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In-situ Observation of Point Defect and Precipitate Evolvement of CLAM Steel under Electron Irradiation

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Journal of Materials Science & Technology 2013年第5期29卷 467-470页

作者： Yong Xin Tongda Ma Xin Ju Jie Qiu Department of Physics University of Science and Technology Beijing General Research Institute for Nonferrous Metals Institute of Nuclear and New Energy Technology Tsinghua University

The point defect and Precipitate evolution of China low activation martensitic steel （CLAM） under electron beam irradiation were characterized by high voltage electron microscopy. The process was recorded in-situ on electronsensitive films. The irradiation dose rate was 1.78 × 10-3 dpa/s and the highest dose was 2.12 dpa/s. Irradiation introduced dislocation loops into the sub-grain, which increased density when the irradiation dose was increased from 0.53 dpa to 1.59 dpa at 723 K. The Precipitate, found to be an M6C type, was irradiated at 773 K at the [011] plane direction. The Precipitate morphology and structure were unchanged when the irradiation dose was increased to 2.12 dpa. Compared with the irradiation at 723 K in the sub-grain, no other defects were generated at the nearby grain boundary at 773 K.

关键词： Martensitic steel Electron microscopy Electron irradiation Defect Precipitate

Gadolinium solubility and Precipitate identification in Mg-Gd binary alloy

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Journal of Rare Earths 2012年第10期30卷 1064-1068页

作者：彭秋明马宁李慧 State Key Laboratory of Metastable Materials Science and Technology Yanshan University

Gadolinium （Gd） solubility in magnesium （Mg） matrix and Precipitate composition in Mg-Gd binary alloys were investigated. The alloys containing different Gd contents （10 wt.%-35 wt.%） were employed to identify Gd solubility after annealing at different temperatures. It was confirmed that the maximum Gd solubility was 22.8 wt.% at 550 ℃based on the regression analysis method. Mg5＋xGd （0〈x〈2） and Mg3Gd Precipitates coexisted in all investigated alloys owing to the strong component segregation during solidification. The fraction of Mg5＋xGd （0〈x〈2） was decreased with the increment of annealing temperature and time. In contrast, Mg3Gd Precipitate could not be elimi- nated even when being annealed at 550℃. This thermal stable Precipitate played a significant role in mechanical properties. Therefore, it is very necessary to consider the effect of Mg3Gd Precipitate on properties of Mg-Gd based alloys in future.

关键词： Mg alloys microstructure Precipitate annealing rare earths

Precipitate evolution of 6005A-T6 aluminum alloy after FSW

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China Welding 2012年第3期21卷 1-6页

作者：董鹏孙大干张月莹汪晓勇李洪梅 Key Laboratory of Automobile Materials of Ministry of Education School of Materials Science and EngineeringJilin UniversityChangchun130025

The 6005A-T6 aluminum alloy was friction stir welded, and the peak temperature as well as microstructure was examined for the joints. A special attention was devoted to the Precipitates evolution within different zones after post-weld natural aging time for 6 months. In the nugget zone （NZ） experiencing the highest peak temperature, the β′ Precipitates dissolved into a-Al matrix and the GP zones re-Precipitated after natural aging. In the thermo-mechanically affected zone （TMAZ）, which is characterized by a high density of dislocation, the Q＇ phases Precipitated and part of them dissolved into α-Al matrix during FSW and the GP zones heterogeneously re-Precipitated on dislocations after natural aging. The heat- affected zone （HAZ） contains the coarsening of β′ Precipitates, the transformation of β″ to β′ and the precipitation of Q＇.

关键词： friction stir welding 6005A-T6 alunimum alloy Precipitate natural aging

Phase-field study for the splitting behaviour of Precipitate under applied stress

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Chinese Physics B 2008年第9期17卷 3523-3530页

作者：张玉祥王锦程杨玉娟杨根仓周尧和 State Key Laboratory of Solidification Processing Northwestern Polytechnical University

This paper employs the phase-field method to study the splitting behaviour of a single coherent particle under an applied uniaxiai stress. It finds that the splitting behaviour is greatly influenced by the initial shape of Precipitates, the bulk free energy condition, the degree of supersaturation and the ratio of the interfacial energy to the elastic strain energy, etc. The simulated results demonstrate that the aspect ratio of the particle determines whether the splitting can occur and how many split plates can be obtained. The splitting of particle is sensitive to the interracial energy, i.e. the splitting becomes more and more difficult with increasing the ratio of the interracial energy to the elastic strain energy. And increasing the magnitude of the applied stress is favourable to the splitting. The splitting process is also explained from the point of view of the corresponding diffusion potential.

关键词： phase-field method splitting Precipitate

High-resolution Transmission Electron Microscopy Characterization of the Structure of Cu Precipitate in a Thermal-aged Multicomponent Steel

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Chinese Journal of Mechanical Engineering 2019年第5期32卷 117-124页

作者： Lizhan Han Qingdong Liu Jianfeng Gu Institute of Materials Modification and Modelling School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration Shanghai Jiao Tong UniversityShanghai 200240China

High-dispersed nanoscale Cu Precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important to understand the formation behaviors of the Cu Precipitates.High-resolution transmission electron microscopy(TEM)is utilized to investigate the structure of Cu Precipitates thermally formed in a high-strength low-alloy(HSLA)steel.The Cu Precipitates were generally formed from solid solution and at the crystallographic defects such as martensite lath boundaries and dislocations.The Cu Precipitates in the same aging condition have various structure of BCC,9 R and FCC,and the structural evolution does not greatly correlate with the actual sizes.The presence of different structures in an individual Cu Precipitate is observed,which reflects the structural transformation occurring locally to relax the strain energy.The multiply additions in the steel possibly make the Cu precipitation more complex compared to the binary or the ternary Fe-Cu alloys with Ni or Mn additions.This research gives constructive suggestions on alloying design of Cu-bearing alloy steels.

