检索结果-南通市图书馆

Achieving Large-area Bulk Ultrafine Grained Cu via Submerged Multiple-pass Friction Stir Processing

在线全文

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2013年第12期29卷 1111-1115页

作者： P. Xue B.L. Xiao z.y. ma Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences 72 Wenhua Road Shenyang 110016 China

Large-area bulk ultrafine grained （UFG） pure Cu was successfully prepared by multiple-pass overlapping friction stir processing （FSP） under additional rapid cooling. Overlapping FSP did not exert a significant effect on the microstructure and mechanical properties of the FSP UFG Cu. Similar average grain size was achieved in the transitional zone （Tz） of the multiple-pass FSP sample compared to that in the nugget zone of the single-pass FSP sample, and the Tz exhibited a strong {111}（112） type A fiber shear texture, Very weak softening occurred in the Tz of the multiple-pass FSP UFG Cu, resulting in a relatively uniform hardness distribution throughout the whole processed zone. A high yield strength of - 310 MPa and a uniform elongation of - 13% were achieved in the bulk FSP UFG Cu. This study provides an effective strategy to prepare large-area bulk IUFG materials.

关键词： Friction stir processing Multiple-pass Ultrafine grains Microstructure Mechanical properties

High Strain Rate Superplasticity in a Micro-grained Al-Mg-Sc Alloy with Predominant High Angle Grain Boundaries

在线全文

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2012年第11期28卷 1025-1030页

作者： F. C. Liu z.y. ma F. C. zhang Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China State Key Laboratory of Metastable materials Science and Technology Yanshan University Qinhuangdao 066004China

Friction stir processing （FSP） was applied to extruded AI-Mg-Sc alloy to produce fine-grained microstructure with a grain size of 2.2μm. Electron backscatter diffraction （EBSD） result showed that the grain boundary misorientation distribution was very close to a random grain assembly for randomly oriented cubes. Super- plastic investigations in the temperature range of 425-500 ℃ and strain rate range of 1x100^-2-1x10 s^-1 showed that a maximum elongation of 1500% was achieved at 475 ℃ and a high strain rate of 1x100^-2-1x10 s^-1. The FSP AI-Mg-Sc exhibited enhanced superplastic deformation kinetics compared to that predicted by the constitutive relationship for superplasticity in fine-grained aluminum alloys. The origin for enhanced superplas- tic deformation kinetics in the FSP alloy can be attributed to its high fraction of high angle grain boundaries （HAGBs）. The analyses of the superplastic data and scanning electron microscopy （SEM） examinations on the surfaces of deformed specimens indicated that grain boundary sliding is the main superplastic deformation mechanism for the FSP AI-Mg-Sc alloy.

关键词： Superplasticity Friction stir processing Aluminum Microstructure Friction stir welding

Effect of Rotation Rate on Microstructures and Mechanical Properties of FSW Mg-zn-y-zr Alloy Joints

在线全文

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2011年第12期27卷 1157-1164页

作者： G.M. Xie z.y. ma z.A. Luo P. Xue G.D. Wang The State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110819 China Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China

Friction stir welding （FSW） of Mg-zn-y-zr plates with 6 mm in thickness was successfully carried out under a wide range of rotation rates of 600-1200 r/rain with a constant traverse speed of 100 mm/min. After FSW, the coarse grains in the parent material （PM） were changed into fine equiaxed recrystallized grains at the＇nugget zone （Nz）. Furthermore, the coarse Mg-zn-y particles （W-phase） were broken up and dispersed homogenously into the Mg matrix. With increasing rotation rates, the size of the W-phase particles at the Nz significantly decreased, but the recrystallized grain size tended to increase. The hardness values of the Nzs for all the FSW joints were higher than those of the PM, and the lowest hardness values were detected in the heat affected zone （HAz）. The fracture occurred in the thermo-mechanical affected zone （Tmaz） on the advancing side for all the FSW joints in the tensile test, due to the incompatibility of the plastic deformation between the Nz and Tmaz caused by remarkably different orientation of grains and W-phase particles. The strength of FEW ioint reaches 90% of that of its PM

