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grain growth in AZ31 alloy after uniaxial compression

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Transactions of Nonferrous Metals Society of China 2010年第12期20卷 2215-2222页

作者： S.ABDESSAMEUD H.AZZEDDINE B.ALILI D.BRADAI Laboratoire Faculty of PhysicsUniversity of Sciences and Technology Houari Boumediene(USTHB)BP32El-Alia Bab EzzouarAlgiers 16111Algeria

The grain growth morphology,kinetics and texture change after uniaxial compression at 430 ℃ of an extruded AZ31 alloy were *** samples were loaded following two routes insuring two initial textures of the samples with compression direction parallel and normal to the extrusion *** both initial textures,a stable grain size is attained upon isothermal annealing and the grain growth kinetics can be described by:dn= dRn+kt with an n value of around *** annealing texture with grown grains is a retained hot deformation texture without emerging or strengthening other *** grain growth is not observed for annealing time up to 10 000 h at 450℃.

关键词： AZ31 magnesium alloy uniaxial compression annealing grain growth texture

grain growth Behavior in Sintered Nd-Fe-B Magnets

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Journal of Rare Earths 2007年第3期25卷 329-335页

作者：刘湘涟周寿增 School of Mechanical Engineering Ningbo University of Technology State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

The Nd2Fe14B grain growth behavior in sintered Nd-Fe-B magnets was quantitatively *** effects of sintering temperature and time,and alloy powder size and its distribution on grain growth process were ***,possible grain growth mechanisms in these magnets were qualitatively *** Nd2Fe14B grain growth proceeded at quite a high rate in the initial 0~1 h of sintering and from then onwards the grain growth rate decreased.A large average particle size or a wide particle size distribution of initial alloy powders was found to remarkably accelerate the grain growth process and even result in the occurrence of abnormal grain *** the basis of experimental results,two grain growth mechanisms were considered to operate during sintering of Nd-Fe-B magnets,that is,dissolution and re-precipitation of Nd2Fe14B particles,and Nd2Fe14B particle growth by *** was believed that Nd2Fe14B particle growth by coalescence not only produced a large average grain size and a wide grain size distribution,but also was the fundamental reason for the formation of abnormally large grains in the microstructure of sintered Nd-Fe-B magnets.

关键词： Nd-Fe-B magnet sintering grain growth powder size rare earths

grain growth of Deformation Induced Ferrite in V Microalloyed Low Carbon Steel During Controlled Cooling Process

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Journal of Iron and Steel Research International 2011年第S1期18卷 377-382页

作者： WANG Kai 1,WANG Li-jun 2,WANG Qiang 1,HE Ji-cheng 1,LIU Chun-ming 2 (1.Key Laboratory of Electromagnetic Processing of Materials,Ministry of Education,Northeastern University,Shenyang 110819,China 2.School of Materials and Metallurgy,Northeastern University,Shenyang 110819,China) Northeastern Univ Minist Educ Key Lab Electromagnet Proc Mat Shenyang 110819 Peoples R China Northeastern Univ Sch Met & Mat Shenyang 110819 Peoples R China

The effect of vanadium on the DIFT (Deformation Induced Ferrite Transformation) microstructure coarsening in low carbon steel during the continuous cooling processes and isothermal processes at different temperatures were investigated using *** results showed that the steel containing a small amount of vanadium had the similar velocity of grain growth with the vanadium free steel during the continuous cooling process,but a lower velocity of grain growth than that of vanadium free steel during isothermal processes at high *** the other hand,the vanadium remarkably inhibited grain growth in the steel containing a high amount of vanadium during both the continuous cooling and isothermal *** dissolved in matrix is indicated as an important factor on restraining grain growth through estimating the driving force of normal grain growth and the resistance of precipitation particles of vanadium on grain *** influencing mechanism of vanadium dissolved in matrix on the grain growth during the controlled cooling process is discussed.

