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Modeling of grain size in isothermal compression of Ti-6Al-4V alloy using fuzzy neural network

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Rare Metals 2011年第6期30卷 555-564页

作者： LUO Jiao LI Miaoquan School of Materials Science and Engineering Northwestern Polytechnical University Xi＇an 710072 China

isothermal compression of Ti-6Al-4V alloy was conducted in the deformation temperature range of 1093-1303 K, the strain rates of 0.001, 0.01, 0.1, 1.0, and 10.0 s-1, and the height reductions of 20%-60% with an interval of 10%. After compression, the effect of the processing parameters including deformation temperature, strain rate, and height reduction on the flow stress and the microstructure was investigated. The grain size of primary a phase was measured using an OLYMPUS PMG3 microscope with the quantitative metallography SISC IAS V8.0 image analysis software. A model of grain size in isothermal compression of Ti-6A1-4V alloy was developed using fuzzy neural net- work （FNN） with back-propagation （BP） learning algorithm. The maximum difference and the average difference between the predicted and the experimental grain sizes of primary a phase are 13.31% and 7.62% for the sampled data, and 16.48% and 6.97% for the non-sampled data, respectively. It can be concluded that the present model with high prediction precision can be used to predict the grain size in isothermal compression of Ti-6Al-4V alloy.

关键词： titanium alloy isothermal compression grain size fuzzy neural network

Estimation of probable maximum aspect ratio of MnS inclusions in non-quenched and tempered steel after isothermal compression

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Journal of Iron and Steel Research International 2024年第11期31卷 2788-2801页

作者： Jun-yu Liu Cheng-song Liu Yong Wang Hua Zhang Rui-juan Bai Wei Wang Qing-bo Wang Hong-wei Ni The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan430081HubeiChina Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education Wuhan University of Science and TechnologyWuhan430081HubeiChina Hubei Provincial Key Laboratory for New Processes of Ironmaking and Steelmaking Wuhan University of Science and TechnologyWuhan430081HubeiChina Henan Jiyuan Iron&Steel(Group)Co. Ltd.Jiyuan459000HenanChina

To clarify the deformation behavior of MnS inclusions in a non-quenched and tempered steel at three different positions (edge, 1/2 radius and center) in the cross-section of the billet in the course of hot rolling, isothermal compression experiments were performed under the deformation temperature range from 1073 to 1473 K, the reduction rates from 25% to 75% and the strain rates from 0.01 to 10 s^(−1). The variations of deformability features (i.e., aspect ratios, size distributions, and morphologies) of MnS inclusions with those isothermal compression parameters were revealed. The evaluation of the probable maximum aspect ratio of MnS inclusions at the three different positions in the cross-section of the billet after hot rolling was examined using the statistical analysis of extreme values. Results showed that the number densities of MnS inclusions at three different positions (edge, 1/2 radius and center) in the cross-section of the steel billet only fluctuated slightly when the deformation parameters varied in the isothermal compression, while the average inclusion aspect ratios in all cases generally have a negative correlation with the deformation temperature and positive correlations with the reduction ratio and the strain rate. Statistical analysis reveals that larger inclusions deform more easily during hot rolling. The effect of rolling temperature on the extreme value of the aspect ratio of inclusions is the smallest, while the effects of initial size, reduction ratio and strain rate are more significant.

关键词： Non-quenched and tempered steel MnS inclusion Probable maximum aspect ratio isothermal compression

Deformation characteristic of semi-solid ZCuSn10 copper alloy during isothermal compression

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Rare Metals 2016年第8期35卷 620-626页

作者： Jia Wang Han Xiao Long-Biao Wu Hai-Lian Hu De-Hong Lu Rong-Feng Zhou Rong Zhou College of Materials Science and Engineering KunmingUniversity of Science and TechnologyKunming 650093China College of Mechanical Engineering Sichuan University ofScience and EngineeringZigong 643000China

The compression tests were carried out by Gleeble-1500 thermo-mechanical simulator with samples of semi-solid ZCuSnl0 alloy prepared by strain-induced melt activation （SIMA） process. The original microstruc- ture and the deformation temperature of semi-solid ZCuSnl0 alloy are different. The strain is 0.2, and the strain rate is 1 s-1 for the compression test. The results show that when the semi-solid ZCuSnl0 alloy was pre- pared by SIMA process, the liquid fraction of semi-solid microstructure increases, and the solid grain is smaller, more uniform and more inclined to be round as the roiling pre-deformation increasing. The results also indicate that the deformation resistance of ZCuSnl0 alloy in semi-solid state decreases with the deformation temperature increas- ing or the solid fraction of original microstructure de- creasing. The stress-strain curves of the isothermal compression can be divided into quasi-elastic deformation stage and plastic deformation stage, and there are three deformation zones in the samples after isothermal com- pression, namely the difficult deformation zone, the large deformation zone and the free deformation zone. In the three deformation zones, the main deformation mechanism is flow of liquid incorporating solid particles （FLS） mechanism, plastic deformation of solid particles （PDS） mechanism and liquid flow （LF） combining with FLS mechanism, respectively.

