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Mechanism for the multi-stage precipitation of Fe-Ni based alloy

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Journal of Materials Science & Technology 2019年第11期35卷 2582-2590页

作者： Yan Jiang Qiang Zuo Feng Liu State Key Laboratory of Solidification Processing Northwestern Polytechnical University

This work lays great emphasis on the distribution evolution of sigma(σ)phase in Fe-Ni based N08028 alloy during aging process,the result of which could provide new insights into phase change and precipitation *** is found that theσphase,in any case,tends to separate out with a granular shape at grain boundaries(GBs)primarily,and with the increment of time,it is obliged to precipitate in grain interiors(GIs)with a lamellar *** mechanisms for the evolving volume fraction and morphology ofσphase are discussed,and a model appropriate for the multi-stage behavior transforming from intergranular to intragranular precipitation is derived,as well as revealing the thermodynamics and transformation kinetics corresponding to this *** results reveal that the occurrence of multi-stage precipitation is correlated with the redistribution of solute atoms and with the difference in coupling effect of thermodynamic driving force and kinetic activation energy between the intergranular and intragranular precipitation.

关键词： Precipitation Intergranular precipitation Intragranular precipitation Thermodynamics transformation kinetics

MATHEMATICAL MODELLING OF PHASE transformation FROM HOT-DEFORMED AUSTENITE IN LOW CARBON STEELS

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Acta Metallurgica Sinica(English Letters) 2003年第3期16卷 204-210页

作者： Y.B.Xu G.D.Wang X.H.Liu State Key Laboratory of Rolling And Automation Northeastern University Shenyang 110004 ChinaState Key Laboratory of Rolling And AutomationNortheastern University Shenyang 110004 ChinaState Key Laboratory of Rolling And AutomationNortheastern University Shenyang 110004 China

On the basis of superelement model, Cahn’s transformation kinetics theory and Scheil’s additivity rule, the CCT diagrams and transformation kinetics in low carbon steel were predicted considering both undeformed and deformed conditions. The influence of deformation on phase equilibria and transformation incubation period was evaluated quantitatively. The recrystallization kinetics and the evolution of dislocation density were calculated during continuous cooling. The results show deformation considerably shortens transformation incubation period, accelerates transformation kinetics and makes CCT curve shift leftwards. The calculated CCT diagrams and the volume fraction of each phase are in good agreement with measurements.

关键词： thermodynamics transformation kinetics continuous cooling hot-deformed austenite

CALCULATION OF transformation VOLUME FRACTION TO HQ590 HOT ROLLED STRIP STEEL DURING CONTINUOUS COOLING

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Acta Metallurgica Sinica(English Letters) 2004年第5期17卷 754-760页

作者： X.G.Zhou X.M.Zhao Y.B.Xu D.Wu TheStateKeyLab.ofRollingTechnologyandAutomation NortheasternUniversityShenyang110004China

On the basis of phase transformation kinetics, the transformation of γ→α,P,B have been investigated through considering the effect of deformation. The calculation methods of volume fraction have also been given. Co... 详细信息

关键词： transformation kinetics volume fraction nucleation rate

Aging kinetics in a CuNiSiCr Alloy

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Journal of Materials Science & Technology 2004年第6期20卷 727-730页

作者： JingguoLEI PingLIU XiaotianJING DongmeiZHAO JinliangHUANG CollegeofMaterial Xi′anUniversityofTechnologyXi′an710048China MaterialsScienceandEngineeringCollege HenanUniversityofScienceandTechnologyLuoyang471003China

The aging precipitation behavior in solution treated Cu-Ni-Si-Cr alloy has been studied in terms of the analyses of the variations in electrical conductivity. On the basis of the linear relationship between the electrical conductivity and the volume fraction of the precipitates, the phase transformation kinetics equation was deduced from the Avrami empiricai formula. On the basis of this equation, transformation kinetics curves corresponding to 5% and 50% transformation were established.

