检索结果-南通市图书馆

Modeling of Solidification Microstructures Based on Fully Coupling of Macro-transport Phenomena with Cellular Automata

同方期刊数据库

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2000年第6期16卷 568-572页

作者： Qiang DU DianZhong li yiyi li Institute of Metal Research Chinese Academy of SciencesShenyang 110015China

This paper has attempted to simulate the microstructure formation based on fully coupling of temperature field, concentration field and velocity field with micro-kinetics. The authors presented a new way, which is the combination of FDM and cellular automata (CAFD) to visualize the microstructure formation of the thin complex superalloy turbine blades cast by the vacuum investment process. The distribution, orientation and mechanism of the heterogeneous nucleation, the growth kinetics of dendrites and the columnar to equiaxed transition (CET) are considered. Capitalizing on these simulating schemes, the comprehensive influence of key process variables on the scale and uniformity of grains has been investigated quantitatively. The simulated grain size and morphology agree well with the experimental results.

关键词： Microstructure

Multi-scale study on the heterogeneous deformation behavior in duplex stainless steel

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2021年第13期72卷 180-188页

作者： Xiao Zhang Pei Wang Dianzhong li yiyi li Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

The heterogeneous deformation behavior of austenite and ferrite in the 2205 duplex stainless steel was subjected to multiscale analysis based on the in situ synchrotron-based high energy X-ray diffraction,microscopic digital image correlation,electron backscatter diffraction,and transmission electron *** is found that the heterogeneous deformation triggers from the yielding of *** this deformation stage,austenite experiences greater strain in the area near the phase boundaries because of the impeded function of the phase boundaries to *** to the relatively small difference in hardness between the constituent phases,the strain in austenite grains extends into the adjacent ferrite grains when entering into the ferrite yielding *** addition,the strain distribution of the austenite grains is more homogeneous than that of the ferrite grains because of the lower stacking fault energy of austenite,which results in a planar slip,and higher stacking fault energy in case of ferrite,causing cross *** interaction between austenite and ferrite becomes considerably obvious when the strain further increases after both constituent phases yielding because of the back stress and forward stress in austenite and ferrite,respectively,which are generated by the pile-up of the geometrically necessary dislocations.

关键词： Duplex stainless steel Heterogeneous deformation behavior Digital image correlation Back stress Geometrically necessary dislocation

Microstructural evolution and stress relaxation cracking mechanism for Super304H austenitic stainless steel weld metal

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5期100卷 82-90页

作者： Xiaopeng Xiao Dianzhong li yiyi li Shanping Lu 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 Key Laboratory of Nuclear Materials and Safety Assessment Insititute of Metal ResearchChinese Academy of SciencesShenyang 110016China

The pre-compressed CT technique was used to quantitatively investigate the formation of stress relaxation cracks under different tensile residual stresses and aging time in Super304H austenitic stainless steel weld *** statistical results revealed that intergranular cracks could occur within 2000 h under 650℃ when the residual stress was applied with greater than 18 KN pre-compression *** grain interior and boundary analyses showed that the growth of intragranular Cu-rich particles could induce a strong grain interior,and the intergranular Nb(C,N)carbides were one of the causes to crack under short-term aging *** long-term aging time conditions,the intergranular M_(23)C_(6)carbides were more susceptible to crack than intergranular Nb(C,N)***,the mechanism responsible for stress relaxation cracking formation was carefully illustrated for the weld metals after short-term aging and long-term aging,respectively.

关键词： Stress relaxation cracking Super304H steel Weld metal Aging treatment Residual stress Precipitates

High-temperature Tensile Behavior in Coarse-grained and Fine-grained Nb-containing 25Cr-20Ni Austenitic Stainless 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11期33卷 1455-1465页

作者： Guodong Hu Pei Wan Dianzhong li yiyi li Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua Road.Shenyang 110016China School of Materials Science and Engineering Universityof Science and Technology of China72 Wenhua RoadShenyang 110016China Centre of Excellence for Advanced Materials Dongguan 523808China Songshan Lake Laboratory for Materials Science Dongguan 523808China

In this study,tensile behavior of Nb-containing 25Cr-20Ni austenitic stainless steels composed of coarse or fine grains has been investigated at temperatures ranging from room temperature to 900℃.Results show that the tensile strength of fine-grained specimens decreases faster than that of coarse-grained specimens,as the test temperature increases from 600℃ to 800℃.The rapidly decreasing tensile strength is attributed to the enhanced dynamic recovery and recrystallization,because additional slip systems are activated,and cross-slipping is accelerated during deformation in fine-grained *** tensile testing at 700-900℃,sigma phases are formed concurrently with dynamic recrystallization in fine-grained *** precipitation of sigma phases is induced by simultaneous recrystallization as the diffusion of alloying elements is accelerated during the recrystallization ***,the minimum ductility is observed in coarse-grained specimens at 800℃,which is caused by the formation of M23C6 precipitates at the grain boundaries.

关键词： Austenitic stainless steels High-temperature tensile properties Grain size Precipitates

Principles Giving High Penetration under the Double Shielded TIG Process

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2014年第2期30卷 172-178页

作者： Dongjie li Shanping Lu Dianzhong li yiyi li Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

A new welding method named double shielded tungsten inert gas （TIG） has been developed to improve the TIG weld penetration. The main principles to increase the weld depth have been discussed. Results show that the critical oxygen content in the weld pool is around 100 × 10 -6 as the temperature coefficient of surface tension changes from negative to positive. The tracer test using pure silver shows that the direction of Marangoni convection changes as the oxygen content increases in the weld pool. The effect of arc constriction on the weld depth has been evaluated on a water-cooled copper plate, and the result indicates that the torch of double shielded can give a more powerful arc. Heavy oxide on the pool surface has undesirable impacts on the increasing of weld depth as the oxygen excessively accumulates in weld pool. It is possible to form chromium oxide in the weld process, while the iron oxide may form as the weld surface exposes to the air after the shielded gas moving away.

