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Static Recrystallization Behavior of SA508-III Steel during Hot Deformation

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Journal of Iron and Steel Research International 2016年第5期23卷 466-474页

作者： Ding-qian DONG Fei CHEN zhen-shan cui Institute of Forming Technology and Equipment Shanghai Jiao Tong University College of Manufacturing Science and Engineering Southwest University of Science and Technology

The static recrystallization behavior of SA508-III steel was investigated by isothermal double-hit hot compression tests at the deformation temperature of 950-1 250 ℃,the strain rate of 0. 01-1 s^（-1）,and the inter-pass time of 1-300 *** effects of deformation parameters,including forming temperature,strain rate,degree of deformation（ pre-strain） and initial austenite grain size,on the softening kinetics were analyzed. Experimental results show that static recrystallization kinetics is strongly dependent on deformation temperature and degree of deformation,while less affected by the strain rate and initial grain size. The kinetics and microstructural evolution equations of static recrystallization for SA508-III steel were developed to predict the softening behavior and the statically recrystallized grain size,respectively. Based on the comparison between the experimental and predicted results,it is found that the established equations can give a reasonable estimate of the static softening behavior for SA508-III steel.

关键词： softening fraction static recrystallization kinetic equation microstructure SA508-III steel

Hot Deformation Stability of Extruded AZ61 Magnesium Alloy Using Different Instability Criteria

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Acta Metallurgica Sinica(English Letters) 2015年第11期28卷 1364-1372页

作者： Ju-Qiang Li Juan Liu zhen-shan cui National Engineering Research Center for Die and Mold CAD School of Materials Science and EngineeringShanghai Jiao Tong University

The hot deformation stability of extruded AZ61 magnesium alloy was investigated by means of hot com- pression tests at the temperature range of 250-400 ℃ and strain rate range of 0.001-1 s^-1. The 3D instability maps considering the effect of strain were developed to delineate the regions of unstable flow on the basis of Jonas＇s, Semiatin＇s, Prasad＇s, Murty＇ s, Gegel＇s and Alexander＇s criteria. Since non-uniform deformation occurs due to the initial microstructure inhomogeneity, the friction, etc., finite element simulations were performed to determine the position of the specimens which can mostly represent the preset deformation parameter. Detailed microstructural investigation on such position was carried out to examine the validity of the instability maps, and the results indicate that for extruded AZ61 magnesium alloy：（1） Jonas＇s and Semiatin＇s criteria conservatively predict the instability regions; （2） Gegel＇s and Alexander＇s criteria inadequately predict the instability regions; （3） Prasad＇s and Murty＇s criteria provide more effective predictions of the instability regions than Jonas＇s, Semiatin＇s, Gegel＇s and Alexander＇s criteria,

关键词： Magnesium alloy Hot deformation stability Finite element simulation Microstructure

Numerical Simulation of Microstructure Evolution for SA508-3 Steel during Inhomogeneous Hot Deformation Process

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Journal of Iron and Steel Research International 2014年第11期21卷 1022-1029页

作者： Da-shan SUI Fei CHEN Pei-pei ZHANG zhen-shan cui National Die & Mold CAD Engineering Research Center Shanghai Jiao Tong University

Based on hot compression tests by a Gleeble-1500D thermo-mechanical simulator, the flow stress model and microstructure evolution model for SA508-3 steel were established through the classical theories on work hardening and softening. The developed models were integrated into 3D thermal-mechanical coupled rigid plastic finite element software DEFORM3D. The inhomogeneous hot deformation （IHD） experiments of SA508 3 steel were designed and carried out. Meanwhile, numerical simulation was implemented to investigate the effect of temperature, strain and strain rate on microstructure during IHD process through measuring grain sizes at given positions. The simulated grain sizes were basically in agreement with the experimental ones. The results of experiment and simulation demonstrated that temperature is the main factor for the initiation of dynamic recrystallization （DRX）, and higher temperature means lower critical strain so that DRX can be facilitated to obtain uniform fine microstructure.

