Ti2AlNb-based alloys have expansive application prospects in advanced automotive and aerospace fields because of their excellent mechanical properties such as high specific strength, good creep resistance at elevated temperature, low thermal expansion and inimitable combination of strength and elongation.
The deformation process of Ti2AlNb-based alloys is inevitably performed at high temperatures because of their limited plasticity at room temperature. Therefore, predicting the hot deformation behavior of Ti2AlNb-based alloys is quite important for numerical modeling of hot working processes.
In recent years, some scholars have constructed some constitutive models to predict the hot deformation behavior of Ti2AlNb-based alloys. Unfortunately, however, few endeavors have been devoted to developing and improving ZA model and KHL model for P/M Ti-22Al-25Nb alloys.
Sim Kyong Ho, a researcher at the Faculty of Materials Science and Technology, has developed improved m-ZA and KHL models which can accurately predict the hot deformation behavior of a fine-grained (FG) Ti-22Al-25Nb alloy fabricated from mechanically alloyed powder by spark plasma sintering.
First, in order to obtain true stress-strain curves of P/M Ti-22Al-25Nb alloy, he conducted isothermal uniaxial compression tests at different deformation conditions of 950 ~ 1 070 ℃ and 0.001 ~ 1 s-1.
Second, using the friction-corrected experimental data, he developed a modified Zerilli-Armstrong model and a Khan-Huang-Liang model in the α2+β/B2 + O triple-phase and α2 + B2 two-phase fields, respectively, and evaluated the predictability of the models.
Finally, based on the analysis of the reason for large deviation, he modified Zerilli-Armstrong and Khan-Huang-Liang models to consider the coupled effects of deformation parameters.
Conclusively, he drew the following conclusions.
First, the m-ZA and KHL models for the P/M Ti-22Al-25Nb alloy showed relatively good predictability at the reference deformation conditions. However, the prediction accuracy of the models was lowered in other deformation conditions.
Second, the improved versions of the m-ZA and KHL models exhibited enhanced prediction accuracy. R2 and AARE of the improved constitutive models were 0.989 6 and 6.14%, 0.989 1 and 6.82%, respectively.
Finally, in comparison with other constitutive models, the improved versions of the m-ZA and KHL models are very appropriate for engineering applications including numerical simulation and control for hot working processes of P/M Ti-22Al-25Nb alloy.
The details of this are found in his paper “Modified Zerilli-Armstrong and Khan-Huang-Liang constitutive models to predict hot deformation behavior in a powder metallurgy Ti-22Al-25Nb alloy” in “Vacuum” (SCI).
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