Dresden 2003 – scientific programme
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M: Metallphysik
M 12: Grenzfl
ächen II
M 12.3: Talk
Monday, March 24, 2003, 12:15–12:30, IFW D
Segregated light elements at grain boundaries in Nb and Mo — •Christian Elsässer1,2 and Rebecca Janisch2 — 1Fraunhofer-Institut für Werkstoffmechanik, Wöhlerstraße 11, 79108 Freiburg — 2Max-Planck-Institut für Metallforschung, Heisenbergstraße 3, 70569 Stuttgart
The influence of the interstitial impurities B, C, N, O and H on the
cohesion and structure of Σ5 (310) [001] grain boundaries (GB) in
body-centered cubic (bcc) Nb and Mo is investigated by the local density
functional theory (LDFT), using the mixed-basis pseudopotential approach.
The analysis of interface energies and geometric translation states,
site-projected densities of states and bonding electron densities yields
systematic trends: B and C form covalent bonds with the nearest host-metal
neighbors, strengthen the interfacial cohesion by inducing covalent
metal-metal bonds across the interface, and favour a mirror-symmetric GB,
while N, O and H form polar bonds, cause interfacial embrittlement and
break the mirror symmetry of the GB.
The LDFT results support the qualitative validity of empirical models of
Cottrell and of Rice and Wang for bcc transition metals.
The talk will be given in German.