Stability and migration of vacancy in V-4Cr-4Ti alloy: Effects of Al, Si, Y trace elements

Addition of trace amounts of Al, Si and Y into V-4Cr-4Ti alloy is beneficial for the mechanical properties under irradiation. It is thus important to investigate the influence of solute/trace elements on stabilities, energetics and diffusion behaviors of vacancy defects. We performed first-principles calculations to evaluate vacancy-solute/trace interaction inside dilute V-X (X = Ti, Cr, Al, Si, Y) and V-4Cr-4Ti-(Al, Si, Y) alloys. With addition of Si and Y, vacancy-based complexes tend to form near Ti-Si and Ti-Y pairs, while the effect of Al is negligible. Moreover, diffusion coefficients of solute/trace element in vanadium were derived using nine-frequency model. With high binding energy and low diffusion coefficient, Si atom is strongly attractive to vacancy in vanadium matrix. Our theoretical results suggest that the interactions between vacancy and solute/trace elements play some role in the evolution of microstructures inside vanadium alloys.