关键词： Marangoni convection Penetration Tungsten inert gas (TIG) Arc Oxide

Effect of Structural Parameters of Double Shielded TIG Torch on the Fusion Zone Profile for 0Cr13Ni5Mo Martensitic Stainless Steel

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2014年第9期30卷 922-927页

作者： Dongjie li Shanping Lu Dianzhong li yiyi li Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences

The effects of double shielded TIG （tungsten inert gas） torch＇s structural parameters, including the flow rate ratio between the inner and outer layers of gas and the extended length of the electrode （abbreviated as ELE in this work）, on the fusion zone profile have been investigated for OCrl3NiSMo martensitic stainless steel. Results show that the double shielded TIG process yields relatively high penetration of the weld pool in a broad range of the structural parameters. ELE over 3 mm is too large and causes adverse reactions on the protection of electrode. The outer gas with relatively high flow rate or the outer layer with high oxygen content is conducive to the oxygen dissolved into the arc, which results in the oxidation of the weld pool surface and the electrode tip. The double shielded TIG welded metal was tested and presented good impact property.

关键词： Structural parameters Flow rate Electrode extended length Impact energy

Effects of rare earth on microstructure and impact toughness of low alloy Cr-Mo-V steels for hydrogenation reactor vessels

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2020年第10期42卷 1-14页

作者： Zhonghua Jiang Pei Wang Dianzhong li yiyi li Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China School of Materials Science and Engineering University of Science and Technology of China72 Wenhua Road.Shenyang 110016China

The effects of rare earth(RE) on the microstructure and impact toughness of low alloy Cr-Mo-V bainitic steels have been investigated where the steels have RE content of 0 to 0.048 wt.%. The results indicate that the normalized microstructures of the steels are typical granular bainite(GB) composed primarily of bainitic ferrite and martensite and/or austenite(M-A) constituents. The M-A constituents are transformed into ferrite and carbides and/or agglomerated carbides after tempering at 700℃ for 4 h. The addition of RE decreases the onset temperature of bainitic transformation and results in the formation of finer bainitic ferrite, and reduces the amount of carbon-rich M-A constituents. For the normalized and tempered samples, the ductile-to-brittle transition temperature(DBTT) decreases with increasing RE content to a critical value of 0.012 wt.%. Lower DBTT and higher upper shelf energy are attributed to the decreased effective grain size and lower amount of coarse agglomerated carbides from the decomposition of massive M-A constituents. However, the addition of RE in excess of 0.012 wt.% leads to a substantial increase in the volume fraction of large-sized inclusions, which are extremely detrimental to the impact toughness.

关键词： Low alloy Cr-Mo-V steel Rare earth Microstructure Impact toughness Granular bainite Martensite-austenite constituents

Effects of Filler Metal Composition on Inclusions and Inclusion Defects for ER NiCrFe-7 Weldments

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5期29卷 458-466页

作者： Wenlin Mo Shanping Lu Dianzhong li yiyi li Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

The effects of filler metal （FM） composition on inclusions and inclusion defects for ER NiCrFe-7 weldments have been investigated and analyzed. Results show that as Al, Ti content in FM increases from 0.14 wt% Al, 0.30 wt% Ti to 0.42 wt% Al, 0.92 wt% Ti, the Al, Ti reduction will increase during welding. Inclusion defects （point-like defects named by welding workers） are prone to form in the high Al, Ti content weldments. Inclusion defects with Mg, Ca, Al, and Ti as major metallic elements have been found on the surface and interior of the weldments, as Al, Ti content in FM is over 0.29 wt% Al, 0.62 wt% Ti. Less -ri content in FM cannot prevent ductility-dip-cracking （DDC） through producing enough intragranular precipitates and lessening intergranular M23C6 precipitates. Nb can be used to replace Ti to reduce the sensitivity of the DDC in the NiCrFe-7 alloy weldments.

关键词： Filler metal composition ER NiCrFe-7 Inclusions Inclusion defects Ductility-dip-cracking

Effect of a modified quenching on impact toughness of 52100 bearing steels

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第29期160卷 96-108页

作者： Yonghan li Zhonghua Jiang Pei Wang Dianzhong li yiyi li Shenyang National Laboratory for Materials Science Institute of Metal ResearchCASShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

In order to improve the uniformity of microstructures,and thus enhance the mechanical properties,espe-cially the impact toughness,of 52100 bearing steels,modified quenching heat treatments with different austenitizing processes have been *** results show that 740°C is the optimal holding tem-perature(approaching Ac 1=750°C)to improve the impact toughness of the steel by 37%after quench-ing and low-temperature *** observations reveal that 740°C holding shortens the nucleation incubation period of austenitization phase transformation,and inhibits the overfast growth of austenite in some regions,which leads to simultaneous nucleation and growth of austenite during austen-itizing,and homogeneous dissolution of carbides in different austenite *** changes in microstruc-ture evolution improve the microstructure uniformity(carbide and grain size)after *** distributed carbides and grain size effectively reduce stress concentration and retard crack propagation during impact loading,thus resulting in high impact toughness.

关键词： Austenitizing process Carbides distribution Impact toughness 52100 steels