检索结果-南通市图书馆

dielectric response of BaZrO_(3)/BaTiO_(3) superlattice

在线全文

学校读者我要写书评

暂无评论

Journal of Advanced dielectrics 2016年第2期6卷 92-97页

作者： d.wang Z.Jiang Electronic Materials Research Laboratory-Key Laboratory of the Ministry of Education Xi'an Jiaotong University Xi'an 710049P.R.China International Center for dielectric Research Xi'an Jiaotong UniversityXi'an 710049P.R.China Physics department and Institute for Nanoscience and Engineering University of Arkansas FayettevilleArkansas 72701USA

We use the first-principles-based molecular dynamic approach to simulate dipolar dynamics of BaZrO_(3)/BaTiO_(3)superlattice,and obtain its dielectric *** dielectric response is decomposed into its compositional,as well as the in-plane and out-of-plane parts,which are then discussed in the context of chemical ordering of Zr/Ti *** reveal that,while the in-plane dielectric response of BaZrO_(3)/BaTiO_(3)superlattice also shows dispersion over probing frequency,it shall not be categorized as relaxor.

关键词： Relaxor molecular dynamics dielectric response

Friction Stir Welding of discontinuously Reinforced Aluminum Matrix Composites:A Review

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

Acta Metallurgica Sinica(English Letters) 2014年第5期27卷 816-824页

作者： d.wang B.L.Xiao d.R.Ni Z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

Friction stir welding （FSW） is considered a promising welding technique for joining the aluminum matrix composites （AMCs） to avoid the drawbacks of the fusion welding. High joint efficiencies of 60%-100% could be obtained in the FSW joints of AMCs. However, due to the existence of hard reinforcing particles in the AMCs, the wearing of welding tool during FSW is an unavoidable problem. Moreover, the low ductility of the AMCs limits the welding process window. As the hard materials such as Ferro-Titanit alloy, cermet, and WC/Co were applied to produce the welding tools, the wearing of the tools was significantly reduced and the sound joints could be achieved at high welding speed for the AMCs with low reinforcement volume fraction. In this article, current state of understanding and development of welding tool wearing and FSW parameters of AMCs are viewed. Furthermore, the factors affecting the microstructure and mechanical properties of the joints are evaluated in detail.

关键词： Metal matrix composite Friction stir welding Particle, microstructure Wear

Achieving superior mechanical properties of selective laser melted AlSi10Mg via direct aging treatment

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2022年第13期108卷 226-235页

作者： H.Zhang Y.wang J.J.wang d.R.Ni d.wang B.L.Xiao Z.Y.Ma Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China College of Materials Science and Engineering Shenyang Aerospace University37 Daoyi South AvenueShenyang 110136China

For additive manufactured aluminum alloys,the inferior mechanical properties along the building direction have been a serious *** this study,an optimized heat treatment was developed as a simple and effective *** effects of direct aging on microstructure and mechanical properties along the building direction of AlSi10Mg samples produced via selective laser melting(SLM)were *** results showed that,compared with the conventional heat treatment at elevated temperatures,direct aging at temperatures of 130-190℃ could retain the fine grain microstructure of SLM samples and promote further precipitation of Si phase,however,the growth of pores occurred during direct *** increasing aging temperature,while finer cell structures were obtained,more and larger pores were developed,resulting in decreased density of the *** types of pore formation mechanisms were *** the balance between the refinement of cell structure and the growth of pores,aging at 130℃ was determined as the optimized heat treatment for SLM AlSi10Mg *** tensile strength along the building direction of the 130℃ aged sample was increased from 403 MPa to 451 MPa,with relatively high elongation of 6.5%.