关键词： ZCuSn10 copper alloy Semi-solid isothermal compression Deformation characteristic

Variation effect of strain rate on microstructure in isothermal compression of Ti-6Al-4V alloy

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Rare Metals 2012年第1期31卷 7-11页

作者： Yu, Weixin Li, Miaoquan Luo, Jiao School of Materials Science and Engineering Northwestern Polytechnical University Xi'an 710072 China

isothermal compression of the Ti-6Al-4V alloy at the deformation temperatures of 950 and 980℃,height reductions of 30% and 60%,and strain rates of 0.001,0.010,0.100 and 1.000 s-1 was conducted,wherein the variations of microstructure with strain rate were *** experimental results showed that the variation of the microstructure with the strain rate under one condition was significantly different from that under another condition,which meaned that the interaction between the processing parameters was *** optimization of the strain rate under one condition was not suitable for another ***,selecting the forging equipment and optimizing the strain rate should be based on simultaneously considering the deformation temperature and height reduction.

关键词： Ti-6Al-4V alloy isothermal compression microstructure strain rate

isothermal compression behavior and constitutive modeling of Ti-5Al-5Mo-5V-1Cr-1Fe alloy

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Transactions of Nonferrous Metals Society of China 2018年第6期28卷 1114-1122页

作者： Li-li CHANG Li-wei ZHENG School of Materials Science and Engineering Shandong UniversityJi＇nan 250061China

Hot compression behavior of Ti-5 Al-5 Mo-5 V-1 Cr-1 Fe alloy with an equiaxed（α＋β） starting microstructure was investigated by isothermal compression test and optical microscopy. Based on the true strain-stress data with temperature correction, constitutive models with a high accuracy were developed and processing maps were established. Strain inhomogeneity at different locations in the compressed sample is reduced by raising temperature, leading to a uniform distribution of α phases. For the temperature range of 800-840 ℃ with a strain rate of 10 s^-1, the transformed volume fraction of α phase increases and the average grain size of α phase decreases slightly with increasing the temperature, indicating co-existence of dynamic recovery and dynamic recrystallization. Flow localization and faint β grain boundaries are observed at the strain rate of 10 s^-1 in the temperature range of 860-900 ℃. The processing map analysis shows that hot working of Ti-5 Al-5 Mo-5 V-1 Cr-1 Fe alloy should be conducted with the strain rate lower than 0.01 s^-1 to extend its workability.

关键词： Ti-5Al-5Mo-5V-1Cr-IFe alloy isothermal compression constitutive equations processing map

Evolution of grain size and grain shape during thermomechanical processing in a powder metallurgical nickel-based superalloy

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Journal of Iron and Steel Research International 2022年第2期29卷 350-358页

作者： Yan-hui Liu Zhao-zhao Liu Miao Wang College of Mechanical and Electrical Engineering Shaanxi University of Science and TechnologyXi’an710021ShaanxiChina School of Materials Science and Engineering Northwestern Polytechnical UniversityXi’an710072ShaanxiChina Zhejiang Wenzhou Research Institute of Light Inousty Wenzhou325002ZhejiangChina

With a strain rate range of 0.01–10 s^(−1) and a deformation temperature range of 1110–1200℃,the isothermal compression test was performed on one powder metallurgy superalloy which is macroscopic segregation *** electron backscatter diffraction,the effect of strain rate and deformation temperature on grain shape and grain size of superalloys during thermal deformation was *** results established that exquisite and equiaxed dynamic recrystallization(DRX)grains are procured at supernal deformation temperature and high strain rate because of the high dislocation *** the same time,the interaction between high DRX nucleation rate and low grain growth rate at high strain rate is favorable in making finer DRX *** equivalent medial grain size expanded with lowering strain rate and elevating proof ***,the grain shape was researched by the effective method of aspect *** aspect ratio of original grains is 0.61,and the aspect ratio has important implications for DRX and grain growth *** average aspect ratio increases slightly when deformation temperature rises from 1110 to 1140℃,while the average aspect ratio increases memorably as the deformation temperature is higher than 1140℃.