关键词： Cu Precipitate High-resolution transmission electron microscopy Thermal aging High-strength low-alloy steel

Precipitate-stabilized surface enabling high-performance Na_(0.67)Ni_(0.33-x)Mn_(0.67)Zn_(x)O_(2) for sodium-ion battery

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eScience 2022年第5期2卷 529-536页

作者： Kuan Wang Zhengfeng Zhang Sulan Cheng Xiao Han Junjie Fu Manling Sui Pengfei Yan Beijing Key Laboratory of Microstructure and Properties of Solids Faculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China

Electrode interfacial degradations are the key challenges for high-performance rechargeable batteries,usually mitigated through surface modification/coating strategies.Herein,we report a novel mechanism to enhance the surface stability of P2 layered cathodes by introducing a high density of dopant-enriched Precipitates.Based on microscopic analysis,we show that forming a high density of Precipitates at the grain surface can effectively suppress surface cracking and corrosion,which not only improves the surface/interface stability but also effectively suppresses the intergranular cracking issue.Increasing the doping level can lead to a greater density of Precipitates at the surface region,which results in higher surface stability and increased cycling stability of the P2 layered cathode for a sodium-ion battery.We further reveal that prolonged cycling can induce the formation of a Precipitate-free surface region due to the loss of Zn dopant and Na.Our in-depth microanalysis reveals cycling-induced dynamic structural evolution of the P2 layered cathodes,highlighting that dopant segregation-induced precipitation is a new approach to achieving high interfacial stability.

关键词： Layered cathode TEM Precipitate Sodium-ion battery Surface stability

Effect of Thermo-Mechanical Processing on Precipitate Formation in Next Generation HSLA Steel

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Journal of Iron and Steel Research(International) 2011年第S1期18卷 478-481页

作者： Mukherjee S Timokhina I B Ringer S P Hodgson P D Centre for Material and Fibre Innovation Deakin UniversityGeelongVic 3217Australia Australian Key Centre for Microscopy and Microanalysis University of SydneyNSWAustralia

Development of advanced high strength steels (AHSS) using a conventional rolling setup is one of the biggest challenges to steel industry.It has been found that fine precipitation in a soft matrix,formed after hot rolling,can markedly improve the mechanical properties.In this work,three dimensional atom probe tomography (3D-APT) has been used to study the formation of Precipitates in thermomechanically simulated steel.3D-APT data reveals co-existence of numerous nano clusters with Precipitates.Also,quantitative analysis of the nano clusters and Precipitates shows clusters are as small as 1nm in size.Precipitates are found to be disc shaped with the composition of equilibrium Precipitates (TiMo)C.Thus,3D-APT is seen as an ideal technique to complement TEM to understand the nanoscale features in thermomechanically processed steel for further improvements in the mechanical properties of AHSS.

关键词： TMCP 3D-APT Precipitate cluster

Effect of Solutionizing and Aging on Microstructure and Mechanical Properties of Warm-rolled 7075 Alloy

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Journal of Wuhan University of Technology(Materials Science) 2023年第2期38卷 408-415页

作者： YANG Xiaorong ZHAO Xiaodong CHU Zhibing TUO Leifeng School of Materials Science and Engineering Taiyuan University of Science and TechnologyTaiyuan030024China

The effect of solution and aging treatments on microstructure and mechanical properties of warm-rolled 7075 alloy was investigated via optical microscope,electron backscattered diffraction,transmission electron microscopy and tensile tests.The 7075 alloy was subjected to solution treatments at 450℃for 1 h(ST1),490℃ for 1 h(ST2)and 1.5 h(ST3).Three aging routes were carried out on samples from ST2:one-step(A1),two-step(A2),and three-step aging(A3).The experimental results show mainly recrystallized equiaxed grains in ST1 and ST3 state but a combination of elongated and equiaxed grains in ST2 condition.Three aged alloys have similar microstructures of sample ST2 while the recrystallization frequency gets decreased after aging.The least recrystallization fraction occurs in A2 state.Three aged 7075 alloys all possess enhanced strength and plasticity.Precipitates characterization reveals the maximum strength is achieved in A2 sample as the matrix Precipitates are composed mainly of smallηand manyη′phases.Aging route A2 appears preferable to other two aging conditions for attaining a pretty excellent combination of strength and plasticity.

关键词： 7075 alloy solutionizing aging Precipitate microstructure mechanical property

Thermal stability of nanograins with grain boundary relaxation in microalloyed Cu-Sb and Cu-Fe

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Journal of Materials Science & Technology 2023年第24期155卷 66-71页

作者： R.J. Zhu X.Zhou X.Y. Li Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering University of Science and Technology of China Shenyang 110016 China

Grain refinement into nanoscale significantly enhances the strength and hardness of metallic materials but generally reduces the thermal stability by the introduced strong tendency for grain boundary(GB)migration.Stabilizing nanograins through GB relaxation had been proven as an effective way in several metals recently when the grain size is below a critical value.Here,we discovered that the abnormally enhanced thermal stability induced by GB relaxation can be realized in 0.5%Sb or Fe doped Cu,similar to that in pure Cu.The observed critical grain sizes for GB relaxation in the two Cu alloys are almost the same as pure Cu.However,the GB relaxation effect on thermal stability is kind of suppressed compared to pure Cu with similar grain sizes because of the segregation/precipitation of Sb/Fe during the annealing process,which accelerates the detwinning and the failure of relaxed GBs.

关键词： Thermal stability Grain boundary relaxation Nanograined Cu alloy Segregation Precipitate