粉末冶金Ti-44Al-2Cr-4Nb-0.2W-0.2B合金高温流变行为及本构模型研究

Research on high temperature rheological behavior and constitutive model of powder metallurgy Ti-44Al-2Cr-4Nb-0.2W-0.2B alloy

利用Gleeble-1500D热模拟实验机对元素粉末法制备的TiAl基合金进行等温压缩实验,实验温度为1100~1200℃,应变速率为0.1~0.001 s^(-1)。研究结果表明:粉末冶金Ti-44Al-2Cr-4Nb-0.2W-0.2B合金在等温恒应变速率压缩过程中产生了明显的动态再结晶,流动应力呈流动软化特征,其流变应力值随着变形温度的上升而降低,随应变速率的增大而增大;获得峰值应力下的激活能为563.67 kJ·mol^(-1)。基于BP神经网络建立了该合金的本构模型,结果显示预测值和实验值的拟合相关系数达0.9995,所建立的本构模型平均相对误差在4%以内。通过与Arrhenius型本构模型预测结果的各项统计参数进行对比,发现BP神经网络模型预测效果较佳,可客观真实地描述Ti-44Al-2Cr-4Nb-0.2W-0.2B合金的高温塑性变形行为。

Isothermal compression experiment was performed on Ti Al-based alloy prepared by the elemental powder method using Gleeble-1500 D thermal simulator at the experimental temperature of 1100-1200℃ and strain rate of 0.1-0.001 s^(-1).The research results show that obvious dynamic recrystallization of powder metallurgy Ti-44 Al-2 Cr-4 Nb-0.2 W-0.2 B alloy appears during isothermal constant strain rate compression process,and the flow stress is characterized by flow softening,and the flow stress decreases with the increase of deformation temperature and increases with the increase of strain rate;the activation energy obtained under peak stress is 563.67 k J·mol^(-1).A constitutive model of the alloy was established based on BP neural network.The results show that the fitting correlation coefficient between the predicted and experimental values is 0.9995.The average relative error of the established constitutive model is within 4%.By comparing with various statistical parameters of the prediction results of Arrhenius-type constitutive model,it is found that the BP neural network model has a better prediction effect and can objectively and truly describe the high temperature plastic deformation behavior of Ti-44 Al-2 Cr-4 Nb-0.2 W-0.2 B alloy.