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MM: Fachverband Metall- und Materialphysik
MM 63: Functional Materials: Performance, Reliability and Degradation
MM 63.5: Vortrag
Donnerstag, 21. März 2024, 16:30–16:45, C 230
Influence of flash lamp annealing on the martensitic microstructure of epitaxial Ni-Mn-Ga films — Yuru Ge1,2, Satyakam Kar3,2,1, Fabian Ganss1, Thomas Schumann1, René Hübner1, Lars Rebole1, and •Sebastian Fähler1 — 1Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, 01328 Dresden — 2TU Dresden, Faculty of Mechanical Science and Engineering, 01062 Dresden — 3Leibniz IFW Dresden, Institute for Metallic Materials, 01069 Dresden
The application of shape memory materials are based on a reversible martensitic transformation, which changes structure and microstructure. All applications like high stroke actuation, sensing, ferroic cooling, and energy harvesting, benefit from a high cycle frequency, as this allows for high power density. For this, thin films are of particular interest as their high surface-to-volume ratio enables fast heating and cooling. However, up to now the influence of fast heating and cooling on the martensitic microstructure is unknown. Here we examine the influence of flash lamp annealing on epitaxial Ni-Mn-Ga films. Single-crystalline films are suitable as a model system since they allow for an undisturbed, well-ordered hierarchical martensitic microstructure after slow cooling. We examine all levels of this twin-within-twins microstructure by a combination of XRD, SEM and TEM before and after flash lamp annealing with a duration of 3 ms at different energy densities. We observe substantial changes at all levels of twinning, which we attribute to the finite time available to form a hierarchical microstructure and the thermal stress between film and substrate.
Keywords: shape memory alloys; epitaxial films; martensitic transformation; time dependency