Improving strength and ductility of Ti-4Al-0.005B titanium alloy through tailoring equiaxed and lamellar microstructure during thermal mechanical process

The Ti-4Al-0.005B alloy were rolled at 940 degrees C or 990 degrees C followed by annealing at 650 degrees C. In order to control the final microstructure, rolling at medium temperature of 550 degrees C was processed in two other plates after rolling at 940 degrees C or 990 degrees C. The rolling and tensile behaviors of Ti-4Al-0.005B alloy with equiaxed and lamellar microstructure are comparatively studied using electron backscatter diffraction (EBSD) technique. It is found that the grain refinement mechanism of 940 degrees C and 940 + 550 degrees C rolled samples is continuous dynamic recrystallization (CDRX), while the 990 + 550 degrees C samples combine CDRX and twinning. The strong basal/near basal textures (B/N textures) in 940 degrees C and 940 + 550 degrees C rolled samples was mainly related to basal slip and pyramidal <c + a> slip. Strong transverse textures (T-type texture) formed in 990 degrees C rolled sample due to variant selection during the beta ->alpha phase transformation and 990 + 550 degrees C rolled sample exhibits a mixed of T-type texture and B/N texture. The 990 + 550 degrees C rolled sample exhibited a best mechanical properties combined of strength and ductility due to its mixed texture and refined alpha grains. (C) 2022 The Author(s). Published by Elsevier B.V.