TB18钛合金热变形行为及动态再结晶机制

High Temperature Deformation Behavior and Dynamic Recrystallization Mechanism of TB18 Titanium Alloy

摘要:

本文利用Gleeble 3800热模拟试验机和电子背散射衍射（EBSD）技术研究了TB18钛合金在700℃~ 900℃、应变速率0.01~10 s-1时的热变形行为和动态再结晶机制。研究表明该合金的流动应力大小对应变速率和变形温度敏感。变形初期流动应力皆在达到峰值应力后快速软化，随后有不同程度的上升。通过数据回归得到了该合金在两相区和单相区的高温变形Arrhenius型本构方程，其变形激活能分别为340 kJ/mol和185 kJ/mol。其单相区的变形软化机制主要为β相的动态回复，两相区主要为β相的动态再结晶。结合了EBSD技术，金相观察和流变曲线特点的分析表明，在高变形温度，低应变速率时（900℃，0.01s-1）主要以几何动态再结晶（GDRX）为主。在温度较低，或变形速率较高下，变形初期发生不连续动态再结晶（DDRX），应变增大后发生连续动态再结晶（CDRX）。

Abstract:

In this paper, the high temperature deformation behavior and the dynamic recrystallization mechanism of TB18 titanium alloy in 700℃ ~ 900℃ with the strain rate of 0.01 ~ 10 s-1 were studied using the Gleeble 3800 simulator and the electron backscatter diffraction (EBSD) technique. The value of flow stress of the alloy was sensitive to the strain rate and the deformation temperature. In the initial stage of the deformation, the flow stress would soften rapidly after reaching the peak stress, and then it increased to different levels. The Arrhenius-type constitutive equations of the high temperature deformation of TB18 titanium alloy in both α +β dual-phase region and β single-phase region were obtained through data regression. The apparent activation energy in both α +β dual-phase region and β single-phase region were calculated to be 340 kJ/mol and 185 kJ/mol, respectively. The deformation softening mechanism was mainly controlled by dynamic recrystallization of β phase in α+β dual-phase region and dynamic recovery of β phase in β single-phase region. According to the EBSD maps, the metallographic observation and the characteristics of stress-strain curves, it was concluded that the geometric dynamic recrystallization (GDRX) prevailed when the deformation was conducted at high temperature and low strain rate (900°C, 0.01 s-1). As the lower temperature or the higher strain rate was applied, the discontinuous dynamic recrystallization (DDRX) took place at the initial stage of the deformation and the continuous dynamic recrystallization (CDRX) was shown after the strain increased.