The effects of Ti and Cr on binding and diffusion of Al in V alloys: A first-principles study

Al diffusion in V play an important part in the formation of aluminide coatings on the surfaces of V alloy, which could be affected by alloying elements, such as Ti and Cr. In order to elucidate the effects of Ti and Cr on Al diffusion in V, firstly the interactions and diffusion of Al/Ti/Cr in V were investigated by means of DFT calculations coupled with LST/QST method. Then, the structures with Al-Vac-Ti/Cr complexes in bcc V were constructed and the most stable configurations were determined. Finally, the migration barriers for Al in V in presence of Ti or Cr atoms were calculated. It is shown that Ti and Al atoms attract the vacancy and Ti-vacancy binding is more energetically favorable. On the other hand, Cr slightly repels from vacancy. Due to the strong attraction between Ti and vacancy, the migration barriers of Al increase when Ti atoms are in the vicinity, which means the diffusion of Al in V is significantly hampered by Ti atoms, and no obvious impact of Cr atoms on Al diffusion in V is found.