Enhanced superplasticity for (α + β)-hot rolled Ti–6Al–4V–0.1B alloy by means of dynamic globularization

• Higher elongation for Ti–6Al–4V–0.1B alloy compared to base Ti–6Al–4V alloy.
• Faster dynamic globularization ensuring narrow distribution of equiaxed α grains.
• Higher amount of α/β interface and increased level of boundary sliding.
• Balance between dynamic globularization and coarsening dictating final grain size.
• Localized cavitation due to strain accumulation around TiB not leading to crack.

Thermo-mechanically processed Ti–6Al–4V alloy, with (0.1 wt.%) and without boron addition, has been subjected to tensile test under superplastic deformation conditions (Temperature, T = 850 °C and initial strain rate, ε̇=3×10-4 s−1). The boron added alloy exhibited higher elongation (∼430%) in comparison to the base alloy without boron (∼365%). Superior ductility of the boron added alloy has been attributed to an enhanced α/β interfacial boundary sliding. This was caused by riotous dynamic globularization leading to the abundant presence of equiaxed primary α grains with refined sizes and narrow distribution in the deforming microstructure. Cavities do occur around TiB particles during deformation; the cavities are, however, extremely localized and do not cause macroscopic cracking.