Berlin 2015 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 36: Nanomaterials I: Excess Volume and Confinement

MM 36.1: Vortrag

Mittwoch, 18. März 2015, 11:45–12:00, H 0107

Redistribution of Excess Volume by Mechanical Deformation in Nanocrystalline Alloys — •Michael Johannes Deckarm, Timo Tscharntke, and Rainer Birringer — Universität des Saarlandes, FR 7.2 Experimentalphysik, D-66123 Saarbrücken

Nanocrystalline (NC) alloys with grain sizes at the low end of the nanoscale (≈ 10nm) are characterised by a large volume fraction of grain boundaries (> 25%), contributing to dramatically increased total excess volume and energy compared to conventional materials. We try to shed light on the interplay between these excess quantities and the altered mechanical properties of NC metals. Using a combination of X-ray diffraction, length and density measurements to detect direction-dependend and absolute excess volume changes before and after uniaxial compression, enabled us to compare our findings qualitatively with the predictions made by Bachurin and Gumbsch in (1). They simulated (MD-simulation) uniaxial deformedation of NC Pd and deduced an anisotropic redistribution of the grain boundary excess volume and an anisotropic change of Young’s modulus. In contrast, we found no evidence for excess volume redistribution but rather an excess volume annihilation along the direction of compression. A possible reconciliation might be related to viscoelastic recovery processes.

(1) D. V. Bachurin, P. Gumbsch, Physical Review B, 85, (2012), 085407 1-9, doi:10.1103/PhysRevB.85.085407