Effect of dopants on alumina grain boundary sliding: implications for creep inhibition
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We investigate by means of periodic density functional theory the mechanism of grain boundary sliding along the α-alumina Σ11 tilt grain boundary. We identify minimum and maximum energy structures along a preferential sliding pathway for the pure grain boundary, as well as for grain boundaries doped with a series of early transition metals, as well as barium, gadolinium, and neodymium. We predict that the segregation of those dopants results in a considerable increase in the grain boundary sliding barrier. Grain boundary sliding occurs by a series of bond breaking and forming across the grain boundary. Our results suggest that the presence of large cations inhibits the regeneration of bonds during sliding, which results in a decrease in total number of bonds across the grain boundary interface, thereby raising the barrier to sliding. Trends in predicted grain boundary sliding energies are in good agreement with recently measured creep activation energies in polycrystalline alumina, lending further credence to the notion that grain boundary sliding plays a dominant role in alumina creep.
KeywordsCreep Rate Lattice Vector Bond Coat Energy Structure Thermally Grown Oxide
We are grateful to the Air Force Office of Scientific Research for financial support, to the NAVO and ERDC DoD high performance computing centers for supercomputing time, and to Drs. Berit Hinnemann and Ashwin Ramasubramaniam, and Prof. Nicholas Mosey for helpful discussions.
- 6.Lifshitz IM (1963) Sov Phys JETP 17:909Google Scholar
- 9.Ashby MF, Verrall RA (1973) Acta Met 21:149Google Scholar
- 12.Rachinger WR (1952–53) J Inst Met 81:33Google Scholar
- 37.Lide DR (ed) (1999) CRC handbook of chemistry and physics, 79th edn. CRC Press, Boca Raton, FloridaGoogle Scholar
- 41.Milas I, Hinnemann B, Carter EA, to be publishedGoogle Scholar