Berlin 2024 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 29: Poster II

MM 29.36: Poster

Dienstag, 19. März 2024, 17:00–19:00, Poster B

Investigation of fatigue-generated vacancies in thin metal films using nanoindenter creep tests — •My Nguyen, Jan Verhoeven, Thomas Brede, Dominik Tönnies, and Cynthia A. Volkert — Institute for Material Physics, Georg-August University of Göttingen, Germany

Vacancies can be created in metals during cyclic loading, however, they have been only rarely directly detected. In this study, we develop an experimental set-up to detect fatigue generated vacancies by measuring their contribution to creep deformation. Our methodology involves performing nanoindenter creep tests on thin metal films while they are being fatigued by cyclic loading. The fatigue is realized by using delay line structures (with thin copper films on top) on which standing surface acoustic waves (SAW) are generated. Contributions from thermal drift during the creep tests have been minimized using a continuous stiffness measurement (CSM) method. The results confirm that using the developed method, it is possible to perform highly reproducible measurements. Turning the SAW loading on and off induces changes in raw displacement depth data which consistently correlate with the applied power. The CSM-corrected data also show SAW-induced changes, although not always assigned to creep behavior, but might be caused by the presence of artifacts and other effects. Initial interpretations of these variations regarding the different samples can be provided by the ellipsoidal concept of surface waves and tip asymmetry.

Keywords: Nanoindenter; Creep; Vacancies; Surface Acoustic Waves; Thin films