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Science Bulletin 2024年第8期69卷 1037-1049页

作者：钟锦璇杨晓玉吕途梁格格张胜楠张朝华敖伟琴刘福生南鹏飞葛炳辉胡利鹏 College of Materials Science and Engineering Shenzhen Key Laboratory of Special Functional MaterialsGuangdong Research Center for Interfacial Engineering of Functional MaterialsGuangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and UtilizationInstitute of Deep Earth Sciences and Green EnergyShenzhen UniversityShenzhen 518060China Information Materials and Intelligent Sensing Laboratory of Anhui Province Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of EducationInstitutes of Physical Science and Information TechnologyAnhui UniversityHefei 230601China Superconducting Materials Research Center Northwest Institute for Nonferrous Metal ResearchXi’an 710016China

In thermoelectrics,doping is essential to augment the figure of merit.Traditional strategy,predomina ntly heavy doping,aims to optimize carrier concentration and restrain lattice thermal conductivity.However,this tactic can severely hamper carrier transport due to pronounced point defect scattering,particularly in materials with inherently low carrier mean-free-path.Conversely,dilute doping,although minimally affecting carrier mobility,frequently fails to optimize other vital thermoelectric parameters.Herein,we present a more nuanced dilute doping strategy in GeTe,leveraging the multifaceted roles of small-size metal atoms.A mere 4%CuPbSbTe_(3)introduction into GeTe swiftly suppresses rhombohedral distortion and optimizes carrier concentration through the aid of Cu interstitials.Additionally,the formation of multiscale microstructures,including zero-dimensional Cu interstitials,one-dimensional dislocations,two-dimensional planar defects,and three-dimensional nanoscale amorphous GeO_(2)and Cu_(2)GeTe_(3)precipitates,along with the ensuing lattice softening,contributes to an ultralow lattice thermal conductivity.Intriguingly,dilute CuPbSbTe_(3)doping incurs only a marginal decrease in carrier mobility.Subsequent trace Cd doping,employed to alleviate the bipolar effect and align the valence bands,yields an impressive figure-of-merit of 2.03 at 623 K in(Ge_(0.97)Cd_(0.03)Te)_(0.96)(CuPbSbTe_(3))_(0.04).This leads to a high energyconversion efficiency of 7.9%and a significant power density of 3.44 W cm^(-2)at a temperature difference of 500 K.These results underscore the invaluable insights gained into the constructive role of nuanced dilute doping in the concurrent tuning of carrier and phonon transport in GeTe and other thermoelectric materials.

关键词： Thermoelectric GeTe Dilute doping interstitial atoms Lattice softening

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interstitial concentration effects on incipient plasticity and dislocation behaviors of face-centered cubic FeNiCr multicomponent alloys based on nanoindentation

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Journal of Materials Science & Technology 2022年第17期112卷 212-221页

作者： Quanqing Zeng Kefu Gan Fei Chen Dongyao Wang Songsheng Zeng Research Institute of Light Alloy Central South UniversityChangsha 410083China School of Materials Science and Engineering Central South UniversityChangsha 410083China Key Laboratory of the Ministry of Education of Nonferrous Metals Central South UniversityChangsha 410083China

interstitial atoms that commonly occupy the octahedral or tetrahedral interstices of face-centered cubic(FCC)lattice,can significantly affect the dislocation behaviors on deformation.Recently,interstitial doping has been applied to tune the mechanical properties of the emerging multicomponent,often termed high-entropy alloys(HEAs)or medium-entropy alloys(MEAs).However,the fundamental mechanisms of the dislocation nucleation and the onset of plasticity of interstitial multicomponent alloys governed by the concentration of interstitial atoms are still unclear.Therefore,in the present work,an instrumented nanoindentation was employed to investigate the interstitial concentration effects of carbon atoms on single FCC-phase equiatomic FeNiCr MEAs during loading.The results show that the pop-in events that denote the onset of incipient plasticity are triggered by the sudden heterogeneous dislocation nucleation via the primary atoms-vacancy exchange with the instant stress field,regardless of the interstitial concentration.Moreover,the measured activation volumes for dislocation nucleation of the FeNiCr MEAs are determined to be increased with the interstitial concentration,which definitely suggests the participation of interstitial atoms in the nucleation process.Besides,it is also found that the average value measured in statistics of the maximum shear stress corresponding to the first pop-in is enhanced with the interstitial concentration.Such scenario can be attributed to the improved local change transfer and lattice cohesion caused by the interstitial atoms with higher concentrations.Furthermore,the significant drag effect of interstitial carbon atoms hinders the mobile dislocations before exhaustion,which severely suppresses the subsequent occurrence of pop-in events in the carbon-doped specimens.The work gives a microscale view of interstitial effects on the mechanical properties of multicomponent alloys,which can further help to develop new interstitial strengthening strategies for structural materials with rem

关键词： Multicomponent alloy interstitial atoms Dislocation Nanoindentation pop-in Incipient plasticity

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Enhanced mechanical properties of a carbon and nitrogen co-doped interstitial high-entropy alloy via tuning ultrafine-grained microstructures

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Journal of Materials Science & Technology 2023年第13期144卷 128-137页

作者： Wei Jiang Heng Wang Zhiming Li Yonghao Zhao Nano and Heterogeneous Materials Center School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing210094PR.China School of Materials Science and Engineering Central South UniversityChangsha410083PR.China

C-N co-doped interstitial high entropy alloy(iHEA)was reported to have high strength and ductility.However,iHEA with fully recrystallized ultrafine grains(UFGs)and underlying thermally activated pro-cesses associated with dislocation slip,twinning,and solute drag have not been reported yet.In this work,a C-N co-doped iHEA with nominal composition Fe_(48.5)Mn_(30)Co_(10)Cr_(10)C_(0.5)N_(1.0)(at.%)was prepared,and the microstructures were tuned by cold-rolling and annealing treatments to improve mechanical properties.Upon cold-rolling with a strain of 1.74,the main microstructures in the iHEA are composed of nano-grains,nano-twins,HCP laminates,and high density of dislocations,leading to ultrahigh hardness of 466.7 HV and tensile strength of 1730 MPa at the expense of ductility(2.44%).Both the nanostructures and the high hardness of the iHEA can be maintained up to an annealing temperature of 600℃(462.5 HV).After annealing at 650℃ for 1 h,the UFG microstructures are obtained in the iHEA,containing re-crystallized grains with an average grain size of 0.91μm and nanoprecipitates with an average diameter of 90.8 nm.The combined strengthening and hardening effects of UFGs,nanoprecipitates,twinning,and solutes contribute to high strain hardening(n=0.81),gigapascal yield strength(984 MPa),and good duc-tility(20%).The C-N co-doping leads to a strong drag effect on dislocation slip,resulting in a nano-scale mean free path of dislocation slip λ(1.44 nm)and much small apparent activation volume V^(∗)(15.8 b^(3))of the UFG iHEA.

关键词： Ultrafine-grained high-entropy alloys interstitial atoms Thermomechanical processing Microstructures Mechanical properties

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