Dresden 2014 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 13: Topical Session: Nanomechanics of nanostructured materials and systems III - Small scale plasticity

MM 13.2: Talk

Monday, March 31, 2014, 16:15–16:30, BAR 205

Finite volume effects on dislocation organization and associated size effects in strength — •Erica Lilleodden and Henry Ovri — Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht

The nearly universal observation of size effects from nanoindentation and microcompression experiments in metals has led to heated debate regarding the physical basis of such behaviors. Much research in this area has focused on the scaling of stress with deformation length scale, and largely ignores the important observation of the inherently jerky load-displacement response common to both experiments. Borrowing ideas from self-organized criticality, it is argued here that consideration of the displacement bursts in relation to the deformation and microstructural length-scales can help provide a framework for understanding size effects in plasticity. The talk will focus on single crystalline high purity Mg and the Mg alloy AZ31 of two orientations associated with dislocation plasticity (i.e., no twinning), where the active slip systems for the two orientations have significantly different Peierls barriers. In this way, we are able to differentiate the influence of intrinsic lattice strength and alloying content. It will be shown that the distribution of displacement bursts and their associated stresses can be used to investigate the combined influences of finite volumes and material & microstructural parameters on the organization of dislocation structure and resultant stress-strain response.