材料期刊网

基于 TC8钛合金的等温压缩实验，对其高温变形过程中的不连续屈服现象(DYP)进行研究。首先引入上、下屈服点差值(?σUL)和应力振荡结束时的应变(εOSC)两个参数，根据应力?应变曲线，对 TC8钛合金的不连续行为进行数值表征；然后，分析变形工艺参数对?σUL 值和εOSC 值的影响。结果表明：?σUL 值和εOSC 值随着应变速率的增大而增大；在不同的应变速率下，变形温度对?σUL 值的影响不同。最后，透射电子显微镜(TEM)观察结果为不连续屈服行为的动态理论提供了证据，不连续屈服行为归因于晶界产生的移动位错。同时，光学显微镜(OM)观察结果表明，初生α相和β相的晶粒尺寸随应变速率的增大而减小，从而揭示了变形工艺参数对?σUL 和εOSC值的影响机制。

The discontinuous yielding phenomenon (DYP) during high temperature deformation was investigated based on the isothermal compression of TC8 titanium alloy. The DYP of TC8 titanium alloy was characterized by quantifying the yield drop of the DYP (?σUL) and ending strain of flow oscillation (εOSC) based on the flow stress?strain curves, and then the effect of deformation parameters on the ?σUL and εOSC values was analyzed. The results show that the ?σUL and εOSC values increase with the increase of strain rate. The effect of deformation temperature on the ?σUL value depends on the strain rate. Finally, the transmission electron microscope (TEM) observation shows the evidence for the dynamic theory, which ascribes the DYP to the generation of mobile dislocation at the grain boundary. Meanwhile, the optical microscope (OM) observation shows that both the primary α grain and βgrain become smaller with the increase of strain, which well interprets the effect of deformation parameters on the ?σUL and εOSC values.