Microstructural Refinement of a Ti-40Al-8Nb-0.5B Alloy by Hot Deformation Within (α+β) Phase Field and Subsequent Tempering

In this work, a refined microstructure is obtained in a Ti-40Al-8Nb-0.5B alloy (at%) by hot deformation in the (α + β) phase region and subsequent tempering at 800 °C. The results show that the dynamic recrystallization of α phase occurred during the hot deformation, which resulted in the grain refinement from 56 to 18 µm. Meanwhile, high-density stacking faults are introduced into the deformed α phase. After tempering at 800 °C for 5 h, ultra-thin γ lamellar precipitated from the ordered α₂ phase by following the Blackburn orientation relationships. The average lamellar spacing is about 10 nm. The refinement of lamellar spacing is mainly attributed to the numerous nucleation sites of γ phase caused by the hot deformation. In addition, fine γ and ω₀ particles formed in the retained B2 phase, leading to the formation of a refined near-lamellar microstructure.