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MM: Fachverband Metall- und Materialphysik
MM 10: Computational Materials Modelling III
MM 10.2: Talk
Monday, March 14, 2011, 16:00–16:15, IFW B
Elasticity and Screw Dislocations in W-Re and W-Ta Alloys — •Hong Li1,2, Lorenz Romaner2, Claudia Ambrosch-Draxl2, and Reinhard Pippan1 — 1Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahn Straße 12, 8700 Leoben, Austria — 2Chair of Atomistic Modelling and Design of Materials, University of Leoben, Franz Josef Straße 18, 8700 Leoben, Austria
Using a first-principles approach, the elastic properties as well as the core structure of the 1/2<111> screw dislocation in W-Me (Me=Ta, Re) alloys are investigated from the atomistic point of view. For a range of Ta/Re concentrations the lattice parameter, bulk modulus, and elastic constants are calculated and compared with pure W to study the influence of solute atoms on the elastic properties. A periodic quadrupolar arrangement of the dislocation is employed to model the core structures. We show that W and W-Ta alloys at all concentrations exhibit a symmetric core structure. In contrast, W-Re alloys exhibit a gradual transition to asymmetric cores. Furthermore, the critical stress which has to be applied to move the dislocation at 0K (Peierls stress σp) is calculated to determine the mobility of dislocations. The reduction of σp and a change of slip plane explain the brittle to ductile transition in W upon Re alloying. However, for W-Ta alloys the reduction of σp is found only with high Ta concentrations. Finally, we investigate the correlation between the core symmetry and the γ-surfaces for both W-Me cases.