Density functional theory study of alloy element interstitials in Al

Abstract

Density Functional Theory calculations were used to study Mg, Si, Cr, Mn, Fe, Co, Ni, and Cu interstitial configurations in Al. Energies of these elements in (100) dumbbell and octahedral configurations were determined. Results show that it is energetically favourable for metal alloying element atoms to replace Al selfinterstitials if the alloying atoms are smaller than the Al atoms, as expected. The system energy can thus be decreased by up to 2 eV. The difference between the energies of (100) dumbbell and octahedral configurations is only a few tenth eV for the alloys with metallic alloying elements. For Si, the difference can be up to 0.9 eV. This exceptional behavior of Si is most likely due to its angularly dependent bonding characteristics. Short ab-initio Molecular Dynamics simulations were performed on Mg and Si interstitials to allow these systems to evolve into different interstitial configurations rather than just the (100) dumbbell and octahedral configurations. For Si an alternative configuration with tetrahedral-like coordination was found. Consequences of the calculation results for radiation-induced segregation are discussed.

Formation mechanism of precipitate T1 in AlCuLi alloys

“…Originally, there are three atoms in the central Al-layer, among which, one is still kept in place, one is replaced by Li-atom, and the other was pushed into the octahedral interstitial position by introduced Li-atom. The last case occurs with the help of interstitial-vacancy pairs (Frenkel pairs, refer to [22,28] i.e., a Li atom moves in and fill the vacancy, the Al atom shifted into the octahedral position will be caged and survive for a relatively longer period, displayed as inset (c) in Fig. 5.…”

The possibilities to lower the stacking fault energies of aluminum materials investigated by first-principles energy calculations

“…The atoms smaller than Al might prefer to locate at the octahedral-interstitial sites in fcc structures [41,42]. In the present work, we have investigated hypothetically the effects of interstitial solute atoms on the SFEs of Al-X (X = Cu, Zn, O, C, H and N) octahedral-interstitial solid solutions.…”