关键词： SA508-3 steel inhomogeneous hot deformation microstructure evolution grain size numerical simulation

Modified artificial neural network model with an explicit expression to describe flow behavior and processing maps of Ti2AlNb-based superalloy

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Journal of Iron and Steel Research International 2021年第11期28卷 1451-1462页

作者： Yan-qi Fu Qing Zhao Man-qian Lv zhen-shan cui School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Institute of Forming Technology and Equipment Shanghai Jiao Tong UniversityShanghai 200030China

The elevated-temperature deformation behavior of Ti2AlNb superalloy was observed by isothermal compression experiments in a wide range of temperatures(950–1200°C)and strain rates(0.001–10 s^(-1)).The flow behavior is nonlinear,strongly coupled,and *** constitutive models,namely the double multivariate nonlinear regression model,artificial neural network model,and modified artificial neural network model with an explicit expression,were applied to describe the Ti2AlNb superalloy plastic deformation *** comparative predictability of those constitutive models was further evaluated by considering the correlation coefficient and average absolute relative *** comparative results show that the modified artificial network model can describe the flow stress of Ti2AlNb superalloy more accurately than the other developed constitutive *** explicit expression obtained from the modified artificial neural network model can be directly used for finite element *** modified artificial neural network model solves the problems that the double multivariate nonlinear regression model cannot describe the nonlinear,strongly coupled,and multivariable flow behavior of Ti2AlNb superalloy accurately,and the artificial neural network model cannot be embedded into the finite element software ***,the modified artificial neural network model is mainly dependent on the quantity of high-quality experimental data and characteristic variables,and the modified artificial neural network model has not physical ***,the processing maps were applied to obtain the optimum processing parameters.

关键词： Modified artificial neural network model Ti2AlNb superalloy Double multivariate nonlinear regression model Explicit expression Processing map

Effects of process parameters on fragment and refinement of millimeter- grade coarse grains for 316LN steel during hot cogging

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Journal of Iron and Steel Research International 2017年第5期24卷 529-535页

作者： Da-shan Sui Hai-ming Zhang Hong-yang Zhu Zhe Zhu zhen-shan cui National Die & Mold CAD Engineering Research Center Shanghai Jiao Tong University Shanghai 200030 China shanghai Heavy Machinery Plant Shanghai 200245 China

The heterogeneous mixed-grain microstructure is a common defect for the heavy forging of 316LN austenitie stainless steel. Isothermal compression experiments were performed on a Gleeble-3500 thermo-mechanical simulator to investigate the effect of process parameters on the fragment and re- finement of millimeter-grade coarse grains （MCGs） during hot cogging. The experimental results in- dicate that the stress of MCG specimens is much larger than that of fine grain （FG） ones at 1150 ℃, while the stress difference between MCG and FG samples became smaller at 1200 ℃. Moreover, the MCGs can be well fragmented and refined under the condition of temperature of 1200 ℃, strain rate of 0.01 s-1 , and reduction rate of 50%. Meanwhile, numerical simulations were conducted to study the influences of temperature, strain and strain rate on microstructure evolution. The results of ex- periments and simulations comprehensively demonstrate that the MCG results in the increase of de- formation resistance and incompatibility of deformation, and it can be fragmented and refined at 1200 ℃ so that the plastic deformation energy decreases remarkably with the increase of temperature from 1 150 to 1200 ℃.

关键词： 316LN steel Hot deformation Coarse grain Microstrueture evolution Numerical simulation

Constitutive Modeling for Elevated Temperature Flow Behavior of30Cr2Ni4MoV Ultra-super-critical Rotor Steel

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Journal of Iron and Steel Research International 2014年第5期21卷 521-526页

作者： Fei CHEN Fa-cai REN zhen-shan cui Xin-min LAI Institute of Forming Technology and Equipment Shanghai Jiao Tong University School of Mechanical Engineering Shanghai Jiao Tong University

In order to perform numerical simulation of forging and determine the hot deformation processing parameters for 30Cr2Ni4MoV steel, the compressive deformation behaviors of 30Cr2Ni4MoV steel were investigated at the temperatures from 970 to 1270 ℃ and strain rates from 0. 001 to 0.1 s-1 on a Gleeble-3500 thermo-mechanical simulator. The flow stress constitutive equations of the work hardening-dynamical recovery period and dynamical recrystallization period were established for 30Cr2Ni4MoV steel. The stress-strain curves of 30Cr2Ni4MoV steel predicted by the proposed model well agreed with experimental results, which confirmed that the proposed equations can be used to determine the hot deformation processing parameters for 30Cr2Ni4MoV steel.

