.By alloying with a small amount of Cu and employing a rapid recrystalliza-tion process,it exhibits a good combination of yield strength(roughly 1300 MPa)and ductility(approach-ing 20%).Firstly,a multi-phase heterogeneous structure is tailored ranging from nano to micron.Cu is efficiently precipitated as nanoscale clusters(4.2 nm),high-density cuboidal L1_(2) particles(20-40 nm)and L2_(1) particles(500-800 nm)are found to be embedded in the matrix and a bimodal heterogeneous grain structure(1-40μm)is constructed.Secondly,the introduction of Cu effectively suppresses the pre-cipitation of coarse L21 phase at grain boundaries,reducing its volume fraction by 80%and replaced by smaller-scale continuous precipitations within the grains.Thirdly,the high mixing enthalpy gap of Cu and the matrix leads to the formation of local chemical fluctuation and the consequential rugged topog-raphy in the matrix,which result in retarded dislocation motion and promotes dislocation plugging and interlocking during strain,enhancing yield stress and work hardening rate.This study provides a valuable perspective to enhance strength and ductility via enlarged local chemical fluctuation-tailored multi-phase heterogeneous structures.展开更多
The development of high-performance structural and functional materials is vital in many industrial fields.High-and medium-entropy alloys(H/MEAs)with superior comprehensive properties owing to their specific microstru...The development of high-performance structural and functional materials is vital in many industrial fields.High-and medium-entropy alloys(H/MEAs)with superior comprehensive properties owing to their specific microstructures are promising candidates for structural materials.More importantly,multitudinous efforts have been made to regulate the microstructures and the properties of H/MEAs to further expand their industrial applications.The various heterostructures have enormous potential for the development of H/MEAs with outstanding performance.Herein,multiple heterogeneous structures with single and hierarchical heterogeneities were discussed in detail.Moreover,preparation methods for compositional inhomogeneity,bimodal structures,dualphase structures,lamella/layered structures,harmonic structures(core-shell),multiscale precipitates and heterostructures coupled with specific microstructures in H/MEAs were also systematically reviewed.The deformation mechanisms induced by the different heterostructures were thoroughly discussed to explore the relationship between the heterostructures and the optimized properties of H/MEAs.The contributions of the heterostructures and advanced microstructures to the H/MEAs were comprehensively elucidated to further improve the properties of the alloys.Finally,this review discussed the future challenges of high-performance H/MEAs for industrial applications and provides feasible methods for optimizing heterostructures to enhance the comprehensive properties of H/MEAs.展开更多
基金supported by the Tianjin Science and Technology Plan Project(No.22JCQNJC01280)the Central Funds Guiding the Local Science and Technology Development of Hebei Province(Nos.226Z1001G and 226Z1012G)+1 种基金the National Natural Science Foundation of China(No.52002109,52071124)the Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001).
文摘Developing alloys with exceptional strength-ductility combinations across a broad temperature range is crucial for advanced structural applications.The emerging face-centered cubic medium-entropy alloys(MEAs)demonstrate outstanding mechanical properties at both ambient and cryogenic temperatures.They are anticipated to extend their applicability to elevated temperatures,owing to their inherent advantages in leveraging multiple strengthening and deformation mechanisms.Here,a dual heterostructure,comprising of heterogeneous grain structure with heterogeneous distribution of the micro-scale Nb-rich Laves phases,is introduced in a CrCoNi-based MEA through thermo-mechanical processing.Additionally,a high-density nano-coherentγ’phase is introduced within the grains through isothermal aging treatments.The superior thermal stability of the heterogeneously distributed precipitates enables the dual heterostructure to persist at temperatures up to 1073 K,allowing the MEA to maintain excellent mechanical properties across a wide temperature range.The yield strength of the dual-heterogeneous-structured MEA reaches up to 1.2 GPa,1.1 GPa,0.8 GPa,and 0.6 GPa,coupled with total elongation values of 28.6%,28.4%,12.6%,and 6.1%at 93 K,298 K,873 K,and 1073 K,respectively.The high yield strength primar-ily stems from precipitation strengthening and hetero-deformation-induced strengthening.The high flow stress and low stacking fault energy of the dual-heterogeneous-structured MEA promote the formation of high-density stacking faults and nanotwins during deformation from 93 K to 1073 K,and their density increase with decreasing deformation temperature.This greatly contributes to the enhanced strainhardening capability and ductility across a wide temperature range.This study offers a practical solution for designing dual-heterogeneous-structured MEAs with both high yield strength and large ductility across a wide temperature range.
