Dresden 2014 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 8: Topical Session: Nanomechanics of nanostructured materials and systems II - Thin films
MM 8.1: Topical Talk
Montag, 31. März 2014, 11:45–12:15, BAR 205
The Fatigue and Time-Dependent Properties of Freestanding and Supported Thin Gold Films Studied by Bulge Tests — •Benoit Merle and Mathias Göken — Department of Materials Science and Engineering, Institute I, Friedrich-Alexander-University Erlangen-Nürnberg, Germany
The bulge test is a method of choice for investigating the mechanical properties of thin films. Its scope was extended to the study of fatigue and time-dependent properties of freestanding and SiNx supported 100 - 400 nm gold films. Fatigue testing is performed by cycling the pressure under the membrane up to 105 times, while the stress and strain in the membrane are continuously measured. Freestanding films experienced a strong ratcheting leading to failure after a few 104 cycles. Observations of the surface showed a sliding of individual grains below the level of the original surface. This grain boundary sliding was obviously eased by the columnar microstructure of the samples. SiNx supported films did neither experience failure nor such strong effects. Only a few abnormally large grains showed extrusions after completion of the fatigue tests. Cyclic creep having been observed for both kinds of samples, creep tests were performed on them. They evidenced widespread grain boundary sliding across the freestanding gold membranes, while this mechanism was prevented by the good adhesion of supported films to their substrate. Strain-rate jump tests showed that this resulted into freestanding gold films having a strain-rate sensitivity 5 times higher than their counterparts bonded to a SiNx substrate.