Berlin 2015 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 33: Structural Materials I: Phase Stability and Mechanical Properties
MM 33.3: Vortrag
Mittwoch, 18. März 2015, 10:45–11:00, TC 010
Correlation between thermodynamic and mechanical properties in Ta-W — •Sandra Hoppe and Stefan Müller — Institute of Advanced Ceramics, Hamburg University of Technology, Hamburg, Germany
Varying an alloy’s concentration or alloying constituents strongly influences its structural and mechanical properties. Modern simulation methods like density functional theory in combination with the cluster expansion make the whole configurational space accessible. This way, also metastable structures may be considered, which are experimentally difficult to obtain. Recent results for several face-centered cubic (fcc) binary metal alloys [1] suggest a linear correlation between thermodynamic stability and elastic properties at a fixed stoichiometry. This study aims to investigate the generality of these findings by considering a similar correlation for binary body-centered cubic (bcc) alloys. As a model system, Ta-W was chosen due to its simple phase diagram with solid solution in the whole concentration range. Interestingly, the elastic constants c44 and c12 show an opposing trend to that observed for fcc alloys: Energetically favorable structures are mechanically weaker than those further away from the ground-state line. This phenomenon may be related to the anomalous behavior of c44 with increasing pressure or temperature, which has been reported in the literature for Ta-W. We will discuss the interesting behavior of Ta-W with regard to its electronic structure.
[1] S. B. Maisel, M. Höfler, and S. Müller. Nature 491 (2012) 740.