关键词： 30Cr2Ni4MoV steel hot compression dynamical recrystallization flow stress

Ductile Fracture Prediction of 316LN Stainless Steel in Hot Deformation Process

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Journal of Iron and Steel Research International 2014年第10期21卷 923-930页

作者： Jian-li HE Juan LIU zhen-shan cui Chao-zhong YANG Fei CHEN School of Materials Engineering Shanghai University of Engineering Science National Engineering Research Center for Die and Mold CAD School of Materials Science and EngineeringShanghai Jiao Tong University

A ductile fracture criterion of 316LN stainless steel, combined with the plastic deformation capacity of ma- terial and the stress state dependent damages, was proposed to predict ductile fracture during hot deformation. To the end, tensile tests at high temperatures were first performed to investigate the fracture behavior of 316LN stain- less steel. The experimental results show the variation of the critical fracture strain as a function of temperature and strain rate. Second, the criterion was calibrated by using the upsetting tests and the corresponding numerical simula- tions. Finally, the proposed fracture criterion was validated by the designed tests and the corresponding finite ele- ment （FE） simulation. The results show that the criterion can successfully predict the onset of ductile fracture at ele- vated temperatures.

关键词： ductile fracture criterion FE simulation upsetting test fracture behavior 316LN stainless steel

Microstructure and properties of high-strength Cu–Ni–Si–(Ti) alloys

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Rare Metals 2021年第11期40卷 3251-3260页

作者： Yi-Hai Yang Sheng-Yao Li zhen-shan cui Zhou Li Yun-Ping Li Qian Lei State Key Lab for Powder Metallurgy Central South UniversityChangsha 410083China School of Physical and Mathematical Science Nanyang Technological UniversitySingapore 637371Singapore School of Materials Science and Engineering Central South UniversityChangsha 410083China

The tradeoff between the strength and the fracture elongation in the high-strength Cu-Ni-Si alloy became a hot research topic ***-Ni-Si-(Ti) alloys were fabricated in a vacuum induction melting furnace to study the effects of titanium on the microstructure and mechanical properties of Cu-Ni-Si alloys with different thermo-mechanical *** homogenization at 900℃ for 4 h,hot-rolled by 80%,solution treatment at 970℃ for 2 h,cold-rolled by 50%,and finally aged at 450℃ for 180 min,the studied Cu-10 Ni-Si-2 Ti alloy achieved the hardness of HV 252.4,electrical conductivity of 23.6% IACS,tensile strength of 764.4 MPa,yield strength of 622.26 MPa,fracture elongation of 10.4%,and strength-elongation product of 7.95 GPa%,which are less than those of the studied Cu-10 Ni-2 Si *** addition of Ti contributed to refining the microstructure,suppressing the decreasing trend in mechanical properties after peak hardening,and arousing a primary substructure strengthening mechanism rather than the precipitation strengthening in Cu-Ni-Si *** findings provide essential understandings of the effects of the Ti on Cu-Ni-Si system alloys,and the designed Cu-Ni-Si alloys with highstrength and fracture elongation could fulfill some requirements of the electronic and electrical industry.

关键词： Copper alloy Microstructure Strength Electrical conductivity

A 2.5-dimensional Analytical Model of Cold Leveling for Plates with Transverse Wave Defects

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Journal of Iron and Steel Research International 2015年第8期22卷 664-671页

作者： Wei-hua CHEN Juan LIU zhen-shan cui Ying-jie WANG Ying-rui WANG National Die & Mold CAD Engineering Research Center Shanghai Jiaotong University Baosteel Co. Ltd.

Waves occurring in cold-rolled plates or sheets can be divided into longitudinal and transverse waves. Classical leveling theories merely solve the problem of longitudinal waves, while no well accepted method can be employed for transverse waves. In order to investigate the essential deformation law of leveling for plates with transverse waves, a 2.5-dimensional （2.5- D） analytical approach was proposed. In this model, the plate was transversely divided into some strips with equal width; the strips are considered to be in the state of plane strain and each group of adjacent strips are assumed to be deformation compatible under stress. After calculation, the bending deformation of each strip and the leveling effect of overall plate were obtained by comprehensNe consideration of various strips along with the width. Bending of roller is a main approach to eliminate the transverse waves, which is widely accepted by the industry, but the essential effect of bending of roller on the deformation of plates and the calculation of bending of roller are unknown. According to the 2.5-D analytical model, it can be found that, for plates, it is neutral plane offsetting and middle plane elongation or contraction under inner stress that can effectively improve plate shape. Taking double side waves as an example, the appropriate values of bending of roller were obtained by the 2.5-D analytical model related to different initial unevenness, which was applicable to the current on-line adjusting of bending of roller in rolling industry.

关键词： plate leveling 2.5-dimensional analytical model transverse wave middle plane deformation