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Crack Initiation Mechanism of Z3CN20.09M Duplex Stainless Steel during Corrosion Fatigue in Water and Air at 290 °C

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Journal of Materials Science & Technology 2015年第11期31卷 1144-1150页

作者： H.C.Wu b.yang y.Z.Shi q.Gao y.q.Wang State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Collaborative Innovation Center of Universal Iron & Steel Technology School of Materials Science and Engineering Anhui University of Technology

The crack initiation mechanism of a Z3CN20.09M duplex stainless steel （DSS） during corrosion fatigue （CF） in water and air at 290 ℃ was investigated by using a CF cracking machine and a scanning electron microscopy （SEM）. The cracks were initiated successively at the persistent stip bands （PSbs）, phase boundaries （Pbs） and pitting corrosion points （PCPs） of the specimens when they were tested in water at 290 ℃, while in airat 290 ℃ the cracks were only initiated at the PSbs and Pbs. And the cracks were found mainly to initiate at the PSbs and Pbs when the specimens were tested in water and air at 290 ℃, respectively. The results also reveal that the cracks were likely to be initiated at the first 20% of fatigue life of the specimens tested in water at 290 ℃. However, the cracks were not found until 50% of fatigue life when tested in air at 290 ℃. Moreover, the crack numbers of the specimens tested in water at 290 ℃ were much more than those tested in air at 290 ℃.

关键词： Duplex stainless steel Corrosion fatigue Crack initiation High temperature water

Reduction effect of final-pass heavy reduction rolling on the texture development,tensile property and stretch formability of ZWK100 alloy plates

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Journal of Materials Science & Technology 2022年第16期111卷 211-223页

作者： b.q.Shi L.y.Zhao X.L.Shang b.H.Nie D.C.Chen C.q.Li y.q.Cheng School of Materials Science and Hydrogen Energy Foshan UniversityFoshan 528000China School of Materials and Energy Guangdong University of TechnologyGuangzhouGuangdong 510006China GD Midea Air-Conditioning Equipment Co. Ltd.Foshan 528311China Guangdong Key Laboratory of Hydrogen Energy Technology Foshan 528000China yunFu(Foshan)R&D Center of Hydrogen Energy Standardization Yunfu 527326China

Obviously planar anisotropy due to‘TD split’orthotropic texture(TD indicates Transverse direction)always exist in the Rare-earth(RE)or Ca containing Mg alloy sheets,which is likely caused by the lowreduction rolling(and annealing)as revealed in our previous *** this work,the as-cast billets of a ZWK100 alloy were subjected to final-pass heavy reduction rolling(FHRR)at 500°C with different reductions(30%-70%)after rough rolling,aiming to investigate the reduction effect on the microstructure and texture *** results show that FHRR with higher reductions above 50%is in favor of shear banding formation but has little effect on the as-deformed texture components,and the excellent formability with single-pass reduction up to 70%is mainly ascribed to the activation of prismatic *** with reduction above 50%and annealing can generate uniform grain structures of~10μm and symmetrical‘oblique-line split’texture in(0001)pole figures,with basal poles tilting by about 50°from ND(Normal direction)towards some oblique-line of TD and RD(Rolling direction)as well as uniform distribution of counter lines as an annular shape,resulting in excellent elongation to failure of~50%and ultra-low planar anisotropyΔr_of~0.1 and high stretch formability(Erichsen value:8.1).The formation‘oblique-line split’texture in(0001)pole figures is mainly correlated with the preferred growth tendency of grains with■//RD,which was suggested to relate to the high mobility of some special boundaries such as 40°-45°■.The influences of starting textures on the mechanical properties,planar anisotropy and related deformation modes,as well as their correlations with the stretch formability were comparatively investigated with the‘TD split’orthotropic texture as a counterpoint.

关键词： Magnesium alloys Texture Plane anisotropy Stretch formability Rolled sheets

AN HREM STUDy OF A LATERAL MICROCRACK bENEATHINDENTATION OF [001] SILICON

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Acta Metallurgica Sinica(English Letters) 1998年第5期11卷 342-346页

作者： y.q.Wu X.y.yang y.b.Xu Inst of Metal Research The Chinese Acad of Sciences Shenyang China

A cross-sectional sample of indentation in [001] silicon was made and a lateral microcrack beneath the indentation was observed by high resolution electron microscope (HREM). The HREM images around the microcrack tip show an alternate distribution of the amorphous and lattice structure. The crack does not propagate by the successive debonding between certain atomic planes, meaning that before a crack completely opens, there may be a stage of amorphization, resulting from severe distortion of lattice.

