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Mobility of grain boundaries in stress fields

Behaviour of grain boundaries under low cycle deformation

Korngrenzenbeweglichkeit unter Low-Cycle-Verformung
Myrjam Winning and Syed Badirujjaman
From the journal Materials Testing

Abstract

The mobility of grain boundaries under certain conditions is a key factor for the evolution of polycrystalline microstructures and material properties. In recent experiments it was shown that grain boundaries can interact with mechanical stress fields and that the motion of planar grain boundaries, low angle as well as high angle grain boundaries, could be induced by an external mechanical stress field [1,2]. Therefore the current study was performed to investigate the details of grain boundary motion and interactions between definite, planar grain boundaries and the mechanical stress field during high temperature low cycle deformation of high purity aluminium bicrystals. The grain boundary planes were in all cases perpendicular to the loading axis. Experiments were made with large as well as small stresses at different temperatures and numbers of cycles. The displacement of grain boundaries was measured by using optical microscopy, and the microstructural features, as well as orientations of individual grains were recorded by the electron backscatter diffraction technique (EBSD) after each deformation experiment.

Kurzfassung

Die Beweglichkeit von Korngrenzen spielt unter bestimmten Bedingungen eine Schlüsselrolle bei der Entwicklung polykristalliner Gefüge und von Werkstoffeigenschaften. Kürzlich konnte experimentell nachgewiesen werden, dass Korngrenzen mit mechanischen Spannungsfeldern in Wechselwirkung treten können und dass die Bewegung planarer Korngrenzen (Kleinwinkel- sowie Großwinkelkorngrenzen) durch externe mechanische Spannungsfelder ausgelöst werden kann [1,2]. Die vorliegende Studie untersucht die Details der Korngrenzenbewegung sowie die Wechselwirkung zwischen definierten planaren Korngrenzen und dem mechanischen Spannungsfeld während der Low Cycle Verformung bei hohen Temperaturen an hochreinen Aluminium Bikristallen. Die Korngrenzenebenen standen in allen Fällen senkrecht zur Beanspruchungsrichtung. Hierzu wurden Versuche mit hohen und niedrigen Spannungen bei verschiedenen Temperaturen und Beanspruchungs-zyklen durchgeführt. Die Korngrenzenverschiebung wurde mittels lichtmikroskopischer Untersuchungen, die mikrostrukturellen Eigenschaften sowie die individuelle Kornorientierung mittels Electron Backscatter Diffraction (EBSD) nach jedem Verformungsversuch aufgenommen.


Myrjam Winning studied physics at the RWTH Aachen and earned her Ph.D. in physics from the RWTH Aachen in 1999. She is currently group leader of the research group “Crystal Plasticity” at the Institute of Physical Metallurgy and Metal Physcis (RWTH Aachen).

Syed Badirujjaman received his academic education at IIT Kanpur. He is admitted to the doctoral program of the Institute of Physical Metallurgy and Metal Physics (RWTH Aachen) and works in grain boundary mechanics in the research group “Crystal Plasticity”.


References

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Published Online: 2013-05-26
Published in Print: 2004-03-01

© 2004, Carl Hanser Verlag, München