基于材料参数演化修正Arrhenius模型与BP-ANN模型的近 β Ti-55511合金等温压缩过程流动应力预测

Flow Stress Prediction of Near-β Ti-55511 Alloy During Iso-thermal Compression Based on Corrected Arrhenius Model with Material Parameter Evolution and BP-ANN Model

摘要:

为了研究Ti-55511合金在近β区域的热流动行为，在温度973–1223 K、应变速率0.001–1 s^-1条件下，利用Gleeble-3500热模拟试验机进行了等温压缩试验。对实验获得的流动应力曲线进行了修正，降低了摩擦与绝热温升等因素对流动应力的影响。采用考虑材料参数演化的修正Arrhenius模型和反向传播人工神经网络（BP-ANN）模型对钛合金热变形过程中的流动应力进行预测，并通过统计分析对预测模型精度进行了评估。将2种预测模型扩展的应力、应变数据植入有限元，模拟了热压缩实验过程。结果表明，Ti-55511合金的流变应力与应变速率呈正相关，与温度呈负相关，合金软化机制主要为再结晶。修正后的Arrhenius模型和BP-ANN模型都能描述流体的流动行为，BP-ANN模型在α+β区域的拟合精度高于修正后的Arrhenius模型，而在β区域的拟合精度低于修正后的Arrhenius模型。

Abstract:

To investigate the hot flow behavior of Ti-55511 alloy in near-β region, isothermal compression tests were conducted at the temperature of 973-1223 K and the strain rate of 0.001–1 s^-1 by Gleeble-3500 thermomechanical simulation equipment. The flow stress curves obtained from experiments were corrected, and the influence of friction and adiabatic temperature rise on flow stress was reduced. The corrected Arrhenius model with consideration of material parameter evolution and the back-propagation artificial neural network (BP-ANN) model were used for flow stress prediction of Ti alloys during hot deformation process, and the precision of these prediction models were evaluated by statistical analysis. The stress and strain data extended by the two prediction models were implanted into finite element to simulate the hot compression process. Results show that the flow stress of Ti-55511 alloy has a positive correlation with strain rate and a negative correlation with temperature. The alloy softening mechanism is primarily the recrystallization. Both the corrected Arrhenius model and BP-ANN model can describe the flow behavior of fluid, and the fitting accuracy of BP-ANN model is higher than that of corrected Arrhenius model in α+β region but lower than that of corrected Arrhenius model in β region.