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MM: Fachverband Metall- und Materialphysik

MM 2: Topical Session: Nanomechanics of nanostructured materials and systems I - Grain size effects

MM 2.2: Vortrag

Montag, 31. März 2014, 10:45–11:00, BAR 205

Nanoindentation of sputter-deposited Al and Al-Li thin films — •Diana Courty, Alla S. Sologubenko, and Ralph Spolenak — Laboratory for Nanometallurgy (LNM), ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland

Bulk, heavily-deformed fine-grained Al-Li-based alloys are known for their superplastic behavior at elevated temperatures. In these materials, grain-rotation is considered to be the major mechanism responsible for large plastic strains (up to 700%). An intrinsic feature of a thin metallic film, the nano-grained morphology, is very advantageous for the activation of this deformation mode, provided the inherent columnarity of the film morphology can be overcome.

Al-x at.%Li (x=0, 2, 5, and 10) thin film alloys have been sputter-deposited on Si wafers by different sputtering modes enabling the control of the grain morphology, breaking the columnar grain growth and tuning the sublayer thickness. These thin film alloys have been tested by nanoindentation at room temperature, 100^∘C and 150^∘C, showing a decrease in hardness for higher indentation temperatures. An effect of film thickness, composition and microstructure on the mechanical behavior of the thin film alloys was studied. Our particular interest is directed to the comparison of films of same thickness and composition but with different grain sizes, were smaller grain sizes showed an increase in hardness - smaller than expected by the Hall-Petch-effect.