Dresden 2014 – wissenschaftliches Programm
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KR: Fachgruppe Kristallographie
KR 12: Functional Materials - Analysis with EBSD, X-Ray Kossel Diffraction and Related Methods (MI jointly with KR)
KR 12.1: Hauptvortrag
Donnerstag, 3. April 2014, 09:30–10:00, MER 02
The martensitic transformation in Co-Ni-Al F-SMA — •Jaromír Kopeček1, Karel Jurek1, Michal Landa2, and Oleg Heczko1 — 1Institute of Physics ASCR, Praha, Czech Republic — 2Institute of Thermomechanics ASCR, Praha, Czech Republic
The Co-Ni-Al alloys were in the focus of physicist from the beginning of research in ferromagnetic shape memory alloys, but as the surprisingly higher and higher magnetic field induced strain due to reorientation or transformation in magnetic field were announced in Ni-Mn-Ga system, the more dubious results emerged for the Co-Ni-Al system. It seemed apparent that Co-based shape memory alloys would quickly return into the structural intermetallics, interesting, complicated and useful, but just as another superalloy. Despite the knowledge accumulated in literature, recently researchers in this field were frustrated by curious disagreement between optical observation showing martensite lamellae at room temperature while magnetic measurement indicates that the martensitic transformation is well below zero. The present work compiled the results of various methods, which - we believe - proved that the martensitic transformation temperature in Co38Ni33Al29 is around -70 ∘C, whereas all higher temperature features are examples of stress induced transformation. Using various microscopies including EBSD together with RUS, magnetic measurements and mechanical testing we were able to explain the evolution of the structure. In comparison with Ni-Mn-Ga systems there are marked differences in transformation path which ultimately may explain why we cannot expect the magnetic shape phenomena in Co-Ni-Al alloys.