SKM 2023 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 17: Phase Transformations: Microstructural Transformations
MM 17.2: Vortrag
Dienstag, 28. März 2023, 10:30–10:45, SCH A 118
Solving the 3D puzzle of the martensitic microstructure in epitaxial NiTi films — •Klara Lünser1,2,3, Andreas Undisz4,5, Kornelius Nielsch2,3, and Sebastian Fähler1 — 1Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany — 2Leibniz IFW Dresden, Dresden, Germany — 3TU Dresden, Dresden, Germany — 4TU Chemnitz, Chemnitz, Germany — 5Friedrich-Schiller-Universität Jena, Jena, Germany.
The shape memory effect in the most frequently used shape memory alloy NiTi is driven by a martensitic transformation, resulting in a complex martensitic microstructure with a variety of interfaces. As shape memory properties depend on the microstructure, a detailed understanding is crucial. However, the martensitic microstructure is still puzzling, especially how it is built up in 3 dimensions. The analysis of this puzzle is complicated by grain boundaries present in polycrystalline NiTi. Here, we eliminate the influence of grain boundaries by using epitaxial NiTi films in (111)-orientation as a model system. We analyze the films with electron microscopy to identify clusters and interfaces and compare results to the phenomenological theory of martensite. With this approach, we generate a scale-bridging understanding of the martensitic microstructure. Three kinds of twin boundaries on different length scales are required for the complete, hierarchical microstructure. Integral X-ray measurements confirmed our microstructure model. The results are transferable to NiTi bulk and polycrystalline films, showing that NiTi epitaxial films are important to extend our understanding of the martensitic microstructure.