关键词： Additive manufacturing Selective laser melting AlSi10Mg alloy,Heat treatment

Superb Strengthening Effect of Net-Like distributed Amorphous Al_(2)O_(3)on Creep Resistance 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) 2022年第12期35卷 2007-2013页

作者： Y.N.Zan X.Lei J.F.Zhang d.wang Q.Z.wang B.L.Xiao Z.Y.Ma Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Shi-Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Nuclear Equipment division Beijing Institute of Nuclear EngineeringChina Nuclear Power Engineering Co.LtdBejing 100840China

B4C reinforced Al composites are widely used as neutron absorbing materials(NAMs)due to excellent neutron absorbing efficiency,however,such NAMs exhibit poor high-temperature *** meet the requirement for structure-function integration,NAMs with enhanced high-temperature mechanical properties are *** this work,a novel(B4 C+Al_(2)O_(3))/Al NAM with netlike distribution of Al_(2)O_(3)was fabricated by powder metallurgy method and subjected to high-temperature tensile creep *** was shown that the creep resistance was enhanced by several orders of magnitude via the addition of only2.1 vol.%netlike-distributed Al_(2)O_(3).(B_(4)C+Al_(2)O_(3))/Al exhibited high apparent stress exponents ranging from 16 to 25 and high apparent activation energy of 364 kJ/*** creep behaviour could be rationalized using the substructure-invariant model and its rupture behaviour could be described by the dobes-Milicka equation.

关键词： Neutron absorber material Al matrix composite Tensile creep B_(4)C/Al

Low-Cycle Fatigue Properties of Nickel-Based Superalloys Processed by High-Gradient directional Solidification

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2017年第9期30卷 878-886页

作者： Z.d.Fan d.wang C.Liu G.Zhang J.Shen L.H.Lou J.Zhang Superalloys division Institute of Metal ResearchChineseAcademy of SciencesShenyang 110016China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Xi'an Thermal Power Research Institute Co. Ltd.Xi'an 710054China

The low-cycle fatigue （LCF） properties of dd10 （single-crystal） and dZ53 （columnar-grained） superalloys solidified by liquid-metal cooling （LMC） and high-rate solidification （HRS） processes have been systematically investi- gated. It was found that the LCF life of dZ53 solidified by LMC was obviously better than that solidified by HRS. In contrast, for dd10, LMC showed no remarkable influences on LCF properties at high temperature and only improved LCF properties at intermediate temperature. Microstructure examination showed that the cracks generally initiated at microp- ores in the subsurface at intermediate temperature. However, the cracks occurred on the surface due to oxidation, or persistent slip bands near script-MC at high temperature. Therefore, the benefits of LMC technique can be attributed to both of the reduced casting defects which significantly affect the LCF properties at intermediate temperature and the improved microstructural homogeneity which was strongly correlated to the LCF properties of alloys at high temperature.

关键词： Superalloys Rapid solidification Low-cycle fatigue Microstructure

Effect of heat-input on pitting corrosion behavior of friction stir welded high nitrogen stainless steel

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7期35卷 1278-1283页

作者： H.Zhang P.Xue d.wang L.H.Wu d.R.Ni B.L.Xiao Z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences

In this study, different welding param eters were selected to investigate the effects of heat-in put on the microstructure and corrosion resistance of the friction stir welded high nitrogen stainless steel joints. The results show ed that, the welding speed had major influence on the duration at elevated tem perature rather than the peak tem perature. The hardness distribution and tensile properties of the nugget zones (NZs) for various joints were very similar while the pitting corrosion behavior of various NZs showed major differences. Large heat-input resulted in the ferrite bands being the pitting location, while tool wear bands were sensitive to pitting corrosion in the low heat-input joints. Cr diffusion and tool wear were the main reasons for pitting. The mechanisms of pitting corrosion in the NZs were analyzed in detail.

