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Seminar on Probing Dislocation - Grain Boundary Interactions and Grain Boundary Phase Transformations: New experiments on Cu bicrystals

Published on: 21-Sep-2018

School of Mechanical & Aerospace Engineering
Seminar Announcement​

Probing Dislocation - Grain Boundary Interactions and Grain Boundary Phase Transformations: New experiments on Cu bicrystals

Professor Gerhard Dehm
Ruhr-Universität-Bochum, Germany
Director, Max-Planck-Institut für Eisenforschung GmbH in Düsseldorf, Germany

Date: Friday, 21 September 2018
Time: 11:30 am – 12:30 pm
Venue: Lecture Theatre 10

This seminar will be hosted by Nanyang Assistant Professor Matteo Seita


Seminar Abstract

Recently, it has been revealed by atomistic simulations that grain boundaries can undergo phase transformations leading to changes in material properties such as grain boundary diffusion. In this talk I will show two examples were experimental evidence is provided at the atomic scale by scanning transmission electron microscopy (STEM) studies on grain boundary phase transformations in Cu, one triggered by segregation of Ag and one occurring in pure Cu. In order to understand in future whether such grain boundary phase transformations also influence mechanical properties in-situ micro-compression testing is explored as a method to probe the “strength” of grain boundaries. As the simplest case, a coherent twin boundary in Cu is studied and the results compared with micro-compression experiments on a penetrable high angle grain boundary. While a transmission stress is difficult to quantify, tests at different strain rates provide useful insights into the dislocation - grain boundary interaction. The experimental insights and limitations will be discussed.​

Acknowledgements: N. Peter, C. Liebscher, N. Malyar and C. Kirchlechner are gratefully acknowledged for their scientific contributions. Part of this research has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 787446; GB-CORRELATE).

Speaker’s Biography​

Gerhard Dehm is director at the Max-Planck-Institut für Eisenforschung GmbH in Düsseldorf and professor at the Ruhr-Universität-Bochum. From 2005 to 2012 he was head of the department Materials Physics at the Montanuniversität Leoben (Austria), and in addition managing director of the Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences. Gerhard studied Materials Science at the University Erlangen-Nuremberg and carried out his PhD thesis at the Max Planck Institut für Metallforschung in Stuttgart. He spent 2 years as a postdoc at the Technion in Haifa. Special focus in his research is laid on advanced S/TEM and in-situ microscopy of interfaces, their structure, chemistry, stability, and impact on material properties. His recent ERC Advanced Grant revolves around phase transitions of grain boundaries in alloys and its impact on materials properties.​

 

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