(1. 长安大学 材料科学与工程学院，西安 710064；
2. Waikato Centre for Advanced Materials and Manufacturing, University of Waikato, Hamilton 3216, New Zealand)
摘 要: 针对铸态亚稳β型Ti-5553钛合金，基于热模拟试验，研究了合金在高温高应变速率条件下的热变形行为，并发现了一种全新的动态再结晶机制。结合多种材料表征技术，揭示了新动态再结晶机制的微观组织演变机理，并分析了变形参数对再结晶行为的影响。结果表明：亚稳β钛合金在高温高速率条件下的显著动态软化是动态再结晶和流变失稳共同作用的结果，动态再结晶产生新晶粒的形核位置、尺寸和组织占比都对热变形参数有较高的敏感性。本文发现和揭示的新动态再结晶机制是连续和不连续这两种常见机制混合而成的耦合机制，既包含了引发不连续动态再结晶的晶界应变集中效应，又包括了连续动态再结晶的亚晶旋转形核过程。
关键字: 亚稳β钛合金；热变形；微观组织演变；变形机制；动态再结晶
（1. School of Materials Science and Engineering, Chang’an University, Xi’an 710064, China;
2. Waikato Centre for Advanced Materials and Manufacturing, University of Waikato, Hamilton 3216, New Zealand）
Abstract:Based on thermal-mechanical simulation, the hot deformation behaviour of as-cast metastable β Ti-5553 titanium alloy under the conditions of high-temperature and high-strain-rate was investigated thoroughly. With the combination of various characterization approaches, the detailed microstructure evolution process of the novel dynamic recrystallization (DRX) mechanism and the effects of deformation parameters on DRX were revealed and analyzed. The results show that the flow softening of the alloy under the conditions of high-temperature and high-strain-rate are dominated by the synergy of dynamic recrystallization and deformation instability. The nucleation site, grain size and fraction of the recrystallized grain show great sensitivity to the deformation parameters. The disclosed DRX process is revealed to be controlled by the coupling mechanism of widely-accepted discontinuous (DDRX) and continuous (CDRX) mechanisms, containing strain localization induced nucleation and sub-grain rotation induced transformation.
Key words: metastable β titanium alloy; hot deformation; microstructural evolution; deformation mechanism; dynamic recrystallization