关键词： High nitrogen stainless steel Friction stir welding Mechanical properties Corrosion resistance Heat-input

Microstructural Evolution and Mechanical Behavior of Friction-Stir-Welded dP1180 Advanced Ultrahigh Strength Steel

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 58-66页

作者： Z.W.wang G.M.Xie d.wang H.Zhang d.R.Ni P.Xue B.L.Xiao Z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

Friction stir lap welding of a dP1180 advanced ultrahigh strength steel was successfully carried out by using three welding tools with different pin lengths. The effects of the welding heat input and material flow on the microstructure evolution of the joints were analyzed in detail. The relationship between pin length and mechanical properties of lap joints was studied. The results showed that the peak temperatures of all joints exceeded A c3, and martensite phases with similar morphologies were formed in the stir zones. These martensite retained good toughness due to the self-tempering effect. The formation of ferrite and tempered martensite was the main reason for the hardness reduction in heat-affected zone. The mechanical properties of the lap joints were determined by loading mode, features of lap interface and the joint defects. When the stir pin was inserted into the lower sheet with a depth of 0.4 mm, the lap joint exhibited the maximum tensile strength of 12.4 kN.

关键词： Advanced ultrahigh strength steel Friction stir welding Microstructure Mechanical behavior

Achieving ultra-high strength friction stir welded joints of high nitrogen stainless steel by forced water cooling

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11期34卷 2183-2188页

作者： H.Zhang d.wang P.Xue L.H.Wu d.R.N B.L.Xiao Z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China University of Chinese Academy of Sciences 19 Yuquan RoadBeijing 100049China

The microstructure and properties of water-cooled and air-cooled friction stir welded（FSW） ultra-high strength high nitrogen stainless steel joints were comparatively studied. With additional rapid cooling by flowing water, the peak temperature and duration at elevated temperature during FSW were significantly reduced. Compared to those in the air-cooled joint, nugget zone with finer grains（900 nm） and heat affected zone with higher dislocation density were successfully obtained in the water-cooled joint,leading to significantly improved mechanical properties. The wear of the welding tool was significantly reduced with water cooling, resulting in better corrosion resistance during the immersion corrosion test.

关键词： Friction stir welding Stainless steels Mechanical properties Corrosion

Bacillus subtilis produces(p)ppGpp in response to the bacteriostatic antibiotic chloramphenicol to prevent its potential bactericidal effect

在线全文

学校读者我要写书评

暂无评论

mLife 2022年第2期1卷 101-113页

作者： Jin Yang Jessica T.Barra danny K.Fung Jue d.wang department of Bacteriology University of WisconsinMadisonUSA

Antibiotics combat bacteria through their bacteriostatic(by growth inhibition)or bactericidal(by killing bacteria)***,it has been proposed that bactericidal antibiotics trigger cellular damage,while bacteriostatic antibiotics suppress cellular ***,we demonstrate how the difference between bacteriostatic and bactericidal activities of the antibiotic chloramphenicol can be attributed to an antibiotic-induced bacterial protective response:the stringent *** targets the ribosome to inhibit the growth of the Gram-positive bacterium Bacillus ***,we found that chloramphenicol becomes bactericidal in *** mutants unable to produce(p)*** observed a similar(p)ppGpp-dependent bactericidal effect of chloramphenicol in the Gram-positive pathogen Enterococcus *** ***,chloramphenicol treatment induces(p)ppGpp accumulation through the action of the(p)ppGpp synthetase RelA.(p)ppGpp subsequently depletes the intracellular concentration of GTP and antagonizes GTP *** GTP regulation is critical for preventing chloramphenicol from killing ***,as bypassing(p)ppGpp-dependent GTP regulation potentiates chloramphenicol killing,while reducing GTP synthesis increases ***,chloramphenicol treatment protects cells from the classical bactericidal antibiotic vancomycin,reminiscent of the clinical phenomenon of antibiotic *** together,our findings suggest a role of(p)ppGpp in the control of the bacteriostatic and bactericidal activity of antibiotics in Gram-positive bacteria,which can be exploited to potentiate the efficacy of existing antibiotics.

关键词： antibiotic tolerance bactericidal antibiotic bacteriostatic antibiotic GTP (p)ppGpp