Ti-25Nb合金的热变形行为及本构关系模型

Hot deformation behavior and constitutive relation model of Ti-25Nb alloy

通过Gleeble-3500热模拟设备对Ti-25Nb合金进行压缩实验,探究当应变速率为0.001~10 s-1和变形温度为743~893 K时其热变形行为,构建了应变补偿型的Arrhenius本构模型,计算出不同应变下的热变形激活能并建立了相对应的激活能图。结果表明:变形温度的降低和应变速率的增加导致Ti-25Nb合金的流动应力上升;其流变应力曲线总体呈现流变软化现象;构建的应变补偿型的本构模型的相关系数为0.982,平均相对误差为7.51%,具有较好的预测能力;通过计算得出其热变形激活能明显高于纯α钛合金和纯β钛合金的自扩散激活能,这意味着其热变形过程中还有除高温扩散以外其他的变形机制;从变形激活能的角度考虑,Ti-25Nb合金的安全加工参数区域为800~820 K,0.01~1 s^-1。

The hot deformation behaviors of Ti-25Nb alloy were studied at the strain rate of 0.001-10 s-1 and deformation temperature of 743-893 K by the compression tests carried out on a Gleeble-3500 thermal simulation equipment.The strain-compensated Arrhenius constitutive model was constructed.The hot deformation activation energy was calculated under different strains and the corresponding activation energy maps were established.The results show that flow stress of Ti-25Nb alloy increases with the decrease of deformation temperature and the increase of strain rate.The flow stress curves mostly show a rheological softening phenomenon.The correlation coefficient is 0.982 and the average relative error is 7.51%in the constructed strain-compensated constitutive model,which show an outstanding prediction ability.It is calculated that the hot deformation activation energy is much higher than the self-diffusion activation energy of the pureα-titanium alloy and the pureβ-titanium alloy,which means that there are other deformation mechanisms besides high-temperature diffusion during the hot deformation process.From the perspective of deformation activation energy,the safe processing parameter zones of Ti-25Nb alloy are 800-820 K,0.01-1 s^-1.