Studying deformation mechanisms of nanocrystalline nickel by thermal activation analysis at subambient temperatures and high strain rates
September 29-October 4, 2019
Electrodeposition and magnetron sputtering are promising methods for depositing thin films with nanocrystalline (nc) microstructures. Nc metals are attractive materials, as they show considerably higher mechanical strength compared to their poly- or monocrystalline counterparts. However, they also feature pronounced time- and rate-dependent inelastic behavior and their microstructure may change drastically when exposed to elevated temperatures or ion irradiation. Therefore, in order to assess the mechanical behavior and deformation mechanisms of these materials under controlled conditions and at a constant microstructure, it is desirable to perform thermal activation analysis at subambient temperatures and high strain rates on pristine samples.
Large arrays of micropillars were fabricated by electrodeposition of nc Ni into lithography molds by LIGA leading to non-tapered, damage-free microspecimens. X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) imaging revealed a grain size of approximately 28nm. EDX analysis showed a homogeneous elemental composition and no concentration of impurities at the grain boundaries. A micromechanical testing device was developed that allows performing nanomechanical experiments at sub-ambient temperatures down to 120K in a large range of strain rates between 10-4 and 103s-1.
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Johann Jakob Schwiedrzik, Rajaprakash Ramachandramoorthy, Patrik Schürch, Thomas Edwards, Laetitia Philippe, Xavier Maeder, Johann Michler, and Jean-Marc Breguet, "Studying deformation mechanisms of nanocrystalline nickel by thermal activation analysis at subambient temperatures and high strain rates" in "Nanomechanical Testing in Materials Research and Development VII", Jon Molina-Aldareguia, IMDEA-Materials Institute, Spain Eds, ECI Symposium Series, (2019). https://dc.engconfintl.org/nanochemtest_vii/106