Achieving Excellent Strength-Ductility Synergy in Ti-6Al-4V Alloy by Warm Rolling and Subsequent Annealing

In the present investigation, warm rolling after rapid cooling form full β phase region was employed, followed by water quenching in Ti-6Al-4V alloy. Subsequently, warm rolled samples were annealed at 600 °C for 1 h and 4 h, respectively. The results show that the microstructure is significantly fragmented and refined after warm rolling, accompanied by high-density dislocation accumulation. Simultaneously, more than 26 ± 2% of β phase is retained after warm rolling and water quenching, which is mainly attributed to the improved thermal stability of β phase due to the microstructure refinement and dislocation accumulation. After annealing for 1 h, both α and β phases are spheroidized without a significant decrease in proportion of β phase, which is primarily due to the more spheroidization sites and sufficient energy induced by warm rolling. The microstructure starts to coarsen after annealing for 4 h. Consequently, a good combination of strength and ductility (YS: 1121 MPa, UTS: 1163 MPa, EL: 12.0%) was obtained by post-deformation annealing for 1 h. Microstructure refinement, spheroidization, and a considerable proportion of retained ultrafine β phase contribute to this synergy of strength and ductility.