基金financially supported by the National Natural Science Foundation of China(Nos.52161019 and 52271054)the Science and Technology Project of Guizhou Province,China(No.[2023]047)+1 种基金the GuiZhou DIIT Innovation Project(No.[2023]153)the One Hundred Person Project of Guizhou Province,China(No.[2020]6006).
文摘In this work,a heterogeneous structure(HS)with an alternating distribution of coarse and fineαlamella is fabricated in bimodal Ti6242 alloy via insufficient diffusion of alloying elements induced by fast heat-ing treatment.Instead of a distinct interface between the primaryα_(p)hase(α_(p))andβ_(t)ransformation microstructure(β_(t))in the equiaxed microstructure(EM),allα_(p)/β_(t)interfaces are eliminated in the HS,and the largeα_(p)phases are replaced by coarseαlamella.Compared to the EM alloy,the heterostruc-tured alloy exhibits a superior strength-ductility combination.The enhanced strength is predominantly attributed to the increased interfaces ofα/βplates and hetero-deformation induced(HDI)strengthening caused by back stress.Meanwhile,good ductility is ascribed to its uniform distribution of coarse and fineαlamella,which effectively inhibits strain localization and generates an extra HDI hardening.This can be evidenced by the accumulated geometrically necessary dislocations(GNDs)induced by strain partitioning of the heterostructure.Significantly,the HDI causes extra<c+a>dislocations piling up in the coarseαlamella,which generates an extra strain hardening to further improve the ductility.Such hetero-interface coordinated deformation mechanism sheds light on a new perspective for tailoring bimodal titanium al-loys with excellent mechanical properties.
基金supported by Yunnan Fundamental Research Projects(No.202201BE070001-014)Doctoral Scientific Research Foundation of Hubei University of Automotive Technology(No.BK202336)+4 种基金National Natural Science Foundation of China(No.52071035)Program for Science and Technology Innovation Team in Colleges of Hubei Province(No.T2021012)Outstanding Young Scientific&Technological Innovation Team Plan of Colleges and Universities in Hubei Province(No.T201518 and No.T201811)Major Science and Technology Project of Hubei Province(No.2022AAA001)Key R&D Project of Hubei Province(No.2021BAB019)。
文摘In recent years,a new class of metallic materials featuring heterogeneous structures has emerged.These materials consist of distinct soft and hard domains with significant differences in mechanical properties,allowing them to maintain high strength while offering superior ductility.Magnesium(Mg)alloys,renowned for their low density,high specific strength,exceptional vibration damping,and electromagnetic shielding properties,exhibit tremendous potential as lightweight and functional materials.Despite their advantageous properties,high-strength Mg alloys often suffer from limited ductility.However,the emergence of heterogeneous materials provides a fresh perspective for the development of Mg alloys with both high strength and ductility.This article provided a fundamental overview of heterostructured materials and systematically reviewed the recent research progress in the design of Mg alloys with strength-ductility balance based on heterostructure principles.The review encompassed various aspects,including preparation methods,formation mechanisms of diverse heterostructures,and mechanical properties,both within domestic and international contexts.On this basis,the article discussed the challenges encountered in the design and fabrication of heterostructured Mg alloys,as well as the urgent issues that require attention and resolution in the future.
