检索结果-南通市图书馆

3D finite element simulation of microstructure evolution in blade forging of Ti-6Al-4V alloy based on the internal state variable models

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2012年第2期19卷 122-130页

作者： Jiao Luo Bin Wu miao-quan li School of Materials Science and Engineering Northwestern Polytechnical UniversityXi'an 710072China

The physically-based internal state variable （ISV） models were used to describe the changes of dislocation density, grain size, and flow stress in the high temperature deformation of titanium alloys in this study. The constants of the present models could be identified based on experimental results, which were conducted at deformation temperatures ranging from 1093 K to 1303 K, height reductions ranging from 20% to 60%, and the strain rates of 0.001, 0.01, 0.1, 1.0, and 10.0 s-1. The physically-based internal state variable models were implemented into the commercial finite element （FE） code. Then, a three-dimensional （3D） FE simulation system coupling of deformation, heat transfer, and microstructure evolution was developed for the blade forging of Ti-6Al-4V alloy. FE analysis was carried out to simulate the microstructure evolution in the blade forging of Ti-6Al-4V alloy. Finally, the blade forging tests of Ti-6Al-4V alloy were performed to validate the results of FE simulation. According to the tensile tests, it is seen that the mechanical properties, such as tensile strength and elongation, satisfy the application requirements well. The maximum and minimum differences between the calculated and experimental grain size of primary α phase are 11.71% and 4.23%, respectively. Thus, the industrial trials show a good agreement with FE simulation of blade forging.

关键词： titanium alloys forging microstructure evolution internal state variables mechanical properties

Three-dimensional Numerical Simulation and Experimental Analysis of Austenite Grain Growth Behavior in Hot Forging Processes of 300M Steel Large Components

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2016年第10期23卷 1012-1019页

作者： Jiao LUO Ying-gang liU miao-quan li School of Materials Science and Engineering Northwestern Polytechnical University

The microstructure models were integrated into finite element（FE）code,and a three-dimensional（3D）FE analysis on the entire hot forging processes of 300 M steel large components was performed to predict the distributions of effective strain,temperature field and austenite grain *** simulated results show that the finest grains distribute in the maximum effective strain region because large strain induces the occurrence of dynamic ***,coarse macro-grains appear in the minimum effective strain ***,300 M steel forging test was performed to validate the results of FE simulation,and microstructure observations and quantitative analysis were *** average relative difference between the calculated and experimental austenite grain size is 7.56%,implying that the present microstructure models are reasonable and can be used to analyze the hot forging processes of 300 M steel.

关键词： 300M steel forging finite element simulation austenite grain size dynamic recrystallization

Microscopic characterization of semi-solid aluminium alloys

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2010年第3期17卷 290-296页

作者： Ya-lin Lu miao-quan li Xing-cheng li Xiao-ping li School of Materials Science and Engineering Northwestern Polytechnical University Xi＇an 710072 China School of Materials Engineering Jiangsu Teachers University of Technology Changzhou 213000 China

The microstructural evolution and element distribution of the Al-4Cu-Mg alloy during semi-solid compression were investigated, and the precipitate behavior and dislocation morphology were discussed. The experimental results show that the microstructure, the number of CuAl2 （θ phase） precipitates, and the dislocation density of the Al-4Cu-Mg alloy depend apparently on the process parameters. More segregation of Cu at the grain boundary happens with an increase of deformatinn temperature and a decrease of strain rate, leading to an increase in the number of θ phase. With an increase of height reduction, Cu segregation at the grain boundary decreases gradually. Moreover, unique dislocation morphologies including helical dislocations and dislocation loops appear at different process parameters and evolve to reduce the stored energy.

关键词： aluminum alloys semi-solid state microstructural evolution dislocation

Significance and interaction of bonding parameters with bonding ratio in press bonding of TC4 alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2016年第3期35卷 235-241页

作者： Hong li miao-quan li Wei-Xin Yu Hong-Bin liu School of Materials Science and Engineering Northwestern Polytechnical University

The variation of bonding ratio in the press bonding of TC4 alloy at temperatures from 850 to 900℃,pressures from 10 to 30 MPa,and time from 5 to 15 min was *** bonding ratio increases with the increase of temperature,time and *** maximum bonding ratio,i.e.98 %,can be obtained at 900℃,30 MPa and 15 *** significance and interaction of bonding parameters with the bonding ratio were *** results demonstrate that the effect of pressure on the bonding ratio is the most effective and the effect of temperature is secondary,while the effect of time is not very *** interaction of bonding parameter on the bonding ratio exists but that is distinguishing in different bonding parameter *** is concluded that increasing pressure can be considered as the primary method to increase the bonding ratio.

关键词： TC4 alloy Press bonding Orthogonal design Bonding ratio

Prediction model for flow stress during isothermal compression in α+β phase field of TC4 alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2018年第5期37卷 369-375页

作者： Shun Yang Hong li Jiao Luo Yin-Gang liu miao-quan li School of Materials Science and Engineering Northwestern Polytechnical University

Isothermal compression of TC4 alloy was performed on a Thermecmaster-Z simulator at the deformation temperatures ranging from 1093 to 1243 K, the strain rates ranging from 0.001 to 10.000 s^-l and a maximum strain of 0.8. The experimental results show that the flow stress increases with the decrease in the deformation temperature and the increase in the strain rate. The apparent activation energy for deformation is much lower at lower strain rates than that at higher strain rates. The flow stress model considering strain compensation was established. The average relative error between the calculated flow stress and experimental results is about 7.69%, indicating that the present model could be used to accurately predict the flow stress during high temperature in α＋β phase field of TC4 alloy.

