Tailoring the Microstructure of Ti-6Al-4V Alloy Fabricated by Hybrid Additive Manufacturing via Rolling Strategies

In situ rolling-assisted laser directed energy deposition (IR-LDED) was employed to fabricate Ti-6Al-4V titanium alloy samples, focusing on the microstructural characteristics under various rolling strategies. The results indicate that the microstructure was primarily governed by the interplay between temperature-dependent deformation and recrystallization processes. In situ rolling at elevated temperature, combined with complex thermal cycling, promoted recrystallization within the deposited material, leading to significant grain refinement. After remelting and high-temperature rolling, the average grain size in the middle region of the sample was refined to 21 μm, accompanied by high kernel average misorientation (KAMavg) value of 1.92. Increasing the number of rolling passes at lower temperatures further reduced the grain size and decreased the KAMavg. Following in situ rolling, the deposited material underwent remelting, and additional rolling at elevated temperatures increased both deformation and KAMavg. The rearrangement of dislocations, formation of subgrain boundaries, and enhanced solute diffusion collectively facilitated the globularization of lamellar α phases, ultimately forming a microstructure composed of globular α, lamellar α/β, and dot-like β phases.