Berlin 2015 – wissenschaftliches Programm
MM 28.35: Poster
Dienstag, 17. März 2015, 18:30–20:30, Poster E
Applying the concept of gradient elastic tensors in the determination of dislocation densities in MAX phases — Christoph Brüsewitz1, Ulrich Vetter1, •Hans Hofsäss1, and Michel W. Barsoum2 — 1II. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany — 2Dep. Mat. Sci. & Eng., Drexel University, Philadelphia, PA 19104, USA
MAX phases provide an unusual combination of both metallic and ceramic properties. Their remarkable mechanical properties, especially their damage tolerance, are still not fully understood and are subject of current debates. In this context, a way to in-situ determine dislocation densities under deformation would be most helpful.
We will present an attempt for this determination that is based on an hyperfine interaction method, the perturbed angular correlation spectroscopy, by using the sensitivity of the electric field gradient (EFG) at a nucleus on the strain field of defects. The relevant parameter is the broadening of the EFG tensor components. The coupling between EFG tensor and strain field is generally described by the gradient elastic tensor whose structure is determined by the point group of the corresponding nucleus. In case of the MAX phases, the tensor components are experimentally not determinable which is why density functional theory calculations implemented in Wien2k were used instead. Based on these calculations, a first estimation of deformation induced dislocation densities is given.