Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 17: Poster Session

MM 17.88: Poster

Monday, March 26, 2012, 17:00–19:00, Poster B

The effect of grain size and grain boundaries on the mechanical behaviour of MAX phases — •Thilo Seliger¹, Cynthia Volkert¹, Christoph Brüsewitz², Hans Hofsäss², and Michael Uhrmacher² — ¹Institut für Materialphysik, Universität Göttingen, D-37073 Göttingen — ²II. Physikalisches Institut, Universität Göttingen, D-37073 Göttingen

It is well known that the MAX phases (layered ternary carbides and nitrides) have unusual mechanical properties. They exhibit features from both metals (machinable, damage tolerant, good thermal and electrical conductivities) and from ceramics (high stiffness and low thermal expansion). This is attributed to the fact that dislocations only move on a single set of parallel planes, which results in kinking and shear band formation during deformation. It has been observed that the formation of kinks and shear bands is influenced by the grain size, leading to an increase in strength with decreasing grain size. We seek to take advantage of the grain size dependent strength and the damage tolerance of the MAX phases to explore the possibility of designing nanocrystalline MAX phases with both high strength and high ductility. We investigate the effect of grain size and individual grain boundaries on the nanoindentation response of Ti-based bulk MAX phases. A combination of EBSD to determine grain orientations, focused ion beam to mark specific locations and Berkovich nanoindentation have been used. The relation between local mechanical properties and local microstructure will be presented and discussed and used to develop guidelines for optimum grain sizes and textures.