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Li H.-B.,Hebei United University | Li H.-B.,Hebei Key Laboratory of Modern Metallurgy | Feng Y.-L.,Hebei United University | Feng Y.-L.,Hebei Key Laboratory of Modern Metallurgy
High Temperature Materials and Processes | Year: 2016

The hot deformation behaviors of a solution-treated Ni-based superalloy are investigated by hot compression tests over wide ranges of strain rate and forming temperature. Based on the experimental data, the effects of forming temperature and strain rate on the hot deformation behaviors are discussed in detail. Considering the effects of strain on material constants, comprehensive constitutive models are developed to describe the relationships between the flow stress, strain rate and forming temperature for the studied superalloy. The three-dimensional processing map is constructed to optimize the hot working parameters. Meanwhile, the microstructures are analyzed to correlate with the processing map. It is found that the flow stress is sensitive to the forming temperature, strain rate and deformation degree. With the increase of forming temperature or the decrease of strain rate, the flow stress significantly decreases. The predicted flow stresses agree well with experimentally measured results, which confirm that the developed constitutive model can accurately estimate the flow stress of the studied superalloy. The three-dimensional processing map shows that the optimum deformation windows for hot working are the domains with 980-1,040°C or 0.001-0.1 s-1 when the strain is 0.6. Also, it is found that the dynamically recrystallized grain size increases with the increase of forming temperature or the decrease of strain rate. © 2016 by De Gruyter.


Li H.-B.,Hebei United University | Li H.-B.,Hebei Key Laboratory of Modern Metallurgy | Feng Y.-L.,Hebei United University | Feng Y.-L.,Hebei Key Laboratory of Modern Metallurgy
High Temperature Materials and Processes | Year: 2016

The thermo-viscoplastic behaviors of AISI 4140 steel are investigated over wide ranges of strain rate and deformation temperature by isothermal compression tests. Based on the experimental results, a unified viscoplastic constitutive model is proposed to describe the hot compressive deformation behaviors of the studied steel. In order to reasonably evaluate the work hardening behaviors, a strain hardening material constant (h0) is expressed as a function of deformation temperature and strain rate in the proposed constitutive model. Also, the sensitivity of initial value of internal variable s to the deformation temperature is discussed. Furthermore, it is found that the initial value of internal variable s can be expressed as a linear function of deformation temperature. Comparisons between the measured and predicted results confirm that the proposed constitutive model can give an accurate and precise estimate of the inelastic stress-strain relationships for the studied high-strength steel. © 2016 by De Gruyter.


Li H.,Hebei United University | Li H.,Hebei Key Laboratory of Modern Metallurgy | Fang F.,Hebei United University
Applied Mechanics and Materials | Year: 2012

The hot deformation behaviors of 97# High Strength Rod was investigated through double-hit compression experiments using Gleeble 3500 thermal-mechanical similar within the temperature range of 850∼1100°C, the strain rate of 5 s-1 and the interval range of 1-100s, the softening fractiong at different pass interval and deforming temperature was determined and analyzed. The results show that when pass intervals is the same, as deformation temperature increase, the volume fraction of static recrystallization of 97# High Strength Rod increases and the recrystallization process is enchanced. Activation energy of austenite static recrystallization of 97# High Strength Rod is 100.476 kJ/mol. The kinetic equation of static recrystallization of 97# High Strength Rod by avrami equation wan obtained. © (2012) Trans Tech Publications.


Chen L.-S.,Hebei Key Laboratory of Modern Metallurgy | Lu J.-W.,Hebei Key Laboratory of Modern Metallurgy | Zhang G.-J.,Hebei Key Laboratory of Modern Metallurgy | Tian Y.-Q.,Hebei Key Laboratory of Modern Metallurgy | And 2 more authors.
Suxing Gongcheng Xuebao/Journal of Plasticity Engineering | Year: 2013

By means of finite element analysis software ANSYS/LS-DYNA, the rolling process of mechanical engineering class channel-guide wheel was qualitatively analyzed. Through laboratory experiments of cast rolling plasticine, the simulation results were verified and compared with the experimental results, which showed they were consistent. The experimental results indicated that the uneven deformation of class channel-guide wheel was mainly caused by the larger deformation velocity and distribution of stress and strain at the round corner of the groove bottom of the class channel. By properly increasing fillet radius of the tank bottom, the distribution of stress and strain was not improved. While the original design led to more reasonable results.


Zhang J.Y.,Hebei Key Laboratory of Modern Metallurgy | Chen L.S.,Hebei Key Laboratory of Modern Metallurgy | Tian Y.Q.,Hebei Key Laboratory of Modern Metallurgy | Song J.Y.,Hebei Key Laboratory of Modern Metallurgy | Qi X.Y.,Hebei Key Laboratory of Modern Metallurgy
Advanced Materials Research | Year: 2014

By using the optical microscopy, scanning electron microscopy, X-ray fluorescence spectrum analyzers and spectrum analyzers, cracking of automotive stamping parts were researched and analyzed. The results showed that the fracture morphology of grainy layered fracture was caused by a long strip of sulfide inclusions. © (2014) Trans Tech Publications, Switzerland.

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