置氢处理对TC4钛合金流变行为的影响

应用材料试验机及霍普金森压杆装置(SHPB)对切削用置氢TC4钛合金进行了静态和动态压缩实验,获得了不同温度和应变率下的应力-应变曲线。实验中应变率范围为0.001～15000s-1,温度范围为293～973K。分析比较了合金流变应力对温度及应变率的敏感性。结果表明,置氢TC4钛合金具有较强的热软化效应,而应变率强化效应则相对较弱。随氢含量的增加,流变应力呈现先减小后增大的规律,氢含量0.3%时,最大降幅达25%。根据流变应力的变化规律及相关切削理论,对实验中切削力及切削温度的变化情况进行了分析。最后基于Johnson-Cook本构模型,拟合了模型中的参数,其预测值与实验结果吻合较好。

Impact of Hydrogenation on Flow Behavior of Titanium Alloy TC4

Static and dynamic compression experiments of a hydrogenated titanium alloy TC4 (Ti-6Al-4V) are carried out by means of a material testing machine and a split Hopkinson pressure bar (SHPB). Stress-strain curves are obtained over the strain rates range from 0.001 s^-1 to 15 000 s^-1 and temperatures from 293 K to 973 K. The sensitivities of the plastic flow stress to strain rate and temperature are analyzed. The experimental results indicate that all hydrogenated titanium alloy TC4 specimens exhibit a distinct heat softening effect, but that the strain rate hardening effect is comparatively weak. In addition, the strain rate hardening effect decreases as the temperature increases. The flow stress increases at first and then decreases gradually with the increase of the hydrogen content. Adding 0.3% of hydrogen in TC4 allows a maximum reduction of 25% in flow stress. The change of experimental cutting force and cutting temperature is analyzed with the flow stress at elevated temperatures in terms of the relevant cutting theory. Finally, the corresponding Johnson-Cook constitutive relation is derived, and the prediction results based on the corresponding model agree well with the experimental data.