基金supported by the National Key R&D Program of China(No.2022YFA1603800)the National Natural Science Foundation of China(No.12274362)the Central Guidance on Local Science and Technology Development Fund of Hebei Province(No.216Z1012G)。
文摘The application of single-phase face-centered cubic(FCC)medium entropy alloys(MEAs)in the engi-neering industry is often hindered by the challenge of insufficient strength.In this study,a novel non-equiatomic ratio Ni_(40)Co_(30)Cr_(20)Al_(5)Ti_(5)MEA was successfully fabricated.Through the well-designed mechan-ical heat treatment processing,we introduced a heterogeneous grain structure comprising 67.4%fine grain and 32.6%coarse grain.Additionally,heterogeneous size L12 phases consisting of 18.7%submicron precip-itates and 11.7%nano-sized precipitates,were incorporated into the alloy.Tensile tests conducted at room temperature revealed that the double heterogeneous structure alloy demonstrated remarkable strength–ductility synergy.It exhibited a yield strength of 1200 MPa,an ultimate tensile strength of 1560 MPa and a total elongation of 33.6%.The exceptional strength of the alloy can be primarily attributed to heteroge-neous deformation induced strengthening,grain boundary strengthening and precipitation strengthening.The excellent ductility is mainly attributed to the high-density stacking faults and Lomer–Cottrell locks.This study not only contributes to the clarification of the strengthening and deformation mechanism of double heterogeneous structure alloys but also provides an effective strategy for the development of high-performance alloys with high strength and ductility.
基金supported by the National Key Research&De-velopment Program of China(No.2022YFF0609002)the National Natural Science Foundation of China(Nos.U1908219,52171163,and 52271157)+4 种基金the Key Research Program of the Chinese Academy of Sciences(No.ZDRW-CN-2021-2-2)the key Research&Devel-opment Plan of Jiangxi Province(No.20192ACB80001)the Natu-ral Science Foundation of Liaoning Province(No.2022-BS-001)the China Postdoctoral Science Foundation(No.2022M713210)the Shenyang National Laboratory for Materials Science.
文摘Although refractory high-entropy alloys(RHEAs)possess excellent softening resistance and thermal sta-bility at high temperatures,their practical application is often limited due to room temperature(RT)brit-tleness.In this work,we successfully achieved RT plasticization in a brittle(TaMoTi)_(92)Al_(8)RHEA via in situ forming heterogeneous structure(HS)with the doping of Zr.Different from the mainstream design con-cept of“soft solid solution matrices with hard intermetallic phases”proposed in the literature,the newly developed TaMoZrTiAl RHEA is featured by a hard disordered BCC phase embedded into a soft intermetal-lic B2 matrix.Such an HS leads to the remarkable strength-plasticity synergy in this alloy at RT,showing a large plasticity of>20%,associated with a high strength of>2380 MPa.It was found that solid solu-tion strengthening and heterodeformation-induced strengthening caused by dislocation pile-ups at phase boundaries are responsible for the enhancement in the yield strength,while deformation-induced strain partition and the frequent operation of dislocation cross-slip substantially improve the work hardening capacity of alloy,thus enabling the high strength and good RT plasticity.In short,the current work not only reveals the micromechanisms of the influence of heterogeneous dual-phase structure on the RT me-chanical behaviour in RHEAs but also provides a useful strategy for plasticizing brittle RHEAs.
基金supported by the National Natu-ral Science Foundation of China(No.12162023)The Key Talent Projects of Gansu Province,Gansu Basic Research Innovation Group Project(No.23JRRA757)Incubation Program of Excellent Doc-toral Dissertation-Lanzhou University of Technology.
