基于内变量的Ti_(2)AlNb合金M-K理论的高温成形极限预测

Prediction on high temperature forming limit for Ti_(2)AlNb alloy M-K theory based on internal variables

Ti_(2)AlNb合金在高温变形过程中,微观组织演变复杂,导致合金的力学性能和成形性能发生改变;且由于微观组织和力学性能的耦合变化,导致高温成形极限的预测更加困难。针对该问题,以Ti_(2)AlNb合金基于内变量的本构模型和M-K理论为基础,将变形过程中的微观组织演变及其对力学性能的影响与M-K理论进行耦合,建立了Ti_(2)AlNb合金基于内变量的M-K理论的高温成形极限预测模型,并进行了Ti_(2)AlNb合金板材成形极限的计算。Ti_(2)AlNb合金板材在高温成形时,随着变形温度(950~985℃)和应变速率(0.001~0.1 s^(-1))的提高,板材的成形极限提高,说明应变软化有利于提高板材的成形极限。最后,进行了变形温度为985℃和应变速率为0.01 s^(-1)条件下的成形极限实验测试,并对理论计算结果进行了验证,证明了建立的高温成形极限预测模型具有良好的预测效果。

During the high temperature deformation process of Ti_(2)AlNb alloy,the microstructure evolution is complicated,which will lead to the change of mechanical properties and formability of alloy.Due to the coupling changes of microstructure and mechanical properties,it is more difficult to predict the forming limit at high temperature.Therefore,for this problem,the microstructure evolution during the deformation process and its influence on mechanical properties were coupled based on the M-K theory and the constitutive model of internal variables and M-K theory,the prediction model of forming limit for Ti_(2)AlNb alloy at high temperature based on internal variables for Ti_(2)AlNb alloy was established,and the forming limit of Ti_(2)AlNb alloy sheet was calculated.When Ti_(2)AlNb alloy sheet was formed at high temperature,the forming limit of sheet increased with the increasing of deformation temperature(950-985℃)and strain rate(0.001-0.1 s^(-1)).Therefore,strain softening was beneficial to improve the forming limit of sheet.Finally,the forming limit test was carried out under the conditions of the deformation temperature of 985℃and the strain rate of 0.01 s^(-1),the theoretical calculation results were verified.Thus,the established prediction model of forming limit at high temperature has a good prediction effect.