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PGI Colloquium:

Prof. Dr. Cynthia A. Volkert,Institute of Materials Physics, University of Göttingen, Germany

PGI Lecture Hall, Building 04.8, 2nd Floor, Room 365

03 Jul 2015 11:00

Watching Things Fall Apart: In-Situ Electron Microscopy of Flow and Fracture

Deformation and fracture are complex and highly non-equilibrium processes which determine the strength of materials. Gaining insights into the mechanisms which control these dynamic processes requires dynamic methods. This presentation will describe in-situ electron microscopy studies of deformation and fracture in nanoscale specimens where we have been able to perform dynamic observations at length scales down to Angstroms and times scales between 0.1 seconds and several hours. 

Our studies on deformation have primarily focused on tensile loading of high quality Au nanowires, where we observe the creation of dislocations by surface nucleation. Here we focus on understanding the conditions under which nucleation occurs and the differences between deformation that is controlled by dislocation nucleation and controlled by the interaction of existing dislocations, which is the usual deformation mode in bulk metals. We point out the weaknesses of current nucleation models and make suggestions for possible experiments to further test our understanding of nucleation.

VolkertCopyright: Prof. Dr. Volkert

Our studies on fracture have focused on crack propagation in nanolaminates, where we attempt to decipher the roles of surfaces and interfaces by propagating cracks parallel and perpendicular to the layer interfaces. We show that we can engineer the toughness and the crack path of materials by varying length scales. By comparing with our results on nucleation controlled deformation, we suggest tactics for designing high strength and high toughness nanostructured materials.


Dr. Martina Luysberg
Phone: +49 2461 61-2417
Fax: +49 2461 61-6444