文摘Developing high-ductility magnesium(Mg)alloys has become an imminent issue for their wide appli-cation.In this work,a new Mg-Sn-Zn-Zr alloy with ultra-high ductility(elongation,El.over 40%)and high ultimate tensile strength(UTS,~309-354 MPa)was prepared by a novel differential thermal equal-channel angular pressing(DT-ECAP).Heterogeneous structures,including bimodal grain structures and in-homogeneous distribution of second phases composed of banded structure and particle free zone(PFZ),were induced by DT-ECAP process.Based on the results of electron backscatter diffraction(EBSD),trans-mission electron microscopy(TEM),high-resolution TEM(HRTEM),and selected area electron diffraction(SAED),the bimodal grain structure originated from incomplete dynamic recrystallization(DRX)domi-nated by Zener pinning,strain-induced grain boundary migration(SIBM)and the limitation of polycrys-tallization due to lower dislocation density.Meanwhile,the bimodal distribution of second phases was highly associated with the defect density and initial structure.More importantly,the enhanced strength of DT-ECAPed alloys can be primarily attributed to hetero-deformation induced(HDI)strengthening,grain boundary strengthening,and precipitation strengthening.Moreover,HDI hardening,texture weakening or randomizing activation of non-basal slip,high density of dislocations in sub-structures,and twining in-duced superior work-hardening effect,which was highly responsible for the ultra-high ductility in sixth pass(6P)alloy.The current work provides a novel DT-ECAP process for inducing heterogeneous structure and offers beneficial insight into the development of ultra-high ductility and high strength for rare-earth-free Mg alloys via a combination of HDI strengthening and hardening and other vital mechanisms.
基金This work was financially supported by the National Key Research and Development Program of China(No.2020YFB0311300ZL)the National Natural Science Foundation of China(No.52071343).
文摘The coarsening-grained single-phase face-centered cubic(fcc)medium-entropy alloys(MEAs)normally exhibit insufficient strength for some engineering applications.Here,superior mechanical properties with ultimate tensile strength of 1.6 GPa and fracture strain of 13.1%at ambient temperature have been achieved in a(CoCrNi)_(94)Ti_(3)Al_(3)MEA by carefully architecting the multi-scale heterogeneous structures.Electron microscopy characterization indicates that the superior mechanical properties mainly originated from the favorable heterogeneous fcc matrix(1-40μm)and the coherent sphericalγ’precipitates(10-100 nm),together with a high number density of crystalline defects(2-10 nm),including dislocations,small stacking faults,Lomer-Cottrell locks,and ultrafine deformation twins.
基金the support by National Key Research and Development Program of China(2018YFA0703000)National Natural Science Foundation of China(Grant No.52105310)+1 种基金Natural Science Foundation of Zhejiang Province(Grant No.LDQ23E050001)the Starry Night Science Fund of Zhejiang University Shanghai Institute for Advanced Study(Grant No.SN-ZJU-SIAS-004)。
文摘In order to mimic the natural heterogeneity of native tissue and provide a better microenvironment for cell culturing,multi-material bioprinting has become a common solution to construct tissue models in vitro.With the embedded printing method,complex 3D structure can be printed using soft biomaterials with reasonable shape fidelity.However,the current sequential multi-material embedded printing method faces a major challenge,which is the inevitable trade-off between the printed structural integrity and printing precision.Here,we propose a simultaneous multi-material embedded printing method.With this method,we can easily print firmly attached and high-precision multilayer structures.With multiple individually controlled nozzles,different biomaterials can be precisely deposited into a single crevasse,minimizing uncontrolled squeezing and guarantees no contamination of embedding medium within the structure.We analyse the dynamics of the extruded bioink in the embedding medium both analytically and experimentally,and quantitatively evaluate the effects of printing parameters including printing speed and rheology of embedding medium,on the 3D morphology of the printed filament.We demonstrate the printing of double-layer thin-walled structures,each layer less than 200μm,as well as intestine and liver models with 5%gelatin methacryloyl that are crosslinked and extracted from the embedding medium without significant impairment or delamination.The peeling test further proves that the proposed method offers better structural integrity than conventional sequential printing methods.The proposed simultaneous multi-material embedded printing method can serve as a powerful tool to support the complex heterogeneous structure fabrication and open unique prospects for personalized medicine.
基金financially supported by a City University of Hong Kong Strategic Research Grant(Project No.7005238)。
文摘A carbon-containing CoCrFeNi high entropy alloy(HEA)with heterogeneous structures was obtained through thermomechanical treatments,which induced concurrent recrystallization and carbide precipitation in the alloy.A combination of high yield strength(556 MPa)and large uniform elongation(45%)was achieved in the investigated alloy.The enhancement of the strength is attributed to the combined effects of grain refinement,precipitation strengthening and microstructural heterogeneity.Our work demonstrated that the heterogeneity design could be realized by thermomechanical processes,which provided a practical strategy for producing HEAs with high performance.