关键词： TC4 alloy Isothermal compression Model Flow stress

Deformation behavior and processing maps during isothermal compression of TC21 alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2017年第2期36卷 86-94页

作者： Jun Gao miao-quan li Ge-Jun liu Shao-Fei liu School of Materials Science and Engineering Northwestern Polytechnical UniversityXi'an 710072China

In this study,isothermal compression tests were conducted at a Gleeble-1500 simulator at deformation temperatures ranging from 1073 to 1283 K,strain rates ranging from 0.01 to 5.00 s^（-1）,and height reductions ranging from 20%to 60%.The flow stress and apparent activation energy for deformation and constitutive equation were used to characterize the deformation behavior of TC21 alloy during the isothermal *** processing maps combined microstructure observations were established based on dynamic material model（DMM） over a range of strain rates and *** results show that an initial yield drop is observed above 1203 K or at higher strain rates ranging from 1.00 to 5.00 s^-1,and oscillatory flow curves are presented particularly at a strain rate of 5.00 s^-*** has some influence on the apparent activation energy for deformation during the isothermal compression of TC21 *** Q-values and microstructure observation confirm that dynamic recrystallization（DRX） occurs in the β single-phase *** constitutive equation during the isothermal compression of TC21 alloy is developed using the Zener-Hollomon parameter in the exponent-type *** maximum and minimum relative errors between the calculated and the experimental flow stress are 14.1%and 0.3%,*** peak efficiency of power dissipation at a strain of 0.7 is about 0.51 occurring at a deformation temperature of 1073 K and strain rate of 0.01 s^-1,corresponding to an optimal deformation condition of TC21 alloy.

关键词： TC21 alloy Flow stress Apparent activation energy for deformation Constitutive equation Processing Maps

Formation of adiabatic shear band and deformation mechanisms during warm compression of Ti–6Al–4V alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2016年第8期35卷 598-605页

作者： Jiao Luo lin-Feng Wang miao-quan li Chang-Jian Ge Xiao-Xiao Ma Yong-Ting Yang School of Materials Science and Engineering Northwestern Polytechnical UniversityXi'an 710072China

Adiabatic shear band （ASB） was narrow region where softening occurred and concentrated plastic defor- mation took place. In present study, the effects of height reduction and deformation temperature on ASB were investigated by means of optical microscopy （OM） and scanning electron microscopy （SEM）. And the deformation mechanisms within the shear band were discussed thor- oughly with the help of transmission electron microscopy （TEM）. There is a critical strain for the formation of ASB during warm compression of Ti-6AI-4V alloy. The width of ASB increases with height reduction increasing. Elon- gated alpha grains within shear band grow up with defor- mation temperature increasing. Some ultrafine grains that confirm the occurrence of dynamic recrystallization are observed within shear band during warm compression of Ti-6AI-4V alloy.

关键词： Titanium alloy Adiabatic shear band Deformation mechanisms Dynamic recrystallization

Effect of predeformation on globularization of Ti-5Al-2Sn-2Zr-4Mo-4Cr during annealing

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2018年第5期28卷 912-919页

作者： lian li miao-quan li School of Materials Science and Engineering Northwestern Polytechnical University Xi＇an 710072 China

The microstructure evolution during annealing of Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy was investigated. The results show that for the alloy compressed at 810 °C and 1.0 s^-1, deformation amount（height reduction） 20% and 50% and annealed at 810 °C, thermal grooving by penetration of β phase is sufficient during the first 20 min annealing, resulting in a sharp increase in globularization fraction. The globularization fraction continuously increases with the increase of annealing time, and a height reduction of 50% leads to a near globular microstructure after annealing for 4 h. For the alloy with deformation amount of 50% by compressing at 810 °C, 0.01 s^-1, and then annealed at 810 °C, thermal grooving is limited during the first 20 min of annealing and large quantities of high-angle grain boundaries（HABs） remain. With long time annealing, the chain-like α grains are developed due to the HABs, termination migration and Ostwald ripening. The present results suggest that a higher strain rate and a larger height reduction are necessary before annealing to achieve a globular microstructure of Ti-5Al-2Sn-2Zr-4Mo-4Cr.

关键词： Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy annealing thermal grooving globularization high-angle grain boundaries

quantitative analysis on microstructure evolution of Ti-6Al-2Zr-2Sn-2Mo-1.5Cr-2Nb alloy during isothermal compression

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2015年第9期34卷 625-631页

作者： Jun Gao miao-quan li Xiao-Di li Dong Zhang Jian-Rui Xue Xue-Qi Jiang Chao-Yue Zhang Lu-Yang liu School of Materials Science and Engineering Northwestern Polytechnical University

Isothermal compression tests of Ti-6Al-2Zr-2Sn-2Mo-1.5Cr-2Nb alloy were conducted at a Gleeble-1500 simulator in deformation temperature range of 1103–1243K, strain rate range of 0.01–5.00 s-1and height reduction range of 50 %–70 %. The effects of processing parameters on morphology, grain size and contents of a and b phases were discussed based on the quantitative microstructure examination, and the detailed explanation was shown. The results show that b transformed matrix will obviously grow up at higher deformation temperature or lower strain rate because of low grain growth activation energies. The content of a phase will decrease at higher deformation temperature or higher strain rate due to the phase transformation. Some elongated a or b grains exist at higher strain rate, implying that the dominant softening mechanism is dynamic recovery. The effect of height reduction on b transformed matrix is negligible, but the height reduction has some effects on the morphology of primary a phase.

关键词： Ti-6Al-2Zr-2Sn-2Mo-1.5Cr-2Nb alloy Flow stress Gra