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MM: Fachverband Metall- und Materialphysik
MM 8: Microstructure and Phase Transformations - Processing
MM 8.3: Vortrag
Montag, 16. März 2020, 12:15–12:30, IFW B
Epitaxial NiTi thin films: a 3D puzzle — •Klara Lünser1,2, Stefan Schwabe1,2, Moritz Döllgast1,2, Kornelius Nielsch1,2, and Sebastian Fähler1 — 1Leibniz IFW Dresden, Germany — 2TU Dresden, Institute of Materials Science, Dresden, Germany
NiTi is the most widely used shape memory alloy. Its superelastic and shape memory properties are the result of a martensitic transformation from a cubic (B2) to a monoclinic (B19') structure. This transformation gives rise to a complex martensitic microstructure. To customize the material for a specific purpose, a thorough understanding of this microstructure is helpful. In polycrystalline materials, however, the microstructure is influenced by grain boundaries, which complicates an analysis substantially.
Here, we use epitaxial NiTi films as a model system to examine the martensitic transformation and microstructure. These single-crystalline films are grown with DC magnetron sputter deposition in different thicknesses and are probed with scanning electron and atomic force microscopy. Due to the well-defined orientation relation between substrate and film, we can identify the orientations of habit planes and Type I and Type II twin boundaries in the B19' martensite. With in-situ measurements, we additionally examine the nucleation and growth processes of the B19' martensite. Our results are the starting point to understand the three dimensional shape of martensitic nuclei in NiTi B19* martensite which results in a hierarchically twinned microstructure on different length scales.
Supported by DFG (FA 453/13).