Influence of direct rolling below β transus and annealing on microstructure and room temperature tensile properties of Ti-6Al-4V plates fabricated by electron-beam melting (EBM)

Microstructure modification and room temperature tensile properties of Ti-6Al-4V plates fabricated by electron-beam melting (EBM) were investigated. Firstly, Ti-6Al-4V slabs were direct rolled at various preheat temperatures below beta transus with various reductions, then the deformed samples were annealed at 800 degrees C for various soaking times. After rolling, the microstructure modification consists of elongation, bending, kinking, and rotation of alpha lamellae. Specimens rolled below 900 degrees C exhibited flow instability (local deformation bands). The mean aspect ratio of alpha lamellae was further decreased following annealing, and the fraction of alpha particles showed a relatively strong dependence on preceding rolling reduction. The variations of mean aspect ratio and spheroidization fraction with annealing time were rationalized on the basis of various processes during spheroidization. The mechanical properties of Ti-6Al-4V plates fabricated by EBM were significantly improved after rolling compared with as-cast Ti-6Al-4V plates. The following annealing of 1 h resulted in significant improvements on elongation without obvious loss of ultimate tensile strength (UTS).