Berlin 2015 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 3: Microstructure and Phase Transformations
MM 3.5: Vortrag
Montag, 16. März 2015, 11:15–11:30, H 0106
Localizing sources of acoustic emission during the martensitic transformation — •Robert Niemann1,2, Jaromír Kopeček3, Oleg Heczko3, Jan Romberg1, Ludwig Schultz1,2, Sebastian Fähler1,2, Eduard Vives4, Lluís Mañosa4, and Antoni Planes4 — 1IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany — 2Technische Universität Dresden, Department of Physics, Institute for Solid State Physics, 01062 Dresden, Germany — 3Institute of Physics, Academy of Science of the Czech Republic, Na Slovance 2, 182 02 Prague, Czech Republic — 4Departament d'Estructura i Constituents de la Matèria, Facultat de Física, Universitat de Barcelona. Diagonal 647, 08028 Barcelona, Catalonia, Spain
Acoustic avalanches are a feature of solids under stress e.g arising from martensitic phase transitions. Local sources of acoustic emission are studied in order to enlight the microscopic mechanisms. From two-dimensionally resolved acoustic emission measurement and simultaneous optical observation of the surface we identify microstructural events at the phase boundary that lead to acoustic emission [1]. A resolution in the 0.1 mm-range was reached for the location of acoustic emission sources on a Ni-Mn-Ga polycrystal. The acoustic activity and the size distribution of the microstructural transformation events exhibit power-law behavior. The origin of the acoustic emission are elastically incompatible areas, such as differently oriented martensitic plates and grain boundaries in proximity to transforming grains. We propose a model to explain the decrease of the critical exponent in mechanical or magnetic fields. [1] Phys. Rev. B. 89, 214118 (2014)