基金support of the Natural Science Foundation of Shanxi Province,China(Nos.201901D111105,201901D111114)Transformation of Scientific and Technological Achievements Programs of Higher Education Institutions in Shanxi(2019)the opening project of State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology,No.KFJJ20-13 M).
文摘High-/medium-entropy stainless alloys(HESAs/MESAs)are a new kind of alloys with great potential to combine excellent properties from high-/medium-entropy alloys(HEAs/MEAs)and stainless steels.A CrFeNi MESA was chosen to investigate its microstructures and mechanical behaviors.After homogenization,the strength and ductility of CrFeNi MESAs with single-phase face-centered-cubic(fcc)structure were higher compared with those of Fe_(100−x-y)Cr_(x)Ni_(y)austenitic stainless steels.Cr-rich body-centered-cubic(bcc)precipitates and heterogeneous structure were introduced by cold rolling and annealing at 800℃.Rolling at 700℃ results in higher dislocation density and the occurrence of lamellar Cr-rich bcc precipitates.High-density dislocations and fcc grains with heterogeneous structure,together with Cr-rich bcc precipitates,contribute to a yield strength improvement of about 50 MPa,and appreciable tensile yield strength of~540 MPa and fracture strain of~20%are obtained.It reveals that not only compositional variations but also grain size and phase structure tuning can be utilized for achieving desired mechanical properties.
基金financial supports of the National Natural Science Foundation of China(No.51901184)Natural Science Foundation of Shaanxi Province(2021JM-061)the 2020 Space Science and Technology Foundation of China
文摘In present work,we successfully fabricated a novel Co-free non-equiatomic Ni_(46)Cr_(23)Fe_(23)Al_(4)Ti_(4)mediumentropy alloy with dual heterogeneous structures,i.e.three-levels grain structures and heterogeneous L1;precipitates.Experimental results revealed the dual heterogeneous structures lead to remarkable strength-ductility synergy properties in this Co-free medium-entropy alloy,showing high yield strength and ultimate tensile strength of~1203 MPa and~1633 MPa,respectively,remaining an excellent ductility of~28.7%.Further analyses about strengthening and deformation mechanisms indicated precipitation hardening and hetero-deformation induced hardening contribute the majority strength enhancement,meanwhile deformation-induced hierarchical stacking-faults networks,high density Lomer-Cottrell locks and microstructure features of heterogeneous grains and precipitates substantially facilitate the high work-hardening capacity and excellent tensile ductility.This work not only offers fundamental understanding of the strength and deformation mechanisms of the dual heterogeneous structural material,but also provides useful strength design strategy for low-price high performance high/medium-entropy alloys.
基金financially supported by the National Natural Science Foundation of China(Nos.52321001,52322105,52130002,U2241245,52261135634 and 52371084)the Youth Innovation Promotion Association(CAS,No.2021192)the IMR Innovation Fund(No.2023-ZD01).
文摘Metastable β titanium alloy is an ideal material for lightweight and high strength due to its excellent comprehensive mechanical properties.However,overcoming the trade-off relation between strength and ductility remains a significant challenge.In this study,the mechanical properties of Ti-38644 alloy were optimized by introducing a heterogeneous bi-grain bi-lamella(BG-BL)structure through a well-designed combination of rolling,drawing and heat treatment.The results demonstrate that the present BG-BL Ti-38644 alloy shows a tensile strength of~1500 MPa and a total elongation of 18%.In particular,the high strength-elongation combination of the BG-BL Ti-38644 alloy breakthroughs the trade-off relation in all the titanium alloys available.The recrystallized grains with low dislocation enhance the ductility of the Ti-38644 alloy,while the highly distorted elongated grains mainly contribute to the high strength.The present study provides a new principle for designing Ti alloys with superior strength and ductility.
