Martensitic transformation from β to α′ and α″ phases in Ti–V alloys: A first-principles study

The ground state properties of the α′ and α″ martensitic phases and energetic pathways of the β → α′/α″ martensitic transformations in Ti–(0–30 at.%)V alloys were investigated by first-principles method in combination with virtual crystal approximation. The results show that lattice parameters withc/aof the α′ phase and lattice parameters withb/a,c/aof the α″ phase are significantly sensitive to composition, and the atomic shuffleyof the α″ phase decreases from that of the α′ phase toward that of the β phase with increasing V content in Ti–V alloys. The compositional α′/α″ phase boundary is about 10 at.% V, from the viewpoints of energetics and mechanical stability of these phases. The principal lattice strains of the β → α′ transformation are insensitive to the V content, while those of the β → α″ transformation change significantly with increasing V content. The volume variation for β → α′ increases, whereas that for β → α″ decreases with increasing V content in Ti–V alloys. The energetic pathway results show that the relative stability of the α′ and α″ phases decrease with increasing V content and temperature and that there is no energy barriers during the β → α′/α″ martensitic transformations at temperatures from 0 to 400 K.