关键词： Powder metallurgy nickel-based superalloy isothermal compression Grain size Grain shape calculation method Electron backscatter diffraction Grain shape aspect ratio

Hot workability characteristics of Rene88DT superalloy with directionally solidified microstructure

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Rare Metals 2015年第1期34卷 51-63页

作者： Fu-Lin Li Rui Fu Di Feng Zhi-Ling Tian Superalloy Department Central Iron & Steel Research Institute

The hot deformation characteristics of Rene88DT superalloy with directionally solidified micro- structure produced by electroslag remelting continuous directionally solidification （ESR-CDS） were studied in the temperature range of 1,040-1,140 ℃ and strain rate range of 0.001-1.000 s-1 by hot compression tests. Flow curves for Rene88DT alloy with initial directionally solidified （DS） microstructure exhibit pronounced peak stresses at the early stage of deformation followed by the occurrence of dynamic softening phenomenon. Rene88DT alloy with DS micro- structure shows higher flow peak stresses compared with HIPed P/M superalloy FGH4096, but the disparities in peak stresses between ESR-CDSed Rene88DT and HIPed P/M superalloy FGH4096 reduce as temperature increases. The improvement of hot workability of DS alloy with columnar grains avoiding the maximum shear stress comes true. A hot deformation constitutive equation as a function of strain that describes the dependence of flow stress on strain rate and temperature is established. Hot deformation apparent acti- vation energy （Q） varies not only with the strain rate and temperature but also with strain. The strain rate sensitivity exponent （m） map is established at the strain of 0.8, which reveals that global dynamic recrystallization （DRX） shows a relatively high m value in a large strain compression. Optimum parameters are predicted in two regions： T = 1,100-1,130 ℃, ε = 0.100-1.000 s-1 and T = 1,080- 1,100 ℃, ε = 0.010-100 s-1, which is based on pro- cessing maps and deformation microstructure observations.

关键词： Rene88DT alloy Directional solidification isothermal compression Constitutive equation Processingmap

Microstructure evolution in the high temperature compression of Ti-5.6Al-4.8Sn-2.0Zr alloy

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Rare Metals 2010年第5期29卷 533-537页

作者： LI Miaoquan,LUO Jiao,and PAN Hongsi School of Materials Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China School of Materials Science and Engineering Northwestern Polytechnical University Xi’an China

isothermal compression of a Ti-5.6Al-4.8Sn-2.0Zr alloy was conducted on a Thermecmaster-Z simulator at the deformation temperatures ranging from 960 to 1060℃, the strain rates ranging from 0.001 to 10.0 s^-1, and the maximum height reduction of 70.0%. In the two-phase region of the Ti-5.6Al-4.8Sn-2.0Zr alloy, the volume fraction of α phase decreases with an increase in deformation temperature, but the grain size has a slight variation with deformation temperature. The strain rate affects both morphologies and grain size of the α phase in the isothermal compression of the Ti-5.6Al-4.8Sn-2.0Zr alloy. The optimal height reduction also contributes to the small and well-distributed α phase in the isothermal compression of Ti-5.6Al-4.8Sn-2.0Zr alloy.

关键词： titanium alloys isothermal compression microstructure mechanism

High Temperature Behavior of isothermally Compressed M50 Steel

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Journal of Iron and Steel Research International 2015年第10期22卷 969-976页

作者： Li-xing SUN Miao-quan LI School of Materials Science and Engineering Northwestern Polytechnical University

The isothermal compression of M50 steel is carried out on a Gleeble-3500 thermo-mechanical simulator in temperature range of 1 223-1 423 K and strain rates range of 10-70 s^-1. The results show that the carbides play a significant role in the flow behavior and microstructure evolution during isothermal compression of M50 steel. The average apparent activation energy for deformation in isothermal compression of M50 steel is （281.1±42.6） kJ·mol^-1 at the strains of 0.4-0.8. The dynamic recrystallization of austenite grains occurs in isothermal compression of M50 steel at 1 363 K and 1 393 K, enhancing with the increase of strain rate and/or strain. The volume fraction of the carbides decreases with the increase of deformation temperature during isothermal compression of M50 steel and the fine carbides inhibit the dynamic recrystallization of austenite grain. With the occurrence of dynamic recrystallization, the austenite grains are refined, leading to a minor increase in the flow stress and apparent activation energy for deformation in isothermal compression of M50 steel. The austenite grains begin to coarsen at 1 423 K and dynamic recrystallization is limited. Hot working of M50 steel should not be performed above 1 393 K in order to achieve good workability.

关键词： M50 steel carbide apparent activation energy dynamic recrystallization isothermal compression