基金financially supported by the National Natural Science Foundation of China(No.22209027,No.22179022,and No.22109023)the FuXiaQuan National Independent Innovation Demonstration Zone Collaborative Innovation Platform(No.2022-P-027)+1 种基金the Hundred Talents Plan of Fujian Province,the Top Young Talents of Young Eagle Program of Fujian Province,the Youth Innovation Fund of Fujian Province(No.2022J05046 and No.2021J05043)the Award Program for Fujian Minjiang Scholar Professorship,and the Talent Fund Program of Fujian Normal University。
文摘The growth of dendrites in Li/Na metal batteries is a multifaceted process that is controlled by several factors such as electric field,ion transportation,temperature,and pressure.Rational design of battery components has become a viable approach to address this challenge.Among the various design strategies,heterogeneous structures have been demonstrated to be effective in mitigating uneven metal deposition by reducing the local current density and regulating the deposition sites.In this review,we discuss comprehensively the underlying principles and factors that influence dendrite growth,as well as the synthesis approaches for heterogeneous structures.Furthermore,we provide an overview of the diverse applications of heterogeneous structures in battery components.Finally,we highlight existing challenges and future directions for the use of heterogeneous structures in regulating metal deposition.
基金support by the National Natural Science Foundation of China(Grant Nos.U23A20546 and 52271010)the Chinese National Natural Science Fund for Distinguished Young Scholars(Grant No.52025015)the Natural Science Foundation of Tianjin City(No.21JCZDJC00510).
文摘1.Introduction The strength-ductility trade-offdilemma has long been a per-sistent challenge in Al matrix composites(AMCs)[1,2].This is-sue primarily arises from the agglomeration of reinforcements at the grain boundaries(GBs),which restricts local plastic flow dur-ing the plastic deformation and leads to stress concentration[3,4].Recently,the development of concepts aimed at achieving hetero-geneous grain has emerged as a promising approach for enhanc-ing comprehensive mechanical properties[5,6].
基金supported by the National Key R&D Program of China(No.2021YFB3201100)the National Natural Science Foundation of China(Nos.51931004,12264012,52172128 and 52472250)+2 种基金111 Project 2.0(No.BP2018008)the Natural Science Foundation of Guangxi(Nos.AB24010230,AA22068080,and AA23023027)the Science and Technology Plan of Guilin(Nos.2022H03 and ZY20220101).
文摘Lead-free dielectric relaxor ferroelectric(RFE)ceramics are one of the promising materials for dielectric energy storage applications.However,the contradiction between high polarization and low hysteresis leads to interior energy storage performance,which greatly limits their applications in high/pulsed power systems.Here,we propose an effective strategy to significantly improve the energy storage properties of 0.94Bi_(0.5)Na_(0.5)TiO_(3)-0.06BaTiO_(3)(0.94BNT-0.06BT)with a morphotropic phase boundary(MPB)composition by constructing multiscale polymorphic domains and local heterogeneous structures.The introduction of Nd(Mg_(1/2)Hf_(1/2))O_(3)(NMH)facilitates the formation of short-range ordered polar nanoregions(PNRs).Moreover,small amounts of nanodomains with high polarization are resulted from local heterogeneous structures with Bi-and Ti-rich regions.Multiscale polymorphic domains with the coexistence of rhombohedral/tetragonal(R+T)nanodomains and PNRs ensure both high polarization and low hysteresis,which is crucial for improving the energy storage performance.Furthermore,the excellent electrical insulation is resulted from the high insulation resistivity,grain size at the submicron scale and a wide band gap by NMH doping.Therefore,a high recoverable energy density(Wrec)of 7.82 J/cm^(3) with an ultrahigh efficiency(η)of 93.1%is realized in the designed BNT-BT-NMH ternary system because of both a largeΔP and high Eb.These findings,together with good temperature/frequency/cycling stability,indicate that the optimum composition ceramics are very promising materials for energy storage applications in high/pulsed power systems.