关键词： Friction stir welding magnesium alloys Microstructure Mechanical property

Formability of friction stir processed low carbon steels used in shipbuilding

在线全文

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2018年第1期34卷 237-244页

作者： D.M. Sekban S.M. Akterer O. Saray z.y. ma G. Purcek Department of Naval Architecture and marine Engineering Karadeniz Technical University Trahzon Turkey Department of Autumotive Technology RecepTayyip Erdogan University Rize Turkey Department of Mechanical Engineering Bursa Technical University. Bursa Turkey Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Department of Mechanical Engineering. Karadeniz Technical University Trabzon Turkey Engineering Faculty Giresun University Giresun Turkey

The stretch formability of a low carbon steel processed by friction stir processing （FSP） was studied under biaxial loading condition applied by a miniaturized Erichsen test. One-pass FSP decreased the ferritic grain size in the processed zone from 25 μm to about 3 μm, which also caused a remarkable increase in strength values without considerable decrease in formability under uniaxial loading. A coarse-grained （CG） sample before FSP reflected a moderate formability with an Erichsen index （EI） of 2.73 mm. FSP slightly decreased the stretch formability of the sample to 2.66 ram. However, FSP increased the required punch load （FEI） due to the increased strength by grain refinement. FSP reduced considerably the roughness of the free surface of the biaxial stretched samples with reduced orange peel effect. The average roughness value （Ra） decreased from 2.90 in the CG sample down to about 0.65 μm in fine-grained （FG） sample after FSP. It can be concluded that the FG microstructure in low carbon steels sheets or plates used generally in shipbuilding provides a good balance between strength and formability.

关键词： Friction stir processing Low carbon shipbuilding steel Formability Microstructure Mechanical properties

Constitutive equation and model validation for a 31 vol.% B_4Cp/6061Al composite during hot compression

在线全文

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2018年第10期34卷 1730-1738页

作者： L. zhou C. Cui Q.z. Wang C. Li B.L. Xiao z.y. ma Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Electromechanical and Vehicle Engineering Yantai University Yantai 264005 China School of Mechanical Engineering Shenyang Ligong University Shenyang 110159 China Nuclear and Radiation Safety Center Ministry of Environmental Protection Beijing 100082 China

An accurate constitutive equation is essential to understanding the flow behavior of B4C/A1 compos-ites during the hot deformation. However, the constitutive equations developed previously in literature are generally for low strain rate deformation. In the present work, we modified the general consti-tutive equation and take the high strain rate correction into account. The constitutive equation for a 31 vol.% B4Cp/6061AI composite was constructed based on the flow stresses measured during isothermal hot compression at temperatures ranging from 375 to 525 ℃ and strain rates from 0.01 to 10 s^-1. The experimental flow stresses were corrected by considering temperature-dependent Arrhenius factor. The modified equation was then verified by using DEFORM-3D finite element analysis to simulate the exper-imental hot compression process. The results show that the modified equation successfully predicts flow stress, load-displacement, and the temperature rise. This helps to optimize the hot deformation process, and to obtain desirable properties, such as reduced porosity and homogenous particle distribution in B4C/AI composites.

关键词： Composites B4C/AI Constitutive equation Hot compression Finite element simulation

Finite Element Prediction of the Thermal Conductivity of GNP/Al Composites

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2022年第5期35卷 825-838页

作者： X.S.yang L.zhou K.y.Liu z.y.Liu Q.z.Wang B.L.Xiao z.y.ma School of Electromechanical and Automotive Engineering Yantai UniversityYantai264005China Shi-Changxu Innovation Center for Advanced materials Institute of Metal ResearchChinese Academy of SciencesShenyang110016China

A 3 D multi-scale finite element model was developed to predict the effective thermal conductivity of graphene nanoplatelet(GNP)/Al *** factors influencing the effective thermal conductivity of the GNP/Al composites were investigated,including the orientation,shape,aspect ratio,configuration and volume fraction of *** results show that GNPs shape has a little influence on the thermal conductivity of GNP/Al composites,and composites with elliptic GNPs have the highest thermal *** addition,with increasing the aspect ratio of GNPs,the thermal conductivity of GNP/Al composites increases and finally tends to be *** GNPs configuration strongly influences the thermal conductivity of GNP/Al composites,and the thermal conductivity of the composites with layered GNPs is the highest among the five *** effective thermal conductivity is sensitive to volume fraction of ***,when the volume fraction of layered GNPs reaches 1.54%,the thermal conductivity of GNP/Al composites is as high as 400 W/m *** findings of this study could provide a good theoretical basis for designing high thermal conductivity GNP/Al composites.

