Mechanical properties of nanomaterials

Hans-Jörg Fecht 

Ulm University, Albert-Einstein-Allee 47, Ulm 89081, Germany
Forschungszentrum Karlsruhe, Institute of Nanotechnology, P.O.B. 3640, Karlsruhe D-76021, Germany

Abstract

After a general introduction to the topic most recent results on the fundamentals of plastic deformation of fully dense nanocrystalline materials and metallic glasses will be presented. The first model system investigated is Pd (fcc) and several single-phase Pd alloys while it is found that “pure” nanocrystalline Pd-samples are inherently unstable against grain growth.
The experiments focus on mechanical tests using new testing equipment for miniaturized specimens with different stress state conditions. The aim is to obtain a significantly improved database of materials behaviour for these alloys at a grain size around 10 nm, since this has previously been explored only sporadically, and to elucidate and describe the microscopic mechanisms that mediate the deformation with maximum stress at fracture up to 1.8 GPa.
These results are in compression whereas under tensile conditions all materials in the nanocrystalline state seem to be inherently brittle. Under compressive conditions these nanocrystalline Pd-Au alloys represent the strongest noble metals ever made. Since the key mechanism of plasticity bears some similarities to shear band formation in bulk metallic glasses this opens a way in the design of new materials.

 

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Presentation: Invited oral at Warsaw and Karlsruhe Nanotechnology Day, by Hans-Jörg Fecht
See On-line Journal of Warsaw and Karlsruhe Nanotechnology Day

Submitted: 2011-08-26 18:22
Revised:   2011-08-29 15:50