关键词： amorphization lateal crack indentation HREM silicon

Corrosion behavior of 13Cr stainless steel under stress and crevice in high pressure CO_(2)/O_(2)environment

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Journal of Materials Science & Technology 2021年第29期88卷 79-89页

作者： G.y.Zhu y.y.Li b.S.Hou q.H.Zhang G.A.Zhang Key Laboratory of Material Chemistry for Energy Conversion and Storage Ministry of EducationHubei Key Laboratory of Materials Chemistry and Service FailureSchool of Chemistry and Chemical EngineeringHuazhong University of Science and TechnologyWuhan430074China

In this work,through the self-developed setup for in situ electrochemical tests,the corrosion behavior of 13 Cr stainless steel under the combined effect of stress and crevice in high pressure CO_(2)/O_(2)environment was *** results show that 13 Cr stainless steel presents a self-passivation *** the action of stress,the anodic dissolution process of steel inside crevice is *** is a galvanic effect between the stressed steel inside crevice and the unstressed steel outside *** applied stress reduces the induction stage of crevice corrosion and induces a larger galvanic current,i.e.,the applied stress promotes the development of crevice ***,adding 0.1 MPa O_(2)is conducive to forming a more stable passive film but causes a greater galvanic effect.

关键词： Stainless steel Crevice corrosion Stress corrosion Galvanic effect

Magnetic/Magnetostrictive Properties Together with Resistivity and Corrosion behaviors of CoFe_2 and Its Composite with CoFe_2N

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Journal of Materials Science & Technology 2017年第7期33卷 744-750页

作者： b.q.Geng y.q.Ma M.Wang Z.L.Ding W.H.Song b.C.Zhao Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Sciences Hefei 230031 China

The CoFe_2alloy（CF） was prepared by reducing CoFe_2O_4 in the H_2 ambient. Subsequently the CF sample was nitrided in the NH_3 atmosphere to produce the composite of CoFe_2N and CoFe_2. The magnetostriction, thermal expansion, resistivity and corrosion resistance of CF sample and the nitrided sample（CFN）at 1000？C were investigated. The saturation magnetostriction coefficiency λ_s and thermal expansion coefficient ？ at 300 K for the nitrided CFN were 50 ppm and 10 ppm/K, respectively, approximately equal to those for the CF sample. However, compared with CF, CFN presents a decrease in temperature coefficient R_λ（300 K） of magnetostriction by 11%. The smaller resistivity and improved corrosion resistance in the H_2SO_4 solution may expand the applications of the CoFe_2 in the fields needing lower resistivity or in the acidic environment.

关键词： CoFe alloy CoFe_2N alloy Magnetostriction Resistivity Corrosion resistance

FATIGUE PROPERTIES OF AUSTEMPERED DUCTILE IRON(ADI)IN WATER ENVIRONMENT

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Acta Metallurgica Sinica(English Letters) 2004年第2期17卷 122-130页

作者： q.Z.Cai b.K.Wei y.Tanaka StateKeyLabofPlasticFormingSimulation＆Dies／MouldTechnology FacultyofMaterialsScienceandEngineeringHuazhongUniversityofScienceandTechnologyWuhan430074China DepartmentofMechanicalSystemsEngineering MuroranInstituteofTechnologyMuroran050-8585Japan

The acicular ferrite in austempered ductile iron (ADI) matrix around graphite wascorroded preferentially in wet condition, promoting crack origination and propagationand resulting in the disappearance of ADI fatigue limit. ADI fatigue strength wasgradually reduced with increasing the time of test and was reduced by 50% in wetcondition at 10~7 cycles compared with the fatigue limit in dry condition. The fatiguestrength variation of ferritic ductile iron in wet condition was similar to that of ADI.The ferritic ductile iron, however, has better corrosion resistance so that the fatiguestrength was lowered only by 10% in wet condition at 10~7 cycles compared with thefatigue limit in dry condition. On the other hand, the fatigue limits of ADI and ferriticductile iron were dropped by 32% and 25% in tap water dipping 480h/dry conditionrespectively compared with those in dry condition. The reduction of fatigue limit wasattributed to corrosion pits formation correlated with stress concentration, resultingin origination and propagation of fatigue crack.