关键词： Multi-scale finite element model Thermal conductivity GNP/Al composites Shape Aspect ratio Configuration

Microstructural evolution of aluminum alloy during friction stir welding under different tool rotation rates and cooling conditions

在线全文

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2019年第6期35卷 972-981页

作者： X.H. zeng P. Xue L.H. Wu D.R. Ni B.L. Xiao K.S. Wang z.y. ma Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China University of Chinese Academy of Sciences Beijing 100049 China School of Metallurgical Engineering Xi'an University of Architecture and Technology Xi'an 710055 China

The microstructural evolution during friction stir welding(FSW) has long been studied only using one single welding parameter. Conclusions were usually made based on the final microstructure observation and hence were one-sided. In this study, we used the "take-action" technique to freeze the microstructure of an Al-Mg-Si alloy during FSW, and then systematically investigated the microstructures along the material flow path under different tool rotation rates and cooling conditions. A universal characteristic of the microstructural evolution including four stages was identified, i.e. dynamic recovery(DRV), dislocation multiplication, new grain formation and grain growth. However, the dynamic recrystallization(DRX)mechanisms in FSW depended on the welding condition. For the air cooling condition, the DRX mechanisms were related to continuous DRX associated with subgrain rotation and geometric DRX at high and low rotation rates, respectively. Under the water cooling condition, we found a new DRX mechanism associated with the progressive lattice rotation resulting from the pinning of the second-phase *** on the analyses of the influencing factors of grain refinement, it was clearly demonstrated that the delay of DRV and DRX was the efficient method to refine the grains during FSW. Besides, ultra-high strain rate and a short duration at high temperatures were the key factors to produce an ultrafine-grained material.

关键词： Aluminum alloys Grain refinement Dynamic recrystallization Severe plastic deformation Friction stir welding

Effect of Al_(2)O_(3)on the Mechanical Properties of(B_(4)C+Al_(2)O_(3))/Al Neutron Absorbing materials

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2024年第8期37卷 1411-1420页

作者： J.X.Cai B.M.Shi N.Li y.Liu z.G.zhang y.N.zan Q.z.Wang B.L.Xiao z.y.ma Shi‑Changxu Innovation Center for Advanced materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Key Laboratory of Nuclear materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Nuclear Equipment Division Beijing Institute of Nuclear EngineeringChina Nuclear Power Engineering Co.Ltd.Beijing 100840China Department of materials Science School of Mechanical EngineeringShenyang UniversityShenyang 110044China

B_(4)C/Al composites are widely utilized as neutron absorbing materials for the storage and transportation of spent nuclear *** order to improve the high-temperature mechanical properties of B_(4)C/Al composites,in-situ nano-Al_(2)O_(3)was introduced utilizing oxide on Al powder *** this study,the Al_(2)O_(3)content was adjusted by utilizing spheroid Al powder with varying diameters,thereby investigating the impact of Al_(2)O_(3)content on the tensile properties of(B_(4)C+Al_(2)O_(3))/Al *** was found that the pinning effect of Al_(2)O_(3)on the grain boundaries could hinder the recovery of dislocations and lead to dislocation accumulation at high *** the result,with the increase in Al_(2)O_(3)content and the decrease in grain size,the high-temperature strength of the composites increased *** finest Al powder used in this investigation had a diameter of 1.4μm,whereas the resultant composite exhibited a maximum strength of 251 MPa at room temperature and 133 MPa at 350℃,surpassing that of traditional B_(4)C/Al composites.

关键词： Al matrix composites Neutron absorbing materials (B_(4)C+Al_(2)O_(3))/Al composites High-temperature strength

On power series statistical convergence and new uniform integrability of double sequences

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Applied mathematics(A Journal of Chinese Universities) 2024年第3期39卷 519-532页

作者： Sevda y■ld■z Kamil Demirci Sinop University Department of MathematicsSinopTurkey

In the present paper,we mostly focus on P_(p)^(2)-statistical *** will look into the uniform integrability via the power series method and its characterizations for double ***,the notions of P_(p)^(2)-statistically Cauchy sequence,P_(p)^(2)-statistical boundedness and core for double sequences will be described in addition to these findings.

关键词： power series methods statistical convergence uniform integrability double sequences