Migration mechanisms of mono-/di-interstitials in vanadium with alloying Ti/Cr

Abstract

Self-interstitial atoms (SIAs) are the dominant self-defects at equilibrium in metals, but many questions such as their diffusion characteristics are still open, and studies of the Ti/Cr effect on the kinetics of SIAs are very scarce in vanadium alloy. In this work, we systemically investigated the migration mechanisms of mono/di-interstitials as well as the effect of alloying elements Ti/Cr on the kinetics of SIAs using first-principles calculations. The findings reveal that 〈111〉SIA exhibits three migration mechanisms, including one dimensional (1D) migration, translation-rotation and translation, corresponding energy barriers of 0.008, 0.19 and 0.44 eV. Different migration pathways are activated at high temperatures, which supports the experimental observation of 3D migration of SIAs under high temperatures. We determined the di-SIA (two parallel 〈111〉SIA) migration by both successive and simultaneous jumping paths, the lowest migration barrier is 0.009 eV via successive jumping path passing a translation state. Moreover, based on three migration mechanisms of SIA, SIA migrating to Ti region possesses the lower barrier than pure vanadium, in verse the barrier is relative high and then hinders the SIA diffusion. The alloying Ti has a pinning effect on SIAs. And we explored how SIA to form mixed V-Cr interstitial and its migration of 〈111〉V-Cr. Finally, we estimated the effect of Ti on SIA diffusivity by empirical formulas.