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- 저자 : Zhengzhi Zhao (검색결과 2 건)
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Hot Deformation Behaviors of Ti-22Al-26Nb-2Ta Alloy Based on GA-LSSVM and 3D Processing Map
Peng Wan,Hang Zou,Kelu Wang,Zhengzhi Zhao 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10
The thermal compression tests of Ti-22Al-26Nb-2Ta alloy under T = 1173 ~ 1423 K and ̇ = 0.001 ~ 10 s−1 were carried out onthe Gleeble-3500 thermo-mechanical simulator. The flow stress curves were obtained, and the high-temperature rheologicalproperties of the alloy were analyzed. The 3D activation energy maps were calculated and constructed. The least squaressupport vector machine (LSSVM) model of constitutive relation was established, and the penalty coefficient and kernelparameter of the LSSVM model were optimized by genetic algorithm (GA). The constitutive model of the alloy based on theGA-LSSVM algorithm was constructed. The predicted value of the model was also compared with the experimental data. The dynamic material model (DMM) and polar reciprocity model (PRM) were used to establish the 3D processing map ofthe alloy and appropriate thermal processing parameters. Our researches indicated that deformation temperature and strainrate have a great influence on the flow stress of Ti-22Al-26Nb-2Ta alloy. Ti-22Al-26Nb-2Ta alloy is a negative temperaturesensitiveand a positive strain rate-sensitive material. The correlation coefficient of GA-LSSVM algorithm constitutive modelis 0.9922, and the relative error of most samples is within 10%, accounting for 93.18%. The model has high prediction accuracyand strong generalization ability. The DMM processing map based on the Prasad instability criterion is more accurate inoptimizing the processing parameters of the alloy than that of the PRM processing map through analyzing the 3D processingmap and observing the microstructure. The instability modes in the instability region of the alloy mainly include adiabaticshear, crack, and local flow. The 1173 ~ 1273 K/0.001 ~ 0.003 s−1 are the best parameters during the processing of the alloy.
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Peng Wan,Huixiang Yu,Feng Li,Pengfei Gao,Lei Zhang,Zhengzhi Zhao 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10
The hot deformation behavior of low-density high-strength Fe–Mn–Al–C alloy steel at T = 900-1150 °C and ̇ = 0.01-10 s−1was studied by the Gleeble-3500 thermo-mechanical simulator. The rheological stress curve characteristics of the steel wereanalyzed through experimental data, and a physical constitutive model considering strain coupling was established. At thesame time, the finite element software DEFORM was used to calculate the critical damage value of the steel, and the influenceof T and ̇ on the maximum damage value was considered. By introducing the dimensionless parameter Zener–Hollomon, thecritical damage model was established. Finally, the workability of the steel was evaluated by using the intuitive processingmap technology. The results indicated that Fe–Mn–Al–C alloy steel is a positive strain rate-sensitive and a negative temperature-sensitive material, and the constitutive model considering physical parameters can well predict the rheological stress ofthe steel during hot deformation (R = 0.997). The critical damage factor of Fe–Mn–Al–C alloy steel varies with the changeof T and ̇ , and the range is 0.359-0.535. At the same time, the critical damage factor is more sensitive to ̇ . At a constantT, the damage factor decreases with the increase of ̇ . Based on the Prasad instability criterion, the dynamic material modelprocessing map and the microstructure verification after thermal compression, the rheological instability characteristics ofthe steel are mainly mechanical instability and local plastic flow, and the stable deformation area is mainly characterized bydynamic recrystallization. The optimal hot working process window of the steel is 975-1050 °C/0.01-0.032 s−1.
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