Formation of equiaxed α phase in Ti-5Al-5Mo-5V-3Cr alloy deformed by high-pressure torsion

Formation of ultrafine equiaxed α phase particles was observed in Ti-5Al-5Mo-5V-3Cr (mass%) alloy after aging of samples deformed by high-pressure torsion (HPT) while acicular α phase was observed in undeformed samples. Burgers orientation relationship was obeyed between equiaxed α and β phases. The numerous nucleation sites and enhanced diffusivity in HPT processed samples due to high density of dislocations promoted the nucleation of and growth of α phase at the early aging stage. The segregation of β stabilizers near the α/β interfaces retarded the growth of α phase during aging, leading to equiaxed α phase with ultrafine particle size.