(燕山大学 机械工程学院，秦皇岛 066004)
摘 要: 将TA15钛合金在Gleeble-3800热模拟试验机上进行热压缩试验，变形温度为800~980 ℃。采用扫描电镜(SEM)分析该合金的微观组织演变规律，结合微观组织定量结果及流变曲线对TA15钛合金热变形过程中热力学进行评价。结果表明：TA15钛合金在两相区热变形时会发生动态相变。动态相变使真实应力-应变曲线呈现明显的流变软化现象，造成屈服应力显著高于稳态应力。初生α相含量对变形温度及应变敏感。随着变形温度温度的升高或应变的增加，初生α相含量降低甚至完全消失，表明动态相变会造成TA15钛合金相变点降低。TA15钛合金动态相变是一种应力驱动型相变，该合金发生动态相变的条件是驱动力克服能量势垒。能量势垒数值上等于最小临界驱动力，且范围约为70~742 J/mol，而最大驱动力范围约为507~3306 J/mol。最大/最小临界驱动力、能量势垒均随着变形温度的升高而降低。
关键字: TA15钛合金；流变软化；动态相变；应力驱动型；热力学评价
（School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China）
Abstract:The hot compression tests of TA15 titanium alloy were carried out on Gleeble-3800 thermomechanical simulator with a deformation temperature range of 800-980 ℃. The microstructure evolution of TA15 titanium alloy was analyzed by scanning electron microscopy (SEM). Combined with the quantitative data of microstructure and flow curve, the thermodynamics evaluation of TA15 titanium alloy during hot deformation was explained. The results show that dynamic transformation (DT) can be observed in TA15 titanium alloy during hot deformation below the β-transus temperature (Tβ), which can cause the true stress-strain curves to show apparently flow softening phenomenon leading to the yield stress significantly higher than the steady stress. The volume fraction of the primary α phase (fαp) is sensitive to deformation temperature and strain. With the increase of deformation temperature or strain, the fαp decreases or even disappears completely, indicating that the DT can cause the Tβ of TA15 titanium alloy to decline. The DT in TA15 titanium alloy is a stress-induced type, and its activation condition is that the driving force overcomes the energy barrier. The energy barrier value is numerically equal to the minimum critical driving force with 70-742 J/mol, and the range of the maximum driving force is 507-3306 J/mol. The maximum and minimum driving force and energy barrier decrease with the increase of deformation temperature.
Key words: TA15 titanium alloy; flow softening; dynamic transformation; stress-induced type; thermodynamics evaluation