关键词： anstempered ductile iron water environment corrosion fatigue crack fatigue strength

FEM SIMULATION FOR LASER FORMING PROCESSING

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Acta Metallurgica Sinica(English Letters) 2004年第3期17卷 317-322页

作者： L.q.Li y.b.Chen X.y Wang S.y Lin State Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China Harbin Research Institute of Welding Harbin 150001 ChinaState Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China Harbin Research Institute of Welding Harbin 150001 ChinaHarbin Research Institute of Welding Harbin 150001 ChinaHarbin Research Institute of Welding Harbin 150001 China

Laser forming involves heating sheet metal workpiece along a certain path with adefocused laser beam directed irradiate to the surface. During laser forming, a tran-sient temperature fields is caused by the irradiation and travelling of a laser beam.Consequently, thermal expansion and contraction take place, and allows the thermal-mechanical forming of complex shapes. This is a new manufacturing technique thatforming metal sheet only by thermal stress. Therefore, the analysis of temperaturefields and stress fields are very useful for studying the forming mechanism and con-trolling the accuracy of laser forming. The non--liner finite element solver, MARC, isemployed to solve the thermal--mechanical analysis. Using this model, the stress andstrain distribution of pure aluminum plate with different thickness are analyzed. Theinfluence of scanning speed on temperature fields and plastic strain of metal sheet un-der the condition of constant line energy are also presented. Numerical results agreewell with the experimental results.

关键词： laser forming FEM simulation temperature fields stress distributton

High-Speed Friction Stir Welding of T6-Treated b4Cp/6061Al Composite

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 67-74页

作者： y.Z.Li y.N.Zan q.Z.Wang b.L.Xiao Z.y.Ma Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China University of Science and Technology of China Shenyang 110016China

T6-treated 20 wt% b4 Cp/6061 Al sheets were joined under welding speeds of 400–1200 mm/min by friction stir welding(FSW) with a threaded cermet pin. The macro-defect-free FSW joints could be achieved at high welding speeds up to 1200 mm/min, but larger plunge depth was required at the welding speeds of 800 and 1200 mm/min to eliminate the tunnel defect. In the nugget zone(NZ) of the joints, the b4 C particles were broken up and uniformly redistributed. The NZ exhibited lower hardness than the base metal(bM), and the hardness value almost did not change with increasing welding speed, attributable to the dissolution of precipitates. Compared with the bM, the joints showed lower tensile strength. As the welding speed increased from 400 to 800 mm/min, the joint efficiencies were nearly the same and up to ~ 73%. When the welding speed increased up to 1200 mm/min, the tensile strength significantly decreased, due to the occurrence of kissing bond defect at the bottom of the NZ. With increasing welding speed, the fracture location of the joints transferred gradually from the heat-affected zone to the NZ due to the kissing bond defects.

关键词： Metal-matrix composites Microstructures Mechanical properties Friction stir welding High-speed welding

Numerical Simulation of Electroosmotic Flow near Earthworm Surface

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Journal of bionic Engineering 2006年第4期3卷 179-186页

作者： y.q. Zu y.y. yan School of the built Environment The University of Nottingham Nottingham NG7 2RD UK

The electroosmotic flow near an earthworm surface is simulated numerically to further understand the anti soil adhesion mechanism of earthworm. A lattice Poisson method is employed to solve electric potential and charge .distributiorts in the electric double layer along the earthworm surface. The external electric field is obtained by solving a Laplace equation. The electroosmotic flow controlled by the Navier-Stokes equations with external body force is simulated by the lattice boltzmann method. A benchmark test shows that accurate electric potential distributions can be obtained by the LPM. The simulation shows that the moving vortices, which probably contribute to anti soil adhesion, are formed near earthworm body surface by the nonuniform and variational electrical force.

关键词： electroosmotic flow earthworm anti-adhesion LbM EDL