关键词： low carbon steel vanadium microalloying DIFT grain growth controlled cooling process

Fatigue life improvement and grain growth of gradient nanostructured industrial zirconium during high cycle fatigue

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Journal of Materials Science & Technology 2021年第28期87卷 101-107页

作者： Conghui Zhang Xiangkang Zeng Jiapeng Cheng Yaomian Wang School of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an710055China

The effect of surface gradient nanostructure on the fatigue life of commercial pure(CP)Zr was *** point bending fatigue tests indicated that the fatigue limit of CP Zr with surface gradient nanostructure was increased by about 28.3%compared with the original sample(annealed state).The microstructure evolution at different fatigue loading stages was *** high strength of surface gradient nanostructure could increase the crack initiation ***,electron back scattered diffraction(EBSD)analysis demonstrated that the surface nanocrystals grew and rotated gradually during the fatigue loading,which was beneficial to reducing stress concentration,inhibit fatigue crack initiation,and prolong crack initiation *** stored distortion energy of CP Zr calculated before and after fatigue indicated that the stored distortion energy decreased dramatically during cyclic loading,which provided the driving force for grain ***,the growth of nanocrystals consumed the mechanical energy produced by the applied load to a certain extent,thus,slowing down the accumulation of fatigue *** coarse grains at the interior could deform plastically and reduce the crack growth *** addition,the compressive residual stress caused by USSP treatment reduced the local effective stress and the driving force of crack growth.

关键词： High cycle fatigue Industrial pure zirconium grain growth Surface gradient nanostructure

A quasi-in-situ EBSD study of the thermal stability and grain growth mechanisms of CoCrNi medium entropy alloy with gradient-nanograined structure

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Journal of Materials Science & Technology 2022年第14期109卷 54-63页

作者： P.-C.Zhao B.Guan Y.-G.Tong R.-Z.Wang X.Li X.-C.Zhang S.-T.Tu Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai 200237China College of Materials Science and Engineering Chongqing UniversityChongqing 400044China College of Automobile and Mechanical Engineering Changsha University of Science and TechnologyChangshaChina

The thermal stability and mechanical properties of a gradient-nanograined structure(GNS)CoCrNi medium entropy alloy(MEA)processed by ultrasonic surface rolling were studied by using isothermal/isochronal annealing tests combined with quasi-in-situ electron backscatter diffraction(EBSD)characterization and Vickers micro-hardness(HV)measurements.A layer by layer high-throughput investigation method was used to quantitatively study the grain growth kinetics and grain boundary evolution with different initial grain sizes,which could effectively save specimen and time *** grain nucleation and growth,as well as shrink and disappearance process throughΣ3 coincidence site lattice boundary migration with slightly lattice rotation during annealing were directly *** layer by layer grain growth kinetics and calculated activation energy indicate that the thermal stability of nanograined top surface layer is relatively higher than that of nano-twined subsurface layer for the gradient CoCrNi MEA processed by ultrasonic surface *** analysis show that the grain boundary relaxation and dynamic recrystallization of the topmost nano-grains led to the decrease of grain boundary energy,thus improving their thermal *** present work provided theoretical basis for the application of CoCrNi MEA at high ***,the high-throughput method on the investigation of grain stability by using gradient structure can be easily extended to other materials and it is of great significance for understanding the microstructural evolution of gradient materials.

关键词： Medium entropy alloy grain growth Gradient materials Nanostructured materials Annealing High throughput

In situ observation of austenite grain growth behavior in the simulated coarse-grained heat-affected zone of Ti-microalloyed steels

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International Journal of Minerals,Metallurgy and Materials 2014年第9期21卷 878-885页

作者： Xiang-liang Wan Kai-ming Wu Gang Huang Ran Wei Lin Cheng The State Key Laboratory of Refractories and Metallurgy Hubei Collaborative Innovation Center for Advanced Steels Wuhan University of Science and Technology

The austenite grain growth behavior in a simulated coarse-grained heat-affected zone during thermal cycling was investigated via in situ observation. Austenite grains nucleated at ferrite grain boundaries and then grew in different directions through movement of grain boundaries into the ferrite phase. Subsequently, the adjacent austenite grains impinged against each other during the α→γtransformation. After the α→γ transformation, austenite grains coarsened via the coalescence of small grains and via boundary migration between grains. The growth process of austenite grains was a continuous process during heating, isothermal holding, and cooling in simulated thermal cycling. Abundant finely dispersed nanoscale TiN particles in a steel specimen containing 0.012wt% Ti effectively retarded the grain boundary migration, which resulted in refined austenite grains. When the Ti concentration in the steel was increased, the number of TiN particles de- creased and their size coarsened. The big particles were not effective in pinning the austenite grain boundary movement and resulted in coarse austenite grains.

