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

摘要

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 ℃ and initial strain rate, ε = 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.