A first-principles study of vacancy formation mechanism and electronic structures in Ti–6Al–4V and Ti–5Al–3V–3Zr–0.7Cr alloys

With the development of nuclear energy technology, titanium alloys have gradually become important candidates for the new generation of nuclear engineering structural materials due to their excellent properties such as light weight, high strength, and corrosion resistance. The evolution of irradiation–induced vacancy dominates the structural stability and service life of titanium alloys. Conventional experimental techniques are constrained by limited spatial resolution, narrow time scales and high testing costs, making it difficult to fundamentally clarify the intrinsic nature of vacancy formation. In this work, first–principles calculations are employed to systematically investigate the vacancy formation mechanism and electronic structure characteristics of hcp Ti–6Al–4V and Ti–5Al–3V–3Zr–0.7Cr alloys. The results reveal that the vacancy formation energy significantly depends on the local atomic configuration and the differences in lattice distortion. In the Al–rich environment, vacancies are more difficult to form compared to the V–rich environment. Vacancies cause local charge redistribution and changes in electronic orbital hybridization. It is worth noting that V_a–Ti and V_a–Zr produce markedly stronger perturbations to the electronic structure than V_a–Al, V_a–V and V_a–Cr. Additionally, vacancies tend to aggregate to form vacancy clusters, which will aggravate irradiation damage and degrade material properties. This study provides microscopic mechanism support for understanding the point defect behavior of titanium alloys in irradiation environments and offers a theoretical basis for the design and optimization of new high–stability nuclear materials.