关键词： alloy steel austenite grain growth heat-affected zone coarsening titanium nitride

Microstructural evolution and grain growth mechanism of pre-twinned magnesium alloy during annealing

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Journal of Magnesium and Alloys 2021年第4期9卷 1238-1251页

作者： Ye Jin Kim Jong Un Lee Young Min Kim Sung Hyuk Par School of Materials Science and Engineering Kyungpook National JJniversityDaegu 41566Republic of Korea Implementation Research Division Korea Institute of Materials ScienceChanson 51508Republic of Korea

The microstructural evolution and underlying grain growth mechanism of a{1012}-twin-containing Mg alloy during annealing are investigated through quasi in situ electron backscatter diffraction measurements of a rolled AZ31 alloy subjected to precompression along the rolling direction(RD).The precompressed material shows a partially twinned structure consisting of a twinned region and a residual matrix region,and this structure changes to an almost twin-free structure consisting of grown grains with serrated grain boundaries in twinand matrix-originated regions after annealing at 250℃ for 1 *** addition,the average grain size almost doubles and the internal strain energy decreases significantly after *** microstructural variations are induced mainly by grain growth through the strain-induced migration of high-angle grain boundaries without the movement of twin *** twinned region of the precompressed material has higher stored strain energy than the residual matrix region because the crystallographic orientation of the former region is favorable for basal slip and because of the occurrence of the dislocation transmutation reaction in the *** reducing the total strain energy accumulated in the precompressed material,the residual matrix region—having lower stored strain energy—preferentially grows while consuming the twinned regions formed in the surrounding grains during *** a result,the area fraction of grains with a matrix texture increases whereas that of grains with a twin texture decreases after *** twin texture intensity increases significantly and this texture becomes more concentrated along the RD because the highly RD oriented twins tend to grow during annealing on account of their fairly low stored strain energy.

关键词： Magnesium Twin Annealing grain growth Strain energy

grain growth simulation with the second phase particle pinning for heat-affected zone of microalloyed steel welds

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China Welding 2006年第4期15卷 63-66页

作者：陈翠欣李午申 School of Materials Science and Engineering Hebei University of Technology Tianjin300130. School of Materials Science and Engineering Tianjin University Tianjin300072.

The second phase particle dispersed in microalloyed steel has different effects on grain growth depending on their size and volume fiaction of the second phase particles which will change during welding thermal cycles. The particle coarsening and dissolution kinetics model was analyzed for continuous heating and cooling. In addition, based on experimental data, the coupled equation of grain growth was established by introducing limited size of grain growth with the consideration of the second phase particles pinning effects. Using Monte Carlo method based on experimental data model, the grain growth simulation for heat-affected zone of microalloyed steel welds was achieved. The calculating results were well in agreement with that of experiments.

关键词： microalloyed steel the second phase particle grain growth pinning effect simulation

Cellular automata modelling of grain coarsening during reheating——Ⅱ. Abnormal grain growth

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Journal of University of Science and Technology Beijing 2005年第1期12卷 26-32页

作者： WanhuaYu E.J.Palmiere S.P.Banks JingtaoHan DepartmentofMaterialsEngineering UniversityofScienceandTechnologyBeijingBeijing100083China DepartmentofEngineeringMaterials UniversityofSheffieldS13JDSheffieldUK DepartmentofAutomaticControlandSystemsEngineering UniversityofSheffieldS13JDSheffieldUK

The 2-dimensional cellular automata (CA) simulation technique has been utilized to investigate the abnormal grain coarsening. The growth of abnormal grains is modelled under this assumption that different grains have different boundary energies and boundary mobilities. As temperature increases, some grains may first get rid of the particle pinning effect. Thus a high probability is obtained for atoms to jump over the boundary, so that they can consume other primary retained grains quickly. From the simulation, the characteristics of the abnormal grain coarsening under different conditions are demonstrated successfully. An experiment has also been carried out to reflect the abnormal grain coarsening on the microalloy steel. Simulation results are quite close to the experimental evidence.

关键词： computer simulation grain growth microstructure reheating