针状Ti-55511合金热变形及后续退火过程中组织演变及其力学性能研究

Chen Wei1,Lv Yaping2,Zhang Xiaoyong1*,Chen Chao1,Zhou Kechao1

摘要:

对针状Ti–55511近β钛合金进行750 °C热轧和600 °C/1h退火，研究合金在热轧及退火中组织演变及力学性能。结果表明，热轧时，针片α相将发生动态再结晶（DRX），与β相的Burgers取向关系（Burgers orientation relationship）发生破坏，进而形成细小的等轴α相，使合金强度及塑性提高。后续退火过程中，α相通过静态再结晶（SRX）进一步发生球化和长大，次生α相析出，β相发生再结晶，合金的强度提高，塑性降低。在变形初期，针片α相内产生两种孪晶变体（交叉状孪晶），随着α相球化程度增加`，α相内将产生三种孪晶变体（针织状孪晶）。在后续退火过程中，这些孪晶将逐渐缩短，进而分解消失，表现在退火样品中α晶粒内存在纳米级孪晶（孪晶缩短）与层错（孪晶分解）。

Abstract:

Lamellar Ti–55511 near-beta Ti alloy was conducted on 750°C hot rolling and subsequent 600°C annealing to investigate the microstructure evolution and mechanical properties. The Burgers orientation relationship between α and β phase is broken down owing to dynamic recrystallization (DRX) of lamellar α phase during hot deformation, forming fine and equiaxed α plates, which leads to the increasing tensile strength and elongation. During annealing, secondary α grains are precipitated from β matrix, resulting in higher strength but lower elongation. Meanwhile, further spheroidization and growth of α phase via static recrystallization (SRX) happen during annealing. The recrystallization of β phase only happens in subsequent annealing rather than hot rolling. At the beginning of the deformation, two twin variants can be found in lamellar α phase. With an increase in deformation, three twin variants are formed in α phase. The nano-scaled twins and stacking fault was formed resulting from twins decomposing during annealing.