Ternary site preference energies, size misfits and solid solution hardening in NiAl and FeAl

The electronic structure of NiAl and FeAl doped with Ti, V, Cr, Mn, Fe, Co, Y, La and Zr additions in both sublattices has been investigated with the local density linear muffin-tin orbital (LMTO) method. The peculiarities of chemical bonding for both undoped and with some ternary additions in NiAl and FeAl were analyzed using the LMTO-Green function method. The preferred sites for ternary additions were found and the sensitivity of site preference energies to crystal relaxation effects was investigated. It was shown that the relaxation has an elastic nature and the values of size misfit parameters for substitutional impurities were estimated. The experimental data concerning solid solution hardening were reanalyzed and the additional contributions to hardening besides the conventional size misfit mechanism were shown to be of importance for Ti ternary additions.