Interactions Between Interstitial And Substitutional Atoms In Snoek Type High Damping Titanium Alloys: First-principles Calculations

The interaction between interstitial and substitutional atoms and diffusion energy barriers during diffusion process in Ti-Nb (Mo, Cr, Cu)-O alloys have been investigated using first-principles calculations based on density-functional theory: the binding energies, formation energies and diffusion energy barriers of oxygen atoms sited in various interstices distinguished by geometries, element species and atomic arrangements have been calculated. In potential Snoek type high damping Ti-Nb (Mo, Cr, Cu)-O alloys, the substitutional atom radius have size gradient and the alloys are eutectic (Nb, Mo) and eutectoid (Cr, Cu) alloy, respectively.According to our results, there is a strong repulsive binding energy between the interstitial and substitutional atoms in the alloy systems mentioned above. Following these information, the energetically favored sites and the contrary distributions of the substitutional niobium and interstitial oxygen atoms are detected by electron energy loss spectroscopy (EELS) method.Additionally, the diffusion activation energies of the interstitial oxygen in Ti- Nb (Mo, Cr, Cu)-O alloys based on the formation energy results are presented. The energy barriers are not exactly tetrahedral sites and the saddle points vary with the number and distribution of substitutional atoms. In some alloy systems, the tetrahedral sites are metastable states. Accordingly the diffusion behaviors of the interstitial oxygen atoms in Ti- Nb (Mo, Cr, Cu)-O alloys may influence the damping performance of Snoek type high damping alloys during its service life.