Ti2AlNb合金高应变率下流动应力特征与本构关系

Flow Stress Characteristics and Constitutive Relation of Ti2AlNb Alloy under High Strain Rate

摘要:

利用电子万能试验机和分离式Hopkinson压杆得到准静态拉伸曲线及高应变率下动态应力-应变曲线,并观察变形后试样的微观组织,研究Ti2AlNb合金高应变率下的流动应力特征。结果表明：在应变率2500~7500S_-1范围内,Ti2AlNb合金的流动应力对应变率有较强的敏感性,且具有应变强化、应变率增强及增塑效应；高应变率下绝热剪切带的出现是流动应力急剧下降的主要原因。改进Johnson-Cook本构模型,拟合实验数据得到Ti2AlNb合金室温下的动态塑性本构关系,与实验对比,改进后的模型能够较好地预测Ti2AlNb合金在高应变率下的流动应力。

Abstract:

_{: In order to study the flow stress characteristics of Ti2AlNb alloy under high strain rate conditions, the quasi-static tensile curves was obtained with electronic universal testing machine, and the dynamic true stress-strain curves under high strain rate was obtained with split Hopkinson pressure bar. The results show that the flow stress of Ti2AlNb alloy has a strong sensitivity to strain rate conditions. Ti2AlNb alloy has strain work-hardening, strain rate strengthening and plasticity-increasing effect under high strain rate conditions. The adiabatic temperature rise in the plastic deformation process has a softening effect on the material. It is found that the appearance of adiabatic shear band is the main reason for the rapid decrease of flow stress under the condition of high strain rate loading. The dynamic constitutive relation of Ti2AlNb alloy at room temperature was obtained by fitting the experimental data with improved Johnson-Cook constitutive model. Compared with the experimental results, it is proved that the improved model can predict the flow stress of Ti2AlNb alloy well under high strain rate conditions.}