关键词： Cu-Ni-Si-Cr alloy Aging precipitation Electrical resistivity Volume fraction transformation kinetics

Effect of Niobium on transformations From Austenite to Ferrite in Low Carbon Steels

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Journal of Iron and Steel Research International 2011年第S1期18卷 208-212页

作者： Parker Sally Rose Andrew West Geoff Thomson Rachel Steel Metallurgy Department Tata Steel RD and TSwinden Technology CentreRotherhamS60 3ARUK Department of Materials Loughborough UniversityLoughboroughLE11 3TUUK

Niobium has an important effect on the transformation behaviour,grain size refinement and precipitation strengthening during hot rolling and subsequent cooling in low carbon steels,with even a low content of niobium having a strong effect on the transformation rate from austenite to ***,the effects of niobium on transformation behaviour have not been fully characterised and understood to *** paper examines in detail austenite grain growth as a function of austenitisation time in high strength low alloy (HSLA) steels with three different niobium contents,together with the effect of niobium on the isothermal transformation kinetics from austenite to ferrite as a function of *** is shown that austenite has the slowest grain growth rate in the steel with the highest niobium *** austenite grain sizes are consistent,the steel with the highest niobium content was found to have the slowest transformation rate from austenite to ferrite.

关键词： niobium transformation kinetics austenite grain growth low carbon steels

Grain Size Prediction after Continuous Cooling transformation from Deformed Austenite to Ferrite

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Journal of Iron and Steel Research International 1998年第2期5卷 42-44页

作者： Qu Jinbo Wang Zhaodong Liu Xianghua Wang Guodong Northeastern University

On the basis of transformation thermodynamics and kinetics theories,an algorithm for predicting ferrite grain size after continuous cooling transformation from deformed austenite to ferrite is *** calculated results of computer simulation with the algorithm are in so good agreement with the measured ones in controlled rolling and controlled cooling experiments that the theoretical algorithm is feasible.

关键词： ferrite grain size transformation kinetics continuous cooling deformed austenite

Ferrite Evolution During Isothermal Process in a High Deformability Pipeline Steel

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Journal of Iron and Steel Research International 2013年第7期20卷 89-93页

作者： TAN Feng-liang LIU Qing-you LEI Ting JIA Shu-jun DUAN Lin-na Faculty of Metallurgical and Energy Engineering Kunming University of Science and Technology Institute for Structure Materials CISRI Kunming Metallurgy College School of Material Science and Engineering University of Science and Technology Beijing

In order to ensure the safety of long-distance oil and natural gas transmission pipeline installed in seismic and/or permafrost region, high strength pipeline steel with excellent deformability has been developed. The ferrite and bainite dual phase pipeline steel is a very important kind of high deformability pipeline steel. Polygonal ferrite is a key microstructure in ferrite and bainite dual phase deformability pipeline steel. Ferrite evolution during isothermal process at 700 ℃ after 50% deformation at 800 ℃ was conducted by using a Gleeble-3800 thermal simulator, and microstructure was characterized by using an optical microscope, a scanning electron microscope and a transmission electron microscope. There are two types of ferrite, ferrite with high density dislocation and ferrite with a little dis location. There is about 7% （volume percent） deformation induced ferrite （DIF） for compression of 50% at 800 ℃ and strain rate of 1 s-1. During the isothermal process at 700 ℃, with the holding time increasing, ferrite volume percent, ferrite grain number and average ferrite grain size increase. As the holding time is prolonged, dislocation re-covery occurs in DIF. There are secondary phases in ferrite when the holding time is too long, and secondary phases and dislocation formation in dislocation pinning.

关键词： transformation kinetics ferrite dislocation transformation driving force

Anisotropic growth of multigrain in equiaxial solidification simulated with the phase field method

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Chinese Physics B 2006年第1期15卷 219-223页

作者：李梅娥肖志英杨根仓周尧和 School of Material Science and Engineering Xi'an Jiaotong University Xi'an 710049 China State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi'an 710072 China

The phase field method has been mainly used to simulate the growth of a single crystal in the past. But polycrystalline materials predominate in engineering. In this work, a phase field model for multigrain solidification is developed, which takes into account the random crystallographic orientations of crystallites and preserves the rotational invariance of the free energy. The morphological evolution of equiaxial multigrain solidification is predicted and the effect of composition on transformation kinetics is studied. The numerical results indicate that due to the soft impingement of grains the Avrami exponent varies with the initial melt composition and the solidification fraction.

关键词： multigrain solidification transformation kinetics phase field method