基金supported by the National Natural Science Foundation of China(Nos.U23A20583,52033005,U21A2090,and 52173040)Department of Science and Technology of Sichuan Province(No.2024NSFTD0003)。
文摘Poly(_(L)-lactide)(PLLA),a leading biodegradable polyester,has demonstrated potential as a sustainable alternative,owing to its excellent biodegradability and rigidity.However,their slow crystallization kinetics and poor heat resistance limit their application scope.Recent advances have highlighted that the combination of extensional flow and thermal fields can achieve toughness–stiffness balance,high transparency,and good heat resistance.However,the effect of extensional flow on the post-non-isothermal crystallization of PLLA during heating and the resulting crystalline texture remains unclear.In this study,PLLA with a heterogeneous amorphous structure and oriented polymorph was prepared by extensional flow.The effect of heterogeneous amorphous structures on non-isothermal crystallization kinetics during the heating process was studied by thermal analysis,polarized optical microscopy,infrared spectroscopy,and ex situ/in situ X-ray characterization.These results clearly illustrate that extensional flow enhances the formation of oriented crystalline structures,accelerates non-isothermal crystallization,and modulates the polymorphic composition of PLLA.Moreover,an unexpected dual cold-crystallization behavior is identified in ordered PLLA samples upon extensional flow,which is from the extensional flow-induced heterogeneous amorphous phase into α' phase(low-temperature peak)and the pristine amorphous phase intoαphase(high-temperature peak).The extensional flow primarily promotes the formation of the more perfectαandα'phases,but has a negative effect on the final content ofαphase formed after cold crystallization andα'-to-αphase transformation.The findings of this work advance the understanding of PLLA non-isothermal crystallization after extensional flow and offer valuable guidance for high-performance PLLA upon heat treatment in practical processing.
基金financial support from the Special Fund for Special Posts of Guizhou University,China(No.[2022]06)the Guizhou Provincial Basic Research Program(Natural Science),China(No.ZK[2023]78)+1 种基金the National Natural Science Foundation of China(No.52365020)the Open Fund Project of Key Laboratory of Advanced Manufacturing Technology,China(No.GZUAMT2022KF[04]).
文摘1060/7050 Al/Al laminated metal composites(LMCs)with heterogeneous lamellar structures were prepared by accumulative roll bonding(ARB),cold rolling and subsequent annealing treatment.The strengthening mechanism was investigated by microstructural characterization,mechanical property tests and in-situ fracture morphology observations.The results show that microstructural differences between the constituent layers are present in the Al/Al LMCs after various numbers of ARB cycles.Compared with rolled 2560-layered Al/Al LMCs with 37.5%and 50.0%rolling reductions,those with 62.5%rolling reductions allow for more effective improvements in the mechanical properties after annealing treatment due to their relatively high mechanical incompatibility across the interface.During tensile deformation,with the increased magnitude of incompatibility in the 2560-layered Al/Al LMC with a heterogeneous lamellar structure,the densities of the geometrically necessary dislocations(GNDs)increase to accommodate the relatively large strain gradient,resulting in considerable back stress strengthening and improved mechanical properties.
基金support from the National Natural Science Foundation of China(No:52061040)China Postdoctoral Science Foundation(No:2021M692512)+1 种基金Opening Project of Material Corrosion and Protection Key Laboratory of Sichuan Province(No:2023CL01)Open Projects of Key Laboratory of Advanced Technologies of Materials,Ministry of Education China,Southwest Jiaotong University(No:KLATM202003).
文摘Integrating a heterogeneous structure can significantly enhance the strength-ductility synergy of composites.However,the relationship between hetero-deformation induced(HDI)strain hardening and dislocation activity caused by heterogeneous structures in the magnesium matrix composite remains unclear.In this study,a dual-heterogeneous TiC/AZ61 composite exhibits significantly improved plastic elongation(PEL)by nearly one time compared to uniform FG composite,meanwhile maintaining a high strength(UTS:417 MPa).This is because more severe deformation inhomogeneity in heterogeneous structure leads to more geometrically necessary dislocations(GNDs)accumulation and stronger HDI stress,resulting in higher HDI hardening compared to FG and CG composites.During the early stage of plastic deformation,the pile-up types of GND in the FG zone and CG zone are significantly different.GNDs tend to form substructures in the FG zone instead of the CG zone.They only accumulate at grain boundaries of the CG region,thereby leading to obviously increased back stress in the CG region.In the late deformation stage,the elevated HDI stress activates the new〈c+a〉dislocations in the CG region,resulting in dislocation entanglements and even the formation of substructures,further driving the high hardening in the heterogeneous composite.However,For CG composite,〈c+a〉dislocations are not activated even under large plastic strains,and only〈a〉dislocations pile up at grain boundaries and twin boundaries.Our work provides an in-depth understanding of dislocation variation and HDI hardening in heterogeneous magnesium-based composites.
