Berlin 2012 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 28: Topical Session Theory meets Experiment I - Intermetallics and Steels

MM 28.3: Vortrag

Mittwoch, 28. März 2012, 11:00–11:15, TC 006

On the dependence of elastic properties on the point-defect content in vacancy-rich β-NiAl — •Sascha B. Maisel and Stefan Müller — Insitute of Advanced Ceramics, Hamburg University of Technology, Hamburg, Germany

The high-temperature alloy β-NiAl can tolerate an exceptionally high number of point defects in the form of vacancies or anti-site atoms. In fact, the B2 phase which Ni₅₀Al₅₀ prominently exhibits is still stable up to vacancy-rich crystals with a stochiometry of around Ni_42.5Al₅₀ [Warlimont77]. However, we find that many assumptions that are commonly used when describing the dependence of elastic constants on point defects in single crystals do not hold for β-NiAl. In particular, the Wagner-Schottky approximation is not valid and common analytical descriptions [Pistorius70] fail due to cell volume changes at high vacancy contents. Moreover, the widely used five parameter extrapolation [Warlimont77] for the elastic moduli in β-NiAl is not correct for very high defect concentrations. We present improved values for the elastic behavior in the high-vacancy regime derived from fully relaxed first-principles structures.

References:

N. Rusovic, H. Warlimont: Phys. Stat. Sol. 44, 609 (1977)

M. Pistorius: Z. angew. Phys. Z9, 145 (1970)