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 β transus with various reductions, then the deformed samples were annealed at 800 °C for various soaking times. After rolling, the microstructure modification consists of elongation, bending, kinking, and rotation of α lamellae. Specimens rolled below 900 °C exhibited flow instability (local deformation bands). The mean aspect ratio of α lamellae was further decreased following annealing, and the fraction of α 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).