基金financial support from the National Natural Science Foundation of China(Nos.52104306,52274301,52334009)the Aeronautical Science Foundation of China(No.2023Z0530S6005)+3 种基金the National Key Research and Development Program of China(No.2023YFB3712401)the Science and Technology Commission of Shanghai Municipality(No.21DZ1208900)the Academician Workstation of Kunming University of Science and Technology(2024),the Ningbo Yongjiang Talent-Introduction Programme(No.2022A-023-C)the Zhejiang Phenomenological Materials Technology Co.,Ltd.,China.
文摘A multi-phase heterogeneous FeCoNi-based high-entropy alloy is developed to overcome the trade-off between strength and ductility.By alloying with a small amount of Cu and employing a rapid recrystalliza-tion process,it exhibits a good combination of yield strength(roughly 1300 MPa)and ductility(approach-ing 20%).Firstly,a multi-phase heterogeneous structure is tailored ranging from nano to micron.Cu is efficiently precipitated as nanoscale clusters(4.2 nm),high-density cuboidal L1_(2) particles(20-40 nm)and L2_(1) particles(500-800 nm)are found to be embedded in the matrix and a bimodal heterogeneous grain structure(1-40μm)is constructed.Secondly,the introduction of Cu effectively suppresses the pre-cipitation of coarse L21 phase at grain boundaries,reducing its volume fraction by 80%and replaced by smaller-scale continuous precipitations within the grains.Thirdly,the high mixing enthalpy gap of Cu and the matrix leads to the formation of local chemical fluctuation and the consequential rugged topog-raphy in the matrix,which result in retarded dislocation motion and promotes dislocation plugging and interlocking during strain,enhancing yield stress and work hardening rate.This study provides a valuable perspective to enhance strength and ductility via enlarged local chemical fluctuation-tailored multi-phase heterogeneous structures.
基金National Natural Science Foundation of China(52261032,51861021,51661016)Science and Technology Plan of Gansu Province(21YF5GA074)+2 种基金Public Welfare Project of Zhejiang Natural Science Foundation(LGG22E010008)Wenzhou Basic Public Welfare Scientific Research Project(G2023020)Incubation Program of Excellent Doctoral Dissertation-Lanzhou University of Technology。
文摘The development of high-performance structural and functional materials is vital in many industrial fields.High-and medium-entropy alloys(H/MEAs)with superior comprehensive properties owing to their specific microstructures are promising candidates for structural materials.More importantly,multitudinous efforts have been made to regulate the microstructures and the properties of H/MEAs to further expand their industrial applications.The various heterostructures have enormous potential for the development of H/MEAs with outstanding performance.Herein,multiple heterogeneous structures with single and hierarchical heterogeneities were discussed in detail.Moreover,preparation methods for compositional inhomogeneity,bimodal structures,dualphase structures,lamella/layered structures,harmonic structures(core-shell),multiscale precipitates and heterostructures coupled with specific microstructures in H/MEAs were also systematically reviewed.The deformation mechanisms induced by the different heterostructures were thoroughly discussed to explore the relationship between the heterostructures and the optimized properties of H/MEAs.The contributions of the heterostructures and advanced microstructures to the H/MEAs were comprehensively elucidated to further improve the properties of the alloys.Finally,this review discussed the future challenges of high-performance H/MEAs for industrial applications and provides feasible methods for optimizing heterostructures to enhance the